Heat illness

 

Nothing to do with pyrexia

 

The three heat illness conditions

Heat cramps

Heat stroke

Heat exhaustion

 

Heat cramps

 

Heat cramps may develop in muscles, due to acute or chronic loss of salt from the ECF

May occur to fit people after a hard day in hot environment who replace water but not salt

 

Heat Stroke - hyperthermia

 

Diagnosis

 

Aetiology

Temperature tolerance depends on ambient humidity

In high humidity or water the body temperature will rise at temperatures above about 34`C

Exercise will greatly contribute to heat gain

Over dressing

In hyperthermia hypothalamic function will be compromised and sweating inhibited

Reduced sweating due to prickly heat - inflammation of sweat glands after prolonged exposure to high temperatures

 

Features

Core temperature greater than 41`C

Dizziness

Headache

Nausea

Vomiting

Confusion

Loss of consciousness

Damage to brain

Damage to organs such as the liver or kidneys can result in death several days after an episode of hyperthermia

Cerebral oedema may develop

 

Treatment

Cool as rapidly as possible

Tepid sponging, air currents

Probably not cold water

 

Heat exhaustion

 

Aetiology

Loss of water and or salt

In hot environments active people may lose 5 - 6 litres of fluid and 20g of salt per day

 

Features

Dizziness

Generalised fatigue

Weakness

Syncope

Hypovolaemia - hypotension

Rise in temp to 38-40`C

Delirium

 

Treatment

5 litres of fluid and 25g of salt in the first 24 hours

Extreme cases may require infusion of isotonic saline

Pay attention to serum sodium and potassium

 

Acclimatisation to heat

1-3 weeks

Increase in maximum rate of sweating

Increase in plasma volume

Increase in levels of aldosterone result in reduced loss of salt in sweat and urine