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Survival to hospital discharge after out-of-hospital cardiac arrest is very unlikely. To simplify cardiopulmonary resuscitation (CPR) protocols and, possibly, improve cardiac and cerebral perfusion, investigators studied a new approach, called minimally interrupted cardiac resuscitation (MICR), which places more emphasis on chest compressions and less on ventilation. The MICR protocol (Table 1) was implemented through 2 emergency medical services (EMS) in Arizona, and a separate comparative study was conducted through 60 Arizona fire departments.
In the EMS study (886 patients), survival to hospital discharge rose from 1.8% before the new protocol was implemented to 5.4% afterward. For 174 patients with witnessed arrests and ventricular fibrillation, the rate rose from 4.7% to 17.6%. In the comparative study (2460 patients), survival to discharge occurred in 9.1% of those who received MICR versus 3.8% of those who received CPR under old guidelines (JW Cardiol Mar 11 2008).
In a position paper from the American Heart Association (AHA), which was published at about the same time, the authors called for compression-only cardiac resuscitation by bystanders who witness out-of-hospital cardiac arrest (JW Emerg Med Apr 11 2008). Based on results from the MICR studies above and others, the AHA proposed simplifying cardiac resuscitation for bystanders and addressed fears of contagion and concerns about proper technique for mouth-to-mouth ventilation. This AHA recommendation applies only to lay bystanders and not to skilled healthcare personnel who follow current cardiac life-support protocols (which I can confirm, having just recertified in Advanced Cardiac Life Support).
The results of the MICR studies are encouraging, but, because the studies were observational and uncontrolled, other factors could have contributed to the difference in survival to discharge. At the least, the findings suggest that a wide range of approaches to cardiac resuscitation likely will lead to comparable outcomes, that an emphasis on cardiac compression over ventilation is appropriate (especially in situations where mouth-to-mouth ventilation is problematic), and that a rigid prescriptive approach to tightly counted compressions and interpolated ventilations is unnecessary.