A 24-year-old man with type 1 diabetes presents drowsy with deep sighing respiration. Glucose is 540 mg/dL, pH 7.08, bicarbonate 5 mEq/L, urine ketones strongly positive. Serum potassium is 3.0 mEq/L. What is the correct next step in management?
- A Start intravenous regular insulin immediately at 0.1 units/kg/hour
- B Give sodium bicarbonate 100 mmol intravenously
- C Give intravenous potassium replacement before starting insulin infusion ✓
- D Start half-strength saline at 500 mL/hour
Correct answer: C. Give intravenous potassium replacement before starting insulin infusion
Explanation
Insulin drives potassium into cells and can precipitate fatal hypokalaemia when the serum level is already below 3.3 mEq/L. Potassium must be replaced first, and insulin started once the level exceeds 3.3 mEq/L. Bicarbonate is reserved for pH below 6.9, not 7.08. Isotonic saline remains the initial fluid of choice; hypotonic saline is used later once corrected sodium is high.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.