A 65-year-old man with CKD stage G4 (eGFR 22 mL/min) develops serum potassium of 6.8 mEq/L with peaked T waves on ECG. His current medications include lisinopril, spironolactone, and trimethoprim-sulfamethoxazole. The FIRST intervention for cardiac membrane stabilisation in hyperkalaemia with ECG changes is:

• A Sodium bicarbonate IV infusion
• B Insulin 10 units IV with 50% dextrose 50 mL
• C Salbutamol nebulisation 10–20 mg
• D Calcium gluconate 10% (10 mL) IV over 2–3 minutes ✓

Explanation

When hyperkalaemia causes ECG changes (peaked T waves, PR prolongation, wide QRS), the immediate priority is membrane stabilisation with calcium gluconate IV, which antagonises the cardiac toxicity of potassium within 1–3 minutes. This does not lower serum potassium but protects against arrhythmia while potassium-lowering measures (insulin-dextrose, salbutamol, resonium) are initiated. Bicarbonate helps but is slower; insulin-dextrose shifts K+ intracellularly but does not instantly stabilise cardiac membranes.

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

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Written and medically reviewed by the StethoPrep medical team.