SAN FRANCISCO – The alphabet is changing for critical care of patients in cardiac arrest.
"A is for airway" is no longer at the top of the list. The ABCs (airway, breathing, and circulation) of cardiopulmonary resuscitation have been replaced by an emphasis on CAB – compressions, airway, and breathing, in that order.
The American Heart Association promotes the "CPR is as easy as C-A-B" slogan, and the key to success in treating cardiac arrest is high-quality, uninterrupted chest compressions, Dr. Robert J. Vissers said at the annual meeting of the American College of Emergency Physicians.
"Airway may not always come first" if the patient has lost perfusion and circulation, said Dr. Vissers, chief of emergency medicine at Legacy Emanuel Medical Center, Portland, Ore. "It’s hard for me to say, because I’m an airway guy."
While "C" stands for compressions, it also serves to remind physicians to attend to cardioversion, capnography, cooling, and catheterization, if needed. Dr. Vissers addressed each of these in more detail. "These are the things that recently have led to pretty substantial improvements in the outcomes of these patients," he said.
Compressions. With high-quality, uninterrupted chest compressions, the patient gets good passive ventilation, which may be superior to positive pressure ventilation in these situations. Aim for 30 compressions per breath. Consider creating a supraglottic airway without interrupting the CPR, he said.
Put some muscle into it to maintain compressions 2 inches in depth with full recoil, at a rate of 100 compressions per minute. If more than one person is available, take turns applying compressions to reduce fatigue. Monitor the patient closely with end-tidal capnography. (See below.)
Proper compressions restore cerebral and coronary perfusion. Sustained coronary perfusion pressure is critical to successful defibrillation.
Cardioversion. The first 4 minutes after cardiac arrest provide the greatest chance of successful cardioversion (defibrillation). If more than 4 minutes have elapsed, reperfuse the myocardium with a few minutes of chest compressions before applying shock. Wait 2 minutes after defibrillation to check the pulse, and maintain compressions during that time.
The traditional admonition to "clear!" before shocking may not be necessary, Dr. Vissers said. Studies have shown that no appreciable electrical current reaches the people applying compressions if they are wearing gloves and a biphasic defibrillator is used for cardioversion.
Capnography. Confirm proper tube placement for capnography, which helps assess the quality of the CPR and identify return of spontaneous circulation without checking pulses. Capnography readings also help predict outcome.
"I think capnography is one of the most underutilized tools that we have for the critically ill patient," Dr. Vissers said.
High-quality compressions and coronary perfusion pressures correlate with end-tidal carbon dioxide (ETCO2) levels of 20-25 mm Hg on capnography. A sudden rise in ETCO2 suggests return of spontaneous circulation and is more sensitive than manual pulse checks. If ETCO2 readings persistently stay below 10 mm Hg, return of spontaneous circulation is unlikely. In studies, an ETCO2 less than 10 mm Hg after 20 minutes of compressions was associated with zero chance of return of spontaneous circulation.
Cooling. For unconscious adults who went into cardiac arrest outside of hospital care, cooling the body to 32-34° C for 12-24 hours improves chances of a good outcome, Dr. Vissers said. Applying ice packs to the groin, axilla, and neck will cool the body about 0.2-1° C per hour. The best cooling method may be cooling blankets that circulate cooled water through material designed to promote heat exchange. The blankets cool a body on average by 1-1.5° C per hour.
Used in combination, the ice packs can be removed when the body temperature reaches 33° C and the blankets left on to maintain the cool temperature for 12-24 hours. "That works very well," he said. Cooled normal saline infusions or cooling catheters also are options for cooling a body after cardiac arrest.
Of every 4-13 patients cooled after cardiac arrest, 1 will leave the hospital neurologically intact, he said.
Catheterization. Early percutaneous coronary intervention benefits patients with cardiac arrest, even those without ST-segment elevation MI, studies suggest. Consider transferring the patient for cardiac catheterization. It’s okay to cool the body and then transfer for catheterization. This may become a more common model as care after cardiac arrest becomes more regionalized, he said.
Dr. Vissers said he has no relevant conflicts of interest.