Hyperkalemia and the electrocardiogram in dogs.

Rapid i.v. injection of 2 ml KCl solution with 0.1 mmol/kg abruptly doubles the basal concentration of coronary artery serum K and produces no ECG change; 2 ml with 0.3 mmol KCl/kg quadruples it and provokes fibrillation of the ventricular myocardium in 18 s, there is no visible effect on atrial activity. Continuous infusion of 2 mEq KCl/kg body weight gradually doubles basal serum K concentration and produces ECG changes that herald the imminent onset of ventricular fibrillation. Ventricular myocardium and, especially, the sinus node are more tolerant of transient than of prolonged hyperkalemia.