ABSTRACT
Hyperthermia is a core temperature >37.5°C. Severe hyperthermia is defined as a core temperature >40°C or an increase in body temperature at a rate greater than 2°C per hour. Hyperthermia increases metabolic rate and oxygen consumption, which precipitates an increase in cardiac output and minute ventilation to meet demand. The increased carbon dioxide production is initially compensated for by tachypnoea, but the patient soon starts to develop a respiratory acidosis. This is compounded by the metabolic acidosis, which is caused by an increasing oxygen debt and lactic acidosis. Sweating and vasodilatation cause hypovolaemia, which exacerbates the metabolic derangement if left untreated. Central nervous system (CNS) dysfunction (delirium, seizures, coma and permanent damage), rhabdomyolysis, acute renal failure, myocardial ischaemia and dysfunction may all follow.
