A 65-year-old man with CKD stage 4 (eGFR 22 mL/min) presents with serum potassium of 6.8 mEq/L. ECG shows tall peaked T-waves, widened QRS (140 ms), and a sine-wave pattern. He is alert and blood pressure is stable. What is the IMMEDIATE first step in management?
- A IV insulin + dextrose to shift potassium intracellularly
- B Sodium bicarbonate infusion
- C IV calcium gluconate to stabilize the cardiac membrane ✓
- D Sodium polystyrene sulfonate (Kayexalate) orally
Explanation
In severe hyperkalemia with ECG changes (peaked T-waves, wide QRS, sine-wave pattern), the immediate priority is cardiac membrane stabilization with IV calcium gluconate (10 mL of 10% solution over 2–3 minutes), which antagonizes the depolarizing effect of hyperkalemia on myocardial cells within 1–3 minutes without lowering serum potassium. This buys time before definitive potassium-lowering measures. Insulin + dextrose shifts potassium intracellularly (onset 15–30 min) and is the second step. Sodium bicarbonate is adjunctive, particularly if metabolic acidosis is present. Kayexalate removes potassium from the body but has slow onset (hours) and is inappropriate as first-line therapy for life-threatening ECG changes.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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