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Hypothermia..the real cost


Most anesthesiologists are aware of the adverse effects associated with mild hypothermia in the perioperative period (e.g. increased risk of wound infection, cardiac morbidity, and PACU stay). However, in the ICU population, some of whom are exposed to environmental extremes, the manifestations of hypothermia become more numerous.

Hypothermia is classified as mild (core temperature 32-35C), moderate (28-32C), and severe (< 28C), and leads to multiple physiologic derangements, including in the CNS (fatigue, ataxia, reduced gag reflex, coma, decreased EEG activity), cardiovascular system (hypovolemia [secondary to diuresis], arrhythmias [including asystole]), pulmonary system (respiratory depression, apnea, pulmonary edema), kidneys (“cold diuresis”), and immune system (immunosuppression).

The mortality rate of hypothermic patients is approximately 17% (based on a multicenter review of over 400 non-operative cases)

In 2002, two large, prospective trials demonstrated that mild hypothermia after resuscitation from cardiac arrest and maintained for 12 to 24 hours improved survival and neurologic outcome in patients suffering from VF/VT arrest [Hypothermia after Cardiac Arrest Study Group. NEJM 346: 549, 2002; Bernard SA et al; NEJM 346: 557, 2002]. Additional studies have suggested that therapeutic hypothermia may be beneficial following respiratory arrest, electrical mechanical dissociation, and asystole, provided that it is initiated within 25 minutes [Oddo M et al. Crit Care Med 36: 2296, 2008].

In 2005, the IHAST trial demonstrated that therapeutic hypothermia was safe in patients undergoing aneurysm surgery (craniotomy) but resulted in no improvement in neurologic outcome [Todd MM et al. NEJM 352: 135, 2005], thus hypothermia cannot be recommended for intraoperative neuroprotection
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