Disorders Due to Heat and Cold

Humans normally regulate body (core) temperature at about 37° C (98.6° F), and fluctuations within the narrow range of 35° to 41° C can be tolerated by healthy acclimatized persons. Rectal, esophageal, and oral measures of core temperature can be used for clinical judgment but not ear or scanned temporal artery temperature. Serious heat illness includes heat exhaustion, heat injury, and heatstroke. Heat illness accounts for substantial morbidity and mortality in the world and appears to be increasing in the United States. With global climate change, the resultant warming has led to severe heat waves that put vulnerable populations at particular risk. Management of serious heat illness should stress early and aggressive whole-body cooling (e.g., cool/cold water immersion or skin soaking with accelerated evaporation), rehydration, and monitoring. Cold injuries are classified as hypothermia (mild, moderate, and profound) and peripheral cold injuries (nonfreezing and freezing), which often occur simultaneously. Moderate (core temperature < 32° C) and profound (core temperature < 26° C) cold require active rewarming with common complications including ventricular fibrillation. Frostbitten tissues should be protected from trauma and not thawed until confident that warmth can be maintained because refreezing causes additional injury. Gentle rewarming in a water-bath (38° to 43° C) with ibuprofen administration is recommended. Imaging can help predict likelihood of tissue viability, and surgical consultation is recommended. Therapeutic hyperthermia and hypothermia are experimental.