Forced air surface rewarming in patients with severe accidental hypothermia
Introduction
Forced air rewarming is an established, simple and non invasive method of treating peri operative hypothermia associated with major surgery [1], [2]. Extensive data are available proving both its efficiency and safety in patients with mild to moderate hypothermia in the operating and recovery room [1], [2], [3], [4]. Although forced air rewarming is a potential therapeutic approach for patients with accidental hypothermia, only limited data are available [5], [6]. In a prospective, randomized study, Steele et al. [5] found the rewarming rate to be almost doubled in patients with accidental hypothermia rewarmed with forced air when compared to patients covered with warmed cotton blankets. In a more recent case series with three patients Koller et al. also found forced air rewarming to be a successful method of treating severely hypothermic patients, even two cases with a history of cardio-circulatory arrest [6]. Based on these data and our own successful management of eight hypothermic patients [7] we have routinely used forced air rewarming as the method of choice for rewarming patients with accidental hypothermia since 1995.
Despite the successful initial experience published in literature [5], [6], [7], there are still concerns about the routine use of forced air rewarming in hypothermic patients with a body core temperature below 30°C. Forced air rewarming is a form of active external rewarming which is considered inadequate for patients with a body core temperature below 30°C [8], [9], [10]. This is predominately due to the danger of an afterdrop in body core temperature caused by a shift of cold blood from the shell to the core of the body [8], [10], [11]. In addition, the preferential rewarming of the shell of the body may increase the workload of the hypothermic heart and induce vasodilation, both predisposing the hypothermic patient to a haemodynamic instability during rewarming [12].
Section snippets
Patients
The medical charts of all patients admitted to the emergency department of the University Hospital Innsbruck with accidental hypothermia between January 1995 and April 1998 were reviewed. Twenty-seven patients with severe accidental hypothermia and a body core temperature below 30°C were identified. Twelve of these patients were admitted in cardiac arrest and according to widely accepted recommendations [8], [9], [10] were rewarmed using extracorporeal circulation. The remaining 15 patients
Outcome
All 15 patients were successfully rewarmed to a body core temperature of 35°C with forced air rewarming. No other forms of rewarming were required. Mean rewarming rate was 1.7±0.7°C/h (0.7–3.4°C/h) [mean+S.D. (range)] and was not significantly different between group 1 [1.9±0.8°C/h (0.7–3.4°C/h)] and group 2 patients [1.5±0.3°C/h (1.2–1.5°C/h)]. Mean arterial pressure could be stabilized in all patients, although catecholamine support was necessary in seven of 15 patients. Catecholamine therapy
Discussion
We observed a mean rewarming rate of 1.7°C/h when using the forced air method. Steel et al. report a slightly higher rewarming rate of 2°C/h, whereas Koller et al. found a lower rewarming rate of 1°C/h [5], [6]. Some variability in the rewarming rates reported is also a common finding for other methods of rewarming [9], [10], [13]. A significant variation in the individual response to cooling and rewarming, an altered vasoconstrictor response in intoxicated patients, age, concomitant disease
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