A 40-year-old woman with diabetic ketoacidosis has a serum potassium of 7.4 mEq/L. ECG shows tall, narrow-based peaked T waves with a shortened QT interval. Which drug is given first to protect the myocardium while other therapies shift potassium intracellularly?

• A IV insulin with dextrose
• B IV calcium gluconate ✓
• C IV salbutamol nebulization
• D Sodium polystyrene sulfonate orally

Explanation

Peaked T waves are the earliest ECG change in hyperkalemia. IV calcium gluconate stabilizes the cardiac membrane by raising the threshold potential, reducing excitability within minutes, though it does not lower serum potassium. Insulin with dextrose, salbutamol, and resins all lower potassium but act later or more slowly. Calcium is therefore the first drug administered, followed immediately by potassium-shifting measures such as insulin-dextrose.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.