Therapeutic Hypothermia

As resuscitation science advances, doctors are always looking for new ways to improve cardiac arrest outcomes. One seemingly promising method is the use of therapeutic hypothermia.

Originally practiced in Europe, therapeutic hypothermia in victims of sudden cardiac arrest involves the purposeful reduction of body temperature to slow the organs’ need for oxygen during. Once cooled, doctors can perform surgical measures to correct the initial cause of the cardiac arrest. The body will then be slowly re-warmed in hopes of returning spontaneous circulation and long term survival.
The reintroduction of oxygen into the brain and other vital organs during Cardiopulmonary Resuscitation (CPR) causes microscopic damage to the cells, known as reperfusion injury. The cell membranes become more permeable, causing the cells to leak fluid into interstitial spaces. This is manifested as swelling. Since the brain is effectively contained within a “box” of finite size, swelling leads to brain herniation and ultimately death. The goal of therapeutic hypothermia is to reduce the amount of brain swelling that occurs during cardiac arrest.
Although therapeutic hypothermia is relatively new to cardiac arrest applications, it has been used successfully for many years in psychiatry, neurology and cardiothoracic surgery. The effectiveness of therapeutic hypothermia continues to be observed in sudden cardiac arrest patients that receive this treatment within an hour of onset. The Virginia Commonwealth University Medical Center reported that the death rate for cardiac arrest patients was cut in half after cooling patients receiving CPR. 1
The American Heart Association changed its guidelines for cardiopulmonary resuscitation and emergency cardiovascular care in 2005 to include the recommendation of therapeutic hypothermia as treatment for cardiac arrest.2 In 2009, the New York City Fire Department (FDNY) announced that cardiac arrest patients treated by any of their ambulances would receive ice saline to begin the cooling process while enroute to the hospital. Additionally, cardiac arrest patients are now only taken to hospitals where therapeutic hypothermia is administered. 3
On Long Island, Stonybrook University Medical Center is begining to practice therapeutic hypothermia for cardiac arrest patients in their ICU with very promising results.4
As resuscitation science continues to advance, we should underscore that good bystander CPR, including the administration of fast, hard and deep chest compressions, along with early defibrillation are important links in the long chain of survival for sudden out-of-hospital cardiac arrest victims. Optimal survival rates are enjoyed by those who receive early intervention and continued care in the hospital.
1Ong, M. Et al. “Controlled therapeutic hypothermia post-cardiac arrest compared to standard intensive care unit therapy”. Presentation to the 2006 Society for Academic Emergency Medicine.
2 “2005 American Heart Association guidelines for cardiopulmonary resuscitation and emergency cardiovascular care”. Circulation 112, no. 24 (DEcember 2005).
3 Gupta, S. (2009). Cheating Death: The doctors and medical miracles that are saving lives against all odds. New York: Wellness Central
4 Personal conversation with Dr. Sam Parnia, June 2011.

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