As the warm months of summer begin to draw closer and closer, getting outside and adventuring becomes a bit easier. I personally love long runs in the hot part of the day and consider this my favorite time of year. Physical exertion in a hot environment carries with it special risks and requires some knowledge about heat related illnesses and basic prevention.
Acclimatization to Heat
This is often a luxury adventurers do not have, especially when a traveler arrives to a new area and begins physical activity in a new and hot environment. Typically, 8-10 days are required for a person to acclimatize to a hotter environment and daily exercise in the new environment can help the process. Exercise for 30 minutes to 1 hour per day is generally sufficient. As the body begins to acclimatize to the heat, it begins to sweat at a lower temperature, helping cool the body earlier. Care should be taken to ensure adequate hydration, with oral water and sports drinks containing both sugar, salt and potassium.
The basic categories of heat illnesses can be divided up based on core body temperature and physical findings of the effected person.
Heat Exhaustion
- Body temperature less than 39 C (102.2 F)
- Presence of sweating
- Increased heart rate (>100 beats per minute)
- Normal mental status and awareness
- Flu-like symptoms may be present such as malaise/fatigue, vomiting and weakness
Treatment of Heat Exhaustion centers around stopping physical exertion and getting the person into a cool and shaded environment. Ensure adequate oral rehydration occurs and remove all restrictive and tight fitting clothing. Ice packs may be placed on chest, arm pits and groin as these areas have blood vessels that run close to the surface and help facilitate cooling. Wrap ice packs in towels to avoid skin damage from prolonged contact. Lastly, spraying cool water on the patient and fanning them will help to reduce their body temperature quite rapidly as well.
Heat Stroke (True medical emergency)
- Body temperature above 40.5 C (105 F)
- Presence of sweating, severe cases may have absence of sweating
- Increased heart rate (>100 beats per minute)
- Changes in mental status (confusion, disorientation)
- Difficulty walking
- Low blood pressure
This condition is a true emergency and requires prompt medical care as this condition can be fatal. Heat stroke occurs after the person passes through the first stage of heat exhaustion and does not receive proper treatment or continues to exert themselves in the heat. Most experts agree that heat stroke can be diagnosed when changes in metal status occur in a patient with heat exhaustion. Treatment centers around rapid re-cooling of the patient and the faster this occurs, the better the prognosis. Icepacks (wrapped in towels) should be placed on groin, axillae and neck. Spraying with cool water and fanning the victim is most effective in rapidly cooling the patient. Intravenous fluids should be given and often require copious amounts to correct deficits. Ensure their airway is protected if their mental status deteriorates or if vomiting occurs. Seizures and shivering can be treated with benzodiazepines and oxygen should be given. This person requires prompt transfer to a medical center and close monitoring. Aggressive cooling should continue until core temperature drops to 38 C (100.4 F).
Heat Cramps
I think of heat cramps as a sign of dehydration and muscle fatigue in a hot environment. Mild heat cramps can be treated by adequately rehydrating the person, generally with a commercial sports drink. The key electrolytes are sodium and potassium, generally found in adequate concentration in products such as Gatorade. I prefer to mix one half cup water with one half cup of electrolyte drink, due to increased osmolality of the sports drink. Also, the sugars found in sports drinks help speed water into the bloodstream from the stomach.
Hyponatremia (low salt)
This is one of my favorite topics and frequently discussed in ultra-distance athletic events. True hyponatremia occurs when the measurement of sodium in the blood drops below 130mEq/liter. A frequent scenario that causes this is a person drinking large amounts of plain water to replace sweat losses which are high in sodium. The person basically loses large amounts of sodium through sweat and water loss and replaces it with a low sodium concentration fluid, like plain water. Difficulty can occur in differentiating heat stroke from hyponatremia and measurement of core body temperature can help with diagnosis. Hyponatremia generally occurs in a setting of a normal core body temperature. Treatment centers around providing intravenous re-hydration with normal saline fluid. If the patient can take oral fluids, use a full-strength (non-diluted) sports drink for fluid replacement. Prevention fo this can be accomplished by not only drinking adequate amounts of water but also regularly drinking a sports drink, before, during and after exercise.