Therapeutic hypothermia for out-of-hospital cardiac arrest

Abstract

The use of therapeutic hypothermia (TH) and its application in out-of-hospital cardiac arrest patients are reviewed. Each year in the United States, an estimated 250,000-300,000 out-of-hospital cardiac arrests occur. Despite advances in prehospital care, the survival rate from TH is only 6-12%. In addition, survivors often have devastating consequences ranging from mild memory impairment to permanent brain damage. It is presumed that early induction of hypothermia produces an optimal effect, though benefits can still be achieved with late induction. Several methods have been devised to induce hypothermia, yet the optimal methods of cooling have not currently been determined. Major adverse effects of cooling include hemodynamic changes, cardiovascular complications, hyperglycemia, coagulopathy, increased rates of infection, fluid and electrolyte disorders, and shivering. The majority of these adverse effects can be prevented or minimized in the intensive care setting. In 2002, the use of TH--cooling the core body temperature to 32-34 degrees C--was supported by two landmark human studies, whose results led to the endorsement of TH by the American Heart Association and its increased use. The studies demonstrated that hypothermia results in favorable neurologic outcomes in patients suffering from out-of-hospital cardiac arrest due to ventricular fibrillation (VF), without increasing complications. TH is an effective strategy for improving neurologic outcomes of patients after out-of-hospital cardiac arrest due to VF. Further studies are needed to confirm the optimal time and methods for cooling to maximize the chance of complete neurologic recovery after cardiac arrest.