How lower body temperatures could save lives and brain cells after cardiac arrest

In good health

By Malka Eisenberg

Therapeutic hypothermia, where the patient’s body temperature is lowered and maintained slightly lower than normal body temperature either in the ambulance or in the hospital following cardiac arrest, has been shown to improve survival and limit brain damage. A new study will be observing this technique in infants and children following cardiac arrest and resuscitation.

Although cardiac arrest is very rare in children and usually happens only following severe illness or trauma “we weren’t sure what to do regarding children,” said Dr. Charles Schleien, a pediatrician and anesthesiologist at Columbia University College of Physicians and Surgeons.

“We’ve known that under cold temperature the metabolism is lower and may protect the brain,” but, explained Schleien, that’s “too overly simplistic. There are many reasons hypothermia works on the brain.” He noted that oxygen radical production is lowered and it changes what happens following the low blood flow caused by the heart’s stopping and the body’s release of chemicals damaging to the brain and other organs.

Therapeutic hypothermia is “current procedure” in adults but still “experimental in newborns deprived of oxygen at birth,” noted Schleien. Data from animal studies indicated a benefit to cooling the body and brain and there has been “a lot of momentum” in the last five years to cool adult brains but clinical studies of newborns had mixed results, said Schleien. “The study is being run to see if cooling of the body in children improves survival and neurologic function,” he said.

The current study began in September 2009 and will run through September 2015 in major children’s hospitals in New York, Toronto, Philadelphia and Washington, D.C. “It’s uncommon for children to have cardiac arrest,” explained Schleien. “That’s why we need six years to get an adequate population.”

The study is a randomized trial with half the population cooled and compared to the other half kept at normal body temperature. The cooling has to start within six hours after cardiac arrest and kept at constant lower temperature for 48 hours. Those who survive will have “very sophisticated neurological and behavioral assessment” three months and one year after.

Schleien stressed that the methods and temperatures are much more “moderate. We found through previous studies that we don’t have to cool as extensively as we once did and it’s much safer now. Now it’s 33 degrees C, it used to be 28 to 30 degrees C with problems of arrythmias, infections, sepsis, coagulation — there’s much less at 33 degrees — almost insignificant.”

Dr Robert Van Amerongen of Priority Pediatrics in Lynbrook and Chief of the Pediatric Emergency Department of New York Methodist Hospital in Brooklyn, noted that not every procedure that works in adults is beneficial to children. He pointed out that the root causes for cardiac arrest are typically different for adults and for children. He said that when adults are resuscitated and cooled in the first 24 hours following cardiac arrest and slowly rewarmed they have “better neurological outcomes.”

“The big if,” emphasized Van Amerongen, “is if the patient is first resuscitated and you get back the pulse,” only then can hypothermia be induced. “Cardiac arrest is much rarer in children than adults,” he said, and is due to different circumstances. Adult cardiac arrest may be due to heart attack where part of the heart muscle stops receiving oxygen needed to function, blockages in blood vessels, plaque ruptures and blocks a blood vessel so blood and oxygen can’t reach the muscle and it slowly dies, myocardial infarction with ventricular fibrulation-a highly irregular rhythm or asystole where the heart stops.

When a child goes into cardiac arrest, explained Van Amerongen, it usually results from a “respiratory problem that’s worsening, asthma or pneumonia — it gets very bad, the child stops breathing, the heart stops pumping. The child goes into shock, maybe from infection or trauma, the heart and other organs don’t get enough blood flow and thus oxygen and organs die. The reasons for cardiac arrest are different in children.” He noted that children generally don’t have sudden cardiac arrest as adults do except in “tragic but uncommon” circumstances such as getting hit in the chest with a baseball or cardiac myopathy, where a child collapses in a basketball game.

“There’s much more damage in a child, it’s harder to resuscitate,” said Van Amerongen. “I’m not saying we shouldn’t do it. People have to realize if, G-d forbid, there is cardiac arrest, it’s not the first thing to cool, the first thing is to resuscitate, start the breathing and pulse again then cool down to prevent further injury to the brain. It’s certainly worth doing the study. We have to examine carefully through scientific studies and see if it is effective before we apply it across the board.”