A 19-year-old man with type 1 diabetes presents with vomiting, abdominal pain, Kussmaul breathing, glucose 480 mg/dL, pH 7.08, and serum potassium 3.4 mEq/L. Intravenous normal saline is started. What is the most appropriate next step regarding potassium?
- A Withhold potassium until serum potassium falls below 3.0 mEq/L
- B Start potassium replacement immediately along with the insulin infusion ✓
- C Give sodium bicarbonate before any potassium
- D Delay all therapy until serum potassium is documented twice
Correct answer: B. Start potassium replacement immediately along with the insulin infusion
Explanation
Insulin drives potassium into cells and will precipitate hypokalaemia in a patient who is already at the lower end of normal (3.4 mEq/L). Potassium 20 to 30 mEq/L of infusion should be added once the patient has adequate urine output, before or with insulin. Bicarbonate is reserved for pH below about 6.9 and is not given here. Waiting for a lower value risks fatal arrhythmia.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.