Heat Stroke and Hyperpyrexia: A Common Disease

The distinction between heat stroke and heat hyperpyrexia is a largely arbitrary. Strictly speaking the diagnosis of heat stroke should be made only in those cases which are characterized by sudden and profound cerebral disturbances like convulsions or coma. In a tropical climate, however, all cases of heat ‘hyperpyrexia’ are likely to develop into heat strokes unless quickly treated. Heat hyperpyrexia, on the other hand implies a state when very high body temperature above 40degree occurs, but without any of the dramatic accompaniments of heat stroke.

The exact mechanism of heat hyperpyrexia or heat stroke is not known. Hyperpyrexia usually results from protracted exposure to high atmospheric temperature during prolonged heat waves. However, it may occurs after only a brief exposure to intensely high environmental temperature; direct exposure to the sun is not essential. The condition in though to result from an acute breakdown of the normal thermo-regulatory mechanism. In many patients complete cessation of sweating occurs 24-48 hours before the onset of serious symptoms, and this ushers in the acute clinical attack. High humidity, heavy manual work in the presence of high temperature, old age, pre-existing chronic disease and alcoholism are some of the predisposing factors.

Diagnosis

The presence of high temperature over 40 degree Cel., and the circumstantial evidence usually make a diagnosis of heat hyperpyrexia an easy matter. Absence of neck regedity differentiates it from acute meningitis which can be conclusively excluded by a lumber punchure. Pontine haemorrhage  can produce unconsciousness associated with high temperature, but unlike heat stroke, here the high fever comes late and follows the coma. The only challenge to diagnosis is likely to come from cerebral malaria. Examination of peripheral blood films may be some help, but in any doubtful case, chloroquine and or quinine must be given parenterally with usual precautions.

Management

Prompt of vigorous measures must be applied immediately to reduce body temperature so as to prevent, as far as possible, damage to vital organs. The patient should be removed to the nearest cool place and most of the clothing removed. The body should be loosely wrapped in a cool wet sheet which is frequently sprinkled with ice – cold water. Ice should be applied to the head of the limbs, and the body massaged with ice to promote vasodilatation. This will accelerate heat loss and also increase the circulation between the cold peripheral blood and internal ‘core’ temperature. An ice water enema is also helpful in reducing body temperature in hyperpyrexia. Such measures should be discontinued when the temperature reaches 39 degree Celsius, otherwise the body temperature may fall to excessively low level to collapse.