Heat Illness : (Heat Syncope, Heat Cramps, Heat Exhaustion)

Presentation

Heat illnesses comprise a spectrum of illnesses resulting from failure of the body’s normal thermoregulatory mechanisms after exposure to excessive heat. Most heat-related illness is mild; however, severe hyperthermia associated with heat stroke, neuroleptic malignant syndrome, or serotonin syndrome is a severe, life-threatening condition and should not be overlooked.

The milder forms of heat-related illness include heat syncope (or presyncope), or heat cramps. These illnesses are usually found after prolonged exposure to excessive heat and humidity in patients who are unable to remove themselves from the situation.

Heat syncope is postural syncope or presyncope related to excessive heat exposure.

Heat cramps are painful muscle cramps after vigorous exertion in hot environments (often several hours later) in the calves, thighs, and/or shoulders.

Heat exhaustion is a slightly more severe form of heat illness, but is easily treated with hydration and cooling. Elderly patients (without air-conditioning on a hot, humid day), workers, or athletes (exerting themselves in a hot climate while taking in an inadequate amount of fluid) may be more symptomatic, with fatigue, weakness, lightheadedness, headache, nausea, and vomiting in addition to orthostatic symptoms and painful muscle spasms. The patient may have a normal temperature (but generally >38 °C), or the temperature may be elevated to 40 °C (104 °F), with tachycardia, clinical evidence of dehydration, and (often, especially with exertion) profuse sweating. Mental status is normal.

Another minor form of heat stress is heat edema , which occurs in elderly individuals and consists of swelling of the feet and ankles in response to extreme heat. Miliaria, also known as heat rash or prickly heat , is common in hot and humid climates and presents with small, red, pruritic papules that result from plugging of sweat gland ducts.

The severe forms of heat-related illness, such as heat stroke, are characterized by alteration in mental status associated with hyperthermia (temperature >40.5 °C). Neuroleptic malignant syndrome and serotonin syndrome are not typically classified as heat-related illnesses but present with severe hyperthermia and altered mental status and can be easily confused with heat stroke.