Association of delay to first intervention with return of spontaneous circulation in a swine model of cardiac arrest☆☆☆

Summary 

Objective

No single drug improves survival after cardiac arrest, despite success in animal studies. We sought to determine the duration of circulatory arrest after which maximal drug treatment and a rescue shock would fail to achieve return of spontaneous circulation (ROSC).

Design/subjects

Retrospective analysis of 271 swine (20–30kg) resuscitation attempts during ventricular fibrillation. Protocols were divided into five categories: immediate countershock, cardiopulmonary resuscitation (CPR) with standard-dose drugs, CPR alone, CPR and high-dose epinephrine (CPR+HDE) (0.1mg/kg), and CPR with a drug cocktail (CPR+DC) of propanolol (1mg), epinephrine (adrenaline) (0.1mg/kg) and vasopressin (40IU). Time to first CPR, time to first drug administration, time to first shock, and protocol were examined as predictors of ROSC using logistic regression with Hosmer–Lemeshow test of fit. Probability of ROSC was calculated from logistic curves.

Main results

ROSC occurred in 119 of the 271 swine (44%). Time to first drug and the CPR+DC group were predictors of ROSC. Time to first CPR, the CPR+DC group, and the CPR+HDE group were also predictors of ROSC. Time to first rescue shock, the CPR+DC group, and the CPR+HDE groups were predictors of ROSC. In the CPR+DC group, 50% ROSC occurred at a first CPR time of 13.4min, first drug time of 14.1min and first rescue shock time of 17.5min.

Conclusions

Pre-shock delivery of CPR+DC increases the likelihood of ROSC, and reaches 50% with a time of drug delivery of 14.1min. ROSC rates of 50% may be achievable using an optimized resuscitation in experimental CPR.

Keywords: Cardiopulmonary resuscitation (CPR), Resuscitation, Heart arrest, Animal model, Drug therapy, Swine