Acid-Base Disorders USMLE Step 1 Practice Question
A 19-year-old woman with a history of generalized anxiety disorder presents to the emergency department with acute onset palpitations, dizziness, and tingling around her mouth and fingers. She reports feeling anxious and "out of control." Vital signs show BP 128/74 mmHg, HR 115 bpm, RR 35/min, SpO2 99% on room air. Physical examination is notable for positive Chvostek sign. Arterial blood gas analysis reveals: pH 7.54, PaCO2 26 mmHg, HCO3- 23 mEq/L. Serum calcium 8.6 mg/dL (normal 8.5-10.2), magnesium 1.8 mEq/L (normal), phosphate normal. ECG shows sinus tachycardia with no ischemic changes. Which of the following is the most appropriate next step in management?
Answer choices
- AAdminister intravenous calcium gluconate
- BStart supplemental oxygen at 2 L/min via nasal cannula
- CObtain chest radiograph and measure troponin levels
- DInstruct the patient to rebreathe expired air using a paper bag or plastic bagCorrect answer
- EAdminister sodium bicarbonate 50 mEq intravenously over 5 minutes
- FAdminister intravenous magnesium sulfate 2 g bolus
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations ā plus adaptive practice that targets your weak areas ā with a free MedBoardPRO account.