The results from exposure to excessive heat manifest themselves in various ways. Any condition which may lessen the resistance of the body to external heat predisposes to heat-stroke; such as privation, fatigue, mental emotions, alcohol, over-eating, and especially previous attacks of the disease.
Sunstroke occurs in those who work under the direct rays of the sun, when the air is hot, still, and humid.
Heat-stroke or thermic fever affects those working in places which are excessively hot and confined, as in glass-works, foundries, stoke-holds, boiler-houses, sugar-refineries, paper-mills, &c.
Heat exhaustion and prostration are brought about in a similar manner, but the effects are not the same, and usually transient and less severe.
Sunstroke or heat-stroke may occur in two forms, the asphyxial or apoplectic, and the hyperpyrexial; it is also classified as sthenic or asphyxial, and asthenic or syncopal.
Asphyxial sunstroke or heat apoplexy is probably the least frequent; prodromal symptoms are headache, vertigo, disturbances of vision, dyspnœa, and dry skin. In some cases sudden unconsciousness, with or without convulsions, may occur, and death rapidly follows.
The coma may not be profound; there may be nausea and vomiting of dark material, bounding pulse, stertorous breathing, contracted pupils, and frequent micturition. The body exhales a “mousey odour.” There may be involuntary dejection, with the same pungent odour, and very watery. Delirium is present in some cases. The temperature may be subnormal, or rise to 102° F., occasionally even to 106° F. When fatal, the coma deepens, the pulse becomes rapid and feeble, and there is Cheyne-Stokes respiration.
In Hyperpyrexial cases the symptoms are similar to the asphyxial, but the temperature may reach 110-115° F., and in profound coma death takes place from asphyxia. A subconscious or automatic state, in which the person may go on working, may precede the “stroke.”
In cases which are not so rapid, pneumonia, meningitis, cardiac and respiratory paralysis may occur and prove fatal.
Heat exhaustion may be more gradual in its onset, or come on suddenly. Prodromal dizziness, faintness, nausea, headache, drowsiness, epigastric and lumbar pains may precede the prostration and muscular weakness. Fever supervenes, a rapid pulse, and in severe cases collapse. Consciousness is seldom completely lost, and in favourable cases is quickly regained. When there is marked prostration the heart may fail.