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.