SAEM: AHA Guidelines for Cardiac Arrest Treatment Increase Survival

By Todd Neale
WASHINGTON, 31 may 2008-- The rate of resuscitation after out-of-hospital cardiac arrests jumped nearly four-fold when new guidelines on CPR were fully implemented in a North Carolina county, according to researchers here.The 2005 American Heart Association guidelines outlined a protocol calling for simple, continuous chest compressions, controlled ventilation, and early use of induced hypothermia.When the guidelines were fully implemented in Wake County, which has urban and suburban areas and a population of about 815,000, cardiac arrest survival increased 3.99-fold (95% CI 2.19 to 7.27), Brent Myers, M.D., M.P.H., medical director of the Emergency Medical Services System in Raleigh, N.C., reported at the Society for Academic Emergency Medicine meeting here.
Overall survival increased from 2.4% using older guidelines to 6.7% after introduction of the full 2005 AHA protocol.
He said that "the neurologic improvement was at least as robust as the survival improvement."
The entire protocol was introduced for less than $200 per patient, he said.
"All of these changes are simple, they are inexpensive, and they are incredibly effective," he said. From January 2004 through October 2007, there were 2,594 out-of-hospital cardiac arrests in patients ages 15 and older (mean age 65; 58% male).
More than a third (36%) were witnessed and received CPR from a bystander before emergency medical services arrived and 26% had ventricular fibrillation/ventricular tachycardia rhythm.
From January 2004 through April 2005, the emergency medical services system followed the older AHA guidelines, which mandated a 15:2 compression-to-ventilation ratio without a focus on interruption of compressions and with an emphasis on intubation.
Survival rates during this period were 2.4% overall and 12.1% for patients with ventricular fibrillation-ventricular tachycardia rhythm.
In April 2005 the system started following the new recommendation for continuous cardiac compression with a 30:2 compression-to-ventilation ratio with minimal interruption. After 12 months, the survival rates had increased to 4% overall and 21.8% for patients with ventricular fibrillation-ventricular tachycardia rhythm.
In April 2006, use of an impedance threshold device, a ResQPod, was introduced to better control ventilation and avoid over-ventilation. The device also helps improve the effectiveness of chest compression by enhancing blood flow to the coronary arteries.
This change was associated with another rise in survival -- 4.5% overall and 28.5% for patients with ventricular fibrillation-ventricular tachycardia rhythm.
Six months later, the system began early induction of hypothermia, the final stage of the protocol. Ice packs and chilled IV fluids were applied within two to three minutes of receiving a pulse and after the patient was found to be unresponsive neurologically.
Survival rates after a year of following the entire protocol were 6.7% overall and 37.4% for patients with ventricular fibrillation-ventricular tachycardia rhythm.
The odds of overall survival increased three-fold (95% CI 1.7 to 5.0) and the odds of survival for patients with ventricular fibrillation-ventricular tachycardia rhythm rose 4.3-fold (95% CI 2.2 to 8.6) from the beginning of the study.
In a multivariate analysis, the odds ratios for survival for each phase of implementation were as follows:
New CPR protocol: 2.13 (95% CI 1.12 to 4.04)
Addition of impedance threshold device: 2.33 (95% CI 1.09 to 5.00)
Addition of early hypothermia: 3.99 (95% CI 2.19 to 7.27)
Patients who received CPR from a bystander were 1.79-fold (95% CI 1.18 to 2.72) more likely to survive.
Dr. Myers defended the decision not to conduct a randomized trial, saying it would be unethical to do so.
"We felt that at each stage the evidence was so compelling to do what we were doing that we shouldn't randomize," he said.
He concluded, "Our findings not only demonstrate beneficial outcomes for victims of cardiac arrest, but also suggest the possibility that such treatment plans can be implemented for other medical conditions."
Dr. Myers and one of his co-authors are on the speaker's bureau for Alsius.
Primary source: Society for Academic Emergency MedicineSource reference:Hinchey P, et al "Out-of-hospital cardiac arrest survival after the sequential implementation of 2005 AHA guidelines for compressions, ventilations, and induced hypothermia" SAEM Meeting 2008; Abstract 167.