Sex Differences In Biomarkers Of End-organ Damage In Exertional Heat Stroke

Men are reported to suffer exertional heat stroke (EHS) at more than double the rate of women. However, there are few data regarding potential sex differences in EHS case severity or biomarkers of end-organ damage. PURPOSE: The purpose of this study was to test whether there are differences in biomarkers of end organ damage between male and female patients presenting with EHS to Martin Army Community Hospital (MACH) Emergency Department (ED). Biomarkers included creatinine (CR), alanine transaminase (ALT), aspartate aminotransferase (AST), and creatine kinase (CK). METHODS: Active-duty service members who were transported to MACH ED and presented with EHS were eligible for inclusion. Volunteers provided written, informed consent and completed a demographic questionnaire. Relevant laboratory data was retrieved from the electronic medical record. Peak core (rectal) temperature was obtained from EMS records. Blood samples were obtained for routine analysis upon admittance to the ED, in six-hour intervals if admitted to the hospital for observation, and at follow-up appointments as necessary. RESULTS: Biomarker data were obtained for 38 EHS cases (28 males, 24 ± 3.5y, 10 females, 28 ± 7.0y, p = 0.03). Men were significantly taller, heavier, with larger BMI and body surface area (BSA) (p < 0.01 for all). Peak rectal temperature was not different (men: 40.7 ± .95 °C; women: 40.8 ± .85 °C, p = 0.87). Men had significantly higher peak CR (1.88 ± 0.63 mg/dL vs. women: 1.32 ± 0.22 mg/dL, p < 0.01) and peak CK (5228 ± 6925 U/L vs. women: 1370 ± 1337 U/L, p = 0.01), but no differences were observed for ALT (men: 191 ± 215 U/L, women 118 ± 87 U/L, p = 0.15) or AST (men: 235 ± 253 U/L, women 128 ± 147 U/L, p = 0.12). Spearman’s correlation showed that height (r = 0.51, p = 0.01), weight (r = 0.43, p = 0.02), and BSA (r = 0.46, p = 0.01) were positively correlated to CR levels, while BMI was correlated to CK (r = 0.44, p = 0.03). CONCLUSIONS: In our cohort of young healthy individuals who developed EHS, peak core temperatures were similar between men and women, but CK and CR were significantly higher in men. This suggests that men may be more susceptible to acute kidney injury and exertional rhabdomyolysis. Further research is necessary to understand the pathophysiology underlying these differences, as end-organ damage severity can impact the return to duty timeline. Funded by USAMRDC