Heat-stroke is a medical emergency that is associated with a potentially high mortality rate. It occurs when the body's main mechanism of heat loss (evaporation of sweat) is blocked. There may be early warning symptoms of headache, malaise, and excessive warmth, or a general picture of heat exhaustion. The onset is usually abrupt with sudden loss of consciousness, convulsions, or delirium. Sweating is absent in the typical case.
On physical examination, the skin is hot, flushed, and dry. In severe cases, tiny rounded haemorrhage spots may appear. Deep body temperature is high, frequently in excess of 41 °C. A rectal temperature above 42 °C is not uncommon, and indicates a poor outlook for the patient. The pulse will be rapid and strong and may go up to a count of 160 or more. Respiration may be rapid and deep, and the blood pressure elevated slightly. The pupils of the eyes will first contract then dilate. Muscular twitching, cramps, convulsions, and projectile vomiting may occur and may be followed by circulatory collapse and deep shock.
Because of the extreme seriousness of heatstroke, all members of the vessel's crew should be taught the importance of recognizing cessation of sweating, so that corrective measures can begin at an early reversible stage.