Clinical Relevance of Impaired Consciousness in Accidental Hypothermia: A Japanese Multicenter Retrospective Study

Abstract

Background: Severe accidental hypothermia (AH) is a life-threatening condition, and early identification can enable transport to an appropriate medical facility. The Swiss staging model has been used to classify patients with AH, but little is known regarding the relationship between the degree of impaired consciousness and core body temperature (BT) in AH. This study aimed to clarify the relationship between the level of consciousness and core BT and determine whether the level of consciousness could be used to predict severe hypothermia and in-hospital mortality among patients with AH.Methods: We retrospectively investigated the clinical relevance of impaired consciousness in AH. We included adult patients with AH and excluded patients with out-of-hospital cardiac arrest. The patients were identified from the J-point registry, which contains information regarding patients treated for AH between April 1, 2011 and March 31, 2016 in any of the 12 participating institutions in Japan. The primary exposure of interest was the level of consciousness at hospital arrival. Odds ratios were calculated for severe hypothermia and in-hospital mortality.Results: Overall, 505 of the 572 patients in the registry were included. Compared to mildly impaired consciousness, the adjusted odds ratio for severe hypothermia was 3.3 (95% confidence interval [CI]: 1.7–6.3) for moderately impaired consciousness and 4.7 (95% CI: 2.4–9.1) for severely impaired consciousness. Severely impaired consciousness as a predictor severe hypothermia had a sensitivity of 0.44 (95% CI: 0.34–0.54), specificity of 0.78 (95% CI: 0.74–0.82), positive likelihood ratio of 2.04, and negative likelihood ratio of 0.71. Compared to mildly impaired consciousness, the adjusted odds ratio for in-hospital mortality was 1.7 (95% CI: 0.95–2.9) for moderately impaired consciousness and 2.1 (95% CI: 1.2–3.8) for severely impaired consciousness.Conclusions: Severely impaired consciousness was a reliable predictor of severe hypothermia and in-hospital mortality in patients with AH. Thus, in an urban out-of-hospital emergency setting, the level of impaired consciousness may be helpful for triaging patients to the appropriate hospital.