Electrolyte Disorders USMLE Step 1 Practice Question
A 45-year-old woman with a 10-year history of hypertension managed with lisinopril presents to the emergency department with acute onset generalized muscle weakness and palpitations. Vital signs show blood pressure 158/92 mmHg and heart rate 102 bpm with an irregular rhythm. Physical examination reveals diminished grip strength bilaterally. Laboratory studies are notable for serum potassium 7.1 mEq/L, creatinine 1.0 mg/dL (baseline 0.9 mg/dL), and normal calcium. A 12-lead EKG demonstrates peaked T waves, prolonged PR interval, and widened QRS complex. Which of the following is the most appropriate initial intervention?
Answer choices
- AAdminister sodium polystyrene sulfonate 15 grams orally
- BInitiate insulin 10 units IV bolus with 25 grams dextrose
- CAdminister calcium gluconate 10% solution IV slowlyCorrect answer
- DAdminister normal saline 500 mL IV bolus over 30 minutes
- EDiscontinue lisinopril and recheck potassium in 4 hours
- FAdminister furosemide 40 mg IV and increase sodium intake
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.