Hazards related to the environment: heat and humidity

Excessive heat and humidity, or overexertion in these conditions, may lead to exhaustion from loss of water and salts and to severe heat-stroke requiring emergency medical attention. Tea and drinks rich in mineral salts (fruit and vegetable juices, clear soups, etc.) are recommended in cases of exhaustion. Unless contraindicated, the addition of a little table salt to food or drinks helps to prevent heat exhaustion, especially during the period of acclimatization.

Heat Exhaustion and Heat Stroke:

Exposure to high ambient temperature may lead either to excessive fluid loss and dehypovolemic shock (heat exhaustion) or to failure of heat mechanisms and dangerous hyperpyrexia (heatstroke) Common sense is the best preventive; strenuous exertion in a very hot environment and insulating clothing should be avoided, and an adequate fluid intake is important.

Heat Exhaustion:
Because of excessive fluid loss, this disorder gives adequate warning by increasing fatigue, weakness, anxiety, and drenching sweats, leading to circulatory collapse with slow thready pulse; low or imperceptible BP; cold, pale, clammy skin; and disorientation followed by a shock-like unconsciousness. Syncope (faint) is a mild form of heat exhaustion and is precipitated by standing or a long time in a hot environment, eg. the soldier on the parade ground, and is due to pooling of blood in the heat-dilated vessels of the lower extremities. Heat exhaustion is more difficult to diagnose than heatstroke, but its prognosis is far better unless circulatory failure is prolonged. Treatment is aimed at restoring normal blood volumes and improving brain perfusion, thus the patient should be placed flat or with their head slightly down. When they start responding, small amounts of sugar water should be given.
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Heatstroke (Sunstroke):
An abrupt onset is sometimes preceded by a headache and fatigue. Sweating is usually but not always decreased, and the skin is hot, flushed, and usually dry. The pulse rate increases rapidly and may reach 160; respirations usually increase, but the blood pressure is seldom affected. Disorientation may briefly precede unconsciousness or convulsions. The temperature climbs rapidly to 41C and the patient feels as if burning up. Circulatory collapse may precede death; after hours of extreme hyperpyrexia, survivors are likely to have permanent brain damage. Old age, debility, or alcoholism worsens the prognosis. Heroic treatment measures must be instituted immediately. If distant from a hospital, the patient should be wrapped in wet bedding or clothing, immersed in a lake or stream. The temperature should be taken every 10 minutes and not allowed to fall below 38C to avoid converting hyperpyrexia to hypothermia. The patient should be taken to hospital as soon as possible after the emergency methods have been instituted for further management. Bed rest is desirable for a few days after severe heatstroke, and temperature lability may be expected for weeks.
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