Heat Stroke

Published on 07/03/2015 by admin

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Last modified 07/03/2015

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Chapter 77 Heat Stroke

William J. Benedetto, MD

1 What is heat stroke?

Heat stroke is a life-threatening illness characterized by a core body temperature above 40° C and central nervous system (CNS) dysfunction. The CNS abnormalities may include delirium, lethargy, convulsions, or coma. Anhidrosis (lack of sweating) may or may not be present, depending on the type and presentation of the illness.

2 What is the pathophysiology of heat stroke?

The body gains heat from metabolism and from the environment, and this heat must be dissipated to maintain a normal temperature of 37° C. This process (thermoregulation) relies primarily on cutaneous vasodilatation and evaporation of sweat. When these processes are overwhelmed, core temperature will rise. When the core temperature exceeds 40° C, an acute phase response is elicited from heat-stressed cells including cytokines and heat shock proteins.

3 What are the two types of heat stroke? How do they present?

Classic heat stroke is associated with high environmental heat and humidity with inadequate cooling. There is generally no history of significant exercise or exertion. Classic heat stroke typically has a slow onset, often developing over days. It generally afflicts the elderly and the chronically ill, who may present with anorexia, nausea, vomiting, headache, dizziness, confusion, and hypotension. Anhidrosis is a common finding. Up to 25% of patients present with hypotension.

Exertional heat stroke usually affects young people in good health who are exercising in a hot, humid environment, often with clothing or equipment that restricts cooling. It is rapid in onset, and nausea, dizziness, and confusion are common. Fatigue, ataxia, coma, and nuchal rigidity or posturing may also occur. Profuse sweating is a typical finding on examination.

4 Which populations are at greater risk for heat stroke?

Extremes of age—because of relatively poor temperature regulation in the young and old, especially during heat waves

Chronically ill—especially those taking drugs that predispose to heat illness

Military recruits—especially Northerners not acclimated to the weather in the Southern region of the United States

Athletes—most commonly football players and runners

Laborers—especially if water losses have not been replaced

Obese individuals—because heat dissipation is compromised

5 Which medications predispose a person to heat stroke?

Drugs increasing heat production through increased motor activity: cocaine, amphetamines, ephedrine, phencyclidine, lysergic acid diethylamide, alcohol withdrawal

Drugs decreasing thirst: for example, haloperidol

Drugs decreasing sweating: antihistamines, anticholinergics, phenothiazines, β-blockers

6 What is the mortality rate of heat stroke?

When treatment is prompt and effectively lowers core temperature, mortality in young, healthy patients is minimal. In the setting of delayed effective treatment and significant comorbidities, mortality can be as high as 70%.

7 What are the common sequelae and complications of heat stroke?

Heat stroke can lead to multiorgan dysfunction syndrome including the following:

Renal failure or rhabdomyolysis (most commonly in exertional heat stroke)

Acute respiratory distress syndrome

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