Heatstroke During Endurance Exercise: Is There Evidence for Excessive Endothermy?

Dale E. Rae; Gideon J. Knobel; Theresa Mann; Jeroen Swart; Ross Tucker; Timothy D. Noakes


Med Sci Sports Exerc. 2008;40(7):1193-1204. 

In This Article

Case 3

This case is somewhat different from the first two. A 32-yr-old man (1.75 m, 110 kg, BMI of 36) participated in his first Argus Cycle Tour. He was reportedly active and without significant medical illness. He began the race at 9 h 1 min and was discovered apneic and unconscious after 5h of cycling, apparently having experienced a cardiac arrest perhaps because of hyperthermia. He was resuscitated by paramedics who intubated him and ventilated him manually. When he arrived at the hospital at 16 h 00 min, he was comatose, with a rectal temperature of 39.0°C, blood pressure of 100/60 mm Hg, and a heart rate of 120 bpm. Initial treatment included ventilation, but there is no traceable record of whether he received electrical defibrillation at any time after his collapse. The results of blood samples taken at that time are presented in Table 4 . Twenty-four hours later, blood tests showed that his myoglobin level was >700 ng·mL-1 (normal range = 16-76 ng·mL-1), CK-MB activity was 48.6 ng·mL-1 (normal range = 0-5 ng·mL-1), and troponin T concentration was 0.26 μg·L-1 (normal range = 0-0.05 μg·L-1), all suggestive of cardiac injury. Unfortunately, the hospital chose not to make the ECG traces available. He experienced seizures for 2 d, for which he was treated with diphenylhydantoin sodium. A CT scan was normal. He also developed acute renal failure for which he underwent hemodialysis. During the following week, his condition stabilized, but he required ventilation. A series of chest x-rays during his hospitalization were normal. Ten days after hospital admission an electroencephalogram (EEG) failed to record any spontaneous brain function. He developed septicemia 2 wk after hospitalization and was treated appropriately with the antibiotics metronidazole, vancomycin, and meropenem. A CT scan revealed diffuse cerebral swelling while his state of oliguric renal failure persisted. His condition deteriorated progressively until his death, 17 d after the race. The final diagnosis made by the physician treating the patient was recorded as cardiac arrest during physical exertion, exertional heatstroke, acute renal failure, brain damage (possibly secondary to hyperthermia or hypoxia), and a terminal septicemia.

Autopsy revealed a mildly enlarged heart with no significant occlusive coronary artery disease, but there was mild to moderate atherosclerosis in the large arteries. There was also evidence of previous episodes of microinfarction. The pathologist's summary stated that the patient had evidence of chronic ischemic heart disease, early bronchopneumonia, and acute tubular necrosis with hemoglobin cylinders. The cause of death was undetermined, but the pathologist considered that the findings were consistent with heatstroke and its consequences.


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