Setting: hospital ward
CC: “I feel tired and confused.”
VS: BP: 102/72 mm Hg; P: 104 beats/minute; R: 23 breaths/minute
HPI: A 27-year-old man came to the ED yesterday after head trauma and loss of consciousness from a motorcycle accident. The initial head CT was normal. He was visibly intoxicated from alcohol and it was unsafe to discharge him without reliable observation. After a few hours, he improved, but now he is confused again.
PMHX/Medications: none
PE:
Neurological: lethargic, confused, and unable to name the date, the president, or the place where he is right now; focal neurological signs cannot be assessed because of patient confusion
Heart, Lungs, Abdomen: normal
Except for reflexes, the neurological examination is based on the ability of the patient to follow commands.
You cannot assess papilledema with a confused person. The head needs to be still.
Initial Orders:
Head CT
CHEM-7
Oximeter
Liver function
Urine toxicology screen
Delirium tremens cannot start on the same day as the last drink.
Alcohol withdrawal is based on the stiffening of cell membrane, which is missing the “relaxing” effect of alcohol.
Report:
Head CT: no bleeding
CHEM-7: sodium 165 mEq/L (normal 135−145 mEq/L); BUN 45 g/dL; creatinine 1.8 mg/dL
Oximeter: normal
Liver function: normal
Urine toxicology screen: no opiates; cocaine and marijuana present
Which of the following is most likely to kill a person who is in withdrawal?
a. Marijuana
b. Alcohol
c. Cocaine
d. Opiates
Answer b. Alcohol
Alcohol can kill a person who is intoxicated or in withdrawal with neurological toxicity. No one has ever died from marijuana intoxication or withdrawal. Marijuana is damaging to short-term memory. This is reversible after abstention for 1 month. This patient is confused because of dehydration.
Dehydration
• High sodium level
• High BUN-to-creatinine ratio >20:1
Order dextrose 5% in water (D5W) as soon as you know that the patient has dehydration. NS will help as well, but because there seems to be a free water deficit, then give free water. The intake and output on the patient has not been recorded. There is no way to assess how much urine he has been putting out over the past day.
Orders:
Bolus D5W and continuous
Repeat CHEM-7
UA
Urine sodium and urine osmolarity
Monitor input and output
D5W acts as free water replacement.
One hundred percent free water would cause hemolysis.
Dextrose prevents hemolysis.
What happens to the dextrose in D5W?
a. It enters the RBC.
b. It is metabolized.
c. Nothing, it stays in circulation in plasma.
d. It is converted into protein.
Answer b. It is metabolized.
D5W is, essentially, pure free water replacement. You cannot give water alone as IV fluids because it would lead to hemolysis in the veins through which it was being infused. The point of the dextrose is to keep the fluid from being so hypotonic or hyposmolar that cells would swell and burst. The pancreas senses the dextrose as sugar. Insulin will put the excess sugar into storage as glycogen or triglycerides (adipose), or the dextrose will simply be consumed as fuel for cells. No matter the metabolic pathway, to storage or consumption, the dextrose goes away, and only the water is left in the body.
Hypernatremia and Dehydration
• High Urine Output = Diabetes Insipidus
• Low Urine Output = Dehydration
Advance the clock 1 hour, then a second hour, and assess the urine output and urine laboratory test values. Nurses report two urinations over the next 2 hours with 400 mL in each one. Normal urine output is 0.5 to 1 mL/kg per hour so this is voluminous, especially considering hypernatremia.
Reports:
Sodium: 167 mEq/L
UA: no white blood cells (WBCs); specific gravity 1.002
Urine sodium: 12 mEq/L
Urine osmolarity: 80 mOsm/kg
Normally, where is the point of maximum osmolarity of the kidney?
a. Glomerular capsule
b. The tip of the loop of Henle
c. The TAL of the loop of Henle
d. DCT
Answer b. The tip of the loop of Henle
Maximum osmolarity should be 1200 mOsm/kg and should be at the tip of the loop of Henle. The ability of any species to survive in hostile environments facing dehydration is based on how high the osmolarity can be made at the tip of the loop of Henle.
Minimum concentration: distal tubule
Orders:
D5W bolus and continuous
Desmopressin acetate (DDAVP) IV
DDAVP can be given IV, by nasal spray, or subcutaneously.
On CCS, if you order a test and a treatment at the same time, the test is done first. So to see the effect of the DDAVP, you have to move the clock forward and repeat the testing. If you order both the urine osmolarity and the vasopressin at the same time, it will not reflect the effect of the drug. CCS does not have delays in the administration of drugs or obtaining tests and results as you would in real life.
Advance the clock 30 minutes. This should be enough time to see an effect of the DDAVP on the urine osmolarity, sodium, and volume. If the patient is severely confused, transfer the patient to the ICU.
After vasopressin administration, which values are consistent with central diabetes insipidus (CDI)?
Answer b. Urine osmolarity 700 mOsm/kg (rises), urine sodium 60 mEq/L (rises), urine volume drops.
CDI will normalize in response to vasopressin administration, nephrogenic diabetes insipidus (NDI) will not. You do not have to see a maximal increase in urine osmolarity (1200 mOsm/kg) in response to vasopressin. You just have to see a significant rise in urine osmolarity and a drop in urine volume. Patients with diabetes insipidus (DI) urinate so much that a decrease in volume in response to vasopressin should be obvious within 1 to 2 hours.
Nephrogenic DI results from hypercalcemia and hypokalemia.
Orders:
Urine sodium
Urine osmolarity
CHEM-7
Do frequent neurological examinations on patients with severe DI. Rapid increases in serum sodium levels can lead to markedly worsening mental status and seizures.
Report:
Urine sodium: 48 mEq/L
Urine osmolarity: 550 mOsm/kg
CHEM-7: sodium 165 mEq/L
What mechanism is responsible for the development of DI in this patient?
a. Alcohol effect on the kidney
b. Trauma to the hypothalamus
c. Undiagnosed electrolyte disturbance
d. Damage to the stalk of the pituitary gland
Answer d. Damage to the stalk of the pituitary gland
Head trauma most often produces a temporary CDI from damage to the pituitary stalk. When the stalk alone is damaged, the hypothalamus is still producing ADH. To have permanent CDI, there has to be loss of both storage of ADH in the posterior pituitary as well as the production of ADH. Electrolyte (calcium, potassium) disturbance and alcohol cause nephrogenic DI, not central DI.
How much fluid is missing or needs to be replaced in this patient?
a. Two liters
b. Five liters
c. Cannot be determined with present information
Answer c. Cannot be determined with present information
You must have the patient’s weight to know. You must calculate the fluid deficit to know how much water to give. You cannot determine how much fluid is missing without the body weight.
• Men: 60% is water weight
• Women: 50% is water weight
This patient’s sodium is 165 mEq/L, which is 25 points above the normal value of 140 mEq/L. There is about 20% of fluid missing (18% to be absolutely precise). (A man weighing 100 kg will have 60 L of water. Sixty percent of 100 kg is 60 L, and 20% of that is 12 L.) This person’s fluid deficit is 10 to 12 L, but you cannot determine that without knowing the body weight.
Move the clock forward; hydration (D5W) and vasopressin continue to be given.
Repeat CHEM-7: sodium 154 mEq/L
Do not lower the sodium more than 0.5 to 1 mEq/h or the patient will seize.
Why do seizures develop with a rapid decrease in sodium level?
a. Hemolysis
b. Cerebral edema
c. Myelinolysis
d. Renal failure
Answer b. Cerebral edema
When the plasma osmolarity is rapidly decreased, the cells of the brain are relatively hypertonic, or hyperosmolar compared to plasma. This will result in brain edema and seizures. All sodium level changes (up or down) must occur slowly.
A high sodium level in brain cells results in osmotic draw into cells, causing edema.
Correct the sodium level over 2 to 3 days. When the neurological examination normalizes, the patient can be transferred out of the ICU. You cannot tell if the CDI will be permanent until you observe the patient over time.