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August 2013
August 2013

Top Tips to Avoid Heat Illnesses this summer

As the mercury in your outdoor thermometers rises, it is important to maintain a healthy body

temperature. People with chronic disease and those taking medications, such as

Immunosuppressive drugs, need to be especially careful.

Heat exchanges with the environment in four ways: conduction, convection, radiation, and evaporation. Conduction refers to heat loss through direct contact with a cooler object. Convection is the dissipation of heat when relatively cool air passes over exposed skin. Radiation is the release of heat from the body directly into the environment. Evaporation through perspiration is the body’s most effective method of cooling under most circumstances, dissipating up to 600 kcal per hour in optimal conditions. Our brain starts a series of ways to control heat exchange when our core temperature increased about 1.8 Fahrenheit degrees.

Heat exchange is dependent on gradients of temperature and moisture; as the ambient temperature and humidity increase, thermal transfer becomes less efficient. Thus hot, humid weather confers the highest risk of heat injury. Heart rate, cardiac work, and respiration increase when temperature increases, while blood supply to different internal organs decreases. Medications such as constrictors of blood vessels and beta blockers (such as metoprolol, atenolol,propanolol) can profoundly impact temperature regulation by decreasing the body’s ability to shunt large volumes of hyperthermic (high temperature) blood away from the core and to the skin.

After several weeks in a hot environment the body can adapt and become more efficient. The primary response involves salt retention and increased fluid secretion through the sweat glands. Other changes include increased circulating blood volume, enhanced kidney filtration rate, and an increase in the kidneys’ ability to withstand exertion.

Medications that can increase risk of for heat related illness include : Alcohol
Blood vessels constrictors such as Alpha and adrenergics
Benzodiazepines ( such as ativan, lorazepam, ativan, etc)
Beta blockers (such as metoprolol, atenolol,propanolol)
Calcium channel blockers ( procardia, nifedipine, cardizem,etc)
Diuretics ( any water pill)
Neuroleptics ( chlorpromazine,ect)
Phenothiazines (phenergan)
Thyroid agonists
Tricyclic antidepressants ( amytriptiline)

Here are our top tips to avoid heat illnesses this summer.

-If you exercise, make sure to start slow. The higher your fitness level the less likely you will be to experience a heat illness. Stop and rest if you need to.

– Stay hydrated. Avoid alcohol and caffeinated beverages. If you become thirsty, you are already dehydrated and are at increased risk of developing a heat illness.

– Select loose-fitting, light color clothing.

– Eat well-rounded meals and increase your fluid intake at meals.

– Sleep well.

– Rest between activities in the shade or out of the heat.

– Recognize the signs and symptoms of the three general types of heat illnesses: heat cramps, heat exhaustion and heat stroke.

-Talk to your providers if you are taking medications that may put at risk for heat illness.

The signs and symptoms of heat cramps include discomfort in the muscles that often leads to a decrease in performance. These are caused by either too little or too much fluid intake, which leads to a decrease in the body’s sodium level.

Heat exhaustion is marked by dehydration, dizziness, gastrointestinal distress, persistent muscle cramps, cool clammy skin, chills, weakness, a change in mental status and hyperventilation.

Heat stroke is the most serious of the three and is considered a medical emergency. Signs and symptoms are similar to exhaustion but also include marked changes in mental status (delirium, hysteria or a loss of consciousness), a rapid heart rate, low blood pressure and a body temperature elevated above 104° F. Rhabdomyolysis is muscle breakdown and can happen with heat stroke and can be so severe that can shut down the kidneys.

Fidel Barrantes MD

Reference: Glazer J. Management of Heatstroke and Heat Exhaustion.