Crea Fusco, M.D., José M. Velasco, M.D.
1 A 76-year-old man with a medical history that includes hypertension, chronic renal insufficiency, and Child class A cirrhosis is admitted to the intensive care unit (ICU) after emergency exploratory laparotomy for ruptured appendicitis. His vitals signs are a temperature of 97.3° F, heart rate (HR) of 129 beats/min, blood pressure (BP) of 220/90 mm Hg, respiratory rate (RR) of 30 breaths/min, and oxygen saturation in arterial blood (SaO2) of 90%. The patient is agitated and trying to pull his drains and nasogastric tube. He does not appear to respond to commands. Select the best choice to sedate this patient.
A Lorazepam, 5 mg intravenously
B Four-point restraints while trying to reason with the patient
C Morphine delivered by patient-controlled anesthesia (PCA) with settings of 1 mg every 6 minutes and a 30-mg 4-hour lockout
D Propofol and fentanyl drip
E Placement of an epidural catheter for analgesia
Ref.: 1-3
Comments
In the ICU, management of pain can be difficult and is often complicated by an inability to communicate with the patient and by the patient’s physiologic instability, comorbid conditions, or delirium. Several methods have been developed to help assess sedation, including the Riker Sedation-Agitation Scale and the Ramsay Scale. This patient has both renal and hepatic dysfunction, which makes lorazepam an incorrect choice. It has a slow onset and intermediate half-life. In this situation, a faster-acting drug is preferable because the patient is obviously agitated. A propofol and fentanyl drip is the best answer because propofol is a general anesthetic agent with a rapid onset and ultrashort duration of action. Side effects with this medication include a risk for hypotension, high cost, pain on injection, and potential for hypertriglyceridemia. It has no analgesic effect and therefore additional medication is required to control the pain. Fentanyl is a better choice for analgesia because of the patient’s renal failure and its rapid onset of action relative to morphine, which can take 5 to 10 minutes.
The use of four-point restraints without additionally sedating the patient is not a good option. Again, PCA is not a good option for a patient intubated and needing further sedation because of agitation. Moreover, morphine and its active metabolites (morphine-3-glucuronide and morphine-6-glucuronide) can accumulate in patients with renal insufficiency. Finally, placing an epidural catheter in an agitated patient would be difficult and dangerous to the patient and staff.
Answer
D
2 A 53-year-old man with a past medical history of coronary artery disease, Child class B alcoholic cirrhosis, and chronic renal insufficiency is admitted to the ICU after undergoing exploratory laparotomy and resection of necrotic small bowel from an incarcerated ventral hernia. Acute respiratory distress syndrome (ARDS) has developed in this patient. He has been intubated and placed on synchronized intermittent mandatory ventilation (SIMV). His ventilator settings are a fractional concentration of oxygen in inspired gas (FIO2) of 90, RR of 24 breaths/min, tidal volume (VT) of 400 mL, pressure support (PS) ventilation of 8 mm Hg, and positive end-expiratory pressure (PEEP) of 15 mm Hg. Arterial blood gas analysis revealed a pH of 7.59, PCO2 of 20 mm Hg, PO2 of 59 mm Hg, HCO3 of 21 mEq/L, base deficit of −2, and SaO2 of 88%. The nurse calls because the respirator alarms continue to go off. The patient is actually breathing at a rate of 43 breaths/min. After adequately sedating him, he is still dyssynchronous with the ventilator. A decision to paralyze him is made. Which paralytic agent is the most appropriate for this patient?
A Pancuronium
B Cisatracurium
C Vecuronium
D Succinylcholine
E Rocuronium
Ref.: 1
Comments
The best choice is cisatracurium, a nondepolarizing neuromuscular blocker and one of the most commonly used paralytics in the ICU. It, along with atracurium, is metabolized by plasma ester hydrolysis and Hofmann elimination and is therefore the best choice in this patient with both hepatic and renal dysfunction. Pancuronium is long acting but contraindicated in patients with coronary artery disease because it has a vagolytic effect and induces tachycardia. Vecuronium is intermediate acting (30 minutes) but is cleared by the kidney and liver. Rocuronium has a rapid onset and intermediate duration, thus making it a better choice for short procedures, as opposed to the needs of this patient, who must be sedated for a longer period.
Answer
B
3 Which of the following statements concerning radial artery cannulation is true?
A Aortic systolic pressure is higher than radial systolic pressure.
B The Allen test is an outdated mode of assessing collateral flow of the ulnar and radial arteries.
C The incidence of infection is higher with catheters placed by surgical cutdown.
D The catheter should be replaced every 3 days.
E Intermittent flushing to keep the catheter free of clots is desirable.
Ref.: 4
Comments
The incidence of complications after arterial catheterization seems to be operator independent, unlike the case with pulmonary artery (PA) catheterization. Known risk factors include intermittent punctures, age younger than 10 years, prolonged catheterization (>4 days), anticoagulant therapy, and use of a catheter larger than 20 gauge or made of polypropylene rather than Teflon. The radial artery is the site most frequently used for catheterization, provided that the ulnar artery and palmar arterial arch are patent. Therefore, the Allen test should be performed before attempting radial artery catheterization. A normal test result consists of a palmar blush within 7 seconds after the ulnar artery is released. Most patients with arterial thrombosis remain asymptomatic. Symptoms can be minimized by placing lines in arteries with good collateral circulation. Most thrombi (43%) are present at the time of catheter removal, and another 30% develop within 24 hours. A higher incidence of thrombosis occurs within the first 24 hours when surgical cutdown is performed (48% versus 23% with percutaneous placement), but the incidence of thrombosis at 1 week is the same for both methods of placement. Brachial artery cannulation has a high incidence of embolic occlusion of the distal arteries (5% to 41%) and should therefore be avoided. Infection remains the most common complication. Predisposing factors are prolonged catheterization, surgical cutdown, local inflammation, preexisting bacteremia, and failure to change the saline flush fluid, transducer, and flush tubing every 48 hours. The need for intermittent arterial catheter replacement is not established and indeed is controversial. The aortic mean arterial pressure (MAP) and diastolic arterial pressure are slightly higher than the radial MAP and diastolic arterial pressure. However, systolic pressure is consistently higher in the radial artery than in the aorta. This discrepancy increases with distal progression, smaller arterial caliber, and age and is explained by the reflection of pressure waves from capillary beds, which results in augmentation of the systolic and reduction of the diastolic values measured.
Answer
C
4 A 70-kg, 72-year-old man known to suffer from congestive heart failure (CHF), arthritis, diabetes mellitus, and a first-degree heart block is intubated in the ICU on postoperative day 2 after exploratory laparotomy for perforated sigmoid diverticulitis. His urine output has dropped to 10 mL/h for the last shift, and he is hypotensive despite several fluid boluses. A PA catheter is placed through the right internal jugular vein with some difficulty. As the line is advanced to 50 cm, the patient has a 14-beat run of ventricular tachycardia, which resolves when the catheter is pulled back. It is finally advanced to 62 cm and the balloon is inflated with 3 cc of air by the resident. As the line is being secured, a large amount of blood is noted in the endotracheal tube and the patient becomes hypotensive. Select the best intervention for this patient:
A Place external pacing wires and administer lidocaine to treat the ventricular tachycardia.
B Place a double-lumen endotracheal tube and occlude the appropriate bronchus with a Fogarty catheter.
C Pull the PA catheter back 2 cm with the balloon inflated.
D Suction the endotracheal tube while deflating the balloon by 2 cc of air.
E Obtain a chest radiograph to confirm correct placement of the line.
Ref.: 5, 6
Comments
The indications for pulmonary artery catheters and their value in patients with sepsis or hemodynamic instability are uncertain, but they may be useful in the management of patients unresponsive to the use of fluids and vasoactive agents. Dysrhythmias occur in 12% to 67% of patients undergoing catheterization but are usually self-limited, premature ventricular contractions. Complete heart block can develop in patients with preexisting left bundle branch block. A prophylactic pacing wire should be used in these patients. Prophylactic lidocaine and full inflation of the balloon may prevent ventricular ectopy. Hemoptysis in patients with a PA catheter suggests the diagnosis of perforation or rupture. Mechanisms involved in PA rupture include (1) overinflation of the balloon, (2) incomplete balloon inflation (<75%) with the exposed tip being forced through the wall, and (3) pulmonary hypertension. An “overwedge” pattern suggests eccentric balloon inflation, overdistention, or both. If hemoptysis develops, the catheter should be pulled back with the balloon deflated. Massive hemoptysis necessitates placement of a double-lumen endotracheal tube and occlusion of the bronchus on the side of the rupture with a Fogarty catheter. Emergency thoracotomy is needed. Looping or knotting of the catheter may occur in the right ventricle during insertion and can be avoided if no more than 10 cm of the catheter is inserted after a ventricular tracing is identified and before a PA tracing appears. Although catheter-related sepsis occurs in only up to 2% of insertions, bacterial colonization takes place in 5% to 35% of catheterizations. Infections are more common when the catheter is left in place for more than 72 hours or when it is inserted via an antecubital vein.
Answer
B
5 Which of the following statements is not correct with regard to cardiac output (CO)?
A CO alone is not an indicator of myocardial contractility.
B Ventricular end-diastolic volume (EDV), vascular resistance, and myocardial contractility determine stroke volume (SV).
C Arterial blood pressure alone is an accurate indicator of CO.
D CO varies directly with a pulse rate of up to 160 beats/min in sinus rhythm, after which it decreases.
E Atrial contraction contributes up to 30% of EDV.
Ref.: 1, 7, 8
Comments
Arterial blood pressure alone is not an accurate indicator of CO. Cardiac output is determined by preload, afterload, and contractility. In simplest terms, CO is equal to HR multiplied by SV, which is equal to EDV minus end-systolic volume (ESV). Therefore, CO = HR × (EDV − ESV). SV is a function of the extent of shortening of myocardial fiber, which depends on preload (initial volume), afterload (resistance to ventricular emptying), and contractility. The relationship between diastolic filling and SV is governed by Starling’s law, which states that as muscle fiber length increases, so does the force of contraction. Increasing fiber length stretches the sarcomere toward the optimal 2.2-µm length. Therefore, CO alone is not an indicator of myocardial contractility. EDV, vascular resistance, and myocardial contractility are the primary determinants of SV. EDV is largely made up of passive ventricular filling during diastole. Diastolic filling time shortens as the pulse rate increases to 160 beats/min, but beyond this rate, CO decreases. Ventricular contractility depends on three interdependent variables: velocity of shortening, force of contraction, and length of displacement. Atrial contraction (the atrial kick) contributes 15% to 30% of EDV.
Answer
C
6 Which of the following factors is not a determinant of CO?
A End-diastolic pressure
B Afterload
C Contractility
D HR
E Ventricular interaction
Ref.: 8
Comments
The four factors that determine cardiac output are preload, afterload, contractility, and heart rate. Preload is defined as end-diastolic sarcomere length, which is related to EDV. Left atrial pressure is correlated with left ventricular end-diastolic pressure in normal hearts. Pulmonary capillary wedge pressure (PCWP) is a reflection of left atrial pressure and is commonly used as an index of preload. The relationship between PCWP and EDV is not constant but is affected by changes in left ventricular compliance, wall thickness, HR, ischemia, and medications. Ventricular interaction also affects CO. Shifts of the interventricular septum, normally slightly convex toward the right ventricle, may compromise ventricular filling. In general, preload must be optimized before afterload manipulation. Afterload is the impedance to ventricular ejection and is estimated by systemic or pulmonary vascular resistance. An increase in afterload produces an increase in contractility. Contractility is an intrinsic property of the myocardium that is manifested as a greater force of contraction for a given preload. All the available inotropic agents increase contractility by increasing intracellular calcium concentrations and availability. HR may influence CO in a number of ways. Bradycardia and excessive tachycardia should be corrected. An increase in HR affects preload and increases contractility.
Answer
A
7 A 57-year-old man with a history of coronary artery disease, hypertension, and hyperlipidemia has complaints of severe abdominal pain, bloody diarrhea, and 20-lb weight loss in the last 3 months. An upright chest radiograph in the emergency department shows free air. The patient is admitted to the hospital. His vitals signs are a temperature of 97.1° F, HR of 119 beats/min, RR of 29 breaths/min, BP of 71/50 mm Hg, and PO2 of 93 mm Hg. Laboratory studies showed a white blood cell (WBC) count of 17, 3/mm3, hemoglobin level of 7.0 g/dL, platelet count of 189,000/mm3, sodium concentration of 134 mEq/L, potassium concentration of 3.5 mEq/L, chloride concentration of 98 mEq/L, CO2 level of 18 mEq/L, blood urea nitrogen (BUN) concentration of 24 mEq/L, and creatinine concentration of 1.5 mEq/L. The patient is intubated and placed on the ventilator. Blood gas analysis show metabolic acidosis. An echocardiogram shows no wall or valvular abnormalities. Which one of the following will not directly affect oxygen delivery (DO2)?
A Rapid infusion of 2 L of saline solution
B Administration of three ampules of sodium bicarbonate to correct the acidosis
C Increasing PEEP by 2.5 units
D Transfusion of 2 units of packed red blood cells (PRBCs)
E Increasing FIO2 to 60%
Ref.: 1
Comments
See Question 8.
Answer
B
8 The patient is taken to the operating room (OR) and found to have perforated colon cancer with fecal peritonitis. On postoperative day 2 he becomes septic, acute renal failure (ARF) develops, and he has high FIO2 requirements to keep SaO2 greater than 90%. With regard to tissue utilization of oxygen, which one of the following statements is false?
A The brain requires 15% of the resting CO and 20% of the total basal oxygen consumption (
).
B The kidneys receive 25% of CO but can tolerate a reduction to a third of their normal blood flow for up to 1 hour.
C The heart extracts 70% of the available oxygen from its arterial supply.
D During acute hypoxia, blood is preferentially shunted to the heart and liver.
E The arterial-venous oxygen difference is a measure of the extent to which blood flow matches the metabolic demand for oxygen.
Ref.: 1
Comments
Do2 = CO × Cao2; Cao2 = [1.31 × (Hgb)(Sao2)] + [0.0031 × Pao2]; Cao2, content of arterial oxygen; Hgb, hemoglobin; Pao2, partial pressure of oxygen. Oxygen delivery depends on the arterial content of oxygen and on CO. Increasing the proportion of CO to satisfy the continuous high requirements of the brain and heart, not the liver, for oxygen is crucial for survival during states of severe deficiency in oxygen transport, such as cardiac arrest. In general, organs with low oxygen extraction ratios tolerate decreased blood flow well. Because the kidneys extract only 10% of the oxygen available in the arterial blood supply, they tolerate decreased blood flow far better than does the heart or brain. Organs other than the heart tend to compensate for decreased blood flow by extracting more oxygen from their blood supply. The extent of this extraction can be estimated by the arterial-venous difference in oxygen content. Normally, the body consumes only 25% of its total oxygen supply. The normal mixed venous blood is 75% saturated, with a partial pressure of oxygen of 40 mm Hg. These values decrease in response to a fall in CO, which can be detected before changes in BP, pulse rate, or central venous pressure (CVP) are noted. Increased extraction is made possible by relaxation of the precapillary sphincters, which enlarges the available capillary beds for exchange of oxygen.
Answer
D
9 A 50-year-old man is admitted to the ICU because of lower gastrointestinal bleeding. He has experienced three episodes of hematochezia, a 20-lb weight loss in the last 4 months, dyspnea, and dizziness. His vitals signs are a temperature of 98.1° F, HR of 108 beats/min, BP of 80/63 mm Hg, and SaO2 of 94%. His hemoglobin level is 9.1 g/dL. The patient receives several liters of crystalloid and his BP improves to baseline. CO remains elevated at 4.3 L/min. Which of the following is primarily responsible for the increase in CO in this patient?
A Tachycardia
B Increased contractility
C Increased afterload
D Decreased sympathetic nervous activity
E Decreased blood viscosity
Ref.: 9
Comments
Oxygen delivery (DO2) is maintained in patients with acute mild to moderate normovolemic anemia by the increased CO, which compensates for the reduction in oxygen-carrying capacity. Decreased blood viscosity is primarily responsible for the increased CO since it results in improved laminar flow. In blood, viscosity depends on particulate concentration and flow. A reduction in hematocrit by 50% produces an eightfold greater reduction in viscosity in the postcapillary venules than in the aorta. Because of the decreased viscosity in acute normovolemic anemia, decreased afterload, improved preload, and increased contractility are observed. Although increased cardiac sympathetic tone is seen during anemia, its direct effect on the heart is not primarily responsible for the increased CO.
Answer
E
10 All of the following are associated with an inaccurate estimation of hemoglobin oxygen saturation (SaO2) by pulse oximetric analysis except:
A Carboxyhemoglobin
B Albinism
C Septic syndrome
D Nail polish
E Hyperbilirubinemia
Ref.: 10
Comments
Pulse oximetric analysis is based on placing a pulsating arterial vascular bed between a diode and a light detector (spectrophotometer with plethysmographic characteristics). It detects the oxygenated part of hemoglobin available for carrying oxygen (SaO2), as opposed to the percentage of total hemoglobin that is oxygenated. An elevated carboxyhemoglobin level causes overestimation of SaO2 by pulse oximetric analysis because its absorption coefficient is similar to that of oxygenated hemoglobin. Inaccurate readings are associated with the following: dark-pigmented skin (not albinos), low-flow states or venous congestion, nail polish, vital dyes (methylene blue or indocyanine green dyes), ambient light, anemia, hyperbilirubinemia, changes in the oxyhemoglobin dissociation curve, and cardiac arrhythmias.
Answer
B
11 A 60-year-old 80-kg patient is in a septic state and febrile when admitted to the ICU. Some measured values include the following: MAP, 50 mm Hg; hemoglobin concentration, 5.8 g/dL; CVP, 8 mm Hg; pH, 7.20; CO, 7 L/min; PCO2, 52 mm Hg; temperature, 102.7° F; and PaO2, 82 mm Hg. Which of the following values apply to this patient?
A P50 greater than 27
B Alveolar-arterial gradient of 20
C P50 less than 27
D Shift of the hemoglobin dissociation curve to the left
E Oxygen-carrying capacity of 6.06 mL/g
Ref.: 11
Comments
The oxyhemoglobin dissociation curve (Figure 9-1) is an important tool for understanding how the blood carries and releases O2, in other words, hemoglobin’s affinity for oxygen. The partial pressure of O2(PO2) is on the x-axis and oxygen saturation (SO2) is on the y-axis, and the from the hemoglobin dissociation curve it can be seen that the amount of O2 carried by hemoglobin increases rapidly up to a PO2 of about 60 mm Hg. Above 60 mm Hg, the hemoglobin dissociation curve flattens out, and there is a much smaller change in hemoglobin saturation for the same change in PO2. Conversely, in the peripheral circulation, hemoglobin can release large amounts of O2 with decreasing hemoglobin saturation and yet maintain a relatively high PO2, which is needed to maintain a gradient for diffusion into the peripheral tissues. The position of the oxyhemoglobin dissociation curve along the horizontal axis, termed the P50 value, is the PO2 at which 50% of the hemoglobin is saturated. The normal value is approximately 27 mm Hg. This patient has not only elevated PCO2, which causes a rightward shift, but also metabolic acidosis secondary to low hemoglobin and low perfusion pressure. A rightward shift would be expected, and the resultant P50 would be greater than 27. A right shift indicates a decreased affinity of hemoglobin for oxygen, thus making it easier for hemoglobin to release oxygen to tissues. Other answers are incorrect because the O2 capacity in our patient is 8.06. (1.39 mL of O2 × Hgb.) The alveolar-arterial (A-a) gradient is PAO2 = [FIO2 × (PB − PH2O)] − PaCO2. PB, atmospheric pressure (760 mm Hg); PH2O, vapor pressure of water (47 mm Hg); PaCO2, alveolar pressure of CO2, which can be calculated by dividing PaCO2 by the respiratory quotient (normally 0.8). In our patient alveolar-arterial gradient is 5.23.
Figure 9-1 Oxyhemoglobin dissociation curve. DPG, diphosphoglycerate.
Answer
A
12 A 53-year-old woman with a 2-year history of metastatic bronchogenic carcinoma is admitted to the ICU after right sleeve lobectomy with an HR of 104 beats/min, BP of 64/43 mm Hg, and RR of 34 breaths/min. After multiple fluid boluses the patient remains hypotensive, so a PA catheter is placed and secured at 43 cm. The following values were determined: PA pressure, 38/27 mm Hg; CVP, 26 mm Hg; pulmonary artery occlusion pressure (PAOP), 27 mm Hg; and cardiac index, 2.0 L/min/m2. Which of the following explains the clinical scenario?
A CHF from sepsis
B Malignant pleural effusion
C Cardiac tamponade
D Hypovolemia
E Pneumothorax
Ref.: 11
Comments
There are many potential causes of pericardial tamponade, with bronchogenic carcinoma, renal failure, tuberculosis, breast carcinoma, and lymphoma and leukemia being among the most common. Hemodynamic monitoring with a PA catheter can help determine the diagnosis by showing equalization of right ventricular diastolic pressure, PA diastolic pressure, and PAOP within 2 to 3 mm Hg of each other, along with elevated mean right atrial pressure. With small effusions most patients are asymptomatic, but with fluid in excess of 500 mL, patients can experience the onset of dyspnea, cough, chest pain, tachycardia, and jugular venous distention. Pulsus paradoxus, hypotension, cardiogenic shock, and paradoxical movement of the jugular venous pulse are also signs to be noted. This patient has pericardial tamponade and is unlikely to improve with medical management. Pericardial drainage is recommended in all patients with large effusions because of recurrence rates in the 40% to 70% range. Administration of a fluid bolus is an appropriate measure but likely to be temporary. For immediate decompression, one can perform bedside pericardiocentesis. Definitive treatment of persistent symptomatic cardiac effusions is surgical pericardiectomy.
Answer
C
13 Which of the following treatments of a hypotensive patient is correct?
A Pericardiocentesis in a 54-year-old man after myocardial infarction (MI) with adequate volume status and hypotension refractory to inotropic agents
B Cardiac pacing in a 73-year-old woman taking digitalis with atrial fibrillation on the electrocardiogram (ECG), a ventricular response rate of 40, and adequate volume status
C Intraaortic balloon pump (IABP) in a 47-year-old woman with sepsis from pyelonephritis, good volume, and an echocardiogram showing no mechanical defects
D Inotropic agents in a 68-year-old woman with metastatic breast cancer, distended neck veins, and PA catheter readings showing normalization of right and left heart pressure
E Clamping of the infrarenal aorta in a patient with a gunshot wound to the chest and low right and left atrial pressure
Ref.: 1
Comments
Cardiogenic shock most commonly occurs as a consequence of acute left ventricular infarction. However, it may also be due to right ventricular infarction, ruptured papillary muscle, ruptured ventricular wall, acute aortic valvular insufficiency, mitral regurgitation, and a ventricular septal defect. However, before assuming that the hypotension is caused by a cardiogenic mechanism, one must be sure that there is adequate blood volume. Therefore, a patient who is hypotensive with low right and left atrial pressure should undergo fluid administration as the initial management. If cardiac performance improves with fluid administration alone, cardiogenic shock is probably not present. If adequate filling pressures are attained and the hypotension persists in the absence of mechanical defects, arrhythmia, and sepsis, a primary pump problem probably exists and should be managed with inotropic agents. One form of cardiogenic shock is cardiac tamponade, which is seen in traumatized patients, postoperative cardiac patients, and those suffering from uremia and certain malignancies. Pericardial tamponade has a trend toward equalization of pressures in the right and left sides of the heart. In a patient who is overdigitalized or hypokalemic, a very low ventricular rate in response to atrial fibrillation or flutter may result in hypotension and should be managed with cardiac pacing. If a patient remains in cardiogenic shock despite adequate blood volume, appropriate HR, absence of a mechanical or valvular defect, appropriate administration of inotropic agents, and restoration of pressure and coronary blood flow, support via IABP counterpulsation may be needed. Intraaortic balloon pump counterpulsation is most beneficial in patients with severe left ventricular dysfunction. It assists in left ventricular systolic unloading by directly reducing stroke work, which in turn reduces myocardial oxygen consumption during the cardiac cycle, and in diastolic augmentation, which raises arterial BP and provides better coronary arterial perfusion during diastole and improved delivery of oxygen to the myocardium. Patients with hemodynamic compromise secondary to right ventricular MI require fluid resuscitation and inotropic support. Any preload reducers must be avoided. Afterload reducers in the presence of hypotension are not warranted.
Answer
B
14 The alarm on the cardiac monitor continues to go off on a 73-year-old man with CHF and diabetes mellitus who was recently transferred to the ICU. He appears calm and is sitting up in bed watching a baseball game. His vitals signs are an HR of 155 beats/min, BP of 125/84 mm Hg, RR of 18 breaths/min, and SaO2 of 96%. An ECG taken 7 days ago is normal. A most recent one, taken 24 hours previously, shows that his previously distinct P waves have been replaced with rapid, polymorphic, irregular P waves that are irregular and occurring at a rate greater than 300/min. The ECG is repeated and confirms the presence of an arrhythmia. At this point, which is the best initial intervention for this patient?
A Anticoagulation with a heparin drip
B Cardioversion with paddles and settings at 260 J up to 3 times
C Repeat ECG in 48 hours
D Restoration of sinus rhythm by pharmacologic means such as amiodarone or diltiazem
E Morphine, 4 mg by intravenous push, to alleviate the pain
Ref.: 1, 12
Comments
The most common sustained dysrhythmia is atrial fibrillation, which has a prevalence of 5% in persons older than 65 years. There are numerous causes that may trigger new-onset atrial fibrillation, including ischemia, MI, hypertension, electrolyte imbalance, pulmonary embolism (PE), and digoxin toxicity. Initially, an ECG should be obtained and if the arrhythmia is symptomatic, it should be treated aggressively. New-onset atrial fibrillation with a duration of less than 48 hours is a clear indication to restore sinus rhythm by either electrical or pharmacologic means. This can be performed with intravenous calcium channel blockers, amiodarone, or β-blockers, which are usually effective in rapid conversion. Cardioversion should be performed in patients who are hemodynamically instable. Cardioversion in patients with atrial fibrillation for longer than 48 hours is contraindicated until they are fully anticoagulated. Acute intervention may not be necessary in patients with a history of well-tolerated arrhythmia.
Answer
D
15 A 58-year-old woman is found to have meningococcemia and sepsis. On examination, she is confused, agitated, and in respiratory distress. She is intubated and placed on assist/control mode (AC) ventilation. A central line is placed and several fluid boluses are given but she is still hemodynamically unstable. A continuous drip of a vasoactive drug is started. After administration, her HR remains at 105 beats/min, MAP rises to 70 from 45 mm Hg, CO drops to 2.8 from 3.3 L/min, and systemic vascular resistance increases to 1150 from 500 dynes•s/cm5. Based on the changes observed, which drug was most likely administered?
A Dobutamine
B Dopamine
C Phenylephrine
D Epinephrine
E Milrinone
Ref.: 1
Comments
Inotropic agents increase cardiac contractility by increasing the concentration and availability of intracellular calcium. Catecholamines act by binding to adrenergic receptors. Each type of receptor controls a particular cardiovascular function (Table 9-1). Epinephrine, norepinephrine, dopamine, and dobutamine are all catecholamines. The α1 receptor mediates arterial vasoconstriction by causing contraction of vascular smooth muscle, and the α2receptor induces constriction of venous capacitance vessels. The β1 receptor stimulates myocardial contractility, and the β2 receptor causes relaxation of bronchial smooth muscle and relaxation of vascular smooth muscle in skeletal muscle beds. The dopamine receptors cause relaxation of vascular smooth muscle. The dopamine-1 receptor induces relaxation of renal and splanchnic vascular smooth muscle, and the dopamine-2 receptor inhibits uptake of norepinephrine at the sympathetic nerve terminal, which results in prolonged action of norepinephrine at the mother end plate. The effects of dopamine are unpredictable and the side effects might be significant, thus its use in ICU has been ebbing. The response to catecholamines in normal individuals is different from that in critically ill patients. Receptor populations change over short periods, and upregulation and downregulation can occur, depending on the disease state. Because receptor numbers and affinities vary with the clinical setting, various and unexpected responses are seen. It is important that catecholamines be administered for a predetermined effect. If the effect is not attained with the particular catecholamine chosen, the dose should be adjusted or another agent used.
TABLE 9-1 Hemodynamic Response Receptors
Answer
C
16 A 68-year-old woman, a known diabetic with chronic renal failure, a distant history of MI, and an inability to climb one flight of stairs because of shortness of breath, has a new 2-cm spiculated mass with multiple calcifications throughout the breast, found on routine screening mammography. On examination, she has a fixed, hard 2.5-cm mass at the 10-o’clock position with small, soft, palpable axillary lymph nodes. She has a sister and aunt who died of invasive breast cancer, so she is very anxious and wants to have her operation as soon as possible. What is the most appropriate answer to her in regard to scheduling her operation?
A The comorbid conditions are not significant; therefore, the operation can be scheduled for tomorrow.
B An ECG, chest radiograph, and blood work are needed first.
C This is a surgical emergency, and β-blockers will be started and the operation performed in the morning.
D Cardiac function should be evaluated first and then plans made for surgery.
E Because the comorbid conditions are significant, she is not a surgical candidate.
Ref.: 1, 13
Comments
Approximately 44 million patients undergo noncardiac surgery in the United States, and of those, 30% have or are at risk for coronary artery disease with a 2.8 times higher risk for postoperative cardiac events. The American College of Cardiology/American Heart Association (ACC/AHA) Task Force on Practice Guidelines published guidelines on perioperative cardiovascular evaluation in 1996 with an update in 2002. The proposed function of these guidelines was to identify high-risk patients, risk-stratify them, and perform preoperative testing as necessary. It also would help determine whether patients needed coronary revascularization before their nonemergency operation. This patient has three intermediate risk factors: diabetes, renal insufficiency, and a previous history of MI. These factors, along with her poor functional status, mandates noninvasive testing of cardiac function, so she should not be scheduled for surgery before these tests are performed. An ECG, chest radiograph, and blood work are a good start, but according to the guidelines, the patient requires a noninvasive cardiac stress test. She does have many comorbid conditions but is undergoing a low-risk operation (breast, endoscopy, cataracts) associated with less than 1% risk. Intermediate-risk surgeries include intrathoracic, major orthopedic, intraperitoneal, head and neck, and prostate surgery, and they have a cardiac risk of less than 5%. High-risk surgeries such as aortic, major vascular, and prolonged procedures with significant fluid shifts have a greater than 5% cardiac risk. If a patient has undergone coronary artery bypass grafting (CABG) or a percutaneous intervention in the last 5 years without return of symptoms, no further work-up is needed. In addition, if there has been a cardiac evaluation in the last 2 years with no change in symptoms, no further work-up is needed. Patients who will not need revascularization will need medical therapy aimed at minimizing perioperative risk. Multiple studies have been performed on the perioperative use of β-blockers, many of which have been inconclusive or have design flaws. It is generally accepted that high-risk patients should take β-blockers, with an HR goal of less than 60 beats/min. Currently, the 2006 recommendations from the ACC/AHA recognize that there are insufficient data available to advocate the use of β-blockade in patients with low cardiac risk who are undergoing intermediate- or high-risk surgery. The POISE trial (PeriOperative ISchemic Evaluation) is currently ongoing and is designed to evaluate the efficacy of 30 days of metoprolol and its effect on cardiac events.
Answer
D
17 Which of the following conditions is not usually associated with elevated dead space ventilation?
A 42-year-old female after MI with CHF and a CO of 1.5 L/min
B 28-year-old woman on partum day 1 with shortness of breath, a PaO2 of 60 mm Hg, and segmental clots bilaterally in the pulmonary arteries
C 52-year-old Hispanic immigrant with a long-standing ventricular septal defect and PA pressure of 80/52 mm Hg
D 22-year-old man after multiple gunshot wounds, massive transfusions, and a mean arterial to inspired oxygen ratio (PaO2/FIO2) of 180
E 62-year-old woman smoker with the following ventilator settings: controlled mandatory ventilation (CMV) at a rate of 12 breaths/min, FIO2 of 60%, VT of 600 mL, and PEEP of 5 cm H2O
Ref.: 14, 15
Comments
The most common causes of increased dead space in critically ill patients are decreased CO, PE, pulmonary hypertension, ARDS, and excessive PEEP, all of which directly cause decreased blood flow to the pulmonary vasculature. In dead space ventilation with a high ventilation/perfusion (
) ratio, there is decreased blood flow to ventilated areas, which primarily affects elimination of carbon dioxide. In ARDS, some areas of lung are perfused but not ventilated. Alveoli may be filled with secretions, exudate, blood, or edema, thereby increasing the shunt fraction. Other areas of the lung may be ventilated but not perfused, which accounts for the dead space ventilation. Positive end-expiratory pressure can cause dead space ventilation by decreasing CO and stenting alveoli open, which causes the surrounding capillaries to collapse and thereby decreases alveolar perfusion. Carbon dioxide production and the dead space–tidal volume ratio (VDS/VT) determine minute ventilation. The anatomic dead space includes the volume of the airways to the level of the bronchiole (150 mL). Dead space can also include alveoli that are well ventilated but poorly perfused. When combined, the anatomic and alveolar dead space constitutes the physiologic dead space, which is essentially the volume of gas moved during each tidal breath that does not participate in gas exchange.
Answer
E
18 A 17-year-old asthmatic girl is brought to the OR for ruptured ectopic pregnancy. Postoperatively on the floor, she is found to be profoundly dyspneic and in acute respiratory failure. She is intubated and transferred to the surgical ICU, where her ventilatory settings are AC mode, RR of 18 breaths/min, FIO2 of 0.80, VT of 600 mL, and PEEP of 0 mm Hg. She was sedated and paralyzed for the intubation and is not breathing over the ventilator settings. After examining the patient and the flow pattern on the ventilator, changes in the ventilatory settings are made. Which change in ventilator setting would best limit intrinsic PEEP?
A Increase VT
B Decrease in the inspiratory flow rate
C Increase in PEEP
D Decreased RR
E Change from AC mode to SIMV
Ref.: 16, 17
Comments
Intrinsic positive end-expiratory pressure (commonly known as auto-PEEP) is a state at end exhalation in which there is incomplete gas emptying, which can elevate alveolar volume and pressure. It is the threshold pressure needed to be overcome to initiate inspiratory flow. Severe bronchospasm increases the expiratory time needed, and patients in status asthmaticus or severe chronic obstructive pulmonary disease (COPD) are at risk for intrinsic PEEP. If combined with narrowed airways, such as in asthma, and parenchymal noncompliance, the inspiratory work of breathing is increased. Therefore, there is an imbalance of respiratory muscle strength and work of breathing leading to respiratory failure.
During mechanical ventilation, when the expiratory time is insufficient to allow full exhalation of a ventilator breath, expiratory flow is still occurring when the next ventilator breath is delivered. To best limit intrinsic PEEP, one can decrease the RR, thereby giving the patient more time to exhale between breaths. In addition, decreasing VT will allow minimal improvement. One should also limit the inspiratory time to leave more time in the respiratory cycle for exhalation. Avoidance of hyperinflation and overdistention at the expense of minute ventilation, otherwise known as permissive hypercapnia, is an important method of ventilatory management in asthmatics.
Answer
D
19 The intensivist in the ICU is called to evaluate multiple patients with respiratory difficulty. The respiratory therapist has been busy collecting data on each of them. Which of the following patients does not need urgent changes in management while ventilatory support is being provided for the others?
A 47-year-old woman with bilateral pneumonia and an RR of 55 breaths/min
B 72-year-old man after quadruple bypass with a PaCO2 of 67 mm Hg
C 64-year-old mechanic after colectomy for ulcerative colitis with an alveolar-arterial oxygen difference of 390 mm Hg.
D 61-year-old woman heavy smoker with ARDS and measured dead space ventilation (VDS/VT) of 0.7
E 28-year-old postal worker after a dog bite to the arm and fasciitis with a shunt fraction greater than 5%
Ref.: 18
Comments
The indications for respiratory support include inadequate parameters of ventilation (RR >35 breaths/min, VDS/VT >0.6, PaCO2 >60 mm Hg), poor oxygenation (A-a O2 difference and PaO2), and impaired respiratory mechanics. Decreased vital capacity (VC = inspiratory reserve volume + VT + expiratory reserve volume) can lead to the need for intubation, and 15 mL/kg is life sustaining. Decreased inspiratory force, the force needed to create negative pressure in the lungs, can also indicate a need for respiratory support. In the absence of metabolic alkalosis or chronic hypercapnia, a PaCO2 greater than 60 mm Hg is abnormal. Dead space ventilation, the amount of VT that does not encounter perfused alveoli, is used as an indirect measure of ventilation-perfusion abnormality. It has been shown that increased physiologic VDS/VT (>0.6) is significantly associated with mortality in patients with ARDS (PaO2/FIO2 ratio of less than 200 mm Hg). The shunt fraction, or pulmonary venous mixture, can be defined as the amount of blood shunted around the lung as a fraction of CO. Shunt fraction is measured at the inspired oxygen concentration required to maintain adequate oxygenation (PO2 of 60 to 70 mm Hg). A shunt fraction greater than 20% requires respiratory support.
Answer
E
20 With regard to ventilatory mechanics, which of the following statements is false?
A The work of breathing at rest consumes 2% of total body oxygen consumption.
B COPD is associated with an increase in the work of breathing as a result of increased inspiratory work.
C The work of breathing may increase to 50% of total-body oxygen consumption in postoperative patients.
D Airway pressure reflects the compliance of the chest wall and diaphragm, as well as that of the lungs.
E Compliance is measured as the change in volume divided by the change in pressure.
Ref.: 19, 20
Comments
For patients with chronic obstructive pulmonary disease, the work of breathing is increased because of increased expiratory work, not inspiratory work. It can be assessed by preoperative pulmonary function testing and optimized by preoperative chest physical therapy, bronchodilators, and antibiotics if infection is present. The work of breathing at rest consumes 2% of total-body VO2 and can be markedly increased, up to 50% of total VO2, in postoperative patients because of increased airway resistance and decreased compliance of the lung, chest wall, and diaphragm. The proper use of volume-cycled ventilators and PS ventilation can take over most of the work of breathing during the postoperative period. Compliance is defined as the change in pressure associated with each milliliter increase in lung volume. Measuring airway pressure reflects the compliance of the chest wall and diaphragm, as well as that of the lungs. In relaxed patients this is of little importance, but in restless patients, intraesophageal or intrapleural pressure provides a more accurate measure of compliance. In acute respiratory failure, decreased compliance is usually associated with decreased functional residual capacity. Less compliant lungs need ventilatory management that maintains inflation of alveoli by the use of PEEP and recruits closed alveoli by elevating peak inspiratory pressure. However, because positive airway pressure may overdistend already ventilated alveoli, the peak inspiratory pressure should be kept below 40 cm H2O.
Answer
B
21 A 53-year-old man suffers an MI, falls from a height of 4 m off the train tracks, and sustains a severe head injury. He has multiple long-bone fractures, severe heart failure, diffuse axonal injury, and ARDS. He is severely hemodynamically unstable and taking multiple vasopressors, and he had had an episode of asystole after bathing. His PaO2/FIO2 ratio is 95 and his peak airway pressure ranges from 42 to 47 cm H2O despite lung-protective ventilation. The family expresses the desire to “do everything.” Which of the following is not a reasonable ventilation strategy for this patient?
A Prone positioning
B Inhaled nitrous oxide (N2O)
C Permissive hypercapnia
D Pharmacologic paralysis
E Partial liquid ventilation
Ref.: 1, 21
Comments
In patients with severe lung disease, it can be a challenge to oxygenate and ventilate. Goals for adequate ventilation include an SaO2 of greater than 90% and airway pressures of less than 35 to 40 cm H2O. There are no definitive answers in a difficult-to-ventilate patient, but all the strategies listed are accepted maneuvers. Because of this patient’s unstable BP and episode of asystole with bathing, prone positioning is not a reasonable strategy for him. It can also lead to loss of tubes and lines and the development of pressure ulcers if teams are unfamiliar with the procedure. When indicated, prone positioning can increase oxygenation by changing the dependent areas of the lung and realigning the distribution of inflated alveoli with pulmonary perfusion. Inhaled N2O is an endogenous compound with vasodilator properties that can improve oxygenation but is expensive and not always available. It has been shown to improve PA pressure and oxygenation in patients with acute lung injury and ARDS, but no overall decrease in mortality has been shown. Permissive hypercapnia, in which accumulation of CO2 and respiratory acidosis are allowed, attempts to minimize barotrauma and volutrauma to the lung. Most centers accept a pH of 7.2 or above. Paralysis can allow synchronization of the ventilator and relax the chest wall musculature. It also decreases the work of breathing by allowing the ventilator to do all the work. Partial liquid ventilation partially fills the lung with perfluorocarbon, which carries respiratory gases and can preserve lung histology, compliance, and systemic oxygenation. Another option not listed, extracorporeal membrane oxygenation (ECMO), bypasses the lungs, oxygenates the blood, and can protect the lungs from high FIO2 and ventilator settings. It requires anticoagulation and is therefore a contraindication in this patient with a severe head injury.
Answer
A
22 A family meeting is called for a 69-year-old man who was intubated 6 days earlier for pneumonia and respiratory distress. He is now awake, alert, and asking for the tube to come out. His family wants to know when and whether he will be extubated. Which of the following characteristics of this patient does not meet conventional weaning criteria?
A Negative inspiratory force of −10 cm H2O
B A respiratory frequency/tidal volume (RF/VT) ratio of 105 or less
C Correction of underlying pulmonary and nonpulmonary complications
D Pulse oximetry reading of 92%
E Vital capacity of 12 to 15 mL/kg and peak inspiratory pressure of less than 25 cm H2O
Ref.: 22
Comments
Many indices have been proposed to predict weaning outcome and success or failure of extubation. Most surgical patients (90%) are weaned from mechanical ventilation in less than 1 week. Conventional weaning criteria include (1) measurements of oxygenation with a pulse oximeter (best determined by arterial blood gas analysis, with an SaO2 >90% and any FIO2 usually being adequate for weaning) and (2) measurements of ventilation, such as an RR less than 24 breaths/min, PaCO2 less than 50 mm Hg, peak inspiratory pressure below 30 cm H2O, VT of at least 5 to 8 mL/kg, and a vital capacity double the VT value. Failure to satisfy these conventional criteria is associated with unsuccessful weaning in as many as 63% of patients. The rapid, shallow breathing test (RF/VT) is performed by having the patient breathe room air for 1 minute as quickly as possible. When RF/VT is 105 or less, successful weaning occurs in 78% of patients, and when RF/VT is less than 80, the success rate is 95%. Conversely, an RF/VT value of 105 or higher is accompanied by a failure rate of 95%. Another method often described is the SOAP assessment: (1) ability to clear secretions, (2) adequate oxygenation (PaO2/FIO2 ratio >200 mm Hg, which requires an FIO2 of 0.4 to 0.5 and PEEP <8 cm H2O), (3) ability to protect the airway, and (4) adequate pulmonary function. Clinical judgment and correction of underlying pulmonary and nonpulmonary complications continue to be the best guide to successful weaning. In addition, helpful ventilation scores include an FIO2 of less than 40%, continuous positive airway pressure (CPAP) of 3 cm H2O, effective static compliance greater than 50 mL/cm H2O, dynamic compliance greater than 40 mL/cm H2O, ventilator minute ventilation of less than 10 L/min, and a triggered ventilatory rate of less than 20 breaths/min. The duration of ventilatory support is not correlated with survival rates at discharge. Forty-one percent of long-term ventilated patients survive. Because muscle atrophy is often present, a progressive ventilatory withdrawal plan designed to restore muscle function should be used. Intermittent mandatory ventilation, PS ventilation, and weaning by T-piece have been used effectively.
Answer
A
23 A 29-year-old firefighter is intubated in the ICU after being exposed to smoke on the job. She has thick yellow secretions that require frequent suctioning along with the administration of bronchodilators. On hospital day 5, she has a percutaneous central venous catheter placed through the right internal jugular vein. Several hours later, she undergoes respiratory arrest. Her peak inspiratory pressure has risen from 24 to 41 cm H2O, and her plateau pressure has stayed at 16 cm H2O. Choose which of the following is the most likely reason for the respiratory arrest:
A Tension pneumothorax
B Flash pulmonary edema
C pulmonary embolus (PE)
D Endotracheal tube obstruction
E Auto-PEEP with breath stacking
Ref.: 20
Comments
This patient has an obstruction of the endotracheal tube. The key to identifying this problem is recognizing the components of the patient’s respiratory pressure in Table 9-2, most importantly the peak inspiratory and plateau pressures. The peak inspiratory pressure is the pressure required to overcome the resistance in the endotracheal tube and airways, as well as the compliance of the airways. The inspiratory plateau pressure is the pressure generated to overcome the elastance of the lung parenchyma, pleural space, and chest wall. This patient had increasing peak inspiratory pressure, so her problem was related to the tube, not the lung itself. Tension pneumothorax and flash pulmonary edema are associated with increases in both peak inspiratory pressure and inspiratory plateau pressure. PE also does not change the inspiratory pressure.
TABLE 9-2 Patient’s Respiratory Pressures
Answer
D
24 A 73-year-old woman weighing 60 kg is admitted to the hospital with acute pancreatitis. She is aggressively resuscitated with fluid but becomes hypotensive and has increasing work of breathing and O2requirements within the next 12 hours. The patient is transferred to the ICU and intubated. A PA catheter is placed and the wedge pressure is 8 cm H2O. Arterial blood gas analysis shows values of a pH of 7.36, a PaO2 of 62, a PCO2 of 42, a serum bicarbonate of 21, and a base deficit of −2 with SaO2 of 90%. Which of the following ventilation strategies is most appropriate for this patient?
A Pressure control ventilation (PCV) with a pressure of 40 cm H2O and an inverse ratio ventilation of 3:1
B SIMV with a VT of 720 mL and RR set to keep the pH at 7.4
C AC ventilation with a VT of 600 mL and prone positioning
D AC ventilation with a VT of 360 mL and RR to keep the pH above 7.2
E SIMV with a VT of 600 and FIO2 of 100%
Ref.: 23-25
Comments
See Question 25.
Answer
D
25 Which one of the following criteria is not included in the definition of ARDS?
A PA wedge pressure of 14 mm Hg
B Chest radiograph showing bilateral pulmonary infiltrates
C Infectious cause
D Onset of 6 hours
E PaO2/FIO2 ratio of 175
Ref.: 23-25
Comments
Because the principal physiologic problem in acute respiratory distress syndrome is hypoxemia refractory to increasing FIO2, therapy is centered on provision of mechanical ventilation to maximize oxygen delivery while minimizing lung injury. PEEP is used to improve oxygenation and lung compliance and should be optimized with the help of pressure-volume curves to facilitate the maintenance of open alveoli and diffusion of oxygen into the pulmonary capillaries. For a given FIO2, PaO2 usually increases on administration of positive end-expiratory pressure in patients with ARDS. However, excessive PEEP (>15 cm H2O) can be hazardous and lead to pneumothorax from barotrauma and decreased venous return to the heart. Overdistention of alveoli can be prevented by keeping the peak inspiratory pressure below 35 cm of H2O. Newer ventilatory methods attempt to enhance alveolar recruitment, maintain alveolar patency throughout the respiratory cycle, maintain an SaO2 of greater than 90%, avoid dynamic hyperinflation (volutrauma), and reduce the risk for oxygen toxicity. Spontaneous, augmented low-volume ventilation, with PS ventilation being used as a primary ventilatory support mode, directs flow to regions of low ventilation/perfusion. Diuretics in cases of obvious fluid overload and cardiac decompensation and broad-spectrum antibiotics in cases of established pulmonary infection or other sources of sepsis may be useful for patients with ARDS. The consensus conference on ARDS (ARDSnet.org) showed that a volume-restricted ventilation strategy reduced mortality. In this well-accepted study, 861 patients were randomly assigned to either a traditional-volume ventilation strategy (12 mL/kg of ideal body weight with plateau pressures of <50 cm H2O) or low-VTventilation (6 mL/kg with plateau pressures <30 cm H2O). The study was halted early because of significantly reduced overall mortality (31.0% versus 39.1%, P < .0007). Permissive hypercapnia was allowed and sodium bicarbonate was given to maintain pH higher than 7.2.
The patient developed ARDS, probably because of acute pancreatitis and systemic inflammatory response syndrome (SIRS). Criteria used to define ARDS include an acute onset, bilateral pulmonary infiltrates on chest radiographs, hypoxemia (PaO2/FIO2 ratio <200 mm Hg), and absence of cardiogenic pulmonary edema (i.e., PCWP <18 mm Hg) or no clinical evidence of left atrial hypertension. There does not have to be an infectious process for a patient to have ARDS. Acute lung injury is a milder form with a PaO2/FIO2 ratio of 201 to 300 mm Hg. The lung response can be divided into an exudative phase (24 to 96 hours), with leakage of proteinaceous fluid into the pulmonary interstitium and corresponding damage to the alveolar-capillary interface; an early proliferative phase (3 to 10 days), with proliferation of alveolar type II cells, cellular infiltration of the septum, and organization of hyaline membranes; and a late proliferative phase (7 to 10 days), with fibrosis of the alveolar septum, ducts, and hyaline membranes. Frequently, the radiographic changes can lag behind the clinical picture in ARDS considerably.
Answer
C
26 A 59-year-old woman with a long-standing history of gastroesophageal reflux disease (GERD) underwent a Nissen fundoplication that was complicated by 2 L of blood loss and hypotension in the OR. Her vitals signs are an HR of 103 beats/min, BP of 100/70 mm Hg, RR of 16 breaths/min, and SaO2 of 96%. Her urine output was 15 mL of urine per hour over the last 4 hours. Laboratory results include a urine osmolality of 600 mOsm/kg, urine sodium concentration of 15 mEq/L, plasma sodium concentration of 140 mEq/L, urine creatinine concentration of 20 mg/dL, and plasma creatinine concentration of 1.5 mg/dL. What is the next step in management?
A Flushing the Foley catheter with 60 mL of normal saline
B Hemodialysis
C Nephrology consultation
D Decompressive laparotomy for abdominal compartment syndrome
E Administration of a 1000-mL fluid bolus of normal saline as a fluid challenge
Ref.: 26, 27
Comments
Acute renal failure is a serious morbidity for postsurgical patients, with mortality rates greater than 50%. Renal failure can be prerenal, renal, or postrenal. The most common cause in surgical patients is hypovolemia, as is the case in this patient from blood loss in the OR. Some indicators for prerenal causes include urine osmolality greater than 500 mOsm/kg, fractional excretion of sodium (FENa) of less than 1%, and urine sodium concentration of less than 20 mEq/L, whereas an FENa greater than 3% and urinary sodium concentration greater than 40 mEq/L are indicative of parenchymal or postrenal causes. Medications, intravenous contrast material–induced nephropathy, rhabdomyolysis, and transfusion reactions are all options to consider. This patient’s FENa is 0.8%.
Answer
E
27 A 46-year-old brittle diabetic and hypertensive woman is brought to the ICU after being found unresponsive in her bed. After undergoing a computed tomographic (CT) scan of her head, abdomen, and pelvis with intravenous contrast media, she is transferred to the ICU. The ICU team places a central line, orders an echocardiogram, and places a bladder catheter. Her urine output has been approximately 10 mL/h for the last 4 hours. Her FENa is calculated to be 2.4%. Which of the following is not consistent with acute tubular necrosis (ATN)?
A Oliguria
B FENa greater than 2%
C Urine osmolality of 200 mOsm/kg
D Creatinine clearance greater than 125 mL/min
E Sodium wasting
Ref.: 26, 27
Comments
A creatinine clearance of 125 mL/min represents normal renal function. ATN is characterized by a rise in plasma creatinine concentration (decrease in creatinine clearance or glomerular filtration rate [GFR]), a urine volume that is reduced (oliguric) or normal, changes in the findings on urinalysis, and an FENa greater than 1% to 2%. Oliguria, or urine output less than 500 mL/24 h, is a frequent but not an absolute feature of ATN. Whether oliguria occurs may depend on the severity of the renal injury or the relative reabsorption of filtrate at the tubular level. Even if a patient’s glomerular filtration rate falls to 10 L/day (normal, 180 L/day), urine output of 1 to 2 L/day would still will be normal as long as 8 to 9 L of filtrate was reabsorbed. In cases of well-preserved tubular function, as in prerenal forms of ARF, fractional excretion of sodium is low, consistent with the sodium-avid state. As tubular dysfunction progresses, the ability of nephrons to reabsorb sodium is disrupted, and a greater percentage of the filtered sodium is excreted in urine. As a result, FENa will be greater than 1% to 2% because of inappropriate sodium wasting by altered tubular function. Loss of urinary concentrating ability is an early feature of ATN. A urine osmolality of less than 350 mOsm/L is consistent with ATN, whereas an osmolality greater than 500 mOsm/L suggests a prerenal cause of ARF. However, lower values can be seen during prerenal ARF, thus limiting the value of this test as a sole indicator of tubular function.
Answer
D
28 A 62-year-old man with peripheral vascular disease, diabetes, and bilateral tissue loss in the lower extremities is admitted for angiography of his lower extremities. He has chronic renal failure and his serum creatinine level is 5.0 mg/dL, which has been his baseline for the last 3 years. Which of the following agents is indicated to reduce the risk for intravenous contrast–induced nephropathy?
A Calcium channel blocker
B Aggressive diuresis
C Saline volume expansion before and after the procedure
D Acetylcysteine given only after exposure to contrast material
E Mannitol and saline hydration
Ref.: 26, 28
Comments
In most cases, radiocontrast agents can lead to a reversible form of ARF. The pathogenesis is not well established, but two proposed mechanisms of injury are renal vasoconstriction and direct tubular toxic effects. The risk is minimal in patients with normal renal function, including those with diabetes, and the renal failure is nonoliguric and transient in most cases. Severe renal failure requiring short- or long-term dialysis is rare and most likely to occur in patients whose baseline creatinine level is greater than 4 mg/dL. Risk factors for the development of contrast-induced nephropathy include underlying chronic renal failure with a plasma creatinine level greater than 1.5 mg/dL, diabetic nephropathy with renal insufficiency, CHF, multiple myeloma, and a large volume of contrast material. Saline volume expansion in the precontrast and postcontrast period is the only preventive measure consistently shown to be of benefit. Hydration with furosemide may increase the risk for contrast-induced nephropathy when compared with saline alone. Furthermore, the use of saline solution and mannitol does not have any benefit over the use of saline alone. Calcium channel blockers given to minimize renal vasoconstriction after exposure to contrast media have not been conclusively shown to prevent renal failure. The role of nonionic contrast agents is not clearly defined. Studies seem to support the use of isosmolar nonionic agents in high-risk patients, especially those with diabetes. There are conflicting data on the role of acetylcysteine and sodium bicarbonate infusions in the prevention of contrast-induced nephropathy, but given its relatively safe side effect profile and the few series supporting its use, use of both can be justified, particularly in high-risk patients. A rational approach to preventing contrast-induced nephropathy in high-risk patients, such as the patient in question, would include acetylcysteine (600 mg orally twice daily the day before and on the day of exposure to contrast material), saline volume expansion before and after the procedure, and an isosmolar nonionic contrast agent. Several recent meta-analyses have shown that sodium bicarbonate infusion can decrease the damage associated with contrast-induced nephropathy if given both before and after the procedure as well. The former may be more important for patients with renal dysfunction and diabetes.
Answer
C
29 Choose the situation that does not require immediate renal replacement therapy.
A 27-year-old bipolar patient, after running a half marathon, taking a prescribed lithium dose and found to have ataxia, confusion, and inverted T waves
B 68-year-old man after sigmoid colectomy with new-onset seizures and BUN of 150 mg/dL
C 58-year-old man after a motor vehicle collision with multiple long-bone fractures, BUN of 120 mg/dL, creatinine of 2.8 mg/dL, and diffuse bleeding
D 71-year-old woman with diabetes maintained on an insulin drip after total abdominal hysterectomy and bilateral salpingo-oophorectomy with an FENa of 0.7% and urine output of less than 20 mL/h for last 7 hours
E 45-year-old man with respiratory distress after massive resuscitation for a septic episode, bilateral lung haziness on chest radiography, and coarse crackles who is unresponsive to diuretics
Ref.: 1, 29-31
Comments
Indications for acute dialysis treatment include (1) persistent hyperkalemia refractory to medical management; (2) pulmonary edema unresponsive to conventional therapy; (3) severe acidemia; (4) symptoms of uremia such as anorexia, nausea, and vomiting; (5) uremic encephalopathy, seizures, asterixis, uremic pericarditis, and uremic bleeding; and (6) overdose with a dialyzable toxin such as lithium or ethylene glycol. Renal replacement therapy is needed in 1% to 2% of patients with ARF, and as many as 15% of patients may ultimately require dialysis at some point in their life. It may be indicated for symptomatic fluid overload, sepsis, uremic complications, and severe electrolyte or acid-base disorders. Frequently in the ICU, continuous renal replacement therapy is superior to intermittent hemodialysis or peritoneal dialysis, but in the United States, it is only used in 10% to 20% of ICU patients. Proponents of this method over others argue that it allows better hemodynamic stability and prevention of shifts in intracerebral water, minimizes the risk for infection, and provides continuous control of fluid status and acid-base abnormalities. Complications include the need for anticoagulation and a high level of nursing care.
Answer
D
30 A 68-year-old woman with history of a GERD, cholelithiasis, and coronary artery disease is seen in the emergency department with nausea, vomiting, and epigastric pain. Laboratory tests showed amylase and lipase values of 259 and 1782 units/L, leukocytosis of 18,300/mm3, and a prothrombin time (PT) and international normalized ratio (INR) of 47 seconds and 1.9 respectively. The patient received 6 L of crystalloid solution because of hypotension and required intubation. After 48 hours the hemoglobin has dropped by 2 g. What are the factors that have the strongest correlation with stress-related bleeding in critically ill patients?
A Mechanical ventilation and hypotension
B Coagulopathy and renal failure
C Steroids and sepsis
D Mechanical ventilation and steroids
E Mechanical ventilation and coagulopathy
Ref.: 1, 32
Comments
Risk factors for stress-related mucosal lesions are mechanical ventilation longer than 48 hours, coagulopathy, significant burns, and head injury. These lesions have been found in 25% to 100% of ICU patients within 48 hours of admission, but clinically significant bleeding occurs in only 5% to 10%. Patients with risk factors should receive prophylaxis until consuming an enteral diet of at least 50% of their caloric intake.
Answer
E
31 One hour after prolonged transurethral resection of the prostate (TURP), a 70-year-old man with mild coronary artery disease, cirrhosis, and hypertension experiences bradycardia, hypertension, confusion, nausea, and headache. Findings on preoperative laboratory tests were normal, and his home medications included lactulose, atenolol, and alendronate (Fosamax). Over the last few hours he was given a 2-L bolus of 0.9% normal saline for hypotension. The patient is transferred to ICU, where on examination he is found to be sluggish and slurring his voice. He is afebrile with an HR of 93 beats/min, BP of 140/73 mm Hg, and RR of 14 breaths/min. He continues to be confused and lethargic and does not follow commands. What is the best explanation for his condition?
A Hypotonic irrigating solution
B Hyperkalemia
C Isotonic saline solution
D Atenolol
E Hepatic encephalopathy
Ref.: 33, 34
Comments
The patient is most likely suffering from transurethral resection (TUR) syndrome, which is caused by excessive absorption of irrigating solution and results in hyponatremia. The usual irrigation fluid is 1.5% glycine, which has an osmolarity of 200 mOsm/L, as compared with the normal serum osmolarity of 290 mOsm/L. Excessive systemic absorption of the irrigating solution can result in a dilutional hyponatremia, hypoproteinemia, and ultimately, decreased serum osmotic pressure. Extremely low sodium levels (<110 mEq/L) may result in severe cerebral edema and cause seizures. Hyponatremia(serum sodium concentration <135 mEq/L) is the most common electrolyte disorder seen in hospitalized patients. Severe hyponatremia (<115 mEq/L) has developed acutely in this patient and can lead to rapid redistribution of water from the extracellular to the intracellular fluid compartment. This shift can lead to increased intracranial pressure and cerebral edema. However, the neurologic symptoms (nausea, vomiting, headache) may all be attributed to other postsurgical problems, with the hyponatremia not being recognized until seizures occur. The first goal of therapy is to raise the serum sodium level sufficient to prevent cerebral herniation. Initially, hypotonic saline solution should be given to achieve a rate of correction not to exceed 8 to 10 mEq/L in a 24-hour period and less than 18 mEq/L at 48 hours. In severely symptomatic patients (e.g., seizures), this rate can be raised to 2 mEq/L/h for the first few hours. Concurrent furosemide diuresis may be used to decrease the risk for pulmonary edema. Chronic asymptomatic hyponatremia may be seen in patients with heart and renal failure, which is associated with increased total body water and salt retention. Water restriction alone may be efficacious for chronic asymptomatic hyponatremia. Rapid correction of hyponatremia risks myelinolysis and poor neurologic outcomes. Treatment of TUR syndrome traditionally consists of terminating the procedure as rapidly as possible, administration of furosemide (Lasix) intraoperatively or postoperatively, and administration of a 0.9% NaCl (and in severe cases 3% NaCl) solution over a 3- to 6-hour period. Newer bipolar resecting equipment allows irrigation with 0.9% normal saline, which has drastically decreased the probability of TUR syndrome. However, these patients may still suffer from fluid overload as a result of absorption of isotonic fluid.
Answer
A
32 A 37-year-old woman comes to the emergency department complaining of a severe headache. She undergoes an emergency head CT scan, which shows subarachnoid hemorrhage; an angiogram identifies an arteriovenous malformation, which is subsequently embolized. Four days later, her serum sodium concentration is 122 mEq/L. Which is the most correct statement regarding the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) and cerebral salt wasting (CSW)?
A SIADH and CSW share the same underlying pathophysiology and cannot be reliably distinguished.
B SIADH and CSW can be differentiated by measuring urine sodium and serum uric acid concentrations.
C SIADH and CSW can be differentiated by measuring urine osmolality and sodium concentration.
D Assessment of extracellular fluid volume will best differentiate between SIADH and CSW.
E Regardless of the diagnosis, treatment of the hyponatremia is the same.
Ref.: 33, 35
Comments
Hyponatremia is common in the setting of central nervous system disease. Most often it results from inappropriate secretion of antidiuretic hormone (ADH). With SIADH, the hyponatremia initially results from ADH-induced water retention. This volume expansion activates natriuretic mechanisms that induce the loss of sodium and water, with the patient typically being restored to a nearly euvolemic state. With chronic SIADH, the loss of sodium (and often potassium) is much more significant than the water retention. Cerebral salt wasting is characterized by hyponatremia and loss of extracellular volume from inappropriate sodium wasting in urine. Patients with CSW meet the laboratory criteria for SIADH: hyponatremia, elevated urine osmolality (>100 mOsm/kg), elevated urine sodium concentration (>40 mEq/L), and low serum uric acid concentration. However, they also have clinical evidence of hypovolemia (decreased skin turgor, elevated hematocrit, decreased weight, hypotension) rather than the nearly euvolemic state seen with SIADH. Furthermore, volume repletion with isotonic saline in patients with CSW will lead to a dilute urine (and eventual correction of the hyponatremia), whereas isotonic saline administration may worsen the hyponatremia of SIADH because the sodium is retained while the water is excreted. SIADH is usually treated by fluid restriction; however, this must be done with caution in patients with SIADH because of the risk of hypotension and cerebral infarction. Isotonic saline may be used but requires careful monitoring of the serum sodium concentration; if a further fall in serum sodium occurs, a switch to hypertonic saline may be necessary. CSW generally responds well to volume repletion with isotonic saline. Salt tablets and mineralocorticoids (such as fludrocortisones) may also be useful as adjunctive measures.
Answer
D
33 In which of the following patients is hypermagnesemia unlikely to be present?
A 38-year-old woman with metastatic breast cancer, anorexia, and an HR of 38 beats/min
B 56-year-old man with pancreatitis and tetany
C 73-year-old man after exploratory laparotomy for an incarcerated ventral hernia with an RR of 5 breaths/min
D 20-year-old woman with headache, elevated liver enzymes, and loss of the patellar reflexes
E 44-year-old woman with severe diarrhea and hypotension
Ref.: 35
Comments
Hypermagnesemia (>2.8 mg/dL) is associated with conditions characterized by depressed neuromuscular excitability, such as bradycardia, hypotension, respiratory depression, and loss of deep tendon reflexes; therefore, all of the patients except for the one in answer B are likely to be hypermagnesemic. It is rare but it can be caused by increased magnesium intake from antacids or laxatives or from renal insufficiency. Hypomagnesemia defined as less than 1.6 mg/dL and is associated with gastrointestinal and renal losses or malnutrition. It is typically manifested as hypocalcemia and leads to neuromuscular hyperexcitability and tetany. Other symptoms include anorexia, vomiting, weakness, depression, psychosis, seizures, ataxia, and ventricular arrhythmias, including torsades de pointes.
Answer
B
34 An 80-kg, 65-year-old woman with severe lupus is admitted to the ICU after exploratory laparotomy for sigmoid diverticulitis (Hinchey type IV). She is given a stoma and brought to the ICU intubated. Her vitals signs are a temperature of 97.5° F, HR of 105 beats/min, BP of 70/50 mm Hg, and SaO2 of 96%. In the first hour her urine output is 20 mL; she has received 4 L of crystalloid and 1 unit of PRBCs, and her antibiotics have been redosed. Her CVP is 10 mm Hg but she remains hypotensive. Choose the next intervention that will be most beneficial?
A Additional 2 L of a normal saline bolus
B Hydrocortisone, 100 mg intravenously
C Administration of furosemide for low urine output
D Initiation of vasopressor therapy with norepinephrine or dopamine
E Aggressive rewarming
Ref.: 36
Comments
In a patient in septic shock who is adequately volume-resuscitated (shown by a CVP of 10 mm Hg) and is unresponsive to fluid challenges, vasopressor therapy should be started. Administration of vasopressin can quickly restore BP; in the Surviving Sepsis Guidelines, norepinephrine or dopamine administered centrally is the initial vasopressor of choice. Epinephrine, phenylephrine, and vasopressin should not be administered as the initial vasopressor to patients in septic shock. Vasopressin may subsequently be added as a second-line therapy. Epinephrine can be used as the first alternative agent in septic shock when blood pressure is poorly responsive to norepinephrine or dopamine. Dobutamine should be used in patients with myocardial dysfunction as evidence by elevated cardiac filling pressures and low CO. In general, the rate of fluid administration should be reduced if cardiac filling pressures increase without concurrent hemodynamic improvement.
Answer
D
35 Norepinephrine therapy is started in the patient in Question 34. Later, vasopressin, 0.03 units/min, is added, but the patient remains hypotensive with a MAP below 55 mm Hg. Her hemoglobin concentration is 9.0 g/dL. After performing an echocardiogram, dobutamine infusion was started at a maximum of 20 mcg/kg/min; pH is 7.21 with a PCO2 of 34 mm Hg. The patient remains hypotensive. What is the next step?
A Increase the cardiac index to predetermined supranormal levels.
B Administer hydrocortisone, 100 mg intravenously.
C Have a family discussion about withdrawing care.
D Perform an adrenocorticotropic hormone (ACTH) stimulation test.
E Switch the ventilatory mode to AC.
Ref.: 37
Comments
Although there is still much debate in the critical care literature about steroids, intravenous corticosteroids are recommended in patients with septic shock who despite adequate fluid replacement require vasopressor therapy to maintain adequate BP. Random cortisol levels may be helpful in determining a patient’s benefit from steroid therapy, although it is not required. Consideration can be made to discontinue corticosteroid therapy in patients with a random cortisol level of greater than 25 mcg/dL. An ACTH stimulation test is not recommended to identify the subset of patients with septic shock who should receive hydrocortisone.
Answer
B
36 A 70-kg, 33-year-old woman who had not seen a physician in 10 years arrives at the emergency department with symptoms of dypsnea, fatigue, weight gain, diplopia, and dysphagia following an urgent laparoscopic cholecystectomy 10 days ago. On examination, she is awake and alert. She is afebrile with an HR of 80 beats/min, BP of 120/70 mm Hg, and RR of 29 breaths/min. Her heart sounds are normal and breaths are bilateral and shallow. She has ptosis and significant prominal muscle weakness in all extremities. She is drooling slightly and having difficulty swallowing. Her vital capacity is 500 mL and her laboratory tests are pending. Which of the following treatments is the most appropriate to initiate next?
A Administration of pyridostigmine
B Endotracheal intubation
C Administration of steroids
D Administration of intravenous immunoglobulin
E Administration of levothyroxine
Ref.: 38
Comments
This patient is having a myasthenic crisis, which is a consequence of an autoimmune attack on the acetylcholine receptor complex. There is clinical weakness that is most marked after prolonged muscle exertion and should be considered in any patient with respiratory distress and cranial nerve findings. Myasthenic crisis with respiratory failure develops in approximately 20% of patients and necessitates intubation. It can be precipitated by bronchopulmonary infections, sepsis, surgical procedures, tapering of steroid medications, pregnancy, and some drugs. Upper airway muscle weakness can lead to collapse of the airways and aspiration. Patients with marginal vital capacity (<15 mL/kg), weak cough or voice, and worsening negative inspiratory force should be considered for intubation.
Answer
B
37 After the patient in Question 36 is treated for myasthenia gravis, the respiratory therapist asks you for the settings on a ventilator. While she is setting up, you think about the different types of modes. Which one of the following do you have correct?
A AC ventilation provides full ventilatory support and is a good mode to use in an agitated, tachypneic patient.
B SIMV allows breaths to be triggered by patients and avoids stacking breaths.
C PCV is good because minute ventilation can be set and hypoventilation and apnea do not occur.
D CMV allows patients to increase minute ventilation by triggering additional breaths.
E AC ventilation, when triggered by the patient, gives only the VT that patients generate on their own.
Ref.: 1
Comments
CMV, AC ventilation, and SIMV are volume-cycled ventilator modes. CMV is generally used only in the OR or in patients under anesthesia because it does not allow patients to trigger additional breaths. Patients receive a set number of fixed-volume breaths. AC ventilation is used for full ventilatory support; it gives a full-volume breath when triggered by a patient, which would lead to significant respiratory alkalosis in a patient who is agitated and tachypneic. SIMV synchronizes a patient’s triggered breath with one that the ventilator is scheduled to deliver and avoids stacking. It is a useful mode when weaning a patient from the ventilator, especially with pressure supportadded. PCV is designed as a protective mode to prevent alveolar overdistention and epithelial injury. Its major advantages are lower mean and peak airway pressure and a decelerating flow pattern. It is patient-triggered, and therefore patients must have an intact respiratory drive. If not, apnea and decreasing minute ventilation can occur.
Answer
B
38 A 50-year-old alcoholic man (40 kg) is brought to the ICU for monitoring of symptoms of alcoholic withdrawal. A nasogastric tube is inserted and tube feeding (1.0 kcal/mL) is initiated with a goal of 50 mL/h in 16 hours. Within 24 hours, he is awake, alert, and not exhibiting any signs of withdrawal and did not need any medications in the last shift. He is cooperative but dyspneic and tachypneic and has a witnessed respiratory arrest. Advanced cardiac life support is started and he is intubated with return of cardiac activity. On review of his morning laboratory results, he has a hemoglobin concentration of 12 g/dL, platelet count of 190,000/mm3, sodium concentration of 136 mEq/L, potassium concentration of 3.0 mEq/L, albumin level of 1.8 g/dL, magnesium concentration of 1.7 mg/dL, and phosphate level of 1.0 mg/dL. What intervention could have been done to decrease the chance of respiratory arrest?
A Administer two doses of naloxone (Narcan) before intubation.
B Administer phosphate and recheck levels before giving a large carbohydrate load.
C Administer total parenteral nutrition through a peripherally inserted central catheter line instead of enteric feeding.
D Infuse an alcohol drip through a peripheral intravenous line on admission to the unit.
E Administer 4 g of magnesium by intravenous piggyback before giving benzodiazepine.
Ref.: 1, 35, 39
Comments
This patient had a respiratory arrest secondary to refeeding syndrome. Hypophosphatemia should be expected when a chronically malnourished patient has nutritional support started. When a carbohydrate load is given, a spike in insulin increases phosphate uptake into cells and causes a significant drop in serum phosphate concentration. Muscle contractility is very dependent on a normal phosphorus level, and diaphragmatic contraction can be limited in hypophosphatemic patients with respiratory failure. Severe hypophosphatemia (<1 mg/dL) is associated with significant morbidity, including acute respiratory failure, ventilator dependence, rhabdomyolysis, altered mental status, cardiomyopathy, and muscle weakness. This can be avoided by the slow introduction of nutritional support, especially carbohydrates, and continual monitoring of serum phosphate levels. This patient already had a low phosphate level, and very quick advancement of the tube feedings to the target rate drove the level even lower than the measured laboratory values. Administration of naloxone is the next reasonable choice, but the question states that he has not required any medications in the recent past and was awake and alert on examination. Oversedation is a risk with intubation, but in this case it is not the best answer.
Answer
B
39 A 66-year-old woman who has been in the ICU for 2 weeks following total hip replacement complicated by massive infection and sepsis is complaining of right calf pain. A bedside ultrasound duplex study demonstrates deep venous thrombosis (DVT) in her right lower extremity. Which statement is correct concerning DVT?
A Duplex bedside ultrasound has a sensitivity and specificity of 75%.
B High-risk factors for DVT include hour-long thoracic procedures, hip fractures, and spinal cord injuries.
C A protocol for determining the level of prophylaxis for DVT is not required for any ICUs.
D All patients with DVT should receive an intravascular inferior vena cava filter.
E Patients determined to have DVT do not require anticoagulation.
Ref.: 1, 40
Comments
See Question 40.
Answer
B
40 After her ultrasound, the patient from Question 39 gets out of bed to go to physical therapy, and severe dyspnea, tachycardia, and hypotension develop. She is taken back to bed, her pulse oximetry reading is 75%, and she is given oxygen. A CT angiogram shows bilateral clots in the pulmonary arteries. With regard to PE, which of the following is true?
A Early chest radiographic abnormalities are rarely present in patients with PE.
B A shunt abnormality is present early after the PE and a abnormality becomes the mechanism for hypoxemia in later stages.
C Thrombolytic therapy has been shown to reduce mortality rates in comparison to heparin in patients with PE.
D Heparin should never be given until the diagnosis of PE is absolute.
E More than 33% of patients with PE have negative lower extremity duplex studies for DVT.
Ref.: 1, 40
Comments
The prevalence of pulmonary embolism in the United States exceeds 600,000, with the incidence of nonfatal PE approaching 20 per 1000 inpatients. Deep venous thrombosis occurs in 30% of ICU patients and is monitored by governing bodies in the United States, and all ICUs should have a prevention protocol. High-risk factors are thoracic or general procedures requiring general anesthesia for longer than 30 minutes, neurosurgical procedures, CABG surgery, surgery for gynecologic cancers, CHF, and respiratory failure, along with long-bone fractures and spinal cord injuries. ICU patients almost always have at least one risk factor and need prophylaxis. Options include pharmacologic treatment with low-molecular-weight heparin (LMWH), unfractionated heparin, or pneumatic compression devices.
In regard to diagnosis, duplex ultrasound has a specificity and sensitivity greater than 95%. Many emboli can be silent, but symptoms of small to medium emboli are usually pulmonary (i.e., dyspnea, chest pain, and cough). Tachypnea and tachycardia are present as well. Massive PE often produces cardiovascular findings such as elevated PA pressure and right heart strain. Angiography is the definitive diagnostic technique for this disease, but a helical CT scan of the chest with infusion has shown excellent specificity. Even without pulmonary infarction, radiographic abnormalities appear as diaphragmatic elevation, atelectasis, and effusion. For treatment of DVT, heparin therapy over a period of 5 to 7 days with an overlap with warfarin constitutes the treatment of choice. Warfarin should be continued for 6 to 12 weeks for calf vein and large-vein thrombosis and up to 6 months for PE. Thrombolytic therapyhas not been shown to reduce mortality rates in comparison to heparin in large prospective series.
Answer
E
41 A 56-year-old man with a past medical history of hypertension and diabetes mellitus is admitted to the ICU after right femoral-popliteal bypass surgery for neurovascular monitoring. In the morning during rounds, his signals are undetectable, and his right foot is cold and painful. He is taken back to the OR for revision of his bypass, and fasciotomies are performed in all four quadrants. An unfractionated heparin drip is started with a weight-based protocol to achieve a partial thromboplastin time (PTT) two times the normal value. His laboratory results immediately before return to the OR showed a WBC count of 11,000/mm3, hemoglobin concentration of 10.2 g/dL, platelet count of 350,000/mm3, potassium concentration of 4.1 mEq/L, BUN of 30 mg/dL, and creatinine concentration of 2.1 mg/dL. A week later on rounds, the patient complains of left calf pain. Duplex ultrasound shows DVT in his left lower extremity. His WBC count is 12,300/mm3 with a hemoglobin level of 9.1 g/dL, platelet count of 97,000/mm3, potassium concentration of 4.6 mEq/L, BUN of 39 mg/dL, and creatinine level of 2.3 mg/dL. Which of the following treatments options is the best choice?
A Discontinuation of anticoagulation
B Discontinuation of unfractionated heparin and initiation of warfarin
C Discontinuation of unfractionated heparin and initiation of argatroban
D Discontinuation of unfractionated heparin and initiation of LMWH
E Bolus heparin drip and increase in the PTT goal to 2.5 times the normal value
Ref.: 1, 41
Comments
See Question 42.
Answer
C
42 The patient from Question 41 tolerates his anticoagulation, but he has been continually oozing from his fasciotomy sites and his hemoglobin has drifted down in the past 3 days to a level of 7.8 g/dL. On review of his chart you see that in the preoperative clearance note from cardiology he had a hemoglobin level of 13.0 g/dL and no significant cardiac disease. His family is concerned about how pale he has been during this ICU stay. His vital signs are an HR of 86 beats/min, BP of 128/69 mm Hg, and SaO2 of 96%. What is the appropriate answer regarding a blood transfusion for this patient at this time?
A Transfuse 5 units of PRBCs to reach the preoperative hemoglobin level of 13 g/dL.
B Check complete blood count (CBC) levels daily and hold transfusion until the hemoglobin level is lower than 9 g/dL.
C Start erythropoietin at 40,000 units daily.
D Transfuse PRBCs to a level greater than 10 g/dL.
E Check daily CBC levels and hold transfusion until the hemoglobin level is lower than 7 g/dL.
Ref.: 1, 41, 42
Comments
Type II heparin-induced thrombocytopenia (HIT) has developed in this patient. Type I HIT occurs in 1% to 2% of patients and causes transient sequestration of platelets with a drop in the count to less than the normal range or a 50% fall in the platelet count within the normal range. In general, this is of little consequence. Platelet levels normalize in a few days after heparin is discontinued. Type II is more severe, and antiplatelet antibodies develop in 0.1% to 0.2% of patients exposed to heparin. It is associated with thrombotic complications in more than 30% of cases and should be suspected in a patient in whom resistance to anticoagulation, thromboembolic events, and a fall in the platelet greater than 30% or a count of less than 100,000/mm3 develop. Once HIT is suspected, all sources of heparin, including LMWH, should be discontinued. Warfarin can actually worsen the prothrombotic state and should not be used before complete anticoagulation is achieved with either argatroban or lepirudin, both antithrombin agents.
Anemia is very common in critically ill patients; in the United States, approximately 85% of patients spending more than 1 week in the ICU receive 1 or more units of PRBCs in their first week. Blood is a scarce and expensive resource and is associated with morbidity, including transfusion reactions, infections, and worse outcomes. Historically, patients received transfusions if their hemoglobin level dropped below 10 g/dL. However, a multicenter prospective randomized clinical trial in 1999 showed that transfusion for a hemoglobin level of less than 7 g/dL had the same 30-day mortality rate as transfusion when the hemoglobin level was less than 10 g/dL (except in patients with significant cardiac disease). This patient had preoperative cardiac clearance and is not presently showing any signs of hemodynamic instability.
Patients with anemia of critical illness have been shown to have a blunted response to both endogenous and exogenous erythropoietin. A multicenter trial showed a mild increase in hemoglobin, but it is unclear in the literature whether this improves clinical outcomes.
Lepirudin undergoes renal elimination, which should be noted in situations such as this patient with renal insufficiency. Argatroban is metabolized hepatically and is the best choice in this situation.
Answer
E
43 The patient from Questions 41 and 42 wants to know whether there are any types of blood substitutes that could be given if he does need a transfusion. You discuss the options and characteristics of an ideal blood substitute. Which of the following is not a characteristic of an ideal substitute?
A Universal compatibility
B Long-term storage capability
C Decreases physiologic loading and unloading of O2
D Capability of volume expansion
E Freedom from disease transmission
Ref.: 1, 43
Comments
There is a worldwide shortage of blood, which has a limited shelf life, is expensive, and has multiple transfusion-associated morbidities. The scientific community has been working to develop an ideal blood substitute that should have the following characteristics: physiologic loading and unloading of O2 (not minimizing it), capability of volume expansion, immediate availability, universal compatibility, no adverse physiologic effects, freedom from disease transmission, and long-term storage capability. Several products have been developed but have not been found to have any benefit in injured patients yet; most studies have involved those with acute blood loss and not long-term anemia.
Answer
C
44 A 24-year-old woman undergoes laparotomy for a class IV injury to her liver and during the procedure is transfused with 12 units of cold, stored PBRCs. Despite appropriate treatment of the liver injury, there is persistent bleeding from the raw surface of the parenchyma, the puncture sites of all intravenous lines, and the skin incision. In addition to aggressive resuscitation, which initial treatment is most appropriate at this time?
A Infusion of 10 mL of a 10% CaCl2 solution
B 5 units of fresh frozen plasma and observation in the OR
C 2 units of platelets while applying compression on the liver
D Halting the operation and transferring to the ICU for correction of hypothermia
E 1 mg/kg of enoxaparin while remaining in the OR
Ref.: 44
Comments
Hypothermia, acidosis, and coagulopathy are frequently encountered in trauma patients and are often referred to as the “deadly triad.” This patient has had a massive transfusion, defined as the administration of more than 10 units of blood or more than one blood volume of the patient within 24 hours. All of the choices will probably be needed to correct the patient’s coagulopathy, but rewarming is the best selection initially. The surgeon should control any surgical bleeding and terminate the procedure to allow warming of the patient and replacement of components in the ICU. Blood warmers, warm saline lavage, blankets, and heated inspired gases are useful adjunctive measures to prevent hypothermia. The known associated complications of massive transfusions include electrolyte and acid-base abnormalities, changes in hemoglobin-oxygen affinity, hypothermia, coagulopathy, and dysfunction of various organs. Coagulation proteins and platelets are consumed in the normal process to achieve hemostasis through clot formation. Despite low levels of factors V and VIII in blood stored for 14 to 21 days, dilutional coagulopathy is rare. Recommendations for combatting coagulopathy have included prophylactic administration of 1 or 2 units of fresh frozen plasma for anywhere from every 2 to 10 units of transfused blood. The indications for administration of calcium should be based on hemodynamic considerations because lowering the ionized calcium level by citrate to a level that blocks coagulation could lead to death from myocardial dysfunction and decreased peripheral vascular resistance. Hypothermia decreases clearance of citrate from the blood, thereby allowing a marked reduction in ionized calcium. The clotting system is impaired because of a decreased ability to form stable clots and decreased production of clotting factors. Enoxaparin is not indicated as the initial step in such a situation.
Answer
D
45 Choose the statement that is not true with regard to ECMO.
A ECMO is an appropriate treatment for patients without prohibitive risk of death from respiratory failure and without other lethal comorbid conditions.
B Low-flow ECMO can be used in patients with primary hypercapnic respiratory failure to improve removal of CO2.
C Indications for ECMO include status asthmaticus and patients maintained on high ventilator settings for more than 7 days.
D Patients with a compliance of less than 0.5 mL/cm H2O/kg and a PaO2/FIO2 ratio of less than 100 are good candidates for ECMO.
E Patients treated with ECMO usually have a 20% predicted survival rate without this bypass.
Ref.: 45-47
Comments
Extracorporeal membrane oxygenation is considered a supportive nontherapeutic intervention that maintains adequate gas exchange and circulatory support while resting the injured lungs or heart (or both). Successful use of ECMO was first reported in 1972; it subsequently lost favor but has enjoyed a resurgence in the last two decades for coronary artery diseases. All of the answers are true except for C. ECMO can be used for patients with status asthmaticus or other forms of airway obstruction with hypercapnia, but it is contraindicated in patients with high ventilator settings for more than 7 days, incurable disease, age older than 70 years, poor neurologic status, and active bleeding because of the need for systemic anticoagulation. Indications are poor gas exchange, compliance of less than 0.5 mL/cm H2O/kg, a PaO2/FIO2 ratio of less than 100, and a shunt fraction greater than 30%. A typical ECMO system has a membrane oxygenator, heat exchanger, roller or pump, circuit tubing, and access catheters. It removes CO2 extracorporeally and gently oxygenates the lungs with low-flow ventilation. Overall, survival to discharge occurs in approximately 50% of patients treated by ECMO, and it is used as a last effort in patients with severe cardiopulmonary failure.
Answer
C
46 A 43-year-old alcoholic is admitted to the hospital with acute pancreatitis and severe abdominal pain. A central line is placed, she is given several liters of fluid resuscitation, and laboratory tests are ordered. Her vital signs are a temperature of 39° C, HR of 92 beats/min, BP of 102/53 mm Hg, RR of 24 breaths/min, and SaO2 of 93%. Admission laboratory results included an amylase concentration of 400 units/L, lipase concentration of 1740 units/L, WBC count of 14,000/mm3, and hemoglobin level of 14 g/dL. You are trying to decide whether she qualifies to be entered into a study for SIRS. You know that she needs two of several characteristics to qualify. Which of the following is not included in the definition of SIRS?
A Temperature lower than 36° C or higher than 38° C
B RR greater than 20 breaths/min
C PaCO2 lower than 32
D Hemoglobin level less than 10 g/dL
E White blood cell count lower than 4000/mm3 or higher than 12,000/mm3
Ref.: 1, 48, 49
Comments
Systemic inflammatory response syndrome is a generalized hyperinflammatory response to a number of different etiologic factors to the body. In 25% to 35% of patients it persists and can lead to multiple organ dysfunction syndrome, sepsis, and septic shock. This patient’s clinical condition qualifies for SIRS because it has all the aforementioned qualifiers except for hemoglobin, which is not in the definition. SIRS does not occur de novo but in response to an instigating process that stimulates the inflammatory cascade of coronary artery disease. It can be caused by noninfectious insults such as trauma, nonseptic shock, drugs, and toxins and may continue even after the initial instigating factor is removed or successfully treated. In addition, it may be perpetuated by poor perfusion from subpar resuscitation.
Answer
D
47 A 54-year-old Hispanic man with uncontrolled diabetes comes to the emergency department because of scrotal edema and tenderness. He complains of fevers and chills but denies nausea, vomiting, or diarrhea. He has a foul odor on rectal examination, pus is expressed, and cellulitis of the skin is noted around his scrotum and anus. He has crepitus along his perineum and extending up along his inguinal crease. His vital signs are a temperature of 101.3° F, HR of 128 beats/min, BP of 90/62 mm Hg, and SaO2 of 92%. Which of the following therapeutic strategies is most appropriate?
A Emergency placement of a central line and administration of vancomycin with transfer to the ICU
B Opening the wound in the ER and packing with iodoform gauze
C Sending the patient for a CT scan with intravenous, oral, and rectal contrast media to evaluate the extent of the problem
D Immediate surgical intervention with débridement of all devitalized tissue
E Admission to the ICU with frequent checks on the cellulitis
Ref.: 36, 50
Comments
See Question 48.
Answer
D
48 The patient in Question 47 has now been in the hospital for 6 hours, is requiring multiple vasopressors, and is showing signs of multiple organ failure (MOF). You just had a grand rounds on early directed-goal therapy. Which one of the goals is not included in the initial resuscitation recommended in the Surviving Sepsis Guidelines?
A Target CVP of 8 to 12 mm Hg
B Central venous SO2 greater than 70%
C Institution of antibiotics within 12 hours of admission
D MAP higher than 65 mm Hg
E Urine output greater than 0.5 mL/kg
Ref.: 36, 50
Comments
Fournier gangrene is a necrotizing fasciitis of the male genitalia and perineum that has a mortality reaching 50%. This disease travels along fascial planes and can spread rapidly. The best answer is immediate surgical débridement, and the area should be irrigated copiously. Both aerobic and anaerobic coverage should be started, with the most common organism being Escherichia coli. At times, diabetic patients do not feel much pain, so a detailed physical examination is important. CT scans can help distinguish the extent of the disease, but insertion of a rectal probe and contrast material in this patient would probably be impossible. In addition, he is hemodynamically unstable, and sending him to the radiology department without securing his airway or adequately resuscitating him would be very dangerous. Opening the wound in the emergency department would not be adequate débridement and unlikely to be tolerated by the patient. The Surviving Sepsis Guidelines, which outlines early goal-directed therapy, has been shown to reduce in-hospital mortality in patients with severe sepsis and septic shock. All of the answers except C are correct and are targeted for initial resuscitation in the first 6 hours in patients with hypotension or elevated serum lactate. If any of the interventions are not achieved, the guidelines published by Society of Critical Care Medicine recommend further fluid and transfusion of PRBCs to a hematocrit of higher than 30% or an infusion of dobutamine (or both). In addition, a targeted CVP of 12 to 15 mm Hg is recommended for mechanically ventilated patients or those with decreased compliance. Antibiotics should be given within 1 hour of recognizing severe sepsis or sooner if suspicion is high. Broad-spectrum agents with good penetration into the presumed source should be started. The guidelines suggest obtaining cultures and performing imaging studies promptly to determine infection if this does not delay the administration of antibiotics.
Answer
C
49 With regard to MOF, which of the following statement is false?
A Sepsis is the major risk factor.
B Injury to the microvascular endothelium is uniformly present.
C Neutrophil-mediated injury is dependent on adherence to the microvascular endothelium.
D There is a bimodal pattern to the development of MOF.
E An increase in the gastrointestinal barrier is often present.
Ref.: 1
Comments
Sepsis is the major risk factor for the development of multiple organ failure. Injury to the microvascular endothelium causes a generalized inflammatory state, and early recognition and adequate treatment are essential if serious ischemia-reperfusion injury and MOF are to be prevented. Several components of the immune defense system are involved. Neutrophil-mediated injury is dependent on adherence to the endothelium and neutrophil aggregation. Platelet-activating factor, produced by various inflammatory cells, causes microvascular injury through ischemia and stasis. Breakdown of the intestinal mucosal barrier may allow ongoing bacterial translocation and stimulation of the immunoinflammatory reaction. There is a bimodal pattern of development of MOF. The first peak occurs within 72 hours of the initial insult, and late MOF is manifested at 6 to 8 days and is typically related to an infection.
Answer
E
50 A 22-year-old man involved in a motor vehicle accident is found to have a thoracic spine fracture (T6) and paraplegia. The patient is hypotensive with a systolic BP of 70 mm Hg, is bradycardic with a pulse of 48 beats/min, and is breathing comfortably. Which of the following would be the most appropriate initial treatment?
A Isotonic fluid administration
B Steroid administration within 24 hours of the injury
C Immediate intubation
D α-Agonist administration
E Immediate magnetic resonance imaging
Ref.: 51, 52
Comments
Neurogenic shock refers to a condition characterized by hypotension and bradycardia that results from interruption of the sympathetic nervous system pathways within the spinal cord. Common causes include sensory stimulation, such as severe pain, exposure to unpleasant events or sights, high spinal anesthesia, and traumatic spinal cord injury. Clinical characteristics include a BP that is often low, as in other forms of shock. However, the pulse rate is usually slower than normal, and the skin is flushed, warm, and dry. CO is reduced secondary to decreased blood return to the heart because of the increased capacitance of the arterioles and venules. Since the heart receives sympathetic input, there is a difference between injuries above and below T4. The former depresses cardiac function and decreases venous return. The bradycardia is caused by sympathectomy of the spinal injury above the level of T4 with no capacity for compensatory tachycardia. Treatment of neurogenic shock secondary to spinal cord injury is usually more complicated, not only because of more prolonged hypotension but also because of the presence of coincident hypovolemic shock resulting from associated injuries. Such patients often require ventilatory support as a result of decreased spontaneous respiration and loss of the accessory muscles for breathing. Aggressive fluid therapy should be instituted early under continuous cardiovascular monitoring. Persistent hypotension necessitates recognition of possible hemorrhagic shock, and a vasopressor such as ephedrine or phenylephrine may be needed. If the injury is below T4, a pure α-agonist may aggravate the reflex bradycardia. Thus, a drug with mixed chronotropic and inotropic effects (e.g., norepinephrine or dopamine) is preferred. A nasogastric tube should be inserted because gastric atony, dilation, and hypersecretion develop in these patients. Treatment of milder forms of neurogenic shock consists of removing the nociceptive stimulus. Neurogenic shock resulting from high spinal anesthesia can usually be treated with a vasopressor such as ephedrine or phenylephrine, each of which increases CO by direct effects on the heart and by increasing peripheral vasoconstriction. Although the administration of steroids remains controversial, their usefulness for blunt spinal cord injury has been suggested when they are given within 8 hours of injury and their administration is extended for 48 hours.
Answer
A
51 A 60-year-old man with renal failure who has been undergone dialysis for the past 2 years is admitted for cellulitis surrounding the fistula site on his right upper extremity. Antibiotics are started and the patient is observed. On hospital day 4, his fistula clots and he is taken to the OR for revision. On the following day, he is febrile, coughing up thick green sputum, and dyspneic despite having undergone dialysis that morning. A chest radiograph shows an infiltrate in his right lower lobe, and laboratory tests show a WBC count of 18,000/mm3. Which characteristic of nosocomial pneumonia listed below is not correct?
A Characterized by onset within 24 hours of hospital admission
B Purulent sputum
C Isolation of the pathogenic organism from blood or the lung
D Elevated WBC count
E Infiltrate on chest radiography
Ref.: 53, 54
Comments
See Question 52.
Answer
A
52 What is the next step in treatment for the patient in Question 51?
A Hold antibiotic coverage until culture-proven infection is noted.
B Start empirical broad-spectrum antibiotics based on risk factors and an antibiogram of the ICU.
C Perform bronchoscopy daily until the secretions have cleared.
D Start one antibiotic based on the most likely pathogen and escalate as needed.
E Intubate and place the patient on a low-volume, lung-protective ventilation protocol.
Ref.: 53, 54
Comments
Hospital-acquired pneumonia (HAP) is the second most common of all nosocomial infections in the United States. The Centers for Disease Control and Prevention’s definition of nosocomial pneumonia is a clinical one that requires pneumonia to occur more than 48 hours after hospital admission and excludes any infections that are present or incubating at admission. The other two criteria include appropriate findings on physical examination or an infiltrate on chest radiography plus one of the following: purulent sputum, isolation of the pathogenic organism from blood or the lung, identification of a virus from the lower respiratory tract, or serologic or pathologic evidence of recent infection. Many clinical studies have shown that early, appropriate, and adequate antibiotic therapy can reduce the mortality rate from HAP, currently listed anywhere from 24% to 76%. The American Thoracic Society presumes that early-onset pneumonia is due to Haemophilus influenzae, methicillin-susceptible Staphylococcus aureus, Streptococcus pneumoniae, or anaerobes. Late-onset HAP occurs more than 4 days after admission and is usually caused by gram-negative organisms, especially Pseudomonas aeruginosa, Acinetobacter, Enterobacteriaceae (Klebsiella, Enterobacter, Serratia), or methicillin-resistant S. aureus (MRSA). Broad-spectrum antibiotics should be started early and deescalated, not escalated, when culture sensitivities are known. This patient does not require intubation at this time, and low-volume, lung-protective ventilation is best used for ARDS. Patients with HAP do not need bronchoscopy daily. Chest therapy, elevation of the head of the bed, and ambulation are all methods to improve pulmonary toilet.
Answer
B
53 A 27-year-old man who ingested 40 tablets of his brother’s lithium, 4000 mg of ibuprofen, and two bottles of antifreeze during a suicide attempt has been in the ICU for 6 days. He was obtunded and on admission had a temporary dialysis catheter placed urgently in his right internal jugular vein and had been undergoing hemodialysis for the first 3 days after admission. What was the best method of gastric decontamination for this patient on initial admission at approximately 3 hours after ingestion?
A Gastric lavage and activated charcoal
B Whole-bowel irrigation
C Intubation and gastric lavage
D Activated charcoal
E Syrup of ipecac
Ref.: 55
Comments
See Question 54
Answer
B
54 He is now complaining of vague pains all over, anorexia, cough with thin white sputum, and malaise and has not had flatus or a bowel movement for 24 hours. Chest radiography shows bilateral haziness at the costophrenic angles. Physical examination showed the patient to not be in acute distress. His lungs have some crackles in the bases bilaterally. His right arm is slightly swollen, and he has some redness around the right side of his neck and chest. His abdomen is soft, distended, tympanitic, and nontender. His vital signs include a temperature of 101.6° F, HR of 100 beats/min, BP of 128/75 mm Hg, and SaO2of 96%. Laboratory findings included a WBC count of 18,500/mm3, sodium concentration of 140 mEq/L, potassium concentration of 4.3 mEq/L, BUN of 21 mg/dL, creatinine level of 0.8 mg/dL, aspartate/alanine aminotransferase (AST/ALT) levels of 54/49 units/L, and total bilirubin of 0.9 mg/dL. What is the most likely diagnosis?
A Acalculous cholecystitis
B HAP
C Catheter-related bloodstream infection
D Perforated peptic ulcer
E Viral respiratory infection
Ref.: 54, 55
Comments
Gastric lavage is not indicated in this patient and is not a proven benefit, even when used within 1 hour of ingestion. Complications can include aspiration, laryngospasm, and mechanical injury. Ipecac causes local irritation of the gastric mucosa, which induces reflex vomiting after 30 minutes of administration. Ipecac should not be used in routine poisoning cases; there is no evidence that it improves outcomes, and it can do more harm by exposing the esophagus to the poison again. Whole-bowel irrigation is not specifically indicated for any poisoning but at times can be used with medications that are sustained-release or enteric-coated drugs, such as lithium, which our patient ingested. Activated charcoal is best given within 1 hour of ingestion and can be considered if the patient has ingested a potentially toxic amount of poison. There is no evidence showing that activated charcoal improves outcomes.
The most likely diagnosis is a catheter-related bloodstream infection. He had a catheter placed on an emergency basis and is now experiencing fevers and malaise, with cellulitis evident in the right side of his neck. His infection can explain the anorexia, ileus, and elevated WBC count. Catheter-related bloodstream infection is seen in approximately 5% of patients with indwelling catheters and should be suspected if any erythema or purulence is identified at the catheter site. The subclavian vein is the preferred site for reduction of infection, over internal jugular or femoral locations. Once an infection is suspected, blood should be drawn through the line and peripherally for culture, and immediate removal of the catheter is suggested and the tip sent for culture. A catheter–peripheral colony-forming unit (CFU) ratio of 8 signifies line sepsis, and a catheter tip culture with 25 CFUs confirms a catheter-related infection.
Answer
C
55 A 45-year-old man is recovering from MOF after an operation for a perforated gastric ulcer. He has been afebrile for 48 hours and is not taking any antibiotics. His WBC count is normal, and his renal failure has resolved. His encephalopathy is improving, and his oxygenation is adequate on 30% oxygen and 5 cm H2O PEEP. Attempts at weaning him off the ventilator have been unsuccessful. His negative inspiratory pressure is 10 cm H2O. Neurologic examination shows a symmetrical quadriparesis with sparing of the face and depressed deep tendon reflexes. Spinal tap fluid is normal. What is the most likely diagnosis?
A Guillain-Barré syndrome
B Myasthenia gravis
C Neuromuscular blockade
D Primary myopathy
E Critical illness polyneuropathy (CPU)
Ref.: 56
Comments
See Question 56.
Answer
E
56 Which of the following statements is true concerning the condition described in the previous question?
A A nerve biopsy often shows demyelinization or inflammation.
B Failure to wean from the ventilator is due to phrenic nerve involvement.
C Corticosteroids are the treatment of choice.
D Serum antibodies against acetylcholine receptors are always present.
E Plasmapheresis is the initial treatment of choice.
Ref.: 56, 57
Comments
CPU is an axonal motor sensory neuropathy that accompanies sepsis with encephalopathy. It is due to primary axonal degeneration and affects motor fibers more than sensory fibers. Frequently, it is manifested as failure to wean a patient from the ventilator because of phrenic nerve involvement despite clinical improvement. Symmetrical quadriparesis with facial sparing and depressed deep tendon reflexes is characteristic, and electromyography confirms the diagnosis. Spinal fluid is normal, unlike the case in patients with Guillain-Barré syndrome. Facial involvement and detection of antibodies against acetylcholine are characteristic of myasthenia gravis. Nerve biopsy shows axonal degeneration without demyelination or inflammation. Treatment is supportive and corticosteroids are contraindicated.
Answer
B
57 A 63-year-old man is admitted to the ICU following a Hartmann procedure for Hinchey type IV diverticulitis 5 days earlier. The patient is intubated and maintained on AC ventilation, is tachycardic, and is febrile to 101° F. The nurse has noticed an increase in tracheobronchial secretions that are purulent in character. A chest radiograph shows a new infiltrate in the right lung. Which of the following statements is false regarding this patient’s condition?
A The most likely organism involved is methicillin-sensitive S. aureus.
B The frequency of ventilator circuit changes does not influence the incidence of this complication.
C Kinetic beds and elevation of the head of the patient to 45 degrees decrease its incidence.
D The risk for development of this complication is highest in the second week.
E Qualitative cultures or secretions are preferred over quantitative culture techniques.
Ref.: 58
Comments
Ventilator-associated pneumonia (VAP) has significant costs and a mortality of about 25%. The risk of acquiring VAP is highest in the first week (3% per day), thereafter decreasing to 2% per day in the second week and to 1% per day in the third week. VAP is generally categorized as early (<48 hours after intubation) or late (occurring after 5 to 7 days of intubation). Early-onset VAP is associated with bacteria that are normally sensitive to antibiotics (S. aureus, H. influenzae, and S. pneumoniae), whereas late-onset VAP is typically associated with antibiotic-resistant bacteria (MRSA, P. aeruginosa, Acinetobacter, and Enterobacter species). The major risk factors for VAP include trauma, burns, and stay in neurosurgical units as opposed medical ICUs. Known risk factors include patients older than 60 years who require prolonged (>48 hours) mechanical ventilatory support, aspiration, a nasogastric tube, failure to elevate the head of the bed, and endotracheal cuff pressures of less than 20 cm H2O. Orotracheal intubation carries a lower incidence of VAP than does nasotracheal intubation. Because contamination of ventilator circuits is universal, the ventilator circuit change interval does not affect the incidence of VAP. Heat and moisture exchangers may be associated with a slightly lower incidence of VAP than heated humidifiers. Drainage of subglottic secretions is associated with a decreased incidence of VAP, especially early-onset VAP. Kinetic beds and positioning of patients at 45 degrees from horizontal are also associated with a decreased incidence. Previous exposure to antibiotics in a prolonged preoperative hospitalization exposes patients to health care–related infections. Selective digestive decontamination has been reported to be associated with a decreased incidence of VAP, yet these therapies should be time-limited to prevent the growth of resistant organisms. The suspicion for VAP in this patient with a prolonged period of ventilation and new onset of fever, leukocytosis, and purulent sputum should be high, particularly if the chest radiograph shows a new infiltrate. The diagnosis is best established by quantitative culture of secretions obtained from the lower respiratory tract. The two techniques used include protected specimen brush (PSB) sampling and bronchoalveolar lavage (BAL). A threshold of 1000 CFU/mL for PSB and 10,000 CFU/mL for BAL is currently recommended. The presence of less than 50% neutrophils in BAL fluid has also been used to exclude pneumonia. Even though the effect of these techniques on patient outcome is unclear, they have resulted in a significant reduction in the use of antibiotics.
Answer
D
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