CHAPTER XLI
HEAT STROKE AND HEAT PROSTRATION
GENERAL CONSIDERATIONS
It has been customary to differentiate etiologically, as well as clinically, the two most common manifestations of the effects of high temperature. Clinically we note cases (1) with a rapidly rising temperature, which often reaches a very high point, together with a hot, dry, reddened skin, heat stroke; and again we note cases (2) with pale clammy skin, marked evidences of cardiac weakness and a normal or subnormal temperature, heat prostration.
Brooks in a most excellent discussion of the subject applies the designation diathermasia to the former group of cases and regards them as connected with an undue retention of heat within the body. To the latter group, which he considers to be connected with exposure to the actinic rays of the sun, he applies the designation phoebism.
In diathermasia he considers that we have so great a strain on the thermotaxic mechanism that there is loss of balance between the heat discharge and heat producing centers, while in phoebism there is primarily an acute cerebral or cerebro-spinal congestion followed by a chronic inflammatory condition of the meninges and due to damage from the actinic or ultra-violet rays of the sun.
While admitting that there may be cases where the effects of certain rays of the sun are responsible for clinical manifestations varying from death of striking suddenness to vague complaints of irritability, headache and defective memory, yet the generally accepted views are that high temperature, high relative humidity and lack of evaporation from the skin, whether from excessive humidity or from lack of circulation of the surrounding air, can and do produce at one time heat stroke and at another heat prostration. Such factors as muscular exertion, disease conditions, alcoholism and dietary indiscretions undoubtedly play a part in the production of and variance in the clinical manifestations brought about by the effects of heat.
Sambon has suggested that there is a possibility that heat stroke or, as it is also designated thermic fever or siriasis, is due to a germ infection, but without advancing any particular evidence in favor of such an hypothesis.
There is undoubtedly, however, much in favor of the views of those who regard heat stroke and heat prostration as due to an auto-intoxication from the accumulation of toxic substances resulting from increased metabolic activity due to excessive heat retention and having a selective action on the nerve cells.
Others think that as the result of more active metabolism there is a retention of carbonic and lactic acid with a demand on the alkali content of the blood resulting in an acidosis. As a matter of fact treatment of heat stroke cases with intravenous or rectal injections of sodium bicarbonate seems to be of marked value.
It would seem advisable to take the ground that heat retention resulting from lack of heat radiation and insufficient skin evaporation causes various manifestations of discomfort or bodily injury. Aron in Manila showed that monkeys exposed to the sun died in about one hour but that a control monkey, similarly placed, but kept in a current of air from an electric fan, suffered little or no injury. The reason that monkey and man react differently to exposure to the sun is on account of the more numerous and more active sweat glands possessed by man which give rise to increased evaporation and resulting loss of heat of the body.
High relative humidity is a potent factor in checking evaporation. The rectal temperature in Haldane’s experiments showed a rise of a little over 1°F. when the wet bulb was at 90°F., 2°F. when at 94°F. while at 98°F. it was about 4°F. per hour. Leonard Hill has noted that the air surrounding the victims of the Black Hole of Calcutta became saturated with water vapour and heated to the temperature of the body so that it was heat stroke and not suffocation that caused death. The power of air to hold water vapour and its evaporative power increase rapidly with rising temperature; thus at 50°F. a cubic foot of air holds 4.08 grains water, at 80°F. 10.9 and at 100°F. 19.7 grains. Hill states that the limit of an Englishman’s power to keep cool is passed when the wet bulb exceeds 88°F. in the still air of a room even when stripped to the waist and resting. If muscular work is performed the limit may be 80°F. Walking in a tropical climate, wet bulb 75° to 80°F., dry bulb 80° to 90°F. may raise the temperature 2° to 3°F. and send the pulse up to 140 to 160. All the students of ventilation stress the importance of circulation of the air in promoting evaporation and comfort. According to Hill with the air saturated and the wet bulb reading 89°F. the wet ‘Kata’ readings would be 3.3 with still air, 8.0 with the wind moving 1 meter a second and 15.1 with a velocity of 9 meters per second. In tropical parts of the world when the wet bulb not infrequently reaches 90°F. the circulation of air by punkahs or electric fans becomes a necessity. There is great variation in capacity for sweating which, according to Hearne, is the basis of heat stroke. He notes that sweating is suppressed from 1 to 48 hours before the attack. With sweating suppressed the body temperature rises until, when 108°F. or more is reached, unconsciousness and convulsions develop. Hearne thinks that the inhibition of sweating is local in the sweat glands, and not central, as diaphoretics fail to cause sweating once it has stopped. As a practical point Hearne watched subjects for dryness of the skin and when discovered they were stripped, covered with a wet sheet and evaporation promoted by a current of air from an electric fan. Doctor Leonard Hill has noted the inefficiency of the application of pieces of ice to the hyperpyrexial body as compared with evaporation. Thus water evaporation at body temperature abstracts 0.59 calories per gram while melting ice only takes away 0.08 calories. Furthermore the application of ice constricts the capillaries and interferes with evaporation. He also notes that 70 grams of water evaporated from the skin takes away as much heat as 1000 grams of ice water used as an enema.
PATHOLOGY
Pathologically, there is usually congestion of the brain and meninges, that of the brain being particularly marked about the region of the medulla. There may even be punctate haemorrhages and the nerve cells show chromatolysis. These changes are much more evident in heat stroke than in heat prostration.
McKenzie and LeCount have noted the following autopsy findings: Generalized passive hyperaemia of brain and lungs, oedema of brain and lungs as well as petechial haemorrhages of various mucous membranes and the skin.
_Susceptibility to Heat Stroke._—As a matter of fact in a body of men exposed to identical conditions of heat of sun and relative humidity we note certain cases exhibiting typical heat stroke while other men will only show evidences of heat prostration.
Alcoholism, obesity, diseases of heart and lungs, overcrowding, muscular fatigue, insufficient circulation of air, with the wet bulb about 90°F., and not drinking a sufficient amount of water, predispose to heat injury.
It must always be kept in mind that the hyperpyrexial type of malignant tertian malaria may give a clinical picture of heat stroke.
Fiske has noted that in oil-burning firerooms, even with a temperature of 140°F., 10° higher than on similar ships burning coal, there were no cases of heat prostration. He attributes this to the less fatiguing work in tending oil-burning furnaces and the smaller number of men required, this reducing overcrowding.
SYMPTOMATOLOGY
_In heat stroke_ there are usually prodromata of dizziness, dry skin, headache, and somnolence, following which the body temperature shoots up to 105°F. or even above 110°F. There is a desire for frequent micturition, which may be considered as a prodromal warning of embarrassment of the sweating function. The skin is hot and dry and the pupils may be contracted. The pulse which is at first full and rapid, soon becomes irregular. There may be delirium or coma or convulsive seizures. The patient is unconscious with irregular or Cheyne-Stokes respiration.
Hiller divides these cases into (1) those showing an asphyxia syndrome, as characterized by cyanosis and collapse, with cessation of respiration and enfeebled circulation. Prolonged artificial respiration is required in such cases. (2) A paralytic type with deep coma, recurring convulsions and extreme hyperpyrexia. These cases exhibit oedema of lungs and brain and necessitate venesection. (3) A psychopathic type in which there is delirium often of a violent type with delusions of persecution. Such cases often commit suicide.
In _heat prostration_ we have giddiness and possibly nausea with pale face, often bathed in cold perspiration and dilated pupils. The pulse is very weak and syncope may ensue. The temperature is not elevated and may be subnormal. Rarely the temperature is slightly elevated. The respiration is shallow and sighing. Headache is often complained of after recovery. Following this or the more dangerous heat stroke we may have lack of mental concentration or loss of memory with recurring headache upon even moderate exposure to the sun.
_Heat Cramps._—Among those working in firerooms on board ships cruising in tropical waters, there is met frequently a condition characterized by cramps of the voluntary muscles, chiefly those of the extremities and abdomen.
Ill health and individual susceptibility appear to predispose toward attacks, but apparently hard physical labor, in conjunction with the environmental conditions, is the factor that determines the occurrence of the cramps. Their causation is usually attributed to dehydration of the tissues, or to accumulation of metabolic products, but some believe that they represent a condition differing from all other conditions recognized as being due to heat. Cases, probably identical in nature and having the same causative factors, have been noted as occurring among workers in steel-mills.
The cramps are usually preceded by fibrillation of the muscles later to be affected. When frankly spastic attacks are developed, they recur at intervals of from 2 to 10 minutes, and may be severe and very painful. The pupil is dilated, but so far as known, no other organs are involved. The cramps are commonly accompanied by signs of heat prostration. This, however, is not necessarily so, there often being absolutely no thermal disturbance.
The treatment is in general that of heat prostration. Immediate relief may be obtained by sudden slapping of an affected muscle. For mild cases, immersion in a warm bath is recommended. Apomorphine in sub-emetic doses is said to confer immediate relaxation.
TREATMENT
With heat stroke we have a condition in which every moment lost before the institution of proper treatment reduces the chances of recovery. The two important measures are reduction of temperature and elimination of toxic material. For the former ice packs or ice baths are the most efficient. When the temperature starts down it may fall with great rapidity and collapse result. Consequently when giving these ice packs or baths the treatment should be discontinued when the temperature by rectum reaches about 103°F., the patient then being removed from the bath and covered with a blanket. If the temperature again shoots up the ice bath can be repeated. Many have reported great benefit from the use of enemata cooled with ice. Some prefer to apply ice to the head and rub the body with pieces of ice. This can be carried out on a rubber sheet placed on a cot. If there is no ice available a sheet wet in dilute alcohol, plus the effects of a current of air from the electric fan or otherwise, may be tried. In a case with marked cyanosis venesection may be necessary. In asphyxial types of sun stroke prolonged artificial respiration is indicated.
Above has been noted the inefficiency of ice in reducing temperature and the far greater effect from evaporation, brought about by directing the current from a fan on the body covered with a wet sheet.
To promote elimination of toxic products venesection plus the use of intravenous injections of normal saline is the best treatment. In those terrible paralytic type cases which show a mortality of more than 50% it is well to think of acidosis and give slowly about a liter of a 1 or 2% solution of sodium bicarbonate. (See under treatment of cholera.) The use of alkaline enemata often gives good results, about a liter of a solution containing 2% of sodium chloride and 2% of sodium carbonate or bicarbonate.
As soon as possible after the more urgent hydrotherapeutic methods have controlled the case we should give calomel followed by salines. The coal tar products should be avoided as far as possible, from the danger of cardiac depression.
In the nonfebrile heat prostration the treatment is entirely eliminative and stimulant. The patient should be placed on his back in a cool shady place and tight clothing released, particularly about the neck. Rubbing the limbs as for any syncope-type affection, with hot water bottles if the collapse is marked, should be one line of treatment. Many give a little aromatic spirits of ammonia or whiskey but a hypodermic of strychnine would be better in a severe case.
Calomel and salines should be given after cardiac weakness disappears. To avoid these dangers of the tropical heat one should keep the body clean to promote good action of the sweat glands. The clothing should be light and loosely fitting and should permit a free circulation of air to assist evaporation. There does not seem to be any indication for the wearing of orange-colored clothes as the actinic rays are apparently unimportant. Puntoni recommends green-colored clothing for neck and spine. The green cloth should be covered with white material.
The head and nape of the neck should be protected by a light well-ventilated helmet. Alcohol should be avoided, or at any rate absolutely so, until evening. Water or lemonade should be taken freely and a siesta in the middle of the day is an important conserver of one’s resisting powers.
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