Chad E. Jacobs, M.D., Walter J. McCarthy, M.D.
A
Perioperative Care
José M. Velasco, M.D., John Butsch, B.A., M.S., M.D.
1 Regarding tight control of serum glucose levels in diabetic patients undergoing cardiac surgery, which of the following statements is true?
A It has no effect on postoperative complications.
B It significantly reduces the incidence of deep sternal wound infections.
C It enhances phagocytosis.
D It increases urine production.
E Tighter glucose control decreases in-hospital mortality.
Ref.: 1-6
Comments
Diabetes mellitus impairs wound healing. In addition, tissue perfusion is decreased because of both macrovascular and microvascular disease. Hyperglycemia may also result in osmotic diuresis, which may lead to a decrease in effective hypovolemia. Hyperglycemia is a known risk factor for postoperative deep sternal wound infection because it alters the normal physiologic response to infection. It is associated with impaired phagocytosis, lymphocyte dysfunction, immunoglobulin inactivation, activation of the complement component C3, and impaired deposition of collagen in wounds. Tight control of blood glucose levels in diabetic patients during the postoperative period via a continuous insulin infusion pump improves wound healing and reduces the incidence of postoperative sternal wound infections. When blood glucose levels are maintained between 80 and 120 mg/dL, the postoperative sternal wound infection rate approaches that found in nondiabetic patients. Correction of the blood glucose level to normal limits restores both neutrophil chemotaxis and phagocytosis. Moreover, it reverses the reduced CD4+ cell counts found in patients with poorly controlled diabetes. Although there are many studies attributing postoperative benefit with tight glucose control, it is difficult to discern the beneficial effects of glucose versus insulin and the adverse effects of hypoglycemia. Insulin plays a role as an antiinflammatory and antioxidant hormone, which might contribute to the benefits seen in these studies. In a recent meta-analysis including 29 studies, tight glucose control was not associated with a significant reduction in hospital mortality, but there was a markedly increased risk for hypoglycemia in 21% of the studies—which may negate the beneficial effects of normoglycemia.
Answer
B
2 The perioperative management of a patient whose diabetes has been controlled by diet alone consists of determination of the blood glucose level and which of the following?
A Continuation of diet and determination of the serum glucose level before surgery
B Subcutaneous administration of regular insulin
C Oral hypoglycemic agents initiated 3 days before surgery
D Insulin infusion beginning 1 hour before surgery
E Increased oral carbohydrate intake to prevent ketosis
Ref.: 7
Comments
Patients whose diabetes is controlled by diet alone do not require any special preoperative measures other than monitoring serum glucose. Insulin and oral hypoglycemic agents are not necessary and may cause hypoglycemia. Oral hypoglycemic agents stimulate insulin secretion (sulfonylurea) or decrease intestinal absorption (metformin). Patients being treated with oral hypoglycemic agents should stop taking them before any major operation, and their blood glucose level should be controlled with insulin as needed. Increasing carbohydrate consumption will cause hyperglycemia and place the patient at risk for infection.
Answer
A
3 Regarding diabetic patients, which of the following statements is false?
A Glycosylated hemoglobin (HbA1c) accounts for 4% to 7% of the total hemoglobin.
B High levels of HbA1c result in a higher complication rate.
C Long-acting insulin should be replaced with intermediate-acting insulin preoperatively.
D Operations commonly result in elevated blood glucose levels and higher ketone body levels.
E Short-acting insulin and 5% to 10% glucose should be administered in separate bags to optimize blood glucose control.
Ref.: 4
Comments
Management of diabetic patients is complex because of the metabolic effects of the disease and the possible presence of complications such as cardiovascular, renal, and neurologic diseases. Tight control of the blood glucose level is imperative. Ideally, blood glucose levels should be 80 to 110 mg/dL during fasting and below 180 mg/dL postprandially. Normally, HbA1c accounts for 4% to 7% of the total hemoglobin. Poor control of glycemia will result in higher HbA1c levels. However, there is no evidence that high levels of HbA1c are associated with a higher risk for complications, provided that the blood glucose level is carefully monitored and controlled. Diabetic and nondiabetic patients experience higher blood glucose levels because of suppression of endogenous insulin secretion, the action of counterregulatory hormones, and infusion of glucose solutions. In preparing diabetic patients for major operations, all use of long-acting insulins and oral hypoglycemic agents should be suspended. When renal function is impaired, metformin may lead to lactic acidosis.
Answer
B
4 When evaluating a patient with known or suspected adrenal insufficiency, which of the following statements is false.
A When indicated, the dose of glucocorticoid (generally hydrocortisone) should be adjusted in response to the anticipated surgical stress.
B The signs and symptoms of acute adrenal insufficiency may mimic those of septic shock.
C Hyponatremia, hyperkalemia, and hypoglycemia are frequently present.
D The sudden development of hypotension in these patients should be treated immediately with 100 mg of hydrocortisone intravenously.
E Appropriate laboratory studies, including determinations of serum cortisol and electrolyte levels, should be conducted and interpreted before initiation of therapy.
Ref.: 1, 2
Comments
Adrenal insufficiency can be classified as primary or secondary. The three main causes of secondary insufficiency include exogenous glucocorticoids, operative correction of endogenous hypercortisolism, and abnormalities of the hypothalamus or pituitary gland. The hypothalamus secretes corticotropin-releasing factor, which stimulates the anterior pituitary to release adrenocorticotropic hormone (ACTH). ACTH stimulates the adrenal production of cortisol. Cortisol activates a negative feedback mechanism that affects both the hypothalamus and the anterior pituitary. Acute, or relative, adrenal insufficiency is a rare condition that may be manifested clinically as septic shock. It is associated with electrolyte abnormalities (hyponatremia and hyperkalemia), hypotension, nausea, vomiting, abdominal pain, weakness, and dizziness. The diagnosis should be considered in any patient with a history of tuberculosis or any patient undergoing long-term glucocorticoid therapy. While laboratory studies are being conducted, suspected adrenal insufficiency should be treated with a 100-mg loading dose of hydrocortisone or its equivalent. The laboratory studies should include determinations of cortisol, electrolyte, blood urea nitrogen, and creatinine levels, as well as a complete blood count. If blood pressure fails to return to normal within 1 to 2 hours after administration of the hydrocortisone bolus, an adrenal crisis is unlikely. If adrenal insufficiency is supported by the patient’s response to hydrocortisone and a serum cortisol level of less than 20 mg/dL, an ACTH stimulation test can be used to confirm the diagnosis.
Answer
E
5 Regarding the ACTH stimulation test in patients with suspected adrenal insufficiency, which of the following statements is true?
A The ACTH stimulation test is useful in determining the functional status of the hypothalamic-pituitary-adrenal (HPA) axis.
B This test is based on the blood glucose response to a standard dose of ACTH.
C If the ACTH test result is abnormal, 6-week perioperative steroid coverage is indicated.
D This test is not indicated for a patient taking chronic topical steroid preparations.
E All of the above.
Ref.: 1, 2, 4
Comments
In patients with adrenal gland suppression or adrenal insufficiency, it is important to determine whether the HPA axis is intact. Basically, the ACTH test determines the response of a patient’s adrenal gland (cortisol) to ACTH stimulation. A normal response includes a baseline cortisol level greater than 20 mg/dL and an elevation of the cortisol level of at least 7 mg/dL following an ACTH bolus. A patient who demonstrates a normal response to ACTH stimulation (i.e., a cortisol level >600 mg/L at 30 minutes) does not need additional glucocorticoid therapy. An abnormal response to ACTH stimulation indicates that either the HPA axis is not intact, the adrenal gland is insufficient, or both. In patients for whom surgical intervention results in the need for perioperative glucocorticoid therapy, the ACTH stimulation test can be used to determine when the function of the HPA axis normalizes. In addition, this test should be used to assess the integrity of the HPA axis in patients being managed with chronic inhaled or topical steroid preparations.
Answer
A
6 A patient with a long-term history of rheumatoid arthritis is scheduled for emergency colon resection. Which of the following statements is true?
A Sudden hypotension and tachycardia should be treated with a 100-mg bolus of hydrocortisone and perioperative glucocorticoid treatment.
B The patient is at increased risk for infection.
C The patient might benefit from an epidural catheter.
D Before elective reversal of the colostomy, the patient needs an ACTH stimulation test.
E All of the above.
Ref.: 4, 8
Comments
This patient suffers from a medical condition that is often treated with long-term steroid therapy, which may lead to acute adrenal insufficiency, particularly during periods of stress. Acute adrenal crisis can be manifested as a shocklike syndrome. Treatment should be instituted while investigating possible causes. If acute adrenal insufficiency is present, the patient will improve following the hydrocortisone injection, and perioperative administration of glucocorticoid should be continued. Patients maintained on long-term steroid therapy are at increased risk for postoperative infection, impaired wound healing, increased skin friability, and gastrointestinal bleeding. Epidural anesthesia reduces the perioperative stress response in patients at risk for adrenal insufficiency. The ACTH stimulation test assesses the integrity of the HPA axis. Although a negative test result indicates that perioperative glucocorticoids are not necessary, a positive result indicates that steroid replacement therapy may be helpful but does not predict the clinical response to surgical stress. There is considerable variation in cortisol secretion among individuals undergoing operations. However, cortisol secretion rates greater than 200 mg/day in the first postoperative day are rare. Patients who have received more than 80 mg/day of hydrocortisone or its equivalent for longer than 3 weeks can be considered to have suppression of the HPA axis. They require perioperative stress therapy with 100 mg of hydrocortisone, followed by 100 to 150 mg in three divided doses. Tapering to preoperative maintenance doses can be accomplished in 2 to 3 days. In general, patients who have taken any dose of corticosteroid for less than 3 weeks or who are being managed chronically with alternative therapy should take the same dose perioperatively. In high-risk patients, one should also consider the anesthetic since etomidate inhibits the 11β-hydroxylase enzyme that converts 11β-deoxycortisol into cortisol and predictably reduces cortisol synthesis for up to 48 hours after a single intubating dose of this hypnotic agent.
Answer
E
7 Which of the following statements concerning preoperative management of patients with pheochromocytoma is true?
A α-Adrenergic blockade with phenoxybenzamine requires a minimum of 4 to 6 weeks.
B A β-blocker is indicated in patients with tachycardia.
C Determination of 24-hour urine metanephrine levels confirms adequate α-adrenergic blockade.
D Intraoperative hypotension following resection of the tumor is best treated with vasopressors and glucocorticoids.
E Morphine and phenothiazines should be avoided preoperatively.
Ref.: 1, 9, 10
Comments
Preoperative management of patients with pheochromocytoma requires control of hypertension and volume contraction. α-Adrenergic blockade prevents intraoperative hypertensive crises and allows fluid replacement to prevent hypovolemia after removal of the tumor. Several classes of medications have been investigated, including α-adrenergic and β-adrenergic blockers, calcium channel blockers, and α-methylparatyrosine. Calcium channel blockers are effective in patients with coronary vasospasm, and there is some evidence that metyrosine decreases intraoperative complications. Phenoxybenzamine is the drug of choice for α-adrenergic blockade. Initial doses begin around 10 mg/day in two divided dose, with ranges of 10 to 240 mg/day being required. The average dose is about 45 mg/day, and therapy may require 2 weeks to become effective. Therapy is considered effective when a patient’s symptoms have disappeared and blood pressure control is adequate (blood pressure <160/90); orthostatic hypotension may be present. The absence of ST-segment depression on the electrocardiogram (ECG) and the presence of no more than one premature ventricular contraction per 5-minute period are indicators of adequate treatment and predictors of relatively few perioperative complications. If a patient’s symptoms have not resolved or if the pulse is higher than 100 beats per minute, β-adrenergic blockade therapy is added. β-Adrenergic blockers should not be used for tachycardia until α-blockade has been established or a hypertensive crisis can occur. Once the catecholamine-secreting tumor is removed, persistent vasodilation may result in hypovolemia, thereby increasing the need for intravenous fluids. All patients should have an arterial line inserted, and a central venous pressure monitor or a pulmonary catheter may prove useful in perioperative management. In addition, patients may seem somnolent or sedated for long as 24 hours postoperatively as a result of α-adrenergic blockade therapy. Morphine and phenothiazines may precipitate a hypertensive crisis and should be avoided preoperatively. Anesthetic agents may trigger catecholamine secretion. Enflurane and isoflurane have been used successfully. Intraoperative hypertension is treated with sodium nitroprusside, and cardiac arrhythmias are best treated with short-acting β-blockers.
Answer
E
8 A 33-year-old woman is scheduled for elective cholecystectomy. Preoperative evaluation shows the presence of mild to moderate hypothyroidism. Select the next most appropriate action:
A Proceed with surgery with the knowledge that minor perioperative complications could develop.
B Postpone surgery until a euthyroid state is achieved.
C Proceed with surgery while beginning treatment with levothyroxine.
D Proceed with surgery while beginning treatment with thionamides.
E Proceed with surgery if severe clinical symptoms are not present.
Ref.: 8-20
Comments
Mild to moderate hypothyroidism is a diagnosis that applies to patients who are not in myxedema coma and do not exhibit severe clinical symptoms. Systolic and diastolic myocardial function is impaired in patients with chronic hypothyroidism, with congestive heart failure occasionally occurring in hypothyroid patients in the absence of underlying heart disease. Hypothyroidism causes a decrease in cardiac output by reducing the heart rate and contractility. Patients with hypothyroidism are predisposed to pericardial effusion and may have a higher incidence of atherosclerotic heart disease. Hypoventilation may be present because of respiratory muscle weakness and impaired pulmonary response to hypoxia and hypercapnia. These patients have decreased gut motility, constipation, and hyponatremia because of a reduction in clearance of free water. Hypothyroidism is also associated with a decrease in red blood cell mass, which causes normochromic normocytic anemia. Although elective procedures may be performed on these patients safely, they are at increased risk for hypotension and congestive heart failure, along with postoperative gastrointestinal and neuropsychiatric complications. Elective operations should be postponed in these patients, but urgent or emergency ones can proceed, provided that thyroid replacement is begun with levothyroxine. Thionamides are used for the treatment of hyperthyroidism.
Answer
B
9 Regarding thyroid dysfunction in surgical patients, which of the following statements is true?
A An operation can precipitate myxedema coma in patients with severe hypothyroidism.
B Iodine administration is more likely to trigger an exacerbation of hyperthyroidism in patients with Graves disease than in those with toxic multinodular goiter.
C Hypothyroidism is unlikely to result in postoperative complications.
D All of the above.
E None of the above.
Ref.: 14-17, 20-25
Comments
Severe hypothyroidism is a medical emergency with a high mortality rate (50%). Symptoms and signs include decreased mental status, hypoventilation, and hypothermia. In both Graves disease and toxic multinodular goiter, iodine may worsen the hyperthyroidism. Antithyroid medication (thionamide) should be given at least 1 hour before the administration of iodine. Postoperative hypothyroidism can occur in any patient with chronic hypothyroidism when replacement therapy is not resumed within 10 days. Treatment of severe hypothyroidism consists of the administration of hydrocortisone followed by levothyroxine. Fluid restriction may be necessary if hyponatremia exists.
Answer
A
10 Which of the following agents is not a recommended treatment for the management of thyroid storm crisis?
A β-Blockers
B Thionamide
C Iodine solution
D Aspirin
E Acetaminophen
Ref.: 22, 26, 27
Comments
Patients with hyperthyroidism should not undergo a surgical procedure until clinical euthyroidism has been achieved. β-Blockers will control the symptoms of increased adrenergic tone, whereas thionamides will block the synthesis of new hormone. Iodine solution has been used both to decrease vascularity of the gland and to block the release of thyroid hormone. Acetaminophen is preferred over aspirin to treat hyperpyrexia because aspirin can cause increased serum levels of free thyroxine (T4) and triiodothyronine (T3) by interfering with protein binding. In emergency situations, hydration, cooling blankets, and a combination of glucocorticosteroids, β-blockers, and iopanoic acid therapy can restore patients with thyrotoxicosis to an acceptable state of clinical euthyroidism within 5 days, even if this treatment does not normalize thyroid-stimulating hormone levels. It can be difficult to diagnose thyroid storm. A medical history, clinical symptoms, and routine laboratory tests are necessary. Burch and Wartofsky developed a score to assess the likelihood of thyroid storm that involves the use of seven clinical variables: body temperature, heart rate, central nervous system (CNS) symptoms, gastrointestinal symptoms, congestive heart failure, atrial fibrillation, and jaundice. Total scores exceeding 45 were “highly suggestive” of thyroid storm.
Answer
D
11 Regarding the use of epidural anesthesia in patients with severe chronic obstructive pulmonary disease (COPD) who are undergoing upper abdominal operations, which of the following statements is true?
A Epidural anesthesia is preferred to avoid the respiratory depressant effects of general anesthetics.
B The use of epidural anesthesia has consistently led to a decreased incidence of postoperative pulmonary complications.
C Postoperative epidural analgesia leads to a higher incidence of postoperative respiratory depression than does patient-controlled analgesia with morphine.
D None of the above.
E All of the above.
Ref.: 28, 29
Comments
In general, epidural or spinal anesthesia is preferred for patients with severe COPD who are scheduled to undergo operations outside the abdominal cavity, particularly lower extremity operations. Although procedures involving the lower part of the abdomen can frequently be performed with epidural or spinal anesthesia, upper abdominal operations usually require supraumbilical incisions, which would necessitate higher levels of epidural anesthesia. Patients with severe COPD may not tolerate such high levels because they may result in decreased expiratory reserve volume, ineffective cough, and inability to clear secretions. General anesthesia allows better control of ventilation in these patients, thus optimizing ventilation and oxygenation. Studies have been inconclusive regarding whether epidural anesthesia results in a decreased incidence of postoperative pulmonary complications. Generally, it is believed that the risk for postoperative pulmonary complications is independent of the choice of intraoperative anesthesia. However, postoperative epidural analgesia may decrease the risk for complications after upper abdominal and thoracic surgery. The ideal anesthesia for patients with severe COPD would include an epidural catheter for postoperative pain control and general anesthesia for intraoperative management. Intravenous narcotics are associated with higher postoperative respiratory depression, and they may not be as effective in treating pain in these patients.
Answer
D
12 Regarding preoperative pulmonary function tests (PFTs), which of the following statements is false?
A PFTs help predict postoperative pulmonary complications in patients undergoing abdominal operations.
B PFTs conducted before and after bronchodilator therapy are useful in determining optimal management.
C The history and physical examination are more useful than PFTs in predicting postoperative pulmonary complications.
D Patients with a functional residual capacity of less than 50% of forced vital capacity should undergo ventilation-perfusion testing before pneumonectomy.
E All of the above.
Ref.: 28, 29
Comments
Routine use of preoperative PFTs in all patients with preexisting pulmonary disease is controversial. Pulmonary function tests have a positive predictive value for postoperative pulmonary complications in patients undergoing lung resection. However, the routine use of PFTs for abdominal operations often does not predict postoperative pulmonary complications. Instead, PFTs can be used as tools to provide optimal preoperative management and assist in the postoperative care of patients (i.e., patients with bronchospastic disease whose PFT results improve after bronchodilator therapy). Clinical factors such as smoking, wheezing, and increased sputum production on the preoperative work-up are more predictive of potential postoperative complications. Patients with a functional residual capacity of less than 50% of forced vital capacity who are scheduled for lung resection should undergo ventilation-perfusion studies to determine their predicted postoperative pulmonary function.
Answer
A
13 A 25-year-old asthmatic patient is scheduled for elective inguinal hernia repair. In the holding area, he exhibits severe wheezing bilaterally. Which of the following would be the best initial approach?
A Administer local anesthesia with sedation and avoid unnecessary airway manipulation.
B Administer albuterol nebulizer treatment in the holding area and proceed with the operation if the patient is not wheezing.
C Postpone surgery until the patient’s asthma is under control.
D Administer spinal anesthesia and intravenous corticosteroids.
E Provide supplemental steroids intraoperatively if the patient states that he uses steroid inhalers.
Ref.: 28, 29
Comments
This patient may have uncontrolled or poorly controlled asthma. Although inguinal hernia repair is considered a low-stress operations, unexpected complications can occur with both the surgical procedure and anesthesia. Since this is an elective procedure, the patient’s asthmatic attack should be managed preoperatively. A single treatment may not be sufficient for adequate therapy. The use of spinal or local anesthesia with sedation does not ensure that the patient will not require a general anesthetic, particularly if the spinal block or sedation is inadequate. Patients using inhaled steroids as part of their asthma management do not require supplemental steroids.
Answer
C
14 An 85-year-old with severe COPD is scheduled for elective cholecystectomy. Preoperatively, which one of the following steps will not help reduce the risk for postoperative pulmonary complications?
A Cessation of smoking for at least 8 weeks
B Prophylactic antibiotics for patients with productive yellowish sputum
C Preoperative incentive spirometry
D Laparoscopic technique
E Inspiratory-to-expiratory ratio of 1 : 1 while intubated
Ref.: 28, 29
Comments
Patients with chronic obstructive pulmonary disease are at increased risk for postoperative pulmonary complications. The risk can be reduced if effective measures are taken in the perioperative period. Patients should be instructed to stop smoking. Frequently, however, there is insufficient time to achieve the beneficial effects of this maneuver. It takes at least 8 weeks of cessation before any decrease in postoperative pulmonary complications can be realized. Cessation for 2 weeks will improve carbon monoxide levels, but secretions still can be a problem, and ciliary function may take longer to return. Patients with COPD should be free of any acute exacerbations of bronchospasm or infection. Increased sputum production or a change in the color of sputum is an indication that an underlying infection could exist. If pulmonary infection is present, antibiotic therapy should be instituted and the patient treated for the appropriate amount of time before undergoing surgery. Incentive spirometry may help prevent postoperative pulmonary complications, along with deep breathing, coughing, and chest physical therapy. In patients with COPD, if at all possible the cholecystectomy should be done via laparoscopy to avoid a painful upper abdominal incision and to preserve better diaphragmatic function. COPD patients need a prolonged expiratory phase while on the respirator.
Answer
E
15 In morbidly obese patients, obstructive sleep apnea often results in all but which of the following conditions?
A Right ventricular failure
B Hypoxemia
C Hypercapnia
D Polycythemia
E Left ventricular failure
Ref.: 28
Comments
Morbidly obese patients (body mass index >40) have an increased incidence of obstructive sleep apnea (25%). Right ventricular failure can occur secondary to the effects of obstructive sleep apnea. Chronic arterial hypoxemia and hypercapnia often lead to polycythemia, pulmonary hypertension, and right heart failure. These patients are at increased risk for the development of left ventricular failure, but not as a direct result of sleep apnea. Increased stroke volume may lead to enlargement of the left ventricle. In addition, systemic hypertension causes left ventricular hypertrophy, which added to the effects of increased stroke volume, ultimately results in systolic and diastolic dysfunction. The higher incidence of ischemic heart disease found in these patients also increases the risk for left ventricular failure.
Answer
E
16 Obese patients have an increased risk for deep venous thrombosis for all but which of the following reasons?
A Increased abdominal weight and venous stasis
B Polycythemia
C Infrequent ambulation
D Increased incidence of ischemic heart disease
E Lengthy operations because of difficult exposure
Ref.: 28
Comments
Obese patients are at much higher risk than nonobese patients for deep venous thrombosis. Venous stasis increases the risk for deep venous thrombosis. Increased abdominal weight leads to decreased venous return secondary to compression of the inferior vena cava. Polycythemia leads to decreased vascular flow. If an obese patient has difficulty walking preoperatively, it is likely that postoperative mobilization will be unsatisfactory and lead to increased risk. Prolonged operations result in longer periods of venous stasis during the intraoperative course, thereby increasing the risk. Preventive therapy should be instituted before induction of anesthesia by administering regular heparin or low-molecular-weight heparin along with intermittent sequential venous compression boots. It is important to encourage early ambulation in this patient population.
Answer
D
17 Regarding tracheal intubation in morbidly obese patients, which of the following statements is true?
A The body habitus of these patients (i.e., short, thick necks) makes intubation difficult. However, it does not compromise ventilation.
B The diagnosis of obstructive sleep apnea should not alter management of the airway.
C Hypoxemia following induction of anesthesia and during intubation is the result of diminished functional residual capacity.
D Awake intubation is contraindicated.
E All of the above.
Ref.: 28
Comments
Management of a morbidly obese patient’s airway can be difficult. The approach to intubation must take into consideration a number of factors. Such patients often have short thick necks, large tongues, limited mouth and neck mobility, and increased thoracic and abdominal pressure. For these reasons, both ventilation and intubation can be difficult. Patients with obstructive sleep apnea frequently have redundant soft tissue in the airway, which makes visualization of the vocal cords extremely difficult. In fact, obese patients with sleep apnea and abnormalities on airway examination should be considered for awake intubation. In experienced hands, awake fiberoptic intubation with prior topical application of local anesthetic and small amounts of sedation is ideal. If general anesthesia is induced and difficulty with intubation and ventilation ensues, obese patients can rapidly become desaturated and hypoxemic. This is due to both an increased rate of oxygen consumption and decreased functional residual capacity. Oxygenation with 100% oxygen before induction of anesthesia helps decrease the rate of desaturation but does not eliminate this risk.
Answer
C
18 A 65-year-old patient with no significant past medical history and normal laboratory values is scheduled for laparoscopic inguinal hernia repair. While waiting in the preoperative holding area, his ECG shows an irregularly irregular rhythm without P waves. His heart rate varies between 70 and 85 beats per minute. Which of the following constitutes appropriate management of this patient?
A Cancel the operation and order a stress test.
B Cancel the operation and immediately start treatment with digoxin.
C Perform transthoracic echocardiography and proceed with the operation if the result is normal and the heart rate is controlled.
D Proceed with the operation and place the patient on an aspirin regimen postoperatively.
E Administer cardioversion.
Ref.: 30
Comments
This patient has atrial fibrillation. Arrhythmias in this setting typically appear in elderly patients and are frequently associated with pain or severe anxiety. The possibility of a new arrhythmia in association with these diseases is less than 1% in the absence of signs suggesting cardiac disease or thyrotoxicosis. Therefore, immediate stress testing is unnecessary. This patient’s heart rate is within normal limits, thus making the administration of digoxin unwarranted. Proceeding with surgery is an acceptable course of management, provided that the ventricular rate is controlled and there are no signs of acute illness. A transthoracic echocardiogram should rule out structural heart disease and atrial clot. Anticoagulation is recommended only if the risk for thromboembolism is higher than the risk for postoperative bleeding. Intravenous heparin with the initiation of oral warfarin, not aspirin, is the anticoagulation therapy of choice.
Cardioversion is not indicated as the initial management step in this patient since there is no hemodynamic instability. Moreover, 85% of the patients in whom atrial fibrillation develops revert to sinus rhythm with medication. Of those who are discharged from the hospital with atrial fibrillation, 98% revert to sinus rhythm within 2 months of the operation. Perioperative atrial fibrillation may be related to autonomic nervous system changes associated with an inflammatory response. Although it may seem logical that rhythm conversion would be more advantageous than rate control, this is not true. Controlling the ventricular response rate either pharmacologically or by ablation of the atrioventricular node and implantation of a pacemaker allows the use of less toxic medications, which results in fewer adverse drug reactions and hospitalizations.
Answer
C
19 A patient in the postanesthesia care unit is in no apparent distress. The vital signs are stable except for a heart rate of 128 beats per minute that is irregular with no P waves. Which of the following treatment options would not be appropriate initial therapy?
A Metoprolol
B Diltiazem
C Digoxin
D Adenosine
E All are appropriate options
Ref.: 31
Comments
This patient has atrial fibrillation with a rapid ventricular response. Treating this patient with β-blockers such as metoprolol or calcium channel blockers such as diltiazem would be appropriate. Calcium channel blockers are especially advantageous in patients who cannot tolerate β-blockade, such as those with bronchospastic disease or congestive heart failure. Digoxin may also be used, although recent studies suggest that it may be ineffective in high adrenergic states such as those that are present postoperatively. Supraventricular tachycardia, not atrial fibrillation, responds to adenosine. Direct current cardioversion is not an appropriate first-line therapy in a hemodynamically stable patient. Had the aforementioned patient been hypotensive, complaining of angina, or in pulmonary edema, cardioversion would have been appropriate.
Answer
D
20 Atrial fibrillation develops in a 65-year-old patient 4 days after a coronary arterial bypass graft operation. The vital signs are stable, and the laboratory test values are normal. Which of the following statements pertains to this patient?
A The patient is not at increased risk for stroke.
B The duration and cost of the patient’s hospital stay will be increased.
C The duration of atrial fibrillation is inconsequential.
D Anticoagulation therapy with heparin should be started immediately.
E All of the above.
Ref.: 30-32
Comments
The risk for stroke in postoperative cardiac patients in whom atrial fibrillation develops doubles in comparison to those without atrial fibrillation. The duration of the hospital stay will increase by an average of 1 to 2 days, and the median cost will increase significantly. The duration of atrial fibrillation is crucial to determining therapy. The risk for thromboembolism in patients without sinus rhythm is markedly increased after 48 hours. Therefore, anticoagulation should be strongly considered in patients with an indeterminate duration of atrial fibrillation, even in the immediate postoperative period. A reasonable treatment plan consists of intravenous heparin, titrated to maintain a partial thromboplastin time of two to three times normal, and subsequent administration of warfarin to maintain an international normalized ratio between 2.0 and 3.0. In general, atrial fibrillation is associated with a fivefold to sixfold increased risk for stroke in comparison to normal individuals. The addition of anticoagulation therapy decreases the risk by 68%.
Answer
B
21 Indicate which of the following statements in regard to delaying elective noncardiac surgery is not true.
A Elective noncardiac surgery should be delayed for at least 2 weeks and optimally for 4 to 6 weeks after coronary artery stenting.
B Elective noncardiac surgery should be delayed at least 3 months after myocardial infarction (MI).
C Elective noncardiac surgery should be delayed at least 1 week after coronary artery angioplasty without stent placement.
D Elective noncardiac surgery should be delayed in patients with stage 3 hypertension.
E All of the above.
Ref.: 30, 33
Comments
The “6-month rule” formerly observed for delaying elective noncardiac surgery after acute myocardial infarction was based on the results of perioperative management of patients with recent MI reported nearly 3 decades ago. Current management and risk stratification do not use the 3- and 6-month intervals traditionally discussed in the past. Rather, current management of MI provides for risk stratification during convalescence, and the risk for adverse perioperative complications depends more on the amount of residual myocardium at risk for severe ischemia and infarction than on the age of the previous MI. Although no specific current studies have evaluated the timing of elective noncardiac surgery after MI, it appears reasonable to delay elective surgery for 4 to 6 weeks after uncomplicated MI, assuming that noninvasive testing does not indicate residual myocardium at risk.
The timing of elective surgery after percutaneous coronary intervention (PCI) involving angioplasty with or without stenting depends on the temporally related risks for vessel thrombosis, restenosis, and bleeding related to the antiplatelet therapy used in the acute phase after PCI. Delaying surgery for at least 1 week after balloon angioplasty has the theoretical benefits of allowing healing of the vessel injury and reducing the risk for vessel thrombosis. Delaying elective surgery for 2 weeks and ideally for 4 to 6 weeks will allow partial endothelialization of a coronary stent, as well as decrease the risk for bleeding related to antiplatelet therapy (typically used for 4 to 6 weeks after stenting). Stage 3 hypertension (systolic blood pressure ≥180 mm Hg and diastolic blood pressure ≥110 mm Hg) should be controlled before elective surgery. Effective control of blood pressure can often be achieved by the administration of oral antihypertensive medication for several days to weeks. If an operation is urgent, more aggressive therapy can reduce blood pressure preoperatively, but there is a significantly greater risk for intraoperative blood pressure lability, with the potential development of hypotension and severe hypertension.
Answer
B
22 A 65-year-old man with a long-standing history of hypertension and a 25-pack-per-year history of smoking is scheduled for elective laparoscopic hernia repair. On examination, his blood pressure is 150/90. The ECG shows nonspecific ST-segment changes. Appropriate interventions would include which of the following?
A Cancelling the procedure
B Obtaining a more detailed history regarding the level of exercise and daily activity
C Requesting a cardiac consultation
D Perioperative administration of a β-blocker and changing the operation to open hernia repair with local anesthesia
E None of the above
Ref.: 30, 33
Comments
Current recommendations regarding preoperative cardiac evaluation for noncardiac surgery are based on the theory that random testing and screening for cardiac disease in the absence of clinical findings or changes in a patient’s history are not cost-effective and do not appear to reduce perioperative cardiovascular morbidity and mortality. The approach to the patient needs to consider both the surgical risk factors for a cardiac complication and the patient’s cardiac risk factors.
High-risk predictors of cardiac complications include known coronary artery disease, unstable angina, severe stenotic valvular disease, essential hypertension, and recent documented MI. Intermediate predictors of coronary disease include advanced age, poor exercise tolerance, congestive heart failure, rhythm other than sinus rhythm, and insulin-dependent diabetes. High-risk surgical procedures include any emergency procedure, procedures involving the aorta or other major vasculature, and long procedures entailing large blood loss and fluid shifts. Intermediate procedures include major orthopedic procedures and prostate, carotid artery, and head or neck operations.
For a patient undergoing a low- to intermediate-risk procedure who has more than two intermediate to high predictors of cardiac risk, the history and physical findings will guide the necessity for further work-up. If the history and exercise tolerance have been stable and routine laboratory studies such as ECGs are unchanged, elective procedures of low to intermediate risk can proceed without additional intervention. When additional history or records cannot be obtained, the urgency of surgery must be considered in situations in which the history and physical findings suggest progression of coronary artery disease.
Cardiac consultation should be used to answer specific questions regarding disease status and not simply to request “clearance.” Appropriate use of consultation services may include further testing when indicated by changes in a patient’s history or findings on physical examination. As a general rule, if nothing in the history or physical examination indicates a need for intervention, an intervention is not required simply because the patient is undergoing an operation.
Although available data indicate that appropriate β-blockade therapy may reduce the incidence of preoperative morbidity and mortality, there is no evidence that one type of anesthetic technique is superior to another. The approach should involve optimizing the patient’s condition and making reasonable predictions of risk rather than attempting alternative measures in the hope of reducing the likelihood of complications.
Answer
B
23 A patient is scheduled for colon resection secondary to diverticulitis. The patient’s history is significant for coronary artery disease, hypertension, and insulin-dependent diabetes. The patient underwent two-vessel angioplasty 6 months previously, is symptom free, and exercises three times per week. Appropriate preoperative testing would include which of the following?
A ECG
B Treadmill stress test
C Dobutamine echocardiographic stress test
D Angiogram
E None of the above
Ref.: 30, 33
Comments
In the absence of a change in a patient’s clinical history or physical findings, only routine testing appropriate for age and gender needs to be conducted. In a patient who has undergone coronary artery bypass grafting within 5 years or had normal findings during an interventional cardiac work-up within 2 years, no further testing is warranted unless dictated by changes in the history or findings on physical examination. When indicated, exercise stress testing is the preferred test. Routine treadmill testing provides much useful information, including the patient’s functional capacity, areas of myocardium in which ischemia may occur, and a heart rate at which ischemia may occur. For patients who cannot exercise on a treadmill, chemical stress testing is the next preferred method of assessing ventricular function. Angiography is generally reserved for patients with known cardiac disease, recent MI or unstable angina, or severe stenotic valvular disease. In such patients, an acute intervention such as angioplasty (stenting) or balloon valvuloplasty may be indicated before noncardiac surgery. In addition, although coronary artery bypass grafting is not generally indicated to improve the outcome after noncardiac surgery, angioplasty may identify patients who do require coronary artery bypass grafting or valve replacement before elective noncardiac surgery. When surgery is needed on an urgent or emergency basis, the patient’s condition should be medically optimized and interventional studies reserved for the postoperative period.
Answer
A
24 In patients with intermediate predictors of cardiac risk who are scheduled for intermediate- or high-risk surgical procedures, which of the following interventions can reduce perioperative morbidity and mortality?
A Continuous intraoperative ST-segment monitoring
B Regional anesthesia when indicated
C Transesophageal echocardiography
D Routine use of intravenous nitroglycerin
E β-Blockade therapy
Ref.: 30, 34, 35
Comments
It is unclear whether certain anesthetic techniques or intraoperative monitors can reliably reduce perioperative morbidity and mortality. Continuous ST-segment monitoring is a noninvasive, safe, readily available, inexpensive component of routine intraoperative monitoring. Even though it has proved useful in the early detection of myocardial ischemia, it has not been shown to favorably affect the overall incidence of perioperative MI or death. Although regional anesthesia seems safer than general anesthesia, no studies have corroborated such a claim. Transesophageal echocardiography is very safe and provides pertinent information regarding volume status, contractility, and regional wall motion abnormalities. However, it requires an experienced operator since adequate views may not always be obtainable, particularly during procedures involving the thorax and upper part of the abdomen.
Perioperative nitroglycerin administration has been used to optimize cardiac perfusion in high-risk patients because it causes dilation of epicardial vessels and is an effective therapy for angina. Topical nitrates are not recommended in the operating room since absorption may be adversely affected by changes in body temperature and cutaneous blood flow. Although intravenous nitroglycerin is commonly used, no studies have clearly demonstrated its efficacy in reducing perioperative cardiac morbidity and mortality. β-Blockade therapy reduces perioperative and long-term complications related to myocardial morbidity and death from MI. It is thought to decrease the incidence of myocardial complications via several mechanisms, including reduction of myocardial oxygen demand and stabilization of intravascular plaques and thrombi. Although there is controversy regarding how soon the medications can be given to see the best benefit, cardiac complications can be reduced in patients with the administration of β-blockers 3 to 4 hours before surgery, and these effects can last for 2 years postoperatively, but such patients may have a higher incidence of stroke and other mortality according to the POISE (PeriOperative Ischemia Evaluation) trial. Other drugs, such as calcium channel blockers and α2-agonists, have not been shown to have the same effect as β-blockade.
Answer
E
25 Which of the following statements regarding perioperative β-blocker use is true?
A Perioperative β-blockade can reduce intraoperative myocardial ischemia in at-risk patients.
B Perioperative β-blockade can reduce postoperative myocardial ischemia in at-risk patients.
C Perioperative β-blockade can reduce postoperative cardiac death and nonfatal MI after major vascular surgery.
D Perioperative β-blockade should be initiated preoperatively and continued for several days postoperatively in patients at risk for cardiac events.
E All of the above.
Ref.: 33, 35
Comments
In 2001, the Agency for Healthcare Research and Quality found sufficient clinical evidence to justify the widespread implementation of perioperative β-blockade. Patients with known coronary disease, positive preoperative stress evaluation results, or known risk factors for cardiac complications and those undergoing intermediate- to high-risk procedures will probably benefit from perioperative β-blockade. This observation has best been documented in vascular surgery patients, in whom reductions in intraoperative and postoperative ischemia, perioperative MI, and cardiac mortality have been demonstrated. The greatest benefit appears to accrue in patients with more than one of the following risk factors: high-risk surgery, known coronary artery disease, cerebrovascular disease, diabetes mellitus, or chronic renal insufficiency. Even though specific guidelines have not yet been developed, continuation of β-blockade for up to a month postoperatively appears logical. Despite widespread use of this protocol, recent trials have begun to question the universality of their use. In the POISE trial, patients who were randomized to the treatment group received a starting dose of 100 mg metoprolol given orally 2 to 4 hours before surgery and 100 mg given 0 to 6 hours after surgery, followed by 200 mg every day for 30 days. They concluded that although major postoperative cardiac events were reduced in the metoprolol group, overall mortality and the incidence of stroke were higher. There are some inherent problems with this study, and the final recommendation may be to dose and titrate high-risk patients 1 to 2 weeks before surgery to achieve the best benefit. The risk for perioperative MI is greatest in the first 24 to 96 hours after surgery, but it persists for up to 1 week postoperatively.
Answer
E
26 Regarding the scenarios listed below, which one of the operations should proceed as scheduled?
A An 80-year-old scheduled for cataract surgery who has a pulse of 60 and blood pressure of 180/110 and is completely asymptomatic
B A 67-year-old scheduled for left total hip arthroplasty who has a pulse of 80 and blood pressure of 180/110, is asymptomatic, and takes β-blockers
C A 65-year-old hypertensive scheduled for bilateral total knee arthroplasty who has a pulse of 90 and blood pressure of 130/70 and who takes angiotensin-converting enzyme (ACE) inhibitors
D An 80-year-old scheduled for bilateral laparoscopic hernia repair who has a pulse of 42 and blood pressure of 100/60 and who has a pacemaker and is taking β-blockers
E None of the above operations should proceed
Ref.: 30, 32
Comments
Management of hypertension in the perioperative period remains controversial. Nonetheless, several studies have consistently shown that a preoperative diastolic blood pressure higher than 110 mm Hg confers an increased risk for major morbidity. Aggressive perioperative normalization may not reduce the risk. However, the patient in scenario A is scheduled for a low-risk operation, unlike the patient in scenario B. Therefore, the operation in scenario A can be performed safely as long as the patient has adequate follow-up. ACE inhibitors have been associated with severe perioperative hypotension during major surgery, especially in patients who receive an epidural catheter as part of their management. The patient in scenario D may have a pacemaker malfunction that needs to be evaluated. β-Blockers have been shown to decrease intraoperative ischemia and should be continued. Calcium channel blockers and diuretics may also be continued.
Answer
A
27 Evidence-based strategies for perioperative renal protection include which of the following?
A Fenoldopam, 0.01 mcg/kg/min intravenously
B Mannitol, 0.5 to 1 g/kg intravenously
C Furosemide, 20 to 40 mg intravenously
D N-Acetylcysteine
E None of the above
Ref.: 36-41
Comments
None of these drugs have been approved as a renoprotective agent by the U.S. Food and Drug Administration, and none has consistently shown clear benefit, although all have theoretical benefits. Fenoldopam preserves medullary blood flow without significant systemic effects. Mannitol promotes diuresis, which should minimize sludging of tubular fluid, and seems to be a free radical scavenger. However, it increases osmolarity and may lead to hypovolemia. Loop diuretics, such as furosemide (Lasix), reduce the metabolism of tubular cells and should enable patients to better tolerate ischemia. Therapeutic measures with proven efficacy are hydration before and after the administration of contrast material and use of the minimal dose required (not exceeding a volume of contrast medium of 5 mL/kg of body weight divided by the serum creatinine level in milligrams per deciliter). Other modalities that have not shown clear evidence of prevention are the use of N-acetylcysteine, isosmolar contrast media, bicarbonate infusion, or purine antagonists (theophylline, aminophylline). The use of continuous venovenous hemofiltration in high-risk patients has been shown to be effective.
Answer
E
28 Regarding urinary retention after ambulatory surgery, which of the following statements is not true?
A Urinary retention is most frequently associated with herniorrhaphy and anorectal procedures.
B Spinal anesthesia, but not general anesthesia, is a predisposing factor for postoperative urinary retention.
C Postoperative urinary retention can frequently be asymptomatic.
D Ambulatory surgery patients must void as a criterion for discharge.
E Overzealous administration of intravenous fluids (>1200 mL) can cause urinary retention.
Ref.: 1, 2, 35, 42
Comments
Patients at risk for postoperative urinary retention include those with a previous history of retention and those undergoing procedures such as herniorrhaphy and anorectal operations. Both spinal anesthesia and general anesthesia are predisposing factors, especially when the latter is associated with the use of anticholinergic drugs. Although bladder overdistention is a significant factor contributing to postoperative urinary retention, many patients are asymptomatic with bladder volumes exceeding 600 mL. Even though low-risk patients may be discharged safely without the requirement to void, consideration should be given to catheterization of high-risk patients before discharge. Patients at high risk for postoperative urinary retention should have ready access to a medical facility and be instructed to return to a medical facility if still unable to void 8 to 12 hours after discharge from an ambulatory surgical facility. Judicious use of intravenous fluids may reduce the incidence of postoperative urinary retention in patients at high risk.
Answer
B
29 Initial treatment of a postoperative headache 24 hours after spinal anesthesia for outpatient knee arthroplasty includes all but which of the following?
A Oral fluids
B Bed rest
C Oral analgesics
D Caffeine
E Epidural blood patch
Ref.: 29
Comments
Post–dural puncture headache (PDPH) results from decreased intracranial pressure (ICP) secondary to leakage of cerebrospinal fluid from the dural defect created by the spinal needle. The incidence of PDPH can be decreased primarily by reducing the needle size and, to a lesser extent, by using needles of improved design. Increased oral fluid intake, remaining recumbent, and the use of oral analgesics can reduce cephalgia, as well as other symptoms, such as visual disturbances, auditory disturbances, and nausea. Caffeine may also be helpful in reducing symptoms. An epidural blood patch is a more aggressive approach that is typically reserved for severe, persistent symptoms. Epidural injection of 10 to 20 mL of autologous blood collected from a fresh venipuncture is associated with successful relief of severe, persistent PDPH symptoms in 90% of patients.
Answer
E
30 Which statement about postoperative nausea and vomiting (PONV) after ambulatory surgery is false.
A PONV is associated with opioid use.
B PONV occurs less frequently following anesthetic induction with propofol than with thiopental.
C PONV prophylaxis should be administered to all patients before ambulatory surgery.
D PONV is increased in adults who are not required to ingest oral fluids before discharge.
E PONV is one of the most prevalent factors leading to delay in discharge after outpatient procedures.
Ref.: 29, 43, 44
Comments
PONV is one of the most prevalent factors leading to delay in discharge from ambulatory surgical centers or unanticipated hospitalization after outpatient procedures. Both pain and the treatment of pain with opioids are associated with increased risk for PONV. “Balanced analgesia” with use of nonopioid medications such as ketorolac (a nonsteroidal anti-inflammatory drug) and adjuvant methods of analgesia such as wound infiltration with local anesthetic and local or regional nerve blocks can substantially reduce the use of opioids and associated PONV. Use of propofol as an induction drug is known to reduce the incidence of PONV, although the effect is lessened after long surgical procedures unless it is infused during the procedure or another dose of propofol is administered toward the conclusion of a long procedure. Because of the cost and side effects of antiemetic drugs, prophylaxis for all patients undergoing ambulatory surgery is not recommended. However, prophylaxis for patients at high risk for PONV can be cost-effective by reducing the length of the postoperative stay and improving patients’ satisfaction. Although in a comparison between ondansetron, 8 mg, and metoclopramide, 10 mg, significant improvement in reducing PONV was noted with ondansetron, a new class of antiemetics, substance P or NK1 receptor antagonists, have shown improvement over ondansetron in terms of vomiting. In a simplified risk score developed by Apfel, when none, one, two, three, or four of the risk factors (being female, history of PONV or motion sickness, nonsmoking status, postoperative opioids) are present, the patient’s risk for PONV is about 10%, 20%, 40%, 60%, or 80% respectively. Although oral fluid intake before discharge does not increase the risk for PONV in adult patients, eliminating oral fluid intake as a discharge criterion does not reduce the risk for PONV. Therefore, patients should be allowed to decide to accept or decline oral fluids as they desire before discharge.
Answer
C
31 Regarding skin preparation in a 35-year-old man scheduled for inguinal hernia repair, which of the following is an effective measure?
A Clip the hair from the operative site.
B Paint the operative site with chlorhexidine gluconate/alcohol.
C Allow the povidone-iodine solution to dry.
D All of the above.
E None of the above.
Ref.: 1
Comments
The sole reason for preparing the patient’s skin before an operation is to reduce the risk for wound infection. A preoperative antiseptic bath is not necessary for most surgical patients. Hair should not be removed from the operative site unless it physically interferes with accurate anatomic approximation of the wound edges. If hair must be removed, it should be clipped in the operating room. Shaving hair from the operative site, particularly on the evening before surgery or immediately before the wound incision, increases the risk for wound infection. The necessary reduction in microorganisms can be achieved by using povidone-iodine or chlorhexidine gluconate both for mechanical cleansing of the intertriginous folds and the umbilicus and for painting the operative site. Simply applying the agents (painting or spraying) is an effective means of disinfection of the skin. Povidone-iodine and chlorhexidine/alcohol should be allowed to dry.
Answer
D
32 Regarding the risk associated with surgery in patients with liver disease, which of the following is not true?
A Halothane and enflurane reduce hepatic arterial blood flow.
B Hypercapnia increases portal blood flow.
C Fentanyl, not morphine or meperidine, is the preferred narcotic agent.
D Patients with Child class B cirrhosis undergoing cardiac operations have a high mortality rate.
E Laparoscopic cholecystectomy can be performed safely in patients with compensated Child class A cirrhosis.
Ref.: 36, 37
Comments
Routine laboratory screening of otherwise healthy surgical candidates for unsuspected liver disease is controversial. However, a carefully taken history to identify risk factors for liver disease permits adequate initial evaluation. Isoflurane is preferred over halothane because it increases hepatic arterial blood flow. Hypercapnia should be avoided since it triggers sympathetic splanchnic stimulation and leads to decreased portal flow. Fentanyl or sufentanil are the narcotic agents of choice. The metabolism of morphine and diazepam can be prolonged in patients with liver disease. Lorazepam is preferred since it is eliminated by glucuronidation. Cardiac operations are associated with a high mortality rate in patients with Child class B cirrhosis because of the higher risk for infection and bleeding. Celiotomy leads to a greater reduction in hepatic arterial blood flow than do extraabdominal or laparoscopic operations. In patients with cirrhosis, the Child-Pugh and Model for End-Stage Liver Disease (MELD) classifications are the most useful predictors of mortality and morbidity. A MELD score of less than 10, 10 to 14, and higher than 14 correspond to classes A, B, and C. Postoperatively, bilirubin levels and the prothrombin time should be monitored closely. Preoperative correction of coagulopathic states is mandatory.
Answer
B
References
1 Neumayer L, Vargo D. Principles of preoperative and operative surgery. In Townsend CM, Beauchamp RD, Evers BM, et al, editors: Sabiston textbook of surgery: the biological basis of modern surgical practice, ed 18, Philadelphia: WB Saunders, 2008.
2 Alarcon LH. Physiologic monitoring of the surgical patient. In Brunicardi FC, Andersen DK, Billiar TR, et al, editors: Schwartz’s principles of surgery, ed 9, New York: McGraw-Hill, 2010.
3 Furnary AP, Zerr KJ, Grunkemeier GL, et al. Continuous intravenous insulin infusion reduces the incidence of deep sternal wound infection in diabetic patients after cardiac surgical procedures. Ann Thorac Surg. 1999;67:352-362.
4 Bartlett RH, Rich PB. Endocrine problems. American College of Surgeons ACS Surgery Principles and Practice. Retrieved May 2003 from www.acssurgery.com
5 Dandona P, Thusu K, Hafeez R, et al. Effect of hydrocortisone on oxygen free radical generation by mononuclear cells. Metabolism. 1998;47:788-791.
6 Wiener RS, Wiener DC, Larson RJ. Benefits and risks of tight glucose control in critically ill adults: a meta-analysis. JAMA.. 2008;300:933-944.
7 Ansara MF, Gryer PE, Scharp DN. Diabetes mellitus. American College of Surgeons ACS Surgery Principles and Practice. Retrieved May 2003 from www.acssurgery.com
8 Vinclair M, Broux C, Faure P, et al. Duration of adrenal inhibition following a single dose of etomidate in critically ill patients. Intensive Care Med. 2008;34:714-719.
9 Kinney MA, Narr BJ, Warner MA. Perioperative management of pheochromocytoma. J Cardiothorac Vasc Anesth. 2002;16:359-369.
10 Steinsapir J, Carr AA, Prisant LM, et al. Metyrosine and pheochromocytoma. Arch Intern Med. 1997;157:901-906.
11 Braverman LE, Utiger RD, editors. The thyroid, ed 6. JP Lippincott, Philadelphia, 1991;1002-1004.
12 Steinberg AD. Myxedema and coronary artery disease: a comparative autopsy study. Ann Intern Med. 1968;68:338-344.
13 Abbott TR. Anaesthesia in untreated myxoedema: report of two cases. Br J Anaesth. 1967;39:510-514.
14 Kim JM, Hackman L. Anesthesia for untreated hypothyroidism: report of three cases. Anesth Analg. 1977;56:299-302.
15 Weinberg AD, Brennan MD, Gorman CA, et al. Outcome of anesthesia and surgery in hypothyroid patients. Arch Intern Med. 1983;143:893-897.
16 Ladenson PW, Levin AA, Ridgway EC, et al. Complications of surgery in hypothyroid patients. Am J Med. 1984;77:261-266.
17 Appoo JJ, Morin JF. Severe cerebral and cardiac dysfunction associated with thyroid decompensation after cardiac operations. J Thorac Cardiovasc Surg. 1997;114:496.
18 Catz B, Russell S. Myxedema, shock and coma: seven survival cases. Arch Intern Med. 1961;108:407-417.
19 Holvey DN, Goodner CJ, Nicoloff JT, et al. Treatment of myxedema coma with intravenous thyroxine. Arch Intern Med. 1964;113:89-96.
20 Ragaller M, Quintel M, Bender HJ, et al. Myxedema coma as a rare postoperative complication. Anaesthesist. 1993;42:179-183.
21 Bennett-Guerrero E, Kramer DC, Schwinn DA. Effect of chronic and acute thyroid hormone reduction on perioperative outcome. Anesth Analg. 1997;85:30-36.
22 Roti E, Robuschi G, Gardini E, et al. Comparison of methimazole, methimazole and sodium ipodate, and methimazole and saturated solution of potassium iodide in the early treatment of hyperthyroidoid Graves’ disease. Clin Endocrinol (OXF). 1988;28:305-314.
23 Baeza A, Aguayo J, Barria M, et al. Rapid preoperative preparation in hyperthyroidism. Clin Endocrinol (OXF). 1991;35:439-442.
24 Nabil N, Miner DJ, Amatruda JM. Methimazole: an alternative route of administration. J Clin Endocrinol Metab. 1982;54:180-181.
25 Walter RMJr., Bartle WR. Rectal administration of propylthiouracil in the treatment of Graves’ disease. Am J Med. 1990;88:69-70.
26 Burch HB, Wartofsky L. Hyperthyroidism. Curr Ther Endocrinol Metab. 1994;5:64-70.
27 Burch HB, Wartofsky L. Life-threatening thyrotoxicosis. Thyroid storm. Endocrinol Metab Clin North Am. 1993;22:263-277.
28 Stoelting RK, Dierdorf SF. Anesthesia and Co-Existing Disease, ed 4. Philadelphia: Churchill Livingstone; 2000.
29 Barash PG, Cullen BF, Stoelting RK. Clinical Anesthesia, ed 4. Philadelphia: Lippincott Williams & Wilkins; 2001.
30 Eagle KA, Berger PB, Calkin H, et al. ACC/AHA guideline update for perioperative cardiovascular evaluation of non-cardiac surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines 2002. Retrieved June 2003 from www.acc.org/clinical/guidelines/perio/update/periupdate_index.htm
31 Amar D, Zhang H, Leung DH, et al. Older age is the strongest predictor of postoperative atrial fibrillation. Anesthesiology. 2002;96:352-356.
32 Bharucha D, Marinchak R, Kowey P. Arrhythmias after cardiac surgery: atrial fibrillation and atrial flutter. Up to Date. 2003. Available at www.uptodate.com
33 Miller RS. ed 5. Anesthesia, vol. 2. Churchill Livingstone, Philadelphia, 2000.
34 Mangano DT, Layug EI, Wallace A, et al. Effect of atenolol on mortality and cardiovascular morbidity after noncardiac surgery. Multicenter Study of Perioperative Ischemia Research Group. N Engl J Med. 1996;335:1713-1720.
35 POISE study group. Effects of extended-release metoprolol succinate in patients undergoing non-cardiac surgery (POISE trial): a randomized controlled trial. Lancet. 2008;371:1839-1847.
36 Newman MF, editor. Perioperative Organ Protection. Philadelphia: Lippincott Williams & Wilkins, 2003.
37 Friedman LS. The risk of surgery in patients with liver disease. Hepatology. 1999;29:1617-1623.
38 Solomon R, Werner C, Mann D, et al. Effects of saline, mannitol, and furosemide to prevent acute decreases in renal function induced by radiocontrast agents. N Engl J Med. 1994;331:1416-1420.
39 Cox CD, Tsikouris JP. Preventing contrast nephropathy: what is the best strategy? A review of the literature. J Clin Pharmacol. 2004;44:327-337.
40 Barrett BJ, Parfrey PS. Clinical practice: preventing nephropathy induced by contrast medium. N Engl J Med. 2006;354:379-386.
41 Guastoni C, De Servi S, D’Amicoc M. The role of dialysis in contrast-induced nephropathy: doubts and certainties. J Cardiovasc Med (Hagerstown). 2007;8:549-557.
42 Pavlin DJ, Pavlin EG, Fitzgibbon DR, et al. Management of bladder function after outpatient surgery. Anesthesiology. 1999;91:42-50.
43 Apfel CC, Malhotra A, Leslie JB. The role of neurokinin-1 receptor antagonists for the management of postoperative nausea and vomiting. Curr Opin Anaesthesiol. 2008;21:427-432.
44 Apfel CC, Korttila K, Abdalla M, et al. A factorial trial of six interventions for the prevention of postoperative nausea and vomiting. N Engl Med. 2004;350:2441-2451.
B Anesthesia
W. Christopher Croley, M.D., F.C.C.P., James A. Colombo, M.D.
1 During a tracheostomy, a flash is noted in the surgical field while using electrocautery. Which of the following is the correct sequence of steps in management of the patient?
A Extinguish the flames with saline solution or water; turn off all anesthetic gases, including O2; and then hyperventilate with 21% O2 through the endotracheal tube (ETT).
B Extinguish the flames with saline solution or water, turn off all anesthetic gases except O2, and then hyperventilate with 100% O2 through the ETT.
C Stop the ventilation; disconnect all anesthetic gas supply, including O2; extinguish the flames with saline solution or water; remove the ETT; ventilate the patient with a mask; and then reintubate.
D Extinguish the flames with saline solution or water; remove all draping immediately; stop the ventilation; disconnect all anesthetic gas supply, including O2; allow the patient to awaken; and then extubate.
E Stop the ventilation; disconnect all anesthetic gas supply, including O2; extinguish the flames with saline solution or water; and resume ventilation.
Ref.: 1
Comments
Airway fires occur most often during laser airway surgery but can take place in any O2-rich environment where igniting stimuli may exist. Any combustible material, including polyvinyl chloride tubing, surgical drapes, and human tissue, can ignite. Both the surgeon and the anesthesiologist should take the following steps simultaneously: stop all gas flow, including O2; extinguish the fire with water or saline solution; and remove the ETT or any foreign body present in the airway (e.g., bronchoscope or gauze). Mask ventilation is performed until the trachea is reintubated. Bronchoscopy is then performed to determine the extent of the airway damage and to remove any foreign bodies that may be present. The trachea should be left intubated for at least 24 hours after an airway fire, and humidified gases should be administered through the ETT or tracheostomy tube. The use of steroids is controversial and probably of no benefit.
Answer
C
2 Effective management of gastric acid aspiration includes which of the following?
A Tracheal intubation and saline lavage of the lungs
B Prophylactic antibiotic therapy
C Prophylactic steroid therapy
D Suctioning and controlled ventilation with positive end-expiratory pressure (PEEP)
E Diuresis
Ref.: 1-4
Comments
Gastric aspiration can be a fatal complication. The severity of the injury is determined by the volume and pH of the gastric fluid aspirated. Fluid with a pH of less than 2.5 and a volume greater than 0.4 mL/kg (approximately 30 mL for an adult) is associated with a greater degree of pulmonary damage.
Initial treatment should begin with intubation, suctioning of aspirated fluid, testing the pH of the fluid (if readily available), and positive pressure ventilation with PEEP. The level of PEEP is determined by the ability to adequately oxygenate (PaO2 >60 mm Hg) the patient, ideally with the fractional concentration of oxygen in inspired gas (FIO2) below 60%. Saline lavage is not indicated because it has been shown to aggravate injury. Prophylactic antibiotic and steroid therapy is not indicated. With the initiation of positive pressure ventilation and loss of fluid into the damaged lung parenchyma, patients are often intravascularly depleted. Thus, empirical diuretic therapy is not appropriate.
Antibiotic therapy may be indicated in cases of aspiration in patients receiving enteral feeding but is not indicated as a general prophylactic maneuver. Steroid medications are not indicated in the initial stages of aspiration.
Answer
D
3 A 30 year old man undergoes hernia repair with spinal anesthesia. He calls the next day complaining of a headache that worsens with moving from a supine to a sitting position. He also has complaints of tinnitus. Initial treatment should include which of the following?
A Bed rest, increased fluid intake, and analgesics
B Urgent computed tomographic scan of brain to check for increased ICP
C Intravenous caffeine administration
D Placement of an epidural blood patch
E Remaining in the sitting position
Ref.: 1
Comments
Post spinal anesthesia headache is typically characterized by frontal or occipital cephalgia that worsens with sitting or standing and is usually relieved by assuming a supine position. Initial treatment is conservative and consists of bed rest, fluids, and analgesics. Caffeine administration may be of benefit if conservative measures fail. PDPH may be associated with neurologic findings. Common complaints are tinnitus, diplopia, and decreased hearing acuity. An epidural blood patch usually provides immediate relief of symptoms and is administered if conservative measures are ineffective in relieving severe symptoms after 24 hours. Factors associated with an increased incidence of PDPH include young age, female gender, large (cutting) spinal needles, and the direction of needle insertion. Insertion of spinal needle with a cutting bevel (Quincke design) in a direction nonparallel to the dural fibers (which are aligned in a vertical plane running cephalad to caudad) is associated with a higher incidence of PDPH. Informing the anesthesiologist that PDPH has occurred is helpful in guiding further treatment if required.
Answer
A
4 For a trauma patient with suspected intracranial hypertension, which intravenous anesthetic agent is contraindicated, even when mechanical ventilation is controlled?
A Midazolam
B Methohexital
C Thiopental
D Ketamine
E Morphine
Ref.: 1, 2
Comments
Benzodiazepines (midazolam), opioids (morphine), and barbiturates (methohexital and thiopental) decrease cerebral blood flow and the cerebral metabolic rate, which in turn decrease ICP. Ketamine is an arylcyclohexylamine structurally related to phencyclidine. Ketamine increases the cerebral metabolic rate and cerebral blood flow and therefore ICP. Hence, ketamine is contraindicated when intracranial hypertension is suspected.
Answer
D
5 Intubation of a spontaneously breathing but obtunded patient with a closed head injury is best accomplished by which of the following?
A Application of topical lidocaine to the nares, spontaneous ventilation, and “blind” nasal intubation
B Induction with thiopental, muscle relaxation with succinylcholine, and oral tracheal intubation
C Awake fiberoptic intubation
D Awake tracheostomy with local anesthesia
E Awake rigid laryngoscopy
Ref.: 1, 3, 4
Comments
Securing an airway in a trauma patient can be difficult. Concurrent cervical injury should be suspected in a patient with a head injury. All airway management should be done while maintaining in-line axial cervical stabilization. All the methods listed are acceptable for intubating this patient, but the ideal method would attenuate increases in ICP via thiopental induction, which can decrease cerebral blood flow and the cerebral metabolic rate by 40% to 60%. Succinylcholine causes small, transient increases in ICP (approximately 4 mm Hg), but these increases are offset by the ICP-reducing effect of thiopental. In addition, the muscle paralysis induced by succinylcholine prevents coughing, which can increase ICP by 50 to 70 mm Hg. Nasal intubation carries the risk of damage to the cribriform plate when preexisting fractures are present, and epistaxis can cause airway compromise in an obtunded patient. Blind intubation under these circumstances is therefore less desirable than other methods of securing an artificial airway. Tracheostomy should be performed whenever airway distortion prevents prompt intubation by other methods. In some situations, tracheostomy is the appropriate initial approach to securing the airway.
Answer
B
6 Use of succinylcholine should be avoided for which of the following patients?
A Patients with burns to 40% of their body surface area in need of emergency intubation 2 hours after injury
B Patients with burns to 40% of their body surface area in need of emergency intubation 5 days after injury
C Patients arriving at the emergency room immediately after sustaining an acute spinal cord injury (complete T4 injury)
D Children younger than 2 years
E Patients with end-stage renal disease and normal serum electrolyte levels
Ref.: 1, 2, 5
Comments
Succinylcholine is a depolarizing muscle relaxant. It causes paralysis by depolarizing the motor end plate via repeated generation of action potentials. This results in an efflux of potassium ions and a transient rise in extracellular potassium levels. This increase is approximately 0.5 mEq/L in patients without neurologic deficits or severe muscular injury. Since the number of motor end plates is markedly increased (i.e., sensitization) 3 to 5 days after neurologic or muscular injury, administration of depolarizing muscle relaxants, such as succinylcholine, at this time can cause large increases in extracellular potassium and cardiac arrest. Therefore, succinylcholine should be used only in an acute setting (immediately after injury) for patients with burns or spinal cord injury in whom such sensitization is not observed within the first 1 to 2 days of injury. There are no contraindications to the use of succinylcholine in healthy children. The presence of renal failure does not preclude the use of succinylcholine if serum potassium levels are within a normal range.
Answer
B
7 Which of the following determines the spread of local anesthetics in cerebrospinal fluid?
A Addition of a narcotic to the local anesthetic
B Baricity of the local anesthetic
C Patient’s body surface area
D Anesthetic volume
E Dose of the agent administered
Ref.: 1, 2
Comments
Spinal anesthesia is accomplished by injecting a local anesthetic into the subarachnoid space. Addition of narcotics to the local anesthetic does not influence the spread of local anesthetic in cerebrospinal fluid unless a sufficient volume is added that changes the baricity of the local anesthetic solution. The degree of spread is determined primarily by the baricity of the solution and the patient’s position. Baricity is the density of the local anesthetic solution in relation to the density of cerebrospinal fluid at normal body temperature. Local anesthetics are characterized as hyperbaric, hypobaric, or isobaric relative to cerebrospinal fluid. Normal lumbar lordosis and thoracic kyphosis of the spine also play a role in determining the final anesthetic level. The dose and specific type of local anesthetic agent used determine the duration of the resultant blockade, but not the spread. Relatively small volumes are used for spinal anesthesia and have little effect on the resultant neural blockade.
Answer
B
8 Which of the following is true regarding malignant hyperthermia (MH)?
A Unusually low end-tidal carbon dioxide may be an early sign of MH.
B MH may be triggered by halogenated anesthetic agents, as well as by nitrous oxide.
C MH may be triggered by succinylcholine.
D Increased core temperature is an early sign of MH.
E MH is common and rarely results in significant morbidity.
Ref.: 1-5
Comments
Malignant hyperthermia is a rare, potentially lethal condition. A fulminant episode is characterized by muscle rigidity, fever, tachycardia, respiratory and metabolic acidosis, severe hypermetabolism, arrhythmias, and eventual cardiovascular collapse. MH can occur minutes to several hours after the administration of triggering agents, such as succinylcholine or potent (halogenated) inhaled agents. The earliest, most sensitive, and most specific sign of MH is an unexplained rise in end-tidal CO2 levels (with venous blood gas acidosis) followed by tachycardia, frequently with multifocal premature ventricular contractions. Increases in temperature are a relatively late finding.
Treatment involves cessation of the triggering anesthetics, administration of dantrolene, forced cooling of the patient, induction of saline diuresis to avoid renal dysfunction from myoglobinuria and widespread rhabdomyolysis, and monitoring of blood gas and potassium levels. MH is transmitted genetically, probably as an autosomal dominant trait with variable penetrance. Elevated serum creatinine phosphokinase levels can be seen in MH-susceptible patients, but this test is not useful for screening because of its poor specificity. Avoidance of triggering agents in patients suspected of MH susceptibility is the safest and easiest method of treatment.
Answer
C
9 Which of the following statements regarding the toxicity of local anesthetics is false?
A Neurologic symptoms almost always precede those of cardiac toxicity.
B The site of injection is an important determinant of toxicity.
C The addition of a 1 : 100,000 epinephrine solution allows the administration of higher doses of local anesthetics.
D The relative toxicity of local anesthetics, in decreasing order, is procaine, lidocaine, bupivacaine, and tetracaine.
E Pregnancy reduces the risk for toxicity because hormones induce resistance to local anesthetics.
Ref.: 1-3, 5
Comments
Systemic toxicity from local anesthetics primarily involves the CNS and the cardiovascular system. CNS toxicity usually occurs at doses well below those that result in cardiovascular toxicity. Manifestations of CNS toxicity include confusion, dizziness, tinnitus, somnolence, and seizures. The seizures are thought to be due to blockade of inhibitory pathways in the cerebral cortex. Cardiovascular toxicity is due to direct blocking effects on both cardiac and vascular smooth muscle and is generally manifested as cardiovascular collapse. Ventricular arrhythmias and asystole are the most common findings on the ECG.
Systemic absorption of local anesthetics is highly dependent on the vascularity of the injection site and the presence or absence of epinephrine. Epinephrine causes vasoconstriction and allows a higher maximum dose of local anesthetic to be safely administered without toxicity. Absorption of local anesthetics occurs most rapidly, with the highest serum levels, from the highly vascular intercostal space and is slowest, with the lowest serum levels, with infiltration of local subcutaneous tissue.
Pregnancy reduces the toxic threshold and the dose of local anesthetic needed for therapeutic purposes. The enlargement of the epidural veins seen with progressive enlargement of the uterus decreases the size of the epidural space and the volume of cerebrospinal fluid in the subarachnoid space. The decreased volume of these spaces facilitates the spread of local anesthetic. Biochemical changes of pregnancy, particularly progesterone, may also play a role in toxicity and spread of local anesthetics. It has been shown to have potent sedative effects.
Answer
E
10 Which of the following statements regarding propofol is false?
A Induction and sedation doses for children are higher than those for adults after adjusting for weight.
B Propofol is a white, milky emulsion that may be contraindicated in patients with egg allergy.
C Unlike other induction agents, propofol does not suppress the respiratory system.
D The incidence of nausea and vomiting is lower with propofol-based anesthesia than with thiopental/isoflurane anesthesia.
E The hemodynamic changes seen with equianesthetic doses are frequently greater with propofol than with thiopental.
Ref.: 1, 2, 6
Comments
Propofol is a nonbenzodiazepine, nonbarbiturate intravenous anesthetic with hypnotic properties. Stemming from its chemical structure as a substituted derivative of phenol, it is insoluble in water and is formulated as a 1% emulsion similar to parenteral lipid formulations. Persons allergic to eggs may have allergies to this formulation. Induction doses are higher for children and adolescents than for adults and should be reduced for elderly patients, hypovolemic patients, and those with poor cardiac reserve. Propofol produces profound dose-dependent respiratory depression that frequently leads to apnea in patients premedicated with other sedatives. After single-bolus administration, propofol is rapidly redistributed (in 2 to 8 minutes) and highly metabolized. For this reason, it is most commonly administered by continuous intravenous infusion. Emergence from anesthesia occurs rapidly after discontinuation of propofol, thus making it particularly suitable for short procedures. Nausea and vomiting are seen less frequently with a propofol-based anesthetic than with thiopental/isoflurane anesthesia, but the hemodynamic alterations are similar to or even greater than those seen with equianesthetic doses of thiopental.
Answer
C
11 Which of the following statements regarding midazolam is true?
A Midazolam is a highly lipid-soluble agent that typically causes pain on injection.
B Midazolam is ten times as potent as diazepam.
C The respiratory depression caused by midazolam is usually minor but can be greatly exacerbated by the concomitant use of other sedatives or opioids.
D Midazolam has no active metabolites, which makes it ideal for use in outpatients.
E Midazolam is renally metabolized.
Ref.: 1, 2, 6
Comments
Midazolam differs from other benzodiazepines in both structure and solubility. An imidazole side ring imparts stability and ease of rapid hepatic metabolism, and a water-soluble structure allows painless injection. Two active metabolites of midazolam exist and accumulate when continuous infusions are used. Like other benzodiazepines, midazolam potentiates respiratory depression (often synergistically) when administered with other sedatives or opioids. Benzodiazepines readily cross the placenta and have been associated with an increased incidence of cleft lip and palate when administered during the first trimester. Safety later in pregnancy has not been definitively established.
Answer
C
12 Which of the following statements regarding neuromuscular blockade by nondepolarizing agents is false?
A The effects are prolonged by aminoglycosides.
B Vagolytic side effects occur with pancuronium.
C Nondepolarizing agents may trigger MH.
D Vecuronium undergoes mostly hepatic metabolism.
E Train-of-four monitoring effectively predicts the degree of blockade.
Ref.: 1, 2, 6
Comments
Nondepolarizing muscle relaxants currently in clinical use include pancuronium, vecuronium, atracurium, cisatracurium, mivacurium, rocuronium, and doxacurium. Nondepolarizing muscle relaxants interfere with transmission at the neuromuscular junction by competing with acetylcholine for available receptor sites. These effects may be reversed by anticholinesterases, which prolong the half-life of acetylcholine to overcome the competitive inhibition of the muscle relaxant. The effect of nondepolarizing agents can be prolonged by aminoglycosides, clindamycin, tetracycline and other antibiotics, hypothermia, hypercapnia, and magnesium. Vagolytic activity is common with pancuronium and rocuronium but not with other agents. Except for mivacurium (which is metabolized by plasma cholinesterase) and atracurium/cisatracurium (which are metabolized by Hofman elimination and nonspecific ester hydrolysis), the metabolism of nondepolarizing agents occurs in the liver, with varying amounts of biliary or renal metabolism and excretion. Train-of-four monitoring involves the administration of stimuli percutaneously to a peripheral nerve four times over a 1-second period and noting the distal muscular response. If fewer than two of the stimuli result in muscle contraction, more than 95% of the receptors are blocked.
Answer
C
13 Which of the following statements regarding flumazenil is true?
A It is a benzodiazepine antagonist that acts by competitive inhibition.
B It has been used successfully to reverse the clinical effects of narcotic overdose.
C It is indicated for patients with suspected cyclic antidepressant overdoses.
D It reverses the respiratory depressant actions but not the sedative effects of all benzodiazepines.
E It is unlikely to improve the encephalopathy associated with hepatic failure.
Ref.: 1, 2, 6
Comments
Flumazenil is a benzodiazepine-specific antagonist that competitively inhibits the activity of benzodiazepines at the benzodiazepine-receptor complex. Flumazenil does not antagonize the CNS effects of GABAergic-acting (leading to the secretion of γ-aminobutyric acid) drugs (ethanol, barbiturates, or general anesthetics), nor does it antagonize the effects of opioids. Flumazenil antagonizes the sedation, impaired recall, psychomotor impairment, and ventilatory depression produced by all benzodiazepines. Use of flumazenil is contraindicated in patients given benzodiazepines for life-threatening conditions (e.g., control of status epilepticus or ICP), patients showing serious signs of cyclic antidepressant overdose (because of an increased occurrence of seizures), and patients with known hypersensitivities. Case reports have demonstrated remarkable improvement in the encephalopathic changes associated with liver failure. Flumazenil should not be used as the only agent for treating hepatic encephalopathy but may be helpful in patients resistant to conventional medical therapy.
Answer
A
14 Mechanisms of heat loss during general anesthesia include which of the following?
A Convection
B Radiation
C Conduction
D Evaporation
E All of the above
Ref.: 1, 2, 5
Comments
Heat loss in the operating room (OR) is a complex problem involving all of the mechanisms mentioned. The contribution of each mechanism depends on the surrounding conditions in the OR. Radiative losses are often cited as the largest contributor to heat loss in the OR. Radiant energy is emitted by every body with a temperature higher than 0° K. Radiation requires no medium for transport because it is electromagnetic. Heat freely radiates from a body at a temperature of 37° C to a room at 25° C as long as the temperature gradient exists. Conductive heat loss requires that bodies be in direct contact with each other. Body heat is conducted to the OR table and other surfaces that come in contact with the patient. Heat is lost from the body by convection when OR air, which is circulated at a speed of approximately 3 cm/s, passes over the body. Finally, heat losses from the latent heat of vaporization (evaporation) occur during mechanical ventilation with dry air, during skin preparation with cold cleansing solutions, through sweating, and from large open wounds.
Answer
E
15 With regard to pulse oximetry studies, which of the following is true?
A Pulse oximetric analysis is unaffected by tissue perfusion.
B Methemoglobinemia results in a displayed arterial oxygen saturation of 85%.
C Oxygen saturation measurements may be artificially decreased in the presence of carboxyhemoglobin.
D A standard pulse oximeter measures light absorption at four wavelengths.
E Ambient light will not affect oximetric readings.
Ref.: 1, 4, 6
Comments
The use of pulse oximetry studies has led to marked improvement in the care and safety of patients not only in the OR but also in the postanesthesia care unit and the intensive care unit. The concept of oximetry is based on Beer’s law, which relates the concentration of a solute in suspension (in this case, hemoglobin) to the intensity of light transmitted through the solution. Pulse oximetric analysis measures the oxygen saturation only of pulsatile blood by using two wavelengths of light (red and infrared). The ratio of the pulse-added absorbencies of these two wavelengths is determined by the arterial oxygen saturation. Pulse oximetry may be difficult to perform in patients who are suffering from any type of shock or tissue hypoperfusion. Because both oxyhemoglobin and carboxyhemoglobin absorb red light similarly, the pulse oximeter reads the sum of the two hemoglobins and produces an artificially elevated reading of oxygen saturation. Direct measurement of saturation from an arterial blood gas sample is required to confirm the presence of carbon monoxide. Methemoglobinemia, a disorder that may occur with nitroglycerin toxicity or inhaled nitric oxide therapy, results in a displayed oxygen saturation of 85%. Methemoglobin does not absorb red light in the same manner as oxyhemoglobin or deoxyhemoglobin does. The absorbance of red and infrared light by methemoglobin is nearly equal and results in a displayed saturation of approximately 85%. Because ambient light can affect pulse oximeter readings, it is occasionally necessary to cover the probe to avoid artifactual readings.
Answer
B
16 While transporting an intubated patient from the OR to the intensive care unit, the pressure gauge on a completely filled size E compressed gas cylinder containing O2 reads 2200 psi. How long can O2 be delivered at a flow rate of 5 L/min from an E cylinder whose pressure gauge reads 1100 psi?
A 60 seconds
B 5 minutes
C 60 minutes
D 125 minutes
E 220 minutes
Ref.: 1, 2
Comments
A full E cylinder reading 2200 psi contains approximately 625 L of O2. Boyle’s law states that for a fixed mass of gas at constant temperature, the product of pressure and volume is constant. Boyle’s law allows estimation of the volume of gas remaining in a closed container by measuring the pressure within the container. When the pressure gauge reads 1100 psi, the volume of gas in the cylinder is half that of a full cylinder (or about 625 L ÷ 2 = 312.5 L). At a flow rate of 5 L/min, the cylinder in question will last approximately 1 hour. This information is important when portable sources of oxygen are being used during transport and diagnostic procedures remote from the OR.
Answer
C
17 After administration of epidural anesthesia to the T3 dermatome of a patient with severe lung disease who is undergoing open cholecystectomy, which of the following is least likely to occur?
A Increased heart rate
B Decreased venous return
C Decreased alveolar ventilation
D Systemic hypotension
E All of the above
Ref.: 1, 2, 5
Comments
On average, after administration of epidural anesthesia, central neuraxial blockade to the T3 sensory dermatome is associated with sympathetic blockade two spinal segment levels higher and motor blockade two spinal segments lower. Blockade of the cardiac accelerator nerves (T1-4) and unopposed vagal activity result in relative bradycardia despite hypotension caused by the reduction in venous return secondary to vasodilation. In addition, motor nerve blockade of intercostal muscle function reduces alveolar ventilation and may precipitate respiratory embarrassment in a patient with underlying pulmonary disease, particularly if a significant fraction of intercostal muscle function is impaired.
Answer
A
18 Which of the following is least likely to occur in conjunction with a surgically induced stress response?
A Increased metabolic rate
B Hypercoagulability
C Suppression of the immune response
D Increased secretion of ACTH
E Increased secretion of thyroid-stimulating hormone
Ref.: 7
Comments
Current evidence suggests that many adverse perioperative events can be attributed to the effects of the stress response. Somatic or visceral pain can trigger the systemic release of catecholamines and neuroendocrine hormones. Hormones released in response to stress include growth hormone, ACTH, vasopressin, prolactin, cortisol, glucagons, and renin-angiotensin-aldosterone. In contrast, secretion of thyroid-stimulating hormone is decreased by the stress response. The overall systemic effects of the stress response lead to increased metabolic activity, a hypercoagulable state, and a less effective immune response to infectious agents.
Answer
E
19 Preoperative noninvasive testing for the presence of inducible myocardial ischemia would be most appropriate for which of the following patients?
A A healthy 60-year-old man without historical cardiac risk factors scheduled for gastrectomy because of gastric carcinoma
B A patient with a history of MI 1 year previously and good exercise tolerance undergoing laparoscopic cholecystectomy
C A patient with diabetes and renal insufficiency undergoing inguinal hernia repair
D A patient with limited exercise tolerance and diabetes undergoing right hemicolectomy
E All of the above
Ref.: 1
Comments
The need for preoperative cardiac testing is determined by assessing a patient’s risk for perioperative cardiac complications and the likelihood that the surgical procedure will produce physiologic conditions that increase myocardial demand. Good exercise tolerance is an important prognostic determinant and can mitigate the need for cardiac testing if patients have known stable cardiac disease and are undergoing intermediate-risk surgery. Operations associated with large fluid shifts or high blood loss, along with vascular surgical procedures, are commonly cited as higher-risk operations. Patients at risk for cardiac complications will benefit from perioperative β-blocker therapy, and β-blockers should be given to all patients with cardiac risk factors unless contraindicated. Patients at high risk for cardiac complications undergoing intermediate- to high-risk surgical procedures (in reference to cardiac outcomes) should have noninvasive assessment of cardiac performance and possibly invasive testing if the noninvasive test results suggest significant cardiac risk. Since surgery in itself is not an indication for cardiac testing, the patient described in scenario A needs no further cardiac work-up.
Answer
D
20 A 67-year-old woman is scheduled for right hemicolectomy because of carcinoma of the colon. She has adult-onset diabetes and shortness of breath when climbing stairs. A 12-lead ECG shows signs of bradycardia with left bundle branch block. Her serum creatinine level is 2.1 mg/dL. What is the most appropriate next step?
A Conduct cardiac catheterization immediately.
B Proceed with surgery and evaluate risk status postoperatively.
C Administer an exercise ECG.
D Administer a dobutamine stress echocardiogram.
E Institute β-blockade.
Ref.: 1
Comments
This patient has a number of intermediate risk factors for perioperative cardiac complications, including an elevated serum creatinine level, limited exercise tolerance, left bundle branch block, and diabetes. It is possible that perioperative risk can be altered by preoperative testing and subsequent interventions. Provocative cardiac tests such as a dobutamine stress echocardiography further stratify risk and help identify patients who need further cardiac work-up or interventions.
Answer
D
References
1 Rogers MC, Tinker JH, Covino BG, et al, editors. Principles and practice of anesthesiology, ed 2, St. Louis: Mosby–Year Book, 1998.
2 Stoelting RK, editor. Pharmacology and physiology in anesthetic practice, ed 3, Philadelphia: JB Lippincott, 1999.
3 Sherwood ER, Williams CG, Prough DS. Anesthesiology principles, pain management, and conscious sedation. In Townsend CM, Beauchamp RD, Evers BM, et al, editors: Sabiston textbook of surgery: the biological basis of modern surgical practice, ed 18, Philadelphia: WB Saunders, 2008.
4 Dorian RS. Anesthesia of the surgical patient. In Brunicardi FC, Andersen DK, Billiar TR, et al, editors: Schwartz’s principles of surgery, ed 9, New York: McGraw-Hill, 2010.
5 De Lanzac KS, Thomas MA, Riopelle JM. Anesthesia. In O’Leary JP, editor: The physiologic basis of surgery, ed 4, Philadelphia: Lippincott Williams & Wilkins, 2008.
6 Rutter TW, Tremper KK. Anesthesiology and pain management. In Mulholland MW, Lillemoe KD, Doherty GM, et al, editors: Greenfield’s surgery: scientific principles and practice, ed 4, Philadelphia: Lippincott Williams & Wilkins, 2006.
7 Fleisher LA, Eagle KA. Clinical practice: lowering cardiac risk in noncardiac surgery. N Engl J Med. 2001;345:1677-1682.