Acid-Base Disorders USMLE Step 1 Practice Question
A 46-year-old man presents with 3 days of weakness and lightheadedness following broad-spectrum antibiotic initiation. He reports profuse watery diarrhea. Vital signs: BP 118/76 mmHg, HR 102/min, RR 20/min, temperature 37.2°C. Serum electrolytes reveal Na+ 138 mEq/L, Cl− 112 mEq/L, and HCO3− 16 mEq/L. Arterial pH is 7.28. Urine electrolytes are normal. Which acid-base disorder best explains these findings?
Answer choices
- ARespiratory acidosis
- BRespiratory alkalosis
- CNonanion gap metabolic acidosisCorrect answer
- DMetabolic alkalosis
- EAnion gap metabolic acidosis
- FMixed metabolic acidosis and respiratory alkalosis
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