The Effect of the Preshock Pause on Coronary Perfusion Pressure Decay and Rescue Shock Outcome in Porcine Ventricular Fibrillation

Abstract

Objective. We sought to determine the effect of the preshock pause (PSP) on coronary perfusion pressure (CPP) decay and subsequent rescue shock (RS) outcome in porcine ventricular fibrillation (VF). Methods. Retrospective analysis of digitally recorded CPP tracings was performed. Ventricular fibrillation was electrically induced in all animals and resuscitation was standardized in all experiments. The first RS was delivered after an average of 10.8 minutes of VF (7.4 minutes of nontreatment and 3.4 minutes of resuscitation). The continuous CPP tracing segments, during the hands-off period prior to the first two rescue shocks, were imported into a spreadsheet and analyzed using descriptive statistics as well as univariate and multivariate statistical methods. The RS outcome for each animal was recorded as failed or return of spontaneous circulation (ROSC) (a systolic blood pressure of 80 mmHg or greater, sustained continuously for at least 1 minute). Results. We included 196 rescue shocks (120 first RS [RS1], 76 second RS [RS2]) from 120 swine. The mean CPP following the last compression before RS was 23.4 mmHg (standard error of the mean [SEM]: 1.3). The median PSP duration was 4.1 seconds (interquartile range [IQR]: 3.3, 6.1). The mean CPP just prior to RS was 7.6 mmHg (SEM: 0.6). Overall, the RS was successful (ROSC) in 57 of 120 (0.47 [95% confidence interval (CI): 0.38, 0.56]) attempts. Univariate results showed a counterintuitive positive correlation between PSP and maximum CPP for RS1 (r = 0.548, p < 0.001). Conclusion. During the resuscitation PSP in these porcine studies of prolonged VF, CPP dropped precipitously, but RS outcome was not adversely affected.

Key words:

• cardiopulmonary resuscitation (CPR)
• resuscitation
• heart arrest
• animal model
• coronary perfusion pressure
• swine
• preshock pause