Key investigations in heat-related illness

Investigations are required in suspected heat stroke, but are not usually indicated in heat exhaustion. Management should be started promptly and not delayed while awaiting test results.

Note: Do not delay cooling measures while awaiting results of investigations in suspected heat stroke.

Heat stroke can cause elevated serum creatine kinase concentrations, impaired kidney function, and an abnormal blood glucose concentration. Measure these markers early and monitor them throughout management. Measurement of serum sodium concentration is important to exclude severe hyponatraemia.

Rhabdomyolysis in heat stroke can be identified by an elevated serum creatine kinase concentration and myoglobinuria. Myoglobinuria produces a false positive for haematuria on a urine dipstick test. Perform urinalysis—if the urine dipstick is positive for blood, request a specific urinalysis for myoglobin.

The risk of disseminated intravascular coagulation (DIC) is high, and liver biochemistry and a coagulation profile should be performed.

An electrocardiogram should be performed to assess for cardiac injury.

Imaging (eg of the brain) is not routinely indicated.