An updated guideline for emergency cardiovascular care has changed the A-B-C mnemonic of cardiopulmonary resuscitation to C-A-B, emphasizing the need to start chest compressions as quickly as possible and worry about the airway second.
It's the biggest – and most important – change in the 2010 update of the American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care, said coauthor Dr. Michael Sayre, chairman of the American Heart Association's Emergency Cardiovascular Care (ECC) Committee.
“For more than 40 years, CPR training has emphasized the ABCs of CPR, which instructed people to open a victim's airway by tilting their head back, pinching the nose and breathing into the victim's mouth, and only then giving chest compressions,” Dr. Sayre said in a press statement. “This approach was causing significant delays in starting chest compressions, which are essential for keeping oxygen-rich blood circulating through the body. Changing the sequence from A-B-C to C-A-B for adults and children allows all rescuers to begin chest compressions right away.”
Any delay in chest compression, either by bystanders squeamish about mouth-to-mouth or clinicians searching for ventilation equipment, increases the risk of death, the statement noted. This change correlates with a British study published recently in Lancet, which found that nonprofessional rescuers are most effective when they use compression-only CPR (Lancet 2010 [doi:10.1016/S0140-6736(10)61454-7]).
The AHA Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care were last updated in 2005, the authors said. Since then, a plethora of evidence has changed the clinical approach to emergency cardiovascular care. The committee, which included 356 resuscitation experts from 29 countries, produced 411 new evidence-based reviews, from which the updates were drawn.
The new recommendations also call for an increase in the rate of chest compressions, to at least 100/minute. “Rescuers should push deeper on the chest, compressing at least two inches in adults and children and 1.5 inches in infants,” the statement notes. “Between each compression, rescuers should avoid leaning on the chest to allow it to return to its starting position.”
The guidelines recommend the new C-A-B approach for adults, teens, and children who suddenly collapse and stop breathing, or display ineffective respiration during collapse. For neonates with no known cardiac etiology, however, the A-B-Cs remain in effect. Ventilation with room air is best for term babies in arrest; to avoid the negative impact of pure oxygen on newborns, the statement calls for a blend of room air and oxygen for infants who need supplemental oxygen. For these babies, the recommendation for a 3:1 chest compression–ventilation ratio remains in effect, because ventilation is critical to reversing neonatal asphyxia arrest.
Advanced Life Support
In addition to providing information for bystander rescue attempts, the guidelines suggest some changes in the way cardiac arrest and stroke patients are treated by emergency medical services, emergency physicians, and those involved with postincident care.
In keeping with the new C-A-B format, the document urges EMS personnel to minimize interruptions in chest compression to what is necessary for rescue ventilation. Even taking time for pulse checks is no longer advised, since pulse is not an effective indicator of cardiac status when blood pressure is low or absent.
Electrical therapy should be employed as soon as possible after CPR begins, but CPR should not cease while readying the defibrillator, the guidelines say. “Rescuers should minimize the interval between stopping compressions and delivering shocks, and should resume CPR immediately after shock delivery.”
The statement recommends an initial biphasic energy dose of 120-200 joules for atrial fibrillation and 50-100 joules for atrial flutter or other supraventricular tachycardias. If the initial shock fails, providers should increase the dose in a stepwise fashion.
For patients with symptomatic arrhythmias, the updates now recommend adenosine for diagnosing and treating stable undifferentiated wide-complex tachycardia when the rhythm is regular and the QRS wave is monomorphic. For symptomatic or unstable bradycardia, intravenous chronotropic agents can be an effective alternative to external pacing if adenosine is ineffective.
The guidelines include a major new class I recommendation for adult airway management: the use of quantitative waveform capnography for confirmation and monitoring of endotracheal tube placement. Additionally, they no longer endorse the routine use of cricoid pressure during airway management.
After the Cardiac Arrest
The recommendations don't stop when the patient regains spontaneous circulation. An entire section of the document is devoted to post–cardiac arrest care, pushing for an integrated, multidisciplinary approach. “Patients with suspected acute coronary syndrome should be triaged to a facility with reperfusion capabilities and a multidisciplinary team prepared to monitor patients for multi-organ dysfunction and initiate appropriate post–cardiac arrest therapy, including hypothermia.”