Heat-related illnesses and conditions include heat stroke, syncope, collapse, edema and cramps which occur in athletes exercising in warm conditions who have an elevated core temperature.
Heat-related illnesses and conditions include heat stroke, syncope, collapse, edema and cramps which occur in athletes exercising in warm conditions who have an elevated core temperature. Hyperthermia is defined as the elevation of core body temperature above the normal diurnal range of 36 to 37.5ºC, due to failure of thermoregulation. Hyperthermia is different from the more common sign of fever, which is induced by cytokine activation during inflammation and regulated at the level of the hypothalamus.
It is important for the clinician to review additional differential diagnoses as outlined in Steps in assessment of severity in a collapsed athlete HEAT STROKE A temperature above 40ºC (or 104ºF) is generally considered to be consistent with severe hyperthermia. The body's heat production results from both metabolic processes and absorption of heat from the environment. As core temperature rises, the preoptic nucleus of the anterior hypothalamus stimulates efferent fibers of the autonomic nervous system to produce sweating and cutaneous vasodilation.
The presence of heat stroke should raise suspicion of other concurrent multifactorial processes such as genetic predisposition, unaccustomed drug use or subclinical viral infection. Evaporation is the primary mechanism of heat dissipation in a hot environment, but this becomes ineffective above a relative humidity of 75 percent. The other major pathways of heat dissipation such as radiation (emission of infrared electromagnetic energy), conduction (direct transfer of heat to an adjacent, cooler object), and convection (direct transfer of heat to convective air currents) – cannot efficiently transfer heat when environmental temperature exceeds skin temperature.
Temperature elevation is accompanied by an increase in oxygen consumption and metabolic rate, resulting in hyperpnea and tachycardia. Above 42ºC (108ºF), oxidative phosphorylation becomes uncoupled, and a variety of enzymes cease to function. A cytokine-mediated systemic inflammatory response then develops, and production of heat-shock proteins is increased.
Blood is shunted from the splanchnic circulation to the skin and muscles, resulting in gastrointestinal ischemia and increased permeability of the intestinal mucosa. Hepatocytes, vascular endothelium, and neural tissue are most sensitive to increased core temperatures, but all organs may ultimately be involved. In severe cases, patients develop multi-organ system failure and disseminated intravascular coagulation (DIC)(2,3,4).
If you are experiencing symptoms that may be related to heat-associated conditions in the athlete, it is important to see a sports medicine physician. Early evaluation and treatment typically lead to better outcomes. Do not ignore pain or symptoms that are limiting your activity.
*This article is for educational purposes only and does not substitute for professional medical advice. Always consult a qualified healthcare provider.*
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