Technology Protects Brain Cells in Critical Situations

An ICU nurse checks on a patient who has been fitted with the Arctic Sun pads.

A new approach to a not-so-new concept is making a dramatic difference for patients in the medical intensive care unit. Critical Care specialists at USC’s School of Medicine are utilizing innovative technology to lower the body temperature of patients who are comatose after cardiac arrest. Effectively reducing the temperature down to 90 – 91 degrees Fahrenheit can minimize injury to the brain after a heart attack.

Physicians have known since the 1950’s that cooling the body after cardiac arrest can protect brain cells from dying. Yet it wasn’t until a decade ago that renewed interest developed in using mild hypothermia for this purpose. Out of that interest emerged a temperature management system that represents a major advance for critically ill patients.

Known as the Arctic Sun, the cooling device uses specially designed energy transfer pads, which are affixed to 40 percent of the patient’s body surface. Temperature-controlled water is then circulated through the pads to systematically bring down the patient’s temperature. “It simulates ice water immersion,” said Dr. William Owens, an assistant professor of clinical medicine in the Division of Pulmonary and Critical Care Medicine. “This is much more controlled than the old fashioned methods of cooling blankets or packing with ice, allowing us to bring the temperature down to a set level,” he added.

While the patient’s temperature is reduced, for a period of 24 hours from when the body starts cooling, physicians are already implementing appropriate cardiac treatment.  “If we can cool the patient down, then we are reducing the oxygen demand of the brain and minimizing the risk of neurologic injury,” Dr. Owens explained. Once the patient is ready to be re-warmed, the system regulates this process at a rate of .9 degrees Fahrenheit per hour and continually monitors the body temperature. “This controlled re-warming is safer,” said Dr. Owens, explaining that complications can ensue when re-warming is done too quickly. When the patient is back up to a normal body temperature, the equipment’s control module maintains that temperature. This prevents the patient from developing hyperthermia or fever, which is also important in minimizing neurologic injury.

"The Arctic Sun translates not just to better survival, but better survival with good neurologic function." – Dr. William Owens

While other options have become available to lower a patient’s body temperature, they require a physician to place a large catheter into the femoral vein, which is an invasive vascular procedure with the potential for serious side effects such as infection or blood clots. “It’s  easier, quicker, and safer to get the Arctic Sun on a patient. If it’s 3:00 a.m. and I get a call from the Emergency Department, I can have a nurse do that immediately,” Dr. Owens said. The temperature management system is also being utilized by School of Medicine physicians with patients who have elevated intracranial pressures caused by a number of medical conditions. “If nothing surgical can be done, we can put the patient in a drug-induced coma and institute hypothermia so we can reduce the endocranial pressure,” Dr. Owens said.

Dr. Owens is sold on the merits of therapeutic hypothermia. “It translates not just to better survival, but better survival with good neurologic function. We can expect more people to live without needing full-time care and have a more satisfying life.” At the same time, the physician advises caution on its use with spinal cord injury, referring to the highly publicized case of Buffalo Bills tight end Kevin Everett. After Everett suffered a spinal cord in-jury during a game last fall, hypothermia was immediately utilized with the player, who is now walking again. “It has a lot of promise and makes sense theoretically, but before we adopt this as a wide-spread practice, we need to do more studies on its wide-spread benefits. Hopefully we will know soon,” he said.

Reprinted from Connections newsletter, August 2008

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