Sudden cardiac death claims approximately 450,000 victims in the United States every year.1 The mortality rate for out-of-hospital cardiac arrest remains a staggering 65% to 95%, with only 10% to 20% of survivors discharged from the hospital with a good neurologic outcome.2 Therapeutic hypothermia for the treatment of comatose survivors of cardiac arrest is the only therapy proven to improve survival and neurological outcome.3
Although many consider therapeutic hypothermia to be a relatively new concept, experiments with deep therapeutic hypothermia actually began in the 1940s with initially mixed results. In the 1950s, studies examining moderate hypothermia in the range of 26°C to 32°C (78.8°F to 89.6°F) in comatose survivors of cardiac arrest reported a trend toward improved outcomes but were complicated by difficult to control side effects. Additional animal studies of mild hypothermia in the range of 32°C to 35°C (89.6°F to 95°F) in the 1980s and small clinical trials in the 1990s demonstrated that even mild hypothermia provided the protective benefits with far fewer side effects.2
Two landmark randomized trials published in 2002 specifically examined the use of mild hypothermia in comatose survivors of witnessed cardiac arrests with initial rhythms of pulseless ventricular tachycardia or ventricular fibrillation.4,5 More recent meta-analysis report that only seven patients need to be treated to save one life and only five patients need to be treated to prevent one poor neurological outcome.6,7 Utilizing these studies' strict screening criteria resulted in only 10% of screened patients being eligible. Follow-up studies suggest a wider benefit in patients with other rhythms at presentation, cardiogenic shock, and those requiring percutaneous cardiac intervention (i.e., angioplasty and stenting).2,3,8–16
Preliminary studies of therapeutic hypothermia for other indications including traumatic brain injury, strokes, subarachnoid hemorrhages, myocardial infarctions, and ARDS have to date reported only limited data or conflicting results. The exception being studies of neonates with perinatal asphyxia that reported similar results to adult cardiac arrest with a number needed to treat of six for one favorable outcome.3 Extensive ongoing research is currently being conducted to determine the effectiveness of therapeutic hypothermia for other indications, as well as the optimal timing, duration, target temperature, and best techniques.
Despite recommendations for therapeutic hypothermia in the 2005 International Liaison Committee on Resuscitation Recom-mendations and American Heart Association Resuscitation Guidelines, a recent survey showed that 74% of physicians in the United States had not used therapeutic hypothermia.15 They cited reasons such as not enough data, not part of ACLS protocol, too technically difficult, or that it had not been considered.15 However, the induction of therapeutic hypothermia for comatose survivors of cardiac arrest is relatively straightforward in any Emergency Department. Similar to Early Goal Directed Therapy (EGDT) for septic shock, the creation of collaborative protocols between Emergency Physicians, Intensivists, Cardiologist, and Neurointensivists is essential to producing the best outcomes at each ...