Comparison of adrenergic agonists for the treatment of ventricular fibrillation and pulseless electrical activity

Risk factor analyses for the return of spontaneous circulation in the asphyxiation cardiac arrest porcine model

Background:

Animal models of asphyxiation cardiac arrest (ACA) are frequently used in basic research to mirror the clinical course of cardiac arrest (CA). The rates of the return of spontaneous circulation (ROSC) in ACA animal models are lower than those from studies that have utilized ventricular fibrillation (VF) animal models. The purpose of this study was to characterize the factors associated with the ROSC in the ACA porcine model.

Methods:

Forty-eight healthy miniature pigs underwent endotracheal tube clamping to induce CA. Once induced, CA was maintained untreated for a period of 8 min. Two minutes following the initiation of cardiopulmonary resuscitation (CPR), defibrillation was attempted until ROSC was achieved or the animal died. To assess the factors associated with ROSC in this CA model, logistic regression analyses were performed to analyze gender, the time of preparation, the amplitude spectrum area (AMSA) from the beginning of CPR and the pH at the beginning of CPR. A receiver-operating characteristic (ROC) curve was used to evaluate the predictive value of AMSA for ROSC.

Results:

ROSC was only 52.1% successful in this ACA porcine model. The multivariate logistic regression analyses revealed that ROSC significantly depended on the time of preparation, AMSA at the beginning of CPR and pH at the beginning of CPR. The area under the ROC curve in for AMSA at the beginning of CPR was 0.878 successful in predicting ROSC (95% confidence intervals: 0.773∼0.983), and the optimum cut-off value was 15.62 (specificity 95.7% and sensitivity 80.0%).

Conclusions:

The time of preparation, AMSA and the pH at the beginning of CPR were associated with ROSC in this ACA porcine model. AMSA also predicted the likelihood of ROSC in this ACA animal model.

Adrenaline, cardiac arrest, and evidence based medicine

In this article we review the evidence supporting the clinical application of adrenaline in cardiopulmonary arrest, and summarize the receptor effects of catecholamines and the basic principles producing perfusion during CPR. Animal and human studies show that in cardiac arrest, adrenaline has positive haemodynamic effects, increasing systemic pressures, myocardial perfusion, and cerebrally directed flow. The problems extrapolating from animal to human data are highlighted. Studies showing improvements in short term survival outcomes with high dose regimens have not been confirmed by other large prospective randomised trials. There is no evidence that high doses of adrenaline improve survival to hospital discharge. Most studies comparing adrenaline with placebo have been non-randomised and uncontrolled, with major methodological problems. Conclusions are difficult, but if anything adrenaline is associated with poorer outcomes.