Heat-Related Illness

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Key points

  • Evaporation is the most effective cooling mechanism in the emergency department; cooling blankets are less effective.

  • Environmental assessment of risk for heat-related illness must include wet bulb global temperature for accurate evaluation of heat stress, including humidity.

  • Do not rule out heat stroke based on lack of sweating.

  • Definitions of heat-related illnesses are less important than is recognition of the severity of presentation, which drives subsequent evaluation and treatment.

  • Elevations

Physiology

Normal human core temperature is maintained at roughly 37°C across all populations. Normal skin temperature is nearly constant at 35°C, creating the temperature gradient necessary to dissipate heat from the core to the periphery. The body’s net exothermic metabolism constantly generates heat at a basal rate ofapproximately100 kcal/h.6

In addition, the body absorbs heat from and dissipates heat to the environment by 4 basic mechanisms: conduction, convection, evaporation, and radiation (Table 1).

Pathogenesis and clinical presentation

When the cooling mechanisms fail, core temperature rises, leading to pathologic changes in several organ systems. The observed pathologic changes are thought to occur via direct cytotoxicity and a severe systemic inflammatory response (SIRS).14 The cellular function of any tissue is affected by elevated temperature by denaturation of proteins, release of proinflammatory cellular mediators, including cytokines, and, at very high temperatures, cell death and apoptosis. The critical thermal

Diagnosis and risk stratification

Strict diagnostic criteria for the heat-related illnesses do not exist, except for agreement that the diagnosis of heat stroke should include a temperature of 40°C and CNS dysfunction. Therefore, recognition of the severity and extent of heat exposure as the root cause of the presenting complaint(s) takes precedence. Early recognition of elevated core temperature, knowledge of environmental exposure, careful consideration of the differential diagnosis (Box 1), and a search for anything in the

Treatment

Because heat-related illness includes a wide spectrum of severity, the therapeutic options range from simple cooling measures and oral hydration to intensive care services. Young, healthy adults with normal examination results, other than mildly elevated core temperature, may be observed in a cool environment and provided oral hydration with cooled, slightly hypotonic solutions. Solutions with high osmolality slow gastric emptying, delaying transition of cooled fluids to the small intestine and

Summary

Heat-related illnesses can be avoided or minimized by using proper preventive measures, such as correct evaluation of the environment and acclimatization or, when a high-temperature environment is unavoidable, reducing activities that create heat stress. Recognition of a primary heat-related illness, while considering the complete differential diagnosis of hyperpyrexia, is key to appropriate treatment. Current research indicates that the most effective means of reducing core temperature is

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  • Cited by (0)

    Disclosures: None.

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