Physiologic Response to Exercise or Rhabdomyolysis? Creatine Phosphokinase Elevation in 16 Asymptomatic Firefighters

BACKGROUND We present a case series of 16 trainee firefighters who presented to the Emergency Department with elevated creatine phosphokinase levels of greater than 14 000 units per liter 3 days after the initiation of intense aerobic exercise. All 16 patients were diagnosed with exercise-induced rhabdomyolysis and were mostly asymptomatic. While exercise-induced rhabdomyolysis often affects untrained individuals who abruptly initiate strenuous exercises, our patients were all physically well-trained and maintained an active training regimen. In review of this unusual case series, we assess the patients' risk factors for exercise-induced rhabdomyolysis and the complications of their elevated creatine phosphokinase levels despite their asymptomatic presentations. CASE REPORT We focus on the exercise routine, hospital admission, and course of treatment for 4 of the 16 patients who gave written consent to participate in the study. Therapy was targeted towards intravenous fluids and the lowering of creatine phosphokinase levels. Patients 1, 2, 3, and 4 were discharged when creatine phosphokinase levels decreased by 17%, 40%, 39%, and 40%, respectively. CONCLUSIONS Given the differing guidelines for diagnosis, treatment, and discharge for asymptomatic exercise-induced rhabdomyolysis, it was unclear if this was a physiologic or pathologic response to exercise, if hospital admission was indicated, and the extent to which creatine phosphokinase had to decrease for discharge. Our aim is to: 1) determine recommendations to prevent muscle injury following exercise, 2) distinguish between physiologic response to exercise and clinically significant muscle damage, and 3) and recommend a course of treatment given asymptomatic presentation.