The cardiac electrophysiology of postresuscitation hypokalemia in dogs.

Hypokalemia has been observed in man after out-of-hospital ventricular fibrillation and after cardioversion from ventricular tachycardia in the electrophysiology laboratory, and also in dogs following ventricular fibrillation (maximal effect 45-60 minutes after resuscitation). Since the electrophysiological effects of postresuscitation hypokalemia are unknown, we evaluated the effects of this hypokalemia on ventricular fibrillation thresholds (group 1) and on right ventricular effective refractory periods (group 2). In both groups, anesthetized dogs with normal hearts were divided into experimental animals that had 2 minutes of ventricular fibrillation followed by cardioversion without medications and control animals without ventricular fibrillation. In group 1, we measured serum potassium before ventricular fibrillation (or time 0 in control dogs) and then measured potassium and ventricular fibrillation threshold at 45, 60, 75, and 90 minutes after baseline. In group 2 animals we measured right ventricular effective refractory periods and serum potassium at baseline and sequentially from 7 to 180 minutes after resuscitation. In group 1, the maximum change in potassium from baseline was -0.8 +/- 0.3 mEq/L at 60 minutes after resuscitation as compared to -0.1 +/- 0.3 mEq/L in control animals at 60 minutes (P less than 0.01). At 60 minutes, ventricular fibrillation threshold was 8 +/- 3 mA in ventricular fibrillation animals and 7 +/- 3 mA in control animals (P = NS). In group 2 animals, the maximum change in serum potassium also occurred 60 minutes after resuscitation and was -0.8 +/- 0.3 mEq/L as compared to -0.2 +/- 0.2 mEq/L in control animals (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)