Abstract P119: Protocol Changes to Increase CPR Also Leave Patients in VF for Longer Periods of Time
The 2005 resuscitation guidelines eliminated stacked shocks and lengthened CPR intervals. Both of these protocol modifications can reduce CPR interruptions, but they can also delay the conversion of initial or recurrent ventricular fibrillation (VF), leaving the heart in this bioenergetically unfavorable state for a longer period of time. We evaluated the cumulative time spent in VF for patients with out-of-hospital cardiac arrest treated with two different automated external defibrillator (AED) CPR protocols.
Methods: Data from a recently completed trial (clinicaltrials.gov NCT00139542) comparing two different AED protocols were used for this post-hoc analysis. In the trial, CONTROL AEDs conformed to Guidelines 2000. STUDY AEDs included longer CPR intervals and single rather than stacked shocks, as in the Guidelines 2005, and prompted for 60 seconds of CPR before the 1st shock. We reviewed ECG and impedance signals in downloaded AED records from all patients presenting with VF to measure the cumulative time a VF rhythm was present during the first 9 minutes of treatment. Results are presented as median [25th, 75th percentiles].
Results: A total of 589 records with a VF initial rhythm were analyzed. As expected, the 306 STUDY group patients received more CPR than the 283 CONTROL group patients (62% [54%, 69%] vs 47% [39%, 55%], p<0.001). The STUDY group also spent a significantly higher fraction of treatment time in VF than the CONTROL group (41% [22%, 69%] vs 22% [6%, 47%], p<0.001). Their cumulative VF time was significantly higher, both for the patients receiving only one shock (78 [76, 84] seconds vs 19 [19, 22] seconds, p<0.001), and the patients receiving multiple shocks (271 [184, 383] seconds vs 168 [89, 261] seconds, p<0.001). There was no difference between groups in the shock VF termination rate (85% vs 82%), nor in the length of the interval from shock to VF recurrence (24 [11, 61] seconds vs 38 [10, 67] seconds).
Conclusion: Patients treated according to a protocol that added initial CPR, prolonged CPR intervals between shocks and eliminated stacked shocks did receive more CPR, but also spent more time in VF than patients treated according to Guidelines 2000. Further research is needed to determine the impact of longer VF periods on patient outcomes.