Acid-Base Disorders USMLE Step 1 Practice Question
A 64-year-old man with multilobar pneumonia and sepsis presents with hypoxemic respiratory failure requiring intubation. Vital signs: BP 92/58, HR 118, RR 32, Temp 39.2°C, SpO2 88%. Arterial blood gas shows pH 7.36, PaCO2 20 mm Hg, HCO3− 11 mEq/L. Serum lactate is 8.2 mg/dL (markedly elevated); creatinine is normal. He denies recent medication use. Which acid-base disturbance best characterizes his current status?
Answer choices
- AMixed respiratory alkalosis and metabolic acidosisCorrect answer
- BMixed respiratory acidosis and metabolic acidosis
- CPure metabolic alkalosis
- DPure respiratory alkalosis
- EPure metabolic acidosis with appropriate compensation
- FPure respiratory alkalosis without metabolic acidosis in sepsis
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