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Exertional heat illness is a largely preventable cause of illness and death among physically active people, including athletes and outdoor workers, and the New England Journal of Medicine is promoting a comprehensive review article that was published this spring to remind clinicians of best practices during these sizzling summer months. The review emphasizes that heat illness can occur even in moderate weather when metabolic heat production exceeds the body’s ability to dissipate heat. Clinicians should recognize that exertional heat stroke in particular may present suddenly and should be suspected in any patient with altered mental status during or after physical activity. Risk factors include inadequate heat acclimatization, dehydration, low fitness, obesity, febrile illness, cardiovascular disease, and protective equipment that limits heat loss. There is also new evidence suggesting that severe heat illness may have lasting cardiovascular consequences, according to the authors. Exertional heat illness places stress on the cardiovascular system by increasing heart rate and cardiac output while reducing circulating blood volume through sweating and redistribution of blood flow to the skin. In severe cases, patients may develop arrhythmias, transient myocardial dysfunction, myocardial injury, or ischemia, with an increased long-term risk of cardiovascular disease and cardiovascular mortality.
What to look for: Because patient outcomes are linked to the duration of hyperthermia, immediate cooling, removal from the hot environment, and circulatory support are best practices in the field, which should be prioritized first before the individual is transported to a healthcare setting for evaluation and treatment. From there, clinical care focuses on continued cooling, support of the circulatory system, and addressing any possible end-organ complications. The authors say individuals’ response to heat makes it challenging to define a specific physiological “threshold” when intervention is clinically necessary. Watch for a core temperature above 40.5°C (104°F), altered mental status (eg, confusion, agitation), and loss of consciousness, which may indicate exertional heat stroke.