THE USMLE TIMES - #87
Welcome to issue #87 of The USMLE Times… We’ve now posted The USMLE TIMES newsletter eighty-seven weeks in a row! Welcome to the 166 new members of the community 👋
Here’s what’s on tap for issue #87 of the USMLE Times:
Question of the Week (Multisystemic disorders)
This week’s video training (50 Step 1 Tips)
Question deep-dive & breakdown
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Let’s dive in!
A 72-year-old female presents to the emergency department with confusion and generalized weakness. She has a history of congestive heart failure and has been taking a diuretic for the past three months. Vital signs reveal a blood pressure of 100/65 mmHg and a heart rate of 85/minute. Laboratory studies show a serum sodium of 120 mEq/L, serum osmolality of 260 mOsm/kg, and a urine osmolality of 450 mOsm/kg. Which of the following consequences is most likely to occur if her electrolyte abnormality is corrected too quickly?
A) Seizures, visual disturbances, and severe headache
B) Memory impairment, confabulation, and ataxia
C) Ascending weakness, areflexia, and sensory deficits
D) Episodic muscle weakness with periods of remission
E) Sudden onset of dysarthria, dysphagia, and quadriplegia
F) Rapid decrease in intracranial pressure and brain herniation
G) Hyperventilation, Kussmaul respirations, and tachycardia
The answer & question breakdown is at the bottom of the post.
🔗 LINKS TO RECENT POSTS
USMLE Times Issue #86 - READ HERE
USMLE Times Issue #85 - READ HERE
USMLE Times Issue #84 - READ HERE
ANSWER + QUESTION BREAKDOWN
The Mental Model for this week’s question:
Step 1. Identify the question’s goal (ID the most concerning consequence if the electrolyte abnormality is corrected too quickly).
Step 2. Identify the electrolyte abnormality.
Step 3. Ask yourself what would happen if it (the electrolyte abnormality) was corrected too quickly.
Step 4. Look to the answer choices and find the answer that most closely resembles your hypothesis (remember to trust your instincts; don’t get pulled into anything that doesn’t match with your hypothesis).
GENERAL ANALYSIS
This question involves a 72-year-old female with confusion and generalized weakness, a history of congestive heart failure, and recent diuretic use. Her laboratory studies reveal hyponatremia with a serum sodium of 120 mEq/L, serum osmolality of 260 mOsm/kg, and urine osmolality of 450 mOsm/kg. The task is to determine the most likely consequence if her electrolyte abnormality (hyponatremia) is corrected too quickly.
ANSWER CHOICES:
ANSWER CHOICE A: Seizures, visual disturbances, and severe headache
These symptoms can be associated with various neurological conditions, including severe hyponatremia, but they are not specific to the rapid correction of hyponatremia.
ANSWER CHOICE B: Memory impairment, confabulation, and ataxia
These symptoms are characteristic of Wernicke-Korsakoff syndrome, typically associated with chronic alcoholism and thiamine deficiency.
ANSWER CHOICE C: Ascending weakness, areflexia, and sensory deficits
These symptoms are characteristic of Guillain-Barré syndrome, an autoimmune condition affecting the peripheral nervous system.
ANSWER CHOICE D: Episodic muscle weakness with periods of remission
These symptoms are characteristic of periodic paralysis, which can be associated with various electrolyte imbalances but not specifically related to hyponatremia correction.
ANSWER CHOICE E: Sudden onset of dysarthria, dysphagia, and quadriplegia
These symptoms are characteristic of osmotic demyelination syndrome (central pontine myelinolysis), which can occur if hyponatremia is corrected too quickly.
ANSWER CHOICE F: Rapid decrease in intracranial pressure and brain herniation
These symptoms are associated with conditions that cause a rapid shift in intracranial pressure, such as trauma or severe cerebral edema.
ANSWER CHOICE G: Hyperventilation, Kussmaul respirations, and tachycardia
These symptoms are characteristic of metabolic acidosis, particularly diabetic ketoacidosis.
FINAL VERDICT…
The patient presents with chronic hyponatremia, likely secondary to diuretic use and possibly exacerbated by congestive heart failure. The serum sodium level is significantly low at 120 mEq/L, and the serum osmolality is also low, indicating hypotonic hyponatremia. The urine osmolality is high, suggesting that the kidneys are concentrating urine, which is common in conditions where antidiuretic hormone is inappropriately elevated.
The primary concern with correcting chronic hyponatremia too quickly is the risk of osmotic demyelination syndrome, also known as central pontine myelinolysis. This condition occurs when the rapid increase in serum sodium levels causes water to move out of brain cells too quickly, leading to cellular dehydration and demyelination. The clinical manifestations of ODS include sudden onset of severe neurological symptoms such as dysarthria, dysphagia, and quadriplegia.
In summary, the most likely consequence of correcting the patient's electrolyte abnormality (hyponatremia) too quickly is osmotic demyelination syndrome, characterized by the sudden onset of dysarthria, dysphagia, and quadriplegia, making option E the correct answer.
FINAL ANSWER: E: Sudden onset of dysarthria, dysphagia, and quadriplegia
That’s it for issue #87 of The USMLE Times!
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