Factors of hospitalization for mild heat illness

Introduction

Untreated mild heat illness (heat exhaustion) becomes progressively more severe (heat stroke). Although the prognosis and risk factors for hospital mortality in patients with severe heat illness are often reported, the epidemiologic data for mild heat illness have been rarely reported. We therefore investigated the hospitalization predictive factors in the patients with mild heat illness.

Methods

Questionnaire sheets were sent to our affiliated hospitals in Yamaguchi prefecture, located at 34° north latitude with a population of 1.5 million, to identify the patients who received medical attentions with heat illness from 1 July to 31 August 2007. The questionnaire included symptoms, vital signs, laboratory data and presence or absence of hospitalization (decided by each doctor).

Results

We analyzed the data from 114 of the 126 patients with mild heat illness. Twelve patients were excluded because of insufficient description. The total number of hospitalizations was 44 (35%) and all patients were discharged without subsequent complications. The significant differences were shown in body temperature, consciousness disturbance, dysfunction of central nerve system including convulsion or cerebellar ataxia, age, levels of serum C-reactive protein, blood urea nitrogen (BUN) and white blood cell count between hospitalized and nonhospitalized patients with mild heat illness. Independent predictive factors for hospitalization were Glasgow Coma Scale < 15 (P = 0.04, OR = 3.56, 95% CI = 1.05–12.01), age ≥ 60 years (P < 0.01, OR = 4.44, 95% CI = 1.50–13.08), and BUN ≥ 21 mg/dl (P = 0.03, OR = 3.35, 95% CI = 1.16–9.67).

Conclusion

Based on the present findings, the factors of hospitalization for mild heat illness were identified as presence of consciousness disturbance, seniority and high BUN level. These factors did not directly show the severity of heat illness, but they do help us to determine the patients who should be hospitalized.