New and Improved CPR
Abstract & Commentary
By John P. DiMarco, MD, PhD
Source: Garza AG, et al. Improved patient survival using a modified resuscitation protocol for out-of-hospital cardiac arrest. Circulation. 2009;119:2597-2605.
This report from Garza et al describes improved outcomes in out-of-hospital cardiac arrest victims after a cardiopulmonary resuscitation (CPR) protocol change by the emergency medical services (EMS) system in Kansas City, MO. In 2005, the Kansas City EMS system undertook a quality improvement program that changed the CPR protocol followed during advanced cardiac life support (ACLS). The new Kansas City cardiac arrest protocol was designed to follow the principle of "minimally interrupted cardiac resuscitation." The ratio of chest compressions to ventilation was increased from 5:1 to 50:2. All cardiac arrest patients received 200 chest compressions before first rhythm analysis and shock unless the cardiac arrest was witnessed by EMS or the patient had previously received chest compressions. Continuous oxygen was delivered through a non-rebreather mask with an oral airway between ventilations. Intubation was not attempted until after a third round of chest compressions or the return of spontaneous circulation. In this paper, outcomes from the first 12 months after the ACLS protocol was instituted in April 2006, were compared to those from an historical control group of cardiac arrest patients during the period from January 2003 to March 2006.
In the historical cohort, there were 1,097 primary cardiac arrests. Of these, 495 (45%) presented with asystole, 345 (31.4%) presented with ventricular fibrillation, and 257 (23.4%) presented with pulseless electrical activity. Twenty-five patients with ventricular fibrillation had the onset of ventricular fibrillation witnessed by EMS. The rate of return of spontaneous circulation (ROSC) was 48.6% for those with ventricular fibrillation, in contrast to 3.4% with asystole and 16.7% for those with pulseless electrical activity. Initial rhythm also influenced the rate of survival-to-hospital discharge. Among the patients with ventricular fibrillation, 27% were discharged alive. Among those with asystole or pulseless electrical activity, only 1% and 5.4%, respectively, were discharged alive.
There were 339 primary cardiac arrests treated using the revised ACLS protocol. Of these, there were 160 patients (42.7%) with asystole, 112 patients (33%) with ventricular fibrillation, and 67 patients (19.8%) with pulseless electrical activity. Return of spontaneous circulation was now noted in 6.9% of the patients with asystole, 23.9% of the patients with pulseless electrical activity, and 59.6% of those with ventricular fibrillation. Survival-to-hospital discharge was observed in 44.4% of those with ventricular fibrillation, in contrast to 1.3% with asystole and 10.4% of those with pulseless electrical activity. Statistical regression analysis identified that use of the Kansas City cardiac arrest protocol was associated with an improved odds ratio for survival of 2.17. Other significant factors predicting survival were: female gender, witnessed cardiac arrest, and bystander CPR; intubation was associated with decreased survival.
Garza et al concluded that an out-of-hospital cardiac arrest resuscitation protocol that emphasizes uninterrupted chest compressions is associated with improvements in survival in a community-based cardiac arrest study.
Commentary
Over the last several years, a three-phase time-dependent model for cardiac resuscitation has become widely accepted. The first five minutes after cardiac arrest are thought to involve primarily electrical abnormalities. Prompt defibrillation within this time period is usually highly effective and, in the absence of complicating factors, should restore a perfusing rhythm. After about five minutes, however, a second phase occurs during which ATP stores become depleted in the fibrillating heart. During this period, electrical shocks may not defibrillate effectively and may, in fact, convert atrial fibrillation into a terminal bradyarrhythmia. This second phase during which resuscitation is still possible lasts approximately five minutes. After 10 minutes of total arrest, resuscitation becomes unlikely. It has been proposed that strategies that emphasize uninterrupted chest compressions and, therefore, improve myocardial metabolism, are key to improving survival for arrest victims.
This paper from the Kansas City EMS system confirms results from other community-based reports. The use of the minimally interrupted compression strategy was associated with improved outcomes within meaningful changes in the survival-to-hospital discharge.
Resuscitation guidelines are periodically reviewed. Data such as those shown in this paper are based on modern concepts of resuscitation and should promote necessary changes in current ACLS guidelines.
This report from Garza et al describes improved outcomes in out-of-hospital cardiac arrest victims after a cardiopulmonary resuscitation (CPR) protocol change by the emergency medical services (EMS) system in Kansas City, MO.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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