Effects of Heat Illness on Hospitalization for Exertional Rhabdomyolysis in the Military

Abstract

Exertional rhabdomyolysis and exertional heat illness are common in military populations due to frequent high intensity physical training. Exertional rhabdomyolysis (ER) is a syndrome of muscle breakdown following exercise and is also a known complication of exertional heat illness. The behavior and clinical course of exertional rhabdomyolysis is not well described, and it is unclear if ER behaves differently in the setting of concomitant heat illness. This study describes laboratory and demographic trends of servicemembers hospitalized for exertional rhabdomyolysis and examines the impact of associated heat illness. 321 hospitalized cases of exertional rhabdomyolysis were reviewed from 2010-2013 and stratified into groups based on the present of associated heat illness or medical comorbidities. 193 (60.1%) were associated with heat illness. Initial creatine kinase (CK) levels were significantly lower in heat illness-related cases. Length of hospital stay was moderately positively correlated to maximal CK. The presence of comorbid medical conditions resulted in longer lengths of stay. Most hospitalizations for exertional rhabdomyolysis (60.1%) were associated with heat illness and these cases had lower initial values of creatine kinase (mean 6,528 U/L).