Therapeutic cooling

POPULAR SCIENCE / COURTESY GRAPHIC William Henderson went into cardiac arrest in December 2007, his wife, Betty, clearly recalls, "The day his heart stopped" and how she believes inducing hypothermia — cooling his body temperature — blessed her with another year to share with her husband of 61 years.

"The room was full of doctors and nurses, it was absolutely freezing in there," Ms. Henderson says. "It was the most wonderful thing, when he opened his eyes. He was in a deep coma and when he opened his eyes, we knew he was going to live."

Lee Memorial Health System implemented the practice of inducing hypothermia for cardiac arrest patients approximately two years ago, after cooling therapy was endorsed by the American Heart Association. In fact, Lee Memorial was one of the first non-teaching hospitals in the nation to start using the treatment. It's currently offered at Gulf Coast Medical Center and HealthPark Medical Center — two of the system's hospitals with major cardiac programs.

Two physicians extremely close to the subject of therapeutic cooling are Dr. Kenneth Tolep and Dr. Jeffrey Scott, medical directors of the Intensive Care Units at HealthPark Medical Center and Gulf Coast Medical Center, respectively.

According to Drs. Tolep and Scott, despite all of the advances in cardiac care, the chances of surviving a cardiac arrest that occurs outside of the hospital remain very low and the chances of waking up with good neurologic function are even worse. This cooling technique improves the patient's chances of waking up and eventually resuming a normal lifestyle.

"This is not a life-saving procedure, but rather a brain-saving procedure," says Dr. Scott. "If the brain is injured, the person may survive, but with a poor quality of life. The cooling process works to preserve the brain from injury due to lack of blood flow."

The exact reason cooling improves neurologic outcomes has not been definitively proven. Some evidence says it slows the metabolism in the brain. Other theories are that hypothermia may improve oxygen delivery to areas of the brain where blood flow has been deficient or possibly, it lowers intra-cranial pressure. Another theory is that hypothermia may decrease the productions of harmful chemicals released when blood flow to the brain has been reestablished. This is called a reperfusion injury.

Not all cardiac arrest patients are eligible for the cooling treatment. Eligible patients are those who have been resuscitated and regain their pulse after the episode, but remain in a coma-like or unconscious state. Physicians believe mild hypothermia treatment assists patients to have a better neurologic outcome, thus better brain function after cardiac arrest.

"It is a very complex process. The first thing is that patients have to be recognized by EMS and the emergency department as candidates," says Dr. Scott. "This involves a lot of training and collaboration between EMS and the hospitals."

Gulf Coast Medical Center and HealthPark Medical Center both have a protocol in place if a patient is a candidate. If the emergency room physician determines that the patient is a candidate, he or she will call a code "ICE." Code "ICE" involves a critical care physician and cardiologist. If the patient does not need immediate cardiac treatment to save his or her life, the critical care physician will take over and coordinate care to start the cooling process.

Although no study so far has shown whether the time cooling begins matters, the teams at Lee Memorial Health System try to start cooling as soon as possible.

There are multiple ways physicians are cooling patients. One commonly used technique is to chill the intravenous fluids given early on to qualifying cardiac patients. Ice packs are often placed at key areas near the arms and legs, to begin the cooling process. Additionally, specialized cooling blankets can be placed around the patient. The teams at Lee Memorial Health System use a combination of these methods on eligible patients. The patient's temperature is lowered to between 90 to 93 degrees Fahrenheit. By keeping the core temperature within this narrow range, maximal benefit is obtained while at the same time reducing possible side effects of hypothermia.

Dr. Tolep says the concept of lowering body temperature to help with certain illnesses happens to be a very old-fashioned idea. Hippocrates observed that sick people who were packed in the snow seemed to fare better. In the 1950s, doctors started using intentional hypothermia to protect brain functions during cardiac surgery.

This practice, which had been previously endorsed by the American Heart Association, has been slow to catch on due to the extremely demanding nature of the treatment. An ICU nurse needs to be at the bedside on a continuous basis and intensive care physicians need to evaluate the patient and initiate therapy as rapidly as possible, even when cardiac arrest occurs in the middle of the night. Furthermore, the equipment needed to keep the patient at the appropriate temperature can be quite expensive. Despite the difficulties in implementing these protocols nationwide, Drs. Tolep and Scott said that this technology may protect brain function.