Literature Review: 2005 Guidelines vs. Nonshockable Rhythms

Kudenchuk PJ, Redshaw JD, Stubbs BA, et al. Impact of changes in resuscitation practice on survival and neurological outcome after out-of-hospital cardiac arrest resulting from nonshockable arrhythmias. Circulation 2012 Apr 10; 125(14): 1,787–94.

Abstract

Out-of-hospital cardiac arrest (OHCA) survival from shockable arrhythmias (ventricular fibrillation/tachycardia) improved in several communities after implementation of American Heart Association resuscitation guidelines that eliminated “stacked” shocks and emphasized chest compressions. The benefit of such treatments on nonshockable rhythms is uncertain. Methods and Results—[Authors] studied 3,960 patients with nontraumatic OHCA from nonshockable initial rhythms treated by prehospital providers in King County, WA, over a 10-year period. Outcomes during a 5-year intervention period after adoption of new resuscitation guidelines were compared with the previous 5-year historical control period. The primary outcome was 1-year survival. Patient demographics and resuscitation characteristics were similar between the control (n=1,774) and intervention (n=2,186) groups, among whom 471 of 1,774 patients (27%) versus 742 of 2,186 patients (34%), respectively, achieved return of spontaneous circulation; 82 (4.6%) versus 149 (6.8%) were discharged from hospital, 60 (3.4%) versus 112 (5.1%) with favorable neurological outcome; 73 (4.1%) versus 135 (6.2%) survived 1 month; and 48 (2.7%) versus 106 patients (4.9%) survived 1 year (all P ≤ 0.005). After adjustment for potential confounders, the intervention period was associated with an improved odds ratio of 1.50 for return of spontaneous circulation, 1.53 for hospital survival, 1.56 for favorable neurological status, 1.54 for 1-month survival, and 1.85 for 1-year survival. Conclusion—Outcomes from OHCA resulting from nonshockable rhythms, although poor by comparison with shockable-rhythm presentations, improved significantly after implementation of resuscitation guideline changes, suggesting their potential to benefit all presentations of OHCA.

Comment

The proportion of cardiac arrests found in ventricular fibrillation or ventricular tachycardia has dropped significantly over the last 30 years, from 40%–50% to now around 20%. Though the trend is clear, the reason is (or reasons are) not fully known. Leading theories are that it is due to the use of beta-blockers or statins (cholesterol-lowering), the aggressive prevention and treatment of heart disease (myocardial ischemia is the leading cause of VF), and/or pre-EMS treatment with implantable (or even wearable) defibrillators. Regardless of the reason(s), nearly 80% of the cardiac arrest patients we treat in the field are in asystole or PEA. In order to make any significant progress in overall survival, we will need to improve outcomes in this large subset.

These authors have shown that moving from the 2000 to the 2005 resuscitation guidelines resulted in more neurologically favorable survivors—from 3.4% to 5.1%, a relative increase of 50%. Additional advances with the 2010 guidelines may further extend these gains. EMS systems should be examining their overall cardiac arrest survival and neurological outcomes. We can no longer just look at the most likely to survive—the witnessed VF/VT cases. And we must continue to focus on improving CPR. Delivering immediate high-quality chest compressions, with the fewest interruptions for the shortest possible duration, is the one essential treatment for all cardiac arrests.

Angelo Salvucci, Jr., MD, FACEP, is medical director for the Santa Barbara County and Ventura County (CA) EMS agencies and a member of the EMS World editorial advisory board.