During major vascular surgery, a patient develops serum potassium of 6.8 mEq/L with peaked T waves on ECG. Which intervention has the FASTEST onset to stabilise the cardiac membrane?

• A IV sodium bicarbonate 50 mEq over 5 minutes
• B IV regular insulin 10 units with 50% dextrose 50 mL
• C IV calcium gluconate 1 g over 2–3 minutes ✓
• D IV salbutamol 0.5 mg over 15 minutes

Explanation

Calcium gluconate (or chloride) acts within 1–3 minutes to antagonise the toxic effect of hyperkalaemia on cardiac myocytes by raising the threshold potential, thereby stabilising the membrane. It does not lower serum potassium but provides immediate cardiac protection. Insulin+dextrose shifts potassium intracellularly (onset 15–30 minutes), sodium bicarbonate promotes K+ shift (onset 30 minutes), and salbutamol also has a slower onset and is less reliable in critically ill patients. Calcium is always the first step when ECG changes are present.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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