Therapeutic hypothermia is back; New recommendation for cardiac arrest survivors: chill out.
This novel therapy is supported by three prospective randomized clinical trials.
The resultant body of favorable evidence has prompted a recent advisory statement by the Advanced Life Support Task Force of the International Liaison Committee on Resuscitation, noted Dr. Sterz of the University of Vienna.
The new recommendation by this influential body is that unconscious adults with return of spontaneous circulation following CPR for out-of-hospital cardiac arrest caused by ventricular fibrillation should be cooled to 32-34[degrees]C for 12-24 hours.
This recommendation is supported by level-1, highest-quality published evidence.
It's an appropriately conservative recommendation; further studies will be needed to establish that resuscitative cooling is also beneficial following cardiac arrest associated with other rhythms, as well as after in-hospital cardiac arrest and perhaps in children who have experienced cardiac arrest, according to the advisory statement (Circulation 108:118-21, 2003).
The largest randomized trial of therapeutic hypothermia after cardiac arrest was conducted at nine European centers and included 275 patients.
At 6 months' follow-up, 41% of patients in the therapeutic hypothermia group were dead, compared with 55% of those in the usual-care group.
In addition, 55% of patients in the hypothermia group had a favorable neurologic outcome, which was defined as the ability to live independently and work at least part time, compared with 39% in the usual-care group.
Combining the results of the European trial with data from a four-center, 77-patient Australian study and a 33-patient single-center randomized trial, patients randomized to therapeutic hypothermia were 68% more likely to be discharged with favorable neurologic recovery.
The number of patients who needed to be treated with therapeutic hypothermia in order to enable one additional patient to leave the hospital neurologically intact ranged from 4 to 13 in the three studies, Dr. Sterz commented.
Therapeutic hypothermia has been used by cardiac surgeons for more than 50 years prior to inducing cardiac arrest during open-heart surgery. Resuscitative cooling after out-of-hospital cardiac arrest was first described in the 1950s.
The practice fell into disfavor and was abandoned until recently, when it was rejuvenated by persuasive animal studies followed by favorable clinical experience.
The turnabout in opinion came too late for a recommendation for therapeutic hypothermia to be included in the International Liaison Committee on Resuscitation's Guidelines 2000 for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. The new advisory statement is intended to update the guidelines on that score.
Several practical issues regarding therapeutic hypothermia require further research. It's unclear, for example, when is the best time to initiate cooling, what is the optimal temperature and duration, and what is the best rewarming strategy.
Even the best cooling method remains uncertain: One randomized trial employed ice packs, another used cold air, and the third used a cooling helmet, Dr. Sterz noted.
BY BRUCE JANCIN
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|Title Annotation:||Cardiovascular Medicine|
|Publication:||Internal Medicine News|
|Date:||Mar 1, 2004|
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