Biomarker Time Course Recovery Profile in Military Exertional Heat Stroke Populations

Abstract

Current return‐to‐duty and training decisions following Exertional Heat Stroke (EHS) are based on ‘best‐guess' criteria. A time‐resolved progression of biomarker changes following EHS has previously not been determined to describe ‘normal’ recovery. In order to characterize EHS injury severity and recovery progression in military populations and identify objective measures of medical readiness, we performed a retrospective clinical records review focusing on available clinical laboratory values assessed on the day of injury, and all follow‐up visits. This dataset was limited to US active duty service members (ADSM) who had at least one EHS during the years 2008–2014. Incidence was identified using the International Classification of Disease 9th (ICD‐9) Revision code for Heat Stroke (992.0). We collated and analyzed daily clinical laboratory values of circulating biomarkers from de‐identified electronic medical records contained in the Medical Health System Data Repository (MDR). Lacking consensus laboratory reference ranges between treatment facilities, the most prevalent reported reference ranges were used as consensus values to orient the analysis. Over the prescribed period, 2,529 ADSM experienced at least one episode of EHS. A total of 181,918 daily clinical laboratory results for 50 laboratory analytes were used for this analysis including a range of blood counts, and serum/plasma or urine assays from 0–340 days following the initial injury. As expected, the median daily value for 11 analytes (ALT, AST, Cl, CK, hematocrit, creatinine, hemoglobin, LDH, myoglobin, WBC, RBC) exceeded the upper limit of the normal reference range, indicating multi‐organ damage or dysfunction. Notably, creatine kinase (CK; consensus reference range 22–269 unit/L) exhibited the highest deviation 3‐days following the initial injury, the median value topped at 4.65‐fold elevation above the upper reference limit; median = 1,251 units/L (interquartile range, 321.25–5,256.75) units/L. Median CK values persisted above the reference range for 8‐days. Each biomarker showed a distinct pattern of peaks (ranging from 0–3 days). In conclusion, this work exploited population‐based EHS responses to characterize injury severity and recovery progression that has not previously been defined. However, due to the high degree of inter‐individual variability in the magnitude and duration of biomarker fluctuations, it remains difficult to set a generalizable criterion for diagnosis, recovery and medical readiness following EHS. The opinions or assertions contained herein are the private views of the authors and should not be construed as official or reflecting the views of the Army or the Department of Defense.Support or Funding InformationSupported, in part, by Defense Health Program grant, award #W81XWH‐13‐MOMJPC5‐IPPEHA.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.