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Controlled hypothermia: a new take on protecting the brain after cardiac arrest

VCU first in North America to report on clinical use of therapy

With steady, rhythmic contractions, the heart works diligently to pump oxygen-rich blood throughout the body. Any disruption of this machine can mean disaster. In the event of cardiac arrest, where the heart suddenly fails to pump enough blood to the brain, severe damage to the brain can result as it starves for nourishment.

At the Virginia Commonwealth University Medical Center, researchers are examining ways to reduce neurological damage and improve the survival of a person who suffers a cardiac arrest. In May, at the 2006 Society for Academic Emergency Medicine’s annual meeting in San Francisco, the VCU team was the first in North America to report on the benefits of controlled hypothermia as post-cardiac arrest therapy.

The team reported an 80 percent survival rate among patients who underwent hypothermia therapy following cardiac arrest, compared with a 40 percent survival rate for patients who were treated before hypothermia was available. The study was based on a sample size of 15 patients.

In controlled hypothermia therapy, a cardiac arrest patient who is in a coma — which is common following a cardiac arrest — is closely monitored as his body temperature is lowered to about 91 degrees Fahrenheit. The patient remains in this mild hypothermic or cold state for a period of typically 24 hours after the cardiac arrest.

According to researchers, the cooling slows a patient’s entire metabolic rate. The brain and the other organs do not require as much blood flow to maintain themselves and less demand is placed on the recently damaged heart. By slowing everything down in the body, the brain is given the opportunity to rest for a period of time. Cooling also decreases swelling in the brain.

Researchers evaluated patients using the Cerebral Performance Category assessment and observed that a higher number of patients recovered with intact neurological function compared to the controls. However, when they evaluated the patients based on the Overall Performance Category assessment, the researchers did not observe a significant difference between the two patient groups.

“Data from our clinical program offers further evidence that hypothermia post-resuscitation is effective in reducing mortality and preserving cerebral function. It is hoped this will encourage other centers to consider adopting hypothermia protocols in their ICUs,” said Marcus E.H. Ong, M.D., who contributed to this study while studying at the VCU School of Public Health.

Previous studies conducted in Europe and Australia have also suggested that controlled hypothermia therapy may benefit patients.

Ong collaborated with Mary Ann Peberdy, M.D., associate professor in the VCU Division of Cardiology; Renata Sampson, R.N., a clinical instructor in the VCU School of Nursing; and Joseph P. Ornato, M.D., chair in the Department of Emergency Medicine.