Electrocardiographic (ECG) changes in hyperkalemia are striking if present and include peaked T-waves, varying degrees of A-V block, QRS-interval widening, or diminutive or lost P-waves. However, the severely hyperkalemic patient (a) does not progress through these ECG changes in a predictable sequence and (b) may not have any of these changes. A benign ECG can move to ventricular fibrillation with no intervening changes. ECG changes alone are not sensitive enough to use their absence to dismiss the danger of hyperkalemia. Regardless of ECG changes, a serum K⁺ of ≥6.0 meq/L merits prompt therapy to rapidly stabilize the myocardium to protect against arrhythmias and to rapidly lower extracellular K⁺ via shifting toward intracellular stores, with an eye toward more definitive therapy thereafter. Values in the range of 5.0 to 5.9 meq/L are also cause for concern if a trend of continuing increase is expected. Otherwise, elevations to this degree (5.0 to 5.9 meq/L) may be treated with definitive therapies alone or simply minimization of offensive medications or K⁺ intake.

Immediate Therapy (for Cardiac Myocyte Membrane Stabilization to Prevent Arrhythmia). Generally reserved for K⁺ levels ≥6.0 meq/L, intravenous calcium salts (most commonly 10 cc [one ampule] of 10% calcium gluconate solution) are usually given concurrently with the short-acting therapies discussed next. The effect is rapid (onset 1 to 3 min) but brief (30 to 60 min).