Association between active cooling and lower mortality among patients with heat stroke and heat exhaustion.

Jun Kanda,Shoji Yokobori,Shinji Nakahara,Shunsuke Nakamura,Tetsuya Sakamoto,Yasufumi Miyake,Arino Yaguchi,Keiki Shimizu,Samuel Penna Wanner

doi:10.1371/journal.pone.0259441

Abstract

Body cooling is recommended for patients with heat stroke and heat exhaustion. However, differences in the outcomes of patients who do or do not receive active cooling therapy have not been determined. The best available evidence supporting active cooling is based on a case series without comparison groups; thus, the effectiveness of this method in improving patient prognoses cannot be appropriately quantified. Therefore, we compared the outcomes of heat stroke patients receiving active cooling with those of patients receiving rehydration-only therapy. This prospective observational multicenter registry-based study of heat stroke and heat exhaustion patients was conducted in Japan from 2010 to 2019. The patients were stratified into the “severe” group or the “mild-to-moderate” group, per clinical findings on admission. After conducting multivariate logistic regression analyses, we compared the prognoses between patients who received “active cooling + rehydration” and patients who received “rehydration only,” with in-hospital death as the endpoint. Sex, age, onset situation (i.e., exertional or non-exertional), core body temperature, liver damage, renal dysfunction, and disseminated intravascular coagulation were considered potential covariates. Among those who received active cooling and rehydration-only therapy, the in-hospital mortality rates were 21.5% and 35.5%, respectively, for severe patients (n = 231) and 3.9% and 5.7%, respectively, for mild-to-moderate patients (n = 578). Rehydration-only therapy was associated with a higher in-hospital mortality in patients with severe heat illness (adjusted odds ratio [aOR], 3.29; 95% confidence interval [CI], 1.21–8.90), whereas the cooling methods were not associated with lower in-hospital mortality in patients with mild-to-moderate heat illness (aOR, 2.22; 95% CI, 0.92–5.84). Active cooling was associated with lower in-hospital mortality only in the severe group. Our results indicated that active cooling should be recommended as an adjunct to rehydration-only therapy for patients with severe heat illness.

Highlights

Heat illnesses, caused by exposure to or exertion in hot environments, are a growing public health concern owing to climate change
Disseminated intravascular coagulation (DIC) and in-hospital death occurred in 28% and 15%, respectively, of the “severe” patients, and in 23% and 5%, respectively, of the “mild-to-moderate” patients
Rehydration-only therapy was mostly provided to individuals aged 65 years

Summary

Introduction

Heat illnesses, caused by exposure to or exertion in hot environments, are a growing public health concern owing to climate change. In July 1995, Chicago, IL (USA) sustained a heat wave that resulted in more than 600 excess deaths and 3300 excess emergency department visits [1]. In France, more than 14 800 people died of a heat stroke caused by a heatwave in August 2003 [2]. In Japan, because of high temperatures and humidity in the summer, heat stroke and heat exhaustion occur more frequently among elderly people. More than 50,000 patients with heat illnesses are taken to hospitals each summer. On account of heat illnesses caused by the heat wave of 2018, 95,137 patients required hospital visits and 1677 patients died [8, 9]; most of these patients were older adults who were affected during daily activities [10]

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Discussion

Conclusion