Hypothermia May Protect Brain after Cardiac Arrest

A phase I/II trial is seeking to determine whether rapid cooling can protect brain cells from damage in patients who suffer cardiac arrest and are then resuscitated. Prior small studies have shown that hypothermia is effective for this purpose.

After cardiac arrest and cessation of heartbeat, four out of five patients who are unconscious following resuscitation suffer serious brain damage or die. In fact, most suffer some mental decline as a result of no blood flow for only 10 minutes. Researchers believe that hypothermia can slow down the cascade of biochemical events that occurs when the brain is deprived of oxygen as well as the cascade of events that occurs when blood flow is restored to the brain, following resuscitation. Other trials cooled patients from the outside, using special cooling blankets. The current trials will cool patients from the inside-out and will sedate them so they don't shiver.

One site involved in the multicenter trial is Duke University Medical Center (Durham, NC, USA). One of the first patients in the new trial was recently treated there after going into cardiac arrest en route to the hospital. Paramedics shocked his heart back into action, but he went about 10 minutes without blood flow to his brain. He arrived at Duke in a coma.

Within minutes, doctors threaded a triple lumen catheter through a vessel in his leg to his vena cava and began circulating cool saline throughout the catheter. Within several hours, the patient's body had cooled from 37o C to 32o C. After spending 24 hours in the neurologic intensive care unit, he was slowly rewarmed back to normal body temperature. Days later, he received an operation to correct a congenital condition that can cause sudden episodes of extremely fast heart rates, the cause of his cardiac arrest. He was discharged the next day.

"Had he been out for 20 to 30 minutes, there would have been only a 10-20% chance he would have survived,” said Dr. Carmelo Graffagnino, a neurologist at Duke who organized and leads the multicenter trial. "He is now back at work and seems perfectly normal. We hope that the cooling played a role in that, but we won't know for sure until the study is done.”



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