The Cardiac Electrophysiology of Postresuscitation Hypokalemia in Dogs

Publisher Website
Google Scholar
Abstract
Hypokalemia has been observed in man after out‐of‐hospital ventricular fibrillation and after cardiover‐sion 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 < 0.01). At 60 minutes, ventricular fibrillation threshold was 8 ± 3 mA in ventricuJar 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 < 0.001). Right ventricular effective refractory periods after an 8‐beat drive at 200 msec were 121 ± 35 msec in the resuscitated animals versus 123 ± 19 msec in control animals 60 minutes after baseline (P = NS). In conclusion, postresuscitation hypokalemia had no effect on the ventricular fibrillation threshold or right ventricular effective refractory period in anesthetized dogs with structurally normal hearts prior to arrest.