An 87-year-old woman is brought to the ED by fire rescue when her neighbors realized they had not seen her for a few days. It is mid-August and the daily temperature has not gone below 87°F for more than a week. The paramedics report that her apartment was “unbearably hot” and apparently cooled only by a small revolving fan. The patient is comatose with a core temperature of 109.3°F and a blood pressure palpable at 60 mm Hg. You institute therapy, knowing that:
Coagulation studies usually stay normal even after severe heatstroke.
Shivering that occurs during treatment must not be suppressed with chlorpromazine.
Sedation, paralysis and intubation reduce temperature by inhibiting muscular activity.
The presence of sweating excludes the diagnosis of heatstroke.
Heatstroke and heat exhaustion are differentiated by the height of fever.
Sweating can be present in early heatstroke, but later in the syndrome most patients develop hot, dry skin and do not sweat. The most common reason for impaired sweating is use of drugs with anticholinergic properties. Although exercise in hot weather is classically associated with its development, the disorder can occur, especially in older patients, even at rest. The earliest clinical abnormality is a change in central neurologic function, usually of the mental status; mental status changes are what differentiate heatstroke from the less severe heat exhaustion. Focal neurologic findings suggesting a mass lesion may be seen. Tachycardia and fever are usually present, but a sort of high-output cardiac failure can develop leading to pulmonary edema and cardiovascular collapse. Purpura, thrombocytopenia, and clinically significant bleeding can occur, sometimes progressing to DIC. Patients with clinically significant bleeding may require plasma and platelet replacement. The object of treatment is to lower the temperature. Ice water baths, hypothermia blankets, and iced saline lavage all have their proponents, but there is no clearly superior method of cooling. Paralysis is employed to decrease temperature through the inhibition of muscular activity. Shivering can and should be suppressed using a phenothiazine or benzodiazepine. Chlorpromazine can be used for this and will not contribute to the hyperpyrexia under these circumstances. Oxygen should be given and urine output measured, with central venous pressure measurements often helpful in determining fluid requirements.