Heat Injuries

Published on 22/03/2015 by admin

Last modified 22/04/2025

Print this page

This article have been viewed 1268 times

Chapter 681 Heat Injuries

Heat illness is the 3rd leading cause of death in U.S. high school athletes. It is a continuum of clinical signs and symptoms that can be mild (heat stress) to fatal (heatstroke) (Chapter 64). Children are more vulnerable to heat illness than adults. They have greater ratio of surface area to body mass than adults and produce greater heat per kilogram of body weight than adults during activity. The sweat rate is lower in children and the temperature at which sweating occurs is higher. Children can take longer to acclimatize to warmer, more humid environments (typically 8-12 near-consecutive days of 30-45 min exposures). Children also have a blunted thirst response compared to adults and might not consume enough fluid during exercise to prevent dehydration.

Three categories for heat illness are generally used: heat cramps, heat exhaustion, and heat stroke. However, symptoms of heat illness overlap and advance as the core temperature rises. Heat cramps are the most common heat injury and usually occur in mild dehydration and or salt depletion, usually affecting the calf and hamstring muscles. They tend to occur later in activity, as muscle fatigue is reached and water loss and sodium loss worsen. They respond to oral rehydration with electrolyte solution and with gentle stretching. The athlete can return to play when ability to perform is not impaired. Heat syncope is fainting after prolonged exercise attributed to poor vasomotor tone and depleted intravascular volume, and it responds to fluids, cooling, and supine positioning. Heat edema is mild edema of the hands and feet during initial exposure to heat; it resolves with acclimatization. Heat tetany is carpopedal tingling or spasms caused by heat-related hyperventilation. It responds to moving to a cooler environment and decreasing respiratory rate (or rebreathing by breathing into a bag).

Heat exhaustion is a moderate illness with core temperature 100-103°F (37.7-39.4°C). Performance is obviously affected, but central nervous system (CNS) dysfunction is mild, if present. It is manifested as headache, nausea, vomiting, dizziness, orthostasis, weakness, piloerection, and possibly syncope. Treatment includes moving to a cool environment, cooling the body with fans, removing excess clothing, and placing ice over the groin and axillae. If a patient is not able to tolerate oral rehydration, IV fluids are indicated. Patients should be monitored, including rectal temperature, for signs of heat stroke. If rapid improvement is not achieved, transport to an emergency facility is recommended.

Heat stroke is a severe illness manifested by CNS disturbances and potential tissue damage. It is a medical emergency; the mortality rate is 50%. Sports-related heat stroke is characterized by profuse sweating and is related to intense exertion, whereas “classic” heatstroke with dry, hot skin is of slower onset (days) in elderly or chronically ill persons. Rectal temperature is usually >104°F (40°C). Significant damage to the heart, brain, liver, kidneys, and muscle occurs with possible fatal consequences if untreated. Treatment is immediate whole-body cooling via cold water immersion. Airway, breathing, circulation, core temperature, and CNS status should be monitored constantly. Rapid cooling should be ceased when core temperature is ~101-102°F (38.3-38.9°C). IV fluid at a rate of 800 mL/m² in the first hour with normal saline or lactated Ringer solution improves intravascular volume and the body’s ability to dissipate heat. Immediate transport to an emergency facility is necessary. Physician clearance is required before return to exercise.

Dehydration is common to all heat illness; therefore, measures to prevent dehydration can also prevent heat illness. Thirst is not an adequate indicator of hydration status because it is initiated at 2-3% dehydration. Athletes are advised to be well hydrated before exercise and should drink every 20 min during exercise (5 oz for those weighing 40 kg, 9 oz for 60 kg, and 10-12 oz for those >60 kg). Free access to cold water should be advocated to coaches. During a football practice, scheduled breaks every 20-30 min with helmets off to get out of the heat can decrease the cumulative amount of heat exposure. Practices and competition should be scheduled in the early morning or late afternoon to avoid the hottest part of the day. Guidelines have been published about modifying activity related to temperature and humidity (Fig. 681-1). Proper clothing such as shorts and t-shirts without helmets can improve heat dissipation. Prepractice and postpractice weight can be helpful in determining the amount of fluid necessary to replace (8 oz for each pound of weight loss).