CPR and defibrillation have long been used to resuscitate a patient who has suffered from cardiac arrest. Now, following up those life-saving techniques with a relatively new advance called therapeutic hypothermia is improving heart attack survival, reducing the chance of brain damage, and giving patients a better chance at a full recovery.

    This increasingly popular technique, which is now available locally at University Medical Center at Princeton, lowers the body’s temperature and helps slow the chemical processes that occur when the brain is deprived of oxygen, thereby helping protect fragile brain cells and neurological processes.

    With therapeutic hypothermia, physicians start administering cold saline intravenously and cover the patient’s body with high- tech cooling pads to lower and maintain body temperature below normal. Hypothermia is induced as the body’s temperature is dropped to between 89 and 93 degrees. The patient is kept in this state for 12 to 24 hours.

    How does cooling the body help?

    In cardiac arrest patients, cells are injured by lack of oxygen. The body naturally wants to remove these damaged cells, but if too many are eliminated, the patient can die. By lowering the body temperature, cells have a chance to recover and stabilize.

    The cooler the body tissue, the lower the metabolic rate. And, studies have shown that the sooner cooling starts, the better the outcomes. The cold body temperature helps preserve brain and heart function and makes the revival process safer. Tissue damage, called reperfusion injury, can occur when the blood supply returns to the tissue after cardiac arrest; however, therapeutic hypothermia helps prevent this damage from happening.

    Candidates for therapeutic hypothermia are patients who have suffered cardiac arrest and regained spontaneous circulation but who remain comatose. The process can only be used in select cases; for instance, it is not for children, pregnant women, victims of major trauma, or those who have had recent surgery.

    While therapeutic hypothermia is considered a safe way to treat cardiac arrest, like most medical procedures there are certain risks. For instance, when the body is cooled down, blood loses some of its clotting ability, which can result in spontaneous bleeding. Additionally, cold bodies are more likely to develop infections or sepsis. Doctors, however, monitor a patient’s blood platelets and other conditions closely to prevent these side effects from occurring.

    The American Heart Association recommends therapeutic hypothermia, citing its benefits both for improving neurological recovery and for saving lives. University Medical Center at Princeton’s therapeutic hypothermia program involves cooperation between the Emergency Department, the Intensive Care Unit, and the Cardiology Department, as well as Neurology.

    While therapeutic hypothermia in cardiac arrest patients is a fairly modern medical advancement, the theory dates to the ancient Greek physician Hippocrates, who proposed packing the wounded in snow. Along those same lines, Napoleon’s doctor noticed during the Russian campaign that troops seemed to recuperate more quickly on the ice.

    Doctors began investigating this technique in the 1950s for cardiac arrest victims, but soon abandoned it due to the constraints of the day. More recently, however, technical advances have made therapeutic hypothermia a promising and viable method of treating cardiac arrest victims. Today, it is expected to improve a patient’s survival rate and even provide the patient a better chance to continue living a normal life.

    Cardiac arrest occurs when the heart stops beating, most commonly because of an irregular heart rhythm that stops blood from pumping. Underlying causes range from heart disease, to choking, drowning, or other trauma. Drug use can also cause abnormal heart rhythms that lead to cardiac arrest.

    According to the American Heart Association, death from cardiac arrest happens most often at about 60 years of age, and more often to men than to women. However, sudden cardiac death has been rising among younger women, and remains higher among young African-Americans.

    Signs of cardiac arrest are often obvious. A victim of cardiac arrest will typically collapse into unresponsiveness and lose normal breathing activity. Brain damage can begin to occur within four to six minutes after the heart stops beating and death can occur in minutes if the victim receives no immediate treatment such as CPR and defibrillation. If someone is experiencing cardiac arrest, call 9-1-1 immediately and begin administering CPR if you are trained to do so.

    Although cardiac arrest is still extremely serious and often fatal, CPR and defibrillation followed by therapeutic hypothermia can increase the chances of survival.

    To find a physician affiliated with Princeton HealthCare System, call 888-742-7496 or visit www.princetonhcs.org.

Craig A. Gronczewski, M.D., is board-certified in emergency medicine and is the chairman of the Department of Emergency Medicine at Princeton HealthCare System.