Hyperkalemia (K⁺ > 6.5 mEq/L) with ECG changes (peaked T-waves, widened QRS) is a life-threatening emergency due to risk of fatal ventricular arrhythmias.

The immediate priority is cardiac membrane stabilization:

1. Calcium gluconate IV (IMMEDIATE) — stabilizes cardiac cell membrane within 1–3 minutes. Does NOT lower serum K⁺ but protects the heart.
2. Sodium bicarbonate IV — shifts K⁺ into cells (takes 15–30 min)
3. Insulin + Dextrose — shifts K⁺ intracellularly
4. Kayexalate (sodium polystyrene sulfonate) — removes K⁺ from body
5. Dialysis — definitive treatment in renal failure

Remember the mnemonic for hyperkalemia management: C-BIG-K-Drop (Calcium, Bicarbonate, Insulin+Glucose, Kayexalate, Dialysis).