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.
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.