Cardiac Arrest Care: Out With the Old CPR, In With the New

For almost two decades, EMS providers have accepted 200, 300, 360 joules as the set of defibrillations delivered by either AEDs or manual defibrillators for ventricular fibrillation or pulseless ventricular tachycardia. The concept of shock early/shock often, however, may be one of many areas that changes dramatically when the American Heart Association releases its new Consensus on Science report in the December issue of the Journal of the American Medical Association. The report may have us changing how we think about cardiac care-saying CBA instead of ABC-and creating a whole new set of treatment options.

In some cases, these treatment options may seem more basic, like returning to the original work of Drs. George Crile, James Elam and Peter Safar, and, in reality, some are. Cardiac arrest survival, of course, has long been a losing proposition. With the science that follows, though, EMS, as the frontline response, may be able to catch up on preventable deaths by improving the effectiveness of CPR.

Circulation

In terms of cardiac arrest and cardiopulmonary resuscitation, there has always been one option only: airway. Specific to ventricular fibrillation, immediate defibrillation is the ultimate choice in care.

New science reveals that while maintaining the airway and defibrillation are important, they may both be secondary to moving blood around the body.1,2 One study noted that while defibrillation is the "essential intervention" for ventricular fibrillation, defibrillation alone is not a cure-all.3 The new data may send EMS in some entirely new directions in the very near future.

Chest compressions have always been considered important in cardiac arrest, but the reasons are changing, and their value may be misunderstood. For the most part, CPR has been considered a bridge to defibrillation, but new science suggests that CPR doesn't just extend the timeline until defibrillation in VF/VT events, but also may improve tissue perfusion by moving blood.

As you may remember from your initial EMS classes, the body burns ATP, or adenosine triphosphate, which is produced using oxygen and glucose stores. When the body is in cardiac arrest, however, there is no oxygen being moved to produce new ATP, and the heart uses its stores quickly because of the body's fight-or-flight response to maintain homeostasis. Without new ATP, the body starts to burn sugar without oxygen, producing lactic acidosis. By moving oxygenated blood through the heart, the myocardium can produce ATP as it normally would. It is believed that when provided its normal "food," the heart will be more inclined to benefit from defibrillation.

Science goes so far as to say that the old plan of action, which said you should use an AED early, may have been wrong. In one study, the authors noted that the time interval between using an AED versus a manual defibrillator could result in a worsened outcome,4 and there is clearly a benefit to doing compressions before defibrillating in downtimes of four minutes or more.

Another important consideration in cardiac arrest is coronary perfusion pressure during CPR. In its 2000 standards, the American Heart Association changed the chest compression-to-ventilation ratio from 5:1 to 15:2. This change was important, because it was taking multiple compressions to build up the minimum coronary perfusion pressures to feed the heart. Typically, this number is a minimum of 20 mmHg; ideally, it will be closer to 40 mmHg. The interruption in compressions to provide ventilation or allow the AED to perform its rhythm analysis was causing loss of this minimal pressure of 20 mmHg, which, in some cases, lasted as much as 20 seconds.5 The 15:2 ratio seems to provide better coronary perfusion pressures longer in the resuscitation.

Another study showed that continuous chest compressions produce "superior neurological outcome."6