Emergency Medicine

202 Environmental Emergencies

HEAT, COLD AND DROWNING

Heat illness

Heat illness occurs when the body’s capacity to dissipate heat is exceeded by

interna l heat production and/or by heat stress from an externa l source.

Heat illness is predisposed to by hot weather, exercise, obesity, fever, lack of

physical fitness or acclimatization, skin disease such as psoriasis or eczema,

alcohol intake, and drugs such as anticholinergic agents, cocaine and amphet-

amines.

DIAGNOSIS

1 Mild to moderate heat illness

Thermoregulatory mechanisms remain intact.

(i) Heat cramps

(a) pain develops in heavily exercising muscles in hot weather

secondary to sodium depletion and dehydration.

(ii) Heat exhaustion

(a) thirst, cramps, headache, vertigo, anorexia, nausea and

vomiting occur

(b) the patient is flushed and sweating, with rectal temperature of

38–39°C

(c) tachycardia and orthostatic hypotension occur secondary to

dehydration.

2 Severe heat illness: Heat stroke

Thermoregulatory mechanisms fail and the rectal temperature is over

40.6°C.

(i) Classic (non-exertional) heat stroke (CHS):

CHS usually occurs in the elderly or very young during a heat wave

secondary to high environmental temperatures.

(ii) Exertional heat stroke (EHS):

EHS is associated with young adults exercising in high temperatures.

(iii) Symptoms include headache, vomiting and diarrhoea associated

with mental state change progressing to aggressive or bizarre

behaviour, collapse, seizures and coma.

(iv) Hot dry skin is usual, but profuse sweating occurs in up to 40% of

patients with exertional heat stroke.

(v) The patient is flushed, tachypnoeic, tachycardic and hypotensive.

Muscle rigidity, transient hemiplegia, dilated pupils,

disseminated intravascular coagulation (DIC) and multi-organ

failure may all occur.