Heat-Related Injuries by Dorcas M. Eaves, MD, MSS, ACPE

Certification: Board Eligible General Surgery, American Board of Medical Quality

Many meteorological and academic circles attribute weather extremes to global warming, secondary to greenhouse emissions. Whether or not you believe this theory, statistical data demonstrates an increasing number of premature deaths associated with climate change.  Several times each year, California along with many other states and countries, experience wide temperature swings that have resulted in premature deaths.

In a report published by Medscape Multispecialty news, there were 658 annual heat-related deaths in the United States, between 1999-2009; Bloomberg News reports 3,000 deaths linked to heatstroke occur each year in Japan.  Dan Lashhof’s Switchboard blog reports: “An average of 1,300 heat related deaths occur per year due to direct or indirect effects of heat exacerbating life threatening illnesses such as heat exhaustion, heat stroke, cardiovascular disease and kidney disease.”

Student athletes who practice and play in hot environments are subject to heat injuries which are preventable.  There is no age group that is exempt from heat-related illnesses.  As a society, we do not adequately prepare for weather extremes, and as a result, heat and cold related illness/deaths become the topic of many news hour programs.  Just recently (May 2014), temperatures reached record highs in many parts of the country with an increase in heat related deaths, compared to the same time last year. While enjoying warm-weather activities, many fail to maintain adequate hydration, thereby threatening well-being.

Heat related illnesses/injuries fall, basically, into 5 categories:

A. Heat Rash or Miliaria

B  Heat Syncope

C. Heat Cramps

D  Heat Exhaustion

E. Heat Stroke

We will explore the signs and symptoms of these heat related illnesses, treatments, outcomes, and prevention.

Heat Rash

Miliaria is an acute inflammatory reaction of the skin that can be seen mainly on the torso of the body and in skin folds.  It causes a burning itching superficial collection of small red vesicles, papules, or pustules on the covered areas of the torso. It is more common in hot moist climates. It can be associated with fever and heat prostration.

Individuals at highest risk are bedridden individuals who also have a fever. The rash is due to pore blockage of the sweat ducts causing secretions to accumulate inside the pore and form a “ball-like collection of secretions” under the skin. This condition is usually mild, but severe forms of this condition can occur if it interferes with the body’s heat regulation system.

Heat Syncope

Heat syncope, or fainting, occurs when the body’s vascular system dilates forcing blood pools in the extremities and depriving the brain, as well as the rest of the body, of needed fluid.  The body’s pulse is weak with a low blood pressure (less than 100), and the skin is cool and clammy.  The fainting is typically preceded by 2 or more hours of vigorous exercise.

Heat Cramps

The most common cause of heat cramps is loss of body fluids and electrolytes. The muscles affected will vary depending on the activity preceding the event.  The upper body muscles react to activities like playing tennis, the lower leg muscles with running. The cramping is secondary to the loss of body salt from heavy perspiration through sweating and replacing the fluid loss with water. Heat cramps can last for 1-3 minutes or longer. The cramping muscles feel like a knot within the substance of the muscle. If the individual’s temperature is taken, it is usually normal or slightly elevated.  Heat cramps are also associated with other vigorous exercise or activity.

Heat Exhaustion

Heat exhaustion is associated with loss of body sodium and subsequent dehydration. With the loss of body sodium, there is a concomitant changes in body hemodynamics. The pulse or heart rate is elevated (usually greater than 100); the blood pressure can be low or high depending on the release of the body’s stress hormones (Adrenalin/Norepinepherine). Core body temperature is around 100.4F (37.8C).  There may be muscle cramping, in addition to nausea, vomiting, malaise (tiredness/fatigue), and muscle pain. The individual can experience extreme thirst, headache, dizziness, anxiety, tingling, impaired judgment, hysteria, and sometimes hallucination.  If breathing is fast (hyperventilation), the lungs blow off more oxygen than it takes in and retains more carbon dioxide changing the body dynamics. This causes a buildup of lactic acid in the body. When this occurs, heat exhaustion can progress to heat stroke.

Heat Stroke

Heat stroke is a life-threatening condition. Symptoms associated with this condition include dizziness, irrational behavior, weakness, nausea, vomiting, diarrhea, confusion, delirium, blurred vision, convulsions, collapse, and unconsciousness. The heart rate will elevate (usually greater than 120), and the blood pressure initially elevates but later decreases as dehydration/hypotension occurs. The core body temperature is around 104F (40C).  The respiratory rate is also elevated, causing hyperventilation and heat exhaustion. When heat stroke is secondary to exertional activities, a clinical condition known as rhabdomyolysis can occur. This is a breakdown of muscle protein, known as myoglobin, which precipitates/deposits in the kidneys and can cause kidney failure. When Myoglobin deposits in the kidneys, the urine looks reddish or bloody in color.

A second type of heat stroke is classical heat stroke.  This condition can be seen in individuals who are hemodynamically compromised, usually secondary to an underlying medical condition or has an underdeveloped heat regulatory system. These individuals are usually elderly adults, infants, and young children who cannot adequately cool their bodies through sweating (body regulatory systems) or their regulatory systems is affected by medications.

TREATMENT:

Heat Rash/Miliaria

Miliaria is treated with topical steroid creams like Triamcinolone Acetonide 1% in a lotion base. Steroid ointments should be avoided as these occlude the pores. The steroid lotion is applied twice daily. If a secondary bacterial infection occurs, it is usually due to Staphylococcus aureus, which is ubiquitous on the skin. The antibiotic of choice is Dicloxicillin 250 mg 4 times daily for 7-10 days. If skin cultures disclose Methicillin Resistant Staph Aureus (MRSA) Bactrim DS is the antibiotic of choice.

Heat Syncope

To battle heat syncope and heat cramps, fluid replacement with an electrolyte solution is recommended. This can be done by consuming Pediolyte, Gatorade, or water with salt; the salt water solution should consist of a mixture of 4 teaspoons of table salt mixed into 1 gallon of water.  The individual should also be moved into a cool shady spot while resting in a recumbent (lying down) position. Fluid resuscitation/replacement can be done by the administration of the oral fluids listed. Recovery to full function takes a few days to approximately one week.

Heat Exhaustion and Heat Stroke

Hospitalization is needed in order to treat heat exhaustion and heat stroke. Resuscitation starts with paramedics doing an assessment and starting an intravenous line in the field, or in the Emergency Room.  Initial treatment starts with intravenous fluid resuscitation/replacement with 1,000-2,000 milliliters of fluid, as well as active cooling measures, such as fans, ice packs, and cooling blankets. Depending on the initial laboratory studies, the resuscitation solutions can be physiologic saline solution (half of normal saline) or an isotonic glucose solution (Dextrose 5% water [D5W]).  If the laboratory studies disclose low sodium levels, the solution of choice would be 3% saline solution (hypertonic saline). Additional testing would include an electrocardiogram (EKG) to look at the heart rhythm and treatment of any abnormalities.

Once hospitalized and depending on the clinical condition, many other cooling measures can be started. These can range in invasiveness from iced gastric lavage where a tube is placed into the stomach through the nose (nasogastric tube), and ice water is injected into the stomach to lower body temperature to cardiopulmonary bypass (a major surgical procedure). Medications will be given for nausea, shivering, and fever, along with any other abnormality found through laboratory studies and the EKG.

Prevention:

When an individual recovers from heat stroke, he/she is at risk for future repeat events. Prevention starts with adequate hydration before, during, and after strenuous exercise. Fluid intake should be increased with heavy perspiration/sweating.  A rule of thumb is 3 liters of fluid (water with added salt/Gatorade/Pediolyte) approximately every 60-90 minutes.  Take frequent rest periods to allow your body to cool down, and rest in a shady area. Do not take salt tablets to replenish lost sodium as the absorption is unpredictable.

Additional References to those cited in the paper

Text book of Clinical Surgery 2012

Current Medical Diagnosis and Treatment 2013