Electrolyte Disorders USMLE Step 1 Practice Question
A 34-year-old man with type 1 diabetes presents with Kussmaul respirations, confusion, and fruity breath. Vital signs show BP 102/68, HR 118, RR 24, temp 37.2°C. Labs reveal glucose 456 mg/dL, pH 7.18, HCO3- 12 mEq/L, K+ 5.8 mEq/L, anion gap 18, and elevated beta-hydroxybutyrate. Urine ketones are present; troponin is normal. Which mechanism best explains the pseudohypokalemia in this patient?
Answer choices
- AInsulin deficiency impairs Na-K-ATPase function and potassium uptake
- BOsmotic diuresis causes selective urinary potassium wasting
- CHypertonicity causes water and potassium shift from intracellular to extracellular spaceCorrect answer
- DGlucagon excess stimulates renal potassium secretion
- EMetabolic acidosis directly increases serum potassium via H+ and K+ exchange
- FBeta-hydroxybutyrate accumulation causes competitive inhibition of potassium reabsorption in the distal convoluted tubule
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