Delaying Defibrillation to Give Basic Cardiopulmonary Resuscitation to Patients With Out-of-Hospital Ventricular Fibrillation A Randomized Trial
This review may be edited
Posted By: Anthony Delaney
Posted Date: 23/3/03
Title: Delaying Defibrillation to Give Basic Cardiopulmonary Resuscitation to Patients With Out-of-Hospital Ventricular Fibrillation A Randomized Trial
Authors: Lars Wik, MD, PhD; Trond Boye Hansen; Frode Fylling; Thorbjørn Steen, MD; Per Vaagenes, MD, PhD; Bjørn H. Auestad, PhD; Petter Andreas Steen, MD, PhD
Reference: JAMA. 2003;289:1389-1395.
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Context Defibrillation as soon as possible is standard treatment for patients with ventricular fibrillation. A nonrandomized study indicates that after a few minutes of ventricular fibrillation, delaying defibrillation to give cardiopulmonary resuscitation (CPR) first might improve the outcome.
Objective To determine the effects of CPR before defibrillation on outcome in patients with ventricular fibrillation and with response times either up to or longer than 5 minutes.
Design, Setting, and Patients Randomized trial of 200 patients with out-of-hospital ventricular fibrillation in Oslo, Norway, between June 1998 and May 2001. Patients received either standard care with immediate defibrillation (n = 96) or CPR first with 3 minutes of basic CPR by ambulance personnel prior to defibrillation (n = 104). If initial defibrillation was unsuccessful, the standard group received 1 minute of CPR before additional defibrillation attempts compared with 3 minutes in the CPR first group.
Main Outcome Measure Primary end point was survival to hospital discharge. Secondary end points were hospital admission with return of spontaneous circulation (ROSC), 1-year survival, and neurological outcome. A prespecified analysis examined subgroups with response times either up to or longer than 5 minutes.
Results In the standard group, 14 (15%) of 96 patients survived to hospital discharge vs 23 (22%) of 104 in the CPR first group (P = .17). There were no differences in ROSC rates between the standard group (56% [58/104]) and the CPR first group (46% [44/96]; P = .16); or in 1-year survival (20% [21/104] and 15% [14/96], respectively; P = .30). In subgroup analysis for patients with ambulance response times of either up to 5 minutes or shorter, there were no differences in any outcome variables between the CPR first group (n = 40) and the standard group (n = 41). For patients with response intervals of longer than 5 minutes, more patients achieved ROSC in the CPR first group (58% [37/64]) compared with the standard group (38% [21/55]; odds ratio [OR], 2.22; 95% confidence interval [CI], 1.06-4.63; P = .04); survival to hospital discharge (22% [14/64] vs 4% [2/55]; OR, 7.42; 95% CI, 1.61-34.3; P = .006); and 1-year survival (20% [13/64] vs 4% [2/55]; OR, 6.76; 95% CI, 1.42-31.4; P = .01). Thirty-three (89%) of 37 patients who survived to hospital discharge had no or minor reductions in neurological status with no difference between the groups.
Conclusions Compared with standard care for ventricular fibrillation, CPR first prior to defibrillation offered no advantage in improving outcomes for this entire study population or for patients with ambulance response times shorter than 5 minutes. However, the patients with ventricular fibrillation and ambulance response intervals longer than 5 minutes had better outcomes with CPR first before defibrillation was attempted. These results require confirmation in additional randomized trials.
Are the Results Valid?
1. Was the assignment of patients to treatments randomized? ( Was allocation concealment maintained?)
Yes, the ambulance personnel opened a sealed envelope with the treatment assignment after confirming VF/VT.
2. Were all patients who entered the trial properly accounted for and attributed at its conclusion?
2a. Was followup complete?
For the primary outcome measure of survival to hospital discharge, follow up was complete
2b. Were patients analyzed in the groups to which they were randomized?
Yes it appears that all patients were analysed in the groups to which they were randomised
3. Were patients, health workers, and study personnel blind to treatment?
The ambulance personnel were not blinded to the treatment allocation. The hospital personnel and the physicians responsible for assessing neurological outcome were blinded to the treatment allocation.
4. Were the groups similar at the start of the trial?
The patients were similar at the start of the trial with respect to the characteristics presented in table 1, apart from the time to first defibrillation attempt (ie the intervention being studied).
5. Aside from the experimental intervention, were the groups treated equally?
Yes, apart from the intervention being studied, both groups were treated according to a protocol based on the 1998 European Resuscitation Council guidelines.
What are the Results?
1. How large was the treatment effect?
22% of patients in the treatment group were discharged from hospital alive, compared to 15% in the standard therapy group. This result was statistically non-significant (p=0.2).
In a pre-specified subgroup of patients who had a response time of longer than 5 minutes the survival to hospital discharge was 22% in the treatment group compared to 4% in the standard therapy group which was statistically significantly different (p=0.006). This represents an absolute risk reduction of 17%.
2. How precise was the estimate of the treatment effect?
The odds ratio for the primary outcome measure was 1.66 favouring CPR first with 95% CI from 0.8-3.46.
For patients with a response time longer than 5 minutes the odds ratio was 7.42 with 95% CI from 1.66-34.3
Will the Results Help Me In Caring For My Patients?
1. Can the results be applied to my patient care?
There was a predominance of males in the study which may not be representative of other populations. Apart from this there is nothing reported that would limit the generalizabilty of the results.
2. Were all clinically important outcomes considered?
The rates of "good" neurological survival were examined and there was no increase in survivors with severe neurological impariment. The treatment itself is not costly. The use of hospital resources is not reported.
3. Are the likely treatment benefits worth the potential harms and costs?
Probably. The results suggest that 3 minutes of CPR prior to defibrillation and 3 minutes of CPR between attempts at defibrillation may lead to improved survival to hospital discharge in patients with VT/VF out-of-hospital cardiac arrests and an ambulance response time of greater than 5 minutes. While this is taken from analysis of a subgroup, it was a single prespecified analysis, based upon previous studies and with some degreee of physiological rationale. The overall result, while not statistically significant, represents an 80% probability that survival could be increased by 7%. While not statistically significant, an improvement in survival of this magnitude for such a common and lethal problem such as VT/VF cardiac arrest may be considered clinically important by many physicians. This result would need to be confirmed or refuted in a larger trial. Until that occurs, the use of 3 minutes of CPR prior to defibrillation and 3 minutes of CPR between defibrillation attempts, should be seriously considered for patients with out-of-hospital VT/VF cardiac arrests and emregency personnel response times of longer than 5 minutes.

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Delaying Defibrillation to Give Basic Cardiopulmonary Resuscitation to Patients With Out-of-Hospital Ventricular Fibrillation A Randomized Trial

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