Body Cooling in Ambulance Not Much Help for Cardiac Arrest

Cardiac arrest treatment with mild hypothermia in the field did not change outcomes

(RxWiki News) Lowering a person’s body temperature after his or her heart stops takes time. Getting a head start in the ambulance may help get things going, but it may not change much else.

A recent clinical trial tested the use of body cooling during ambulance rides to the hospital in patients who experienced cardiac arrest.

The results of the study showed that body cooling in the field did not help people live through the heart event or recover more brain function at the time of hospital discharge.

"If someone is having chest pains, call 9-1-1 immediately."

Francis Kim, MD, of the School of Medicine at the University of Washington in Seattle, led a team to study the use of mild body cooling to preserve brain function after experiencing cardiac arrest.

Cardiac arrest refers to when a person’s heart has stopped beating. It is possible to start the heart beating again, but time is important. The longer the heart goes without pumping blood filled with nutrients and oxygen throughout the body, the greater the risk of brain damage and death.

Lowering a person’s body temperature — known as therapeutic hypothermia — has been used previously to promote brain healing after certain medical events.

For this clinical trial, the researchers instructed paramedics in the field to follow normal procedure with 1,359 cardiac arrest patients from 2007 to 2012. After getting the heart beating again, the paramedics began administering hypothermia in a subgroup of those patients.

Patients treated with mild hypothermia had their body temperature lowered from 98.6 degrees Fahrenheit to somewhere between 89.6 degrees to 93.2 degrees with an IV of 2 liters of cool saline before reaching the hospital. Cooling continued for 12 to 24 hours in the hospital.

Most of the patients who had a specific type of cardiac arrest — called ventricular fibrillation — were treated with hypothermia in the hospital even if they were not cooled in the field.

The researchers found that starting the cooling process in the field helped to achieve lower body temperature around one hour faster than waiting until the patient reached the hospital.

Similar rates of pre-hospital hypothermia and normal procedure patients lived through cardiac arrest and hospital discharge:

  • 62.7 percent versus 64.3 percent for ventricular fibrillation cardiac arrest
  • 19.2 percent versus 16.3 percent for non-ventricular fibrillation cardiac arrest

Pre-hospital hypothermia did not have much influence on whether or not patients made a full recovery of brain function after cardiac arrest:

  • 57.5 percent versus 61.9 percent of patients with ventricular fibrillation cardiac arrest had full recovery or only mild impairment.
  • 14.4 percent versus 13.4 percent of non-ventricular fibrillation cardiac arrest had full recovery or only mild impairment.

Patients treated with pre-hospital hypothermia were more likely to have a second cardiac arrest in the field compared to normal procedure patients, 26 percent versus 21 percent, respectively.

The study's authors noted that patients treated with pre-hospital hypothermia were more likely to have fluid in their lungs during their first chest x-ray, but the fluid generally went away within 24 hours.

The authors concluded that the use of pre-hospital cooling helped to lower body temperature by the time of hospital arrival and shortened the time to reach a body temperature of 93.2 degrees Fahrenheit, but it did not improve chances of living through cardiac arrest or recovering optimal brain function.

This study was published in November in JAMA.

The National Heart, Lung, and Blood Institute and the Medic One Foundation provided funding for this project. Dr. Nichol reported a financial relationship with Velomedic Inc, Philips Healthcare Inc, HealthSine Technologies Inc and Zoll Inc.

Review Date: 
November 19, 2013