Heat Illness and Heat Stroke

Chuck Peterson, MD

Arizona Sports Medicine Center

Heat illness can affect about anyone.  Temperature, humidity, age, genetics, illness, dehydration, activity and duration can all contribute to the development of heat injury.  There are two main types of heat illness and varying levels of injury:

Classic Heat Illness:  Vulnerable individuals.  Examples include young, elderly, chronic illness, and sick.

Exertional Heat Illness:  Health, physically active individuals.  Examples include athletes, workers, and military.

Heat Exhaustion:  mild to moderate, moderate to high temperature (98 to 104 F), generally hospitalization not required, though may be treated in emergency department..

Exertional Heat Injury:  moderate to severe with cellular, organ, and tissue injury.  Possible hospitalization.

Exertional Heat Stroke:  severe with organ and tissue injury, central nervous system (CNS) effects of confusion, seizure, or unconsciousness.  May progress to death.

Background:

Heat in the body is usually finely balanced to maintain a normal temperature.  The body and the environment both can produce and dissipate heat.

Heat production:  muscle (80% of energy to muscles becomes heat), sun, friction, work against gravity.

Heat dissipation:  evaporation from skin and airway, radiation to ground and air (except Arizona summers!), convection to ground and air.

As the body's inner heat (core temperature) rises, the body is stressed.  If the core temperature exceeds the body's ability to release the excess heat, injury can occur.  Initially cells can be injured, which can lead to organ damage and may even result in death if not recognized early and treated appropriately.

A core temperature of 104 F (40 C) signals extreme danger.  The temperature can rapidly increase to 106 F (41 C) with resultant cell injury.  A temperature above this (107 F or 41.5 C) is generally terminal.  The core temperature must be taken as a rectal temperature to be accurate.

At-risk populations:

Children, the elderly, and people with chronic illness can be especially susceptible to heat illness.  The may have difficulty regulating their temperature as compared to the general population.  They may also be more vulnerable in that they may be unable to remove themselves from a potentially dangerous situation.  To avoid injury and death, children should never be left alone in a car, even for "a few minutes".  If we find a child alone in a car we should call 911 and make immediate efforts to get the child out.

Athletes are usually healthy people used to working hard, often in stressful conditions.  Despite their ability, athletes can also be susceptible to injury and death from heat.  Historically, the 1912 Stockholm Olympics had a heat-related death in a marathon runner.  This was a reflection of the original run from Marathon, as that runner's death may have also been related to heat stroke.

More recently, the deaths of Korey Stringer, of the Minnesota Vikings, and Steve Bechler, of the Baltimore Orioles, illustrate that even elite athletes can succumb to heat stroke.  Tragedy can occur in almost any sport at any level, including recreational and high school.  Those most commonly considered at risk are runners and football players.

Much can be done to treat heat illness, but it must first be diagnosed.  More importantly, much can be done to prevent it.

Prevention strategies:

• Check the forecast and the relative heat index (combining heat and humidity).  High risk times occur with the temperature above 95 F, but this number is lower with higher humidity.
• Avoid exercise during the hottest hours.
• Avoid use of heat trapping clothing and equipment on hot days
• Avoid dehydration.  An athlete can perspire 1-2 liters (or more) at peak activity in the heat.  Drink before, during, and after exercise.  Obtaining weights before and after exercise can illustrate water loss.  One pound of weight loss is equivalent to one pint of fluid (1 kg = 1 L).  This must be restored before exercise the next day.  Supplements and alcohol can also contribute to dehydration.
• Become conditioned to the heat rather than attempting strenuous activity in the heat while out-of-shape.  Poor conditioning or obesity can contribute to heat problems.
• Those with a history of heat illness must be carefully watched.  Special attention should also be paid to those who are salty sweaters (leave salty residue on shirt).  Some people are more genetically prone to heat illness than others.
• Avoidance of heat-producing supplements and drugs.  Common examples include ephedra (weight-loss supplements generally work through heat production) and cocaine.
• Do not exercise in the heat when ill.  This can push an athlete beyond her reserves.

Diagnosis:

Flushing

Dry skin

Hot skin

Confusion

Nausea or vomiting

Cramping

Unconsciousness

Seizure

Rectal temperature >102 F

Poor performance, lethargy

Treatment:

• Get out of the sun and into the shade.
• Oral fluids (water is fine; may use sports drink if desired).
• Cool off with ice water-soaked sheet, ice packs, ice bath.
• Fan off to help with evaporation.
• Rub the skin intermittently to promote blood flow to skin to help release heat.
• Monitor temperature closely.  Remember, this should be a rectal temperature.
• Call 911 with severe symptoms or if not sure.  The athlete may require more intensive therapy, IV fluids, and laboratory work.  In extreme circumstances, too rapid of fluid replacement can be very dangerous.