Acid-Base Disorders USMLE Step 1 Practice Question
A 71-year-old man with stage 4 chronic kidney disease and hypertension presents with fatigue and nausea. Labs show pH 7.32, HCO3- 14 mEq/L, PaCO2 32 mmHg, K+ 6.2 mEq/L, BUN 78 mg/dL, and creatinine 5.1 mg/dL. Which acid-base disorder is present, and what is the expected PaCO2 by Winter's formula?
Answer choices
- AMetabolic acidosis; expected PaCO2 32-36 mmHg
- BMetabolic acidosis; expected PaCO2 14-18 mmHgCorrect answer
- CMixed metabolic and respiratory acidosis; expected PaCO2 40 mmHg
- DHigh anion gap acidosis; expected PaCO2 50-55 mmHg
- ERespiratory acidosis; expected PaCO2 42-48 mmHg
- FMetabolic alkalosis; expected PaCO2 48-52 mmHg
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