Heat Stroke

The organs in the body, especially the brain, only function adequately when within a normal temperature of 36 to 38 degrees Celsius. Usually the body is able to maintain a normal temperature, even when exposed to heat. However, if exposed to excessive heat for a prolonged period then the body may no longer be able to maintain the temperature within the normal limits. Heat stroke is when exposure to environmental heat causes severe hyperthermia.

Causes
Heat stroke is most commonly caused by excessive exercise in the heat for a prolonged period. People who undertake excessive physical exertion include marathon runners, soldiers, firefighters, and construction workers. Risk factors are poor physically fitness, obesity and dehydration.

Heat stroke can also happen without exercise, if a person is exposed to excessive heat for a prolonged period. People who are at high risk for this include children and elderly, people intoxicated with drugs or alcohol, people who are neurologically impaired, as all these people may not choose to remove themselves from the heat.

Signs and Symptoms
The temperature of the body will be more than 40 degrees. There may be abnormal brain functioning, such as confusion, hallucinations and lethargy. It can cause lightheadedness, weakness in the limbs and syncope. The patient may also complain of headache, muscles cramps, ataxia, vomiting and diarrhea. If severe it can cause coma and seizures. If untreated, heat stroke can lead to rhabdomyolysis, acute kidney injury, liver injury, and even death.

Investigations
Diagnosis is made from the history and physical examination. 

A blood glucose should be checked on anyone with altered mental status. Routine blood tests include electrolyte levels, kidney function, liver function and coagulation studies.

A urinary catheter should be inserted for monitoring of urinary output if acute kidney injury is suspected.

Other investigations (such as CT head and lumbar puncture) are required if another diagnosis is suspected.

Treatment
Treatment is to cool the patient. An effective method of cooling is spraying the naked body with water whilst fans blow on the body. Shivering can be suppressed with benzodiazepines (such as diazepam). Alternatively, ice packs can be applied to the axilla, neck and groin.

Paracetamol is ineffective in heat stroke. This is because the high temperature is not due to a fever inside the body, but due to heat exposure from outside the body.

Rehydration by administration of intravenous fluids may be required.

If the patient is unconscious then an open airway must be maintained, and oxygen administered as required. If seizures occur then they must be treated with benzodiazepines (such as diazepam) and repeated as required.