Core Temperature Response to Cold Water Immersion in Heat Stroke Patients Is Nonlinear and Unrelated to Sex or Body Size.

Purpose: Cold water immersion (CWI) is the most effective treatment for exertional heat stroke (EHS). However, knowledge on core temperature response during CWI treatment and the relation with patient characteristics (i.e., sex, anthropometrics) is limited. Therefore, the current study aimed to examine the core temperature response (in °C) during CWI treatment of recreational athletes participating in large running events and investigate the impact of sex and anthropometric characteristics on the cooling rate (in °C·min -1 ).

Methods: This observational study includes 57 athletes ( n = 22 females; 39%) who suffered from EHS during an exercise event in the Netherlands. After admission to the medical facilities, a rectal temperature ( Trec ) probe was inserted and all clothing was removed before immersion in an ice bath (6.4 ± 1.6°C). Rectal temperature was continuously measured throughout treatment, and treatment was continued until Trec ≤ 38.9°C or based on the decision of the emergency physician.

Results: Initial Trec did not differ between males (41.3 ± 0.9°C) and females (41.2 ± 0.8°C, P = 0.83). A nonlinear response to CWI was observed, with the decrease in Trec beginning after 6 min of CWI. The decrease in Trec did not differ between both sexes (p time*sex = 0.96). The cooling rate did not differ between males (0.21 ± 0.15°C·min -1 ) and females (0.19 ± 0.08°C·min -1 , P = 0.55), and was not related to body mass, body surface area and body surface area to mass ratio (all P values >0.05).

Conclusions: We demonstrated that the cooling rate during CWI did not differ between men and women suffering from EHS, and that the Trec response to CWI is nonlinear and not dependent on anthropometric characteristics. This suggests that no sex differentiation is needed in the EHS treatment guidelines and confirms the necessity to continuously monitor Trec during treatment.