Hard, fast and don t stop. Sound like your last shift? Actually, this is the current recommendation for cardiopulmonary resuscitation (CPR), leaning toward the cardio part, at least initially. Providing rapid (at least 100 per minute) compressions hard enough to depress the chest two inches while allowing full chest recoil on the rebound increases survival.
Survival is low regardless of what we do, but the best chance is with aggressive chest compressions and defibrillation. We know electricity works; otherwise, we wouldn t implant thousands of internal defibrillators in patients who tend to develop frequent ventricular tachycardia or fibrillation. For these patients, defibrillation is automatic and instantaneous, with almost universal return to an organized rhythm. For the patient without this device who suffers ventricular fibrillation or pulseless ventricular tachycardia, defibrillation is still the key to successful resuscitation. But are there other considerations?
In 2002, Myron L. Weisfeldt, MD; Lance B. Becker, MD described a three-phase time-sensitive model for cardiac arrest: electrical, circulatory and metabolic phases. The electrical phase lasts for the first four minutes, during which the heart and brain should have enough oxygen and nutrients that defibrillation has the best chance in restarting the heart and preserving the brain. The circulatory phase is from four to 10 minutes, during which the heart and brain experience decreasing levels of oxygen and nutrients. Chest compressions and ventilation increase the potential for successful defibrillation during the circulatory phase. After 10 minutes, the metabolic phase begins and the heart is generally unresponsive to treatment. Even if restarted, the brain often suffers irreversible damage unless metabolic factors come into play, such as hypothermia, which may be protective.
This agrees with information from the American Heart Association that most cardiac arrest victims can be successfully treated in the first few minutes with defibrillation; however, the chance of survival drops 7-10% each minute without CPR and defibrillation. And after 10 minutes, there are few survivors.
This model helps us understand the recommendation for immediate defibrillation of the witnessed cardiac arrest patient and for immediate CPR in an unwitnessed arrest.
But think about it the only way to provide immediate defibrillation is through an internal defibrillator, which most cardiac arrest patients don t own. So really, treatment of any arrest patient should start with CPR until the defibrillator is ready and then be interrupted only briefly for shock.
Effective chest compressions produce an increase in cardiac output in a stepwise manner; each compression builds on the previous compression. When we stop compressions, the cardiac output immediately begins dropping. And since the best chest compressions can only generate a cardiac output in the range of 25-30% of normal, we don t want any unnecessary decreases in that cardiac output due to delayed, lost or ineffective compressions.
Well, what about ventilations? For the electrical phase, there appears to be enough oxygen and nutrients that chest compressions are more important than ventilations if providing ventilations will interrupt compressions. Obviously, you ll need to interrupt briefly for defibrillation.
In the circulatory phase, there is an increasing need to begin ventilations, but every effort should be made to minimize any break in chest compressions. Having oxygenated red blood cells in the lungs won t do any good if the cardiac output is too low to push them to the heart and brain.
So after you defibrillate the patient, what s the next thing you should do? Look for a change in rhythm? Not yet! You shouldn t even look at the monitor yet. Immediately following defibrillation, you should start up compressions. The cardiac output you generate can help any organized electrical activity survive and increase the chance it will stimulate cardiac muscle contractions to support a return of circulation.
Our objective is a fully successful resuscitation. This is not defined by the return of an organized rhythm, the return of spontaneous circulation, or even the patient s return to consciousness. All of these are only stepping-stones. Resuscitation is only fully successful when the cardiac arrest patient returns to his or her pre-arrest level of cardiac and neurological function.
It appears that success depends on early recognition, effective chest compressions and rapid defibrillation. So whether you are bystander or provider, CPR begins with pump hard, pump fast and don t stop.
- Weisfeldt ML, Becker LB: Resuscitation after cardiac arrest: a 3-phase time-sensitive model. Journal of the American Medical Association.288(23):3035 3038, 2002.
- Ewy GA: Cardiocerebral resuscitation: the new cardiopulmonary resuscitation. Circulation.111(16):2134 2142, 2005.
- American Heart Association: Highlights of the 2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Currents in Emergency Cardiovascular Care. Volume 16; Number 4.
- Yu T, Weil MH, Tang W, et al: Adverse outcomes of interrupted precordial compression during automated defibrillation. Circulation.106(3):368 372, 2002.
- Wik L, Hansen TB, Fylling F, et al: Delaying defibrillation to give basic cardiopulmonary resuscitation to patients with out-of-hospital ventricular fibrillation: a randomized trial. JAMA.289(11):1389 1395, 2003.
- Eftestol T, Sunde K, Steen PA: Effects of interrupting precordial compressions on the calculated probability of defibrillation success during out-of-hospital cardiac arrest. Circulation.105(19):2270 2273, 2002.
- Hess EP, White RD: Ventricular fibrillation is not provoked by chest compression during post-shock organized rhythms in out-of-hospital cardiac arrest. Resuscitation.66(1):7 11, 2005.