Early defibrillation is critical for
ventricular fibrillation, but limited preclinical data and one human
trial suggest that performing cardiopulmonary resuscitation
before defibrillation may increase the likelihood of defibrillation
success and improve patient outcome. These investigators conducted a
prospective, randomized study to evaluate CPR before defibrillation
in patients with out-of-hospital (not witnessed by ambulance
personnel) VF.
Two hundred patients received either
standard care with immediate defibrillation or CPR for 3 minutes
followed by defibrillation. In the standard-care group, if initial
defibrillation was not successful, patients received CPR for 1
minute before defibrillation was attempted again. The CPR and
standard-care groups did not differ in the primary outcome measure
of survival to discharge (22% vs. 15%) or in the secondary outcome
measures of return of spontaneous circulation (ROSC; 56% vs. 46%)
and 1-year survival (20% vs. 15%). In a subgroup of 81 patients with
ambulance response times less than 5 minutes, there also were no
differences between the CPR and standard-care groups. However, in a
subgroup of 119 patients with ambulance response times greater than
5 minutes, the CPR group had significantly higher rates than did the
standard-care group in survival to discharge (22% vs. 4%), ROSC (58%
vs. 38%), and 1-year survival (20% vs. 4%).
Comment: In patients with VF arrest for whom
out-of-hospital care is delayed for more than 5 minutes, the lack of
oxygen and depletion of metabolic substrates and high-energy
phosphate stores may diminish the effectiveness of applied electricity.
The promising result -- that CPR was beneficial in patients with
longer response times -- must be corroborated before we stratify
patients into different management pathways.
— John A. Marx, MD, FACEP
Published in Journal Watch Emergency Medicine May 14, 2003