Cardiac arrest secondary to environmental hypothermia: Incidence and outcomes in an urban emergency department in the Upper Midwestern United States

Objectives: Data describing hypothermic cardiac arrest (HCA) outcomes predominantly originate from patients involved in wilderness accidents. We describe the incidence and outcomes of HCA in an urban environment, with a subgroup analysis of patients with witnessed HCA in the prehospital or emergency department (ED) setting. Methods: We completed a retrospective, single center cohort analysis of consecutive adult patients with environmental exposure and core body temperature ≤ 32 °C. We describe characteristics of this cohort and evaluate the relationship between initial core temperature and occurrence of HCA. Results: 171 patients met eligibility criteria from January 2007 to September 2023. 43 (25 %) sustained HCA, including 6/98 (6 %) of those with moderate hypothermia (28.01–32 °C), 21/55 (38 %) with severe hypothermia (24–28 °C) and 16/18 (89 %) with profound hypothermia (<24 °C). Risk of HCA increases 2.06 times (95 % CI 1.66 to 2.69) for each 1 °C decrease in initial core temperature below 32 °C. Among HCA patients, 18/43 (42 %) had a witnessed HCA during prehospital (n = 8) or ED (n = 10) care. The overall survival rate of HCA was 53 % but was higher in patients with initial core temperature < 28 °C versus those >28C (62 % vs 0 %). Survival of hypothermic patients who experienced their first HCA after arrival in the ED approached that of hypothermic patients without HCA (90 % vs 94 %). Conclusion: Patients with severe hypothermia secondary to environmental exposure in an urban environment are at high-risk of HCA. Witnessed HCA accounts for a significant portion of HCA patients, and patients with witnessed HCA in an ED setting can achieve excellent outcomes.