Heat hyperpyrexia (heat stroke)
Hyperpyrexia means ‘high fever’ and some specialists regard it, or rather the condition it describes, as the first stage in the development of heat stroke, while others use the terms as alternatives. ‘Sunstroke’ is a misnomer as the illness may occur without direct exposure to the sun.
This serious condition begins with impairment of the heat-regulating mechanisms of the body, although how this occurs is not yet fully understood. Sweating diminishes and the body temperature rises—a sufferer who is still sufficiently alert will complain that he or she is feeling peculiar and is not sweating very much. The body temperature will be in the region of 39°C to 41°C (102-106°F), and the higher it rises, the worse the likely outcome: this condition can result in death within two to four hours of the first symptoms.
In the areas where sweating has ceased, the skin becomes flushed and red. A headache develops and soon becomes severe, often described as dull and pounding. Walking soon changes to staggering, and signs of mental confusion and perhaps unusual aggression appear. Unable to stand, the sufferer becomes delirious, develops stertorous breathing, and may convulse. 7.
In the total absence of sweating, the temperature continues to rise until death occurs at about 43°C to 44°C (109-111°F). The only treatment is immediate cooling once the illness is recognized or suspected. Under shelter from the sun, remove all clothing and cover the patient with a wetted bedsheet, towel, or other lightweight material and start fanning to promote cooling by evaporation. Keep the coverings wet, and fanning and wetting must continue all the way to the hospital, where electrical fans and needlespraying of cooled water will hopefully be available.
Definitive prevention of the condition is difficult because the cause of the failure of the body’s regulatory system is not yet fully understood. Factors that play a part in its occurrence are these:
- Continuous heat stress, day and night.
- A lack of fitness, overindulgence in alcohol, or excessively strenuous exercise.
- A premature return to activity after a previous episode of heat exhaustion, particularly in an unacclimatized person.
- Any of the above in a person whose sweating ability is seriously impaired by a skin complaint or disorder.
Do not forget that the patient may have a fever-producing illness in addition, which may not have been recognized. It is essential to treat hyperpyrexia patients with cerebral malaria as well as cooling them if there is a danger of malaria in the area.
Heat exhaustion may be one of the three types, namely water- deficiency, salt-deficiency, or anhidrotic heat exhaustion (anhidrotic = absent sweat). Each is serious and the first and third can go on to heat stroke because of the implied interference with cooling by evaporation of sweat.
Water-deficiency heat exhaustion occurs when there is a restriction of water intake in a heat-stress situation. Extreme examples occur in people stranded in a desert or adrift in tropical seas without water. Remember that water requirements in a hot climate may be very high (10 liters or 17*5 pints a day in the example cited above). The potential victim is thirsty and complains of vague discomforts, then lack of appetite, giddiness, restlessness, and tingling sensations. Any urine passed is in small quantity and deeply colored. Lips, mouth, and tongue become so dry that speaking is hardly possible. The temperature rises steadily, the pulse rate increases, breathing becomes faster, and the lips are blue. Hollow cheeks and sunken eyes complete the picture before the victim sinks into a coma and, if not treated, death.
The comatose patient requires cooling and fluids supplied intravenously, if possible, with medical assistance. The patient who can still understand and walk is quickly restored in cool surroundings with the following regime: 0-5 liters (nearly 1 pint) of water of any flavor to be drunk every 15 minutes for two hours or until a large quantity of pale urine is passed. Thereafter keep him cool for two days and advise on drinking past the point of thirst-quenching.
Salt-deficiency heat exhaustion commonly occurs in the inexperienced newcomer, after two or three days of heavy sweating and work, with plenty to drink but no salt replacement because of lack of appetite. Quite frequently, vomiting and/or diarrhoea have hastened the onset. The body’s salt ‘reserves’ have vanished and the cells and tissues that require it are malfunctioning. Increasing fatigue is soon followed by lethargy, headache, giddiness, and extremely severe muscle cramps. Pallor of the face and around the lips is very typical as the patient collapses, still soaked with sweat.
Do not allow the casualty to sit up or move as this may precipitate a fatal collapse. Urgent treatment with bed-rest in cool surroundings, and a high intake of salted drinks—one level teaspoonful of salt per half a litre (nearly 1 pint) given hourly for six hours will supply some 15 g of the daily requirement of 20 g of salt. Thereafter, return to the pre-salted water regime mentioned above—had this been observed in the first place, the condition might not have occurred! The pre-salted water replaces one half of the salt lost in unacclimatized sweat, and the rest should come from the diet. Be prepared, however, to supervise your patient’s eating habits and to insist on empty plates. A return to work should be gradual.
Anhidrotic heat exhaustion arises as a disorder of sweating in people who have been in a hot climate for several months. It may be defined as a state of exhaustion and heat intolerance. The skin, mainly of the trunk and upper arms, shows a rash of little vesicles (called miliaria profunda) and there is little or no sweat in these parts when all around are sweating freely. Fairly rare, it is worst in the heat of the day—symptoms include fatigue, unpleasant sensations of warmth, giddiness on standing up, frightening palpitations, and rapid, sometimes gasping breathing. The face sweats profusely, and there is a frequent and insistent urge to pass urine, sometimes in larger quantities than usual. The disorder is often preceded by an attack of prickly heat (see below). These seriously heat-intolerant individuals should be removed to a cool environment for one month’s rest, and then be supervised carefully on return, because another attack may lead to heat stroke.
Other conditions caused by heat
Prickly heat or miliaria rubra (literally red millet seeds) consists of a vast number of vesicles or tiny blisters set in red, mildly inflamed skin, worst around the waist, upper trunk, armpits, the front of the elbows, and even on the scalp. The rash is accompanied by intensely aggravating prickling sensations. The cause is not yet clear, but an important factor is the constant wetting of the skin by unevaporated sweat as occurs at times of high humidity in hot/wet climes. The skin becomes unhealthy and waterlogged, sweat ducts are blocked by debris and infection starts, causing a large number of pimples. Sleep is almost always upset and is delayed until the coolest period of the night, around 4 to 5 a.m. As a result, bad temper and irritability are usual, with a diminution in working efficiency. The prickling can be relieved by taking a cool shower, gentle dab-drying of the skin to prevent further damage, then calamine lotion and zinc oxide dusting powder. The clothing should be starch-free and of a loose fit.
Heat edema (heat swelling) of the ankles used to be called ‘deck ankles’ and appeared in passengers when the ships first entered tropical waters. Now it is indistinguishable from the swollen ankles of long air journeys and is found to last for a few days in the unacclimatized newcomer to extreme heat. The condition requires no treatment and will disappear as acclimatization progresses.
Heat cramps may occur without the signs and symptoms of salt- deficiency heat exhaustion described above, and are due to the same problem—salt lack—from whatever cause. They are excruciatingly painful and occur at random intervals in whichever muscle groups are used most. The treatment is the same as for salt-deficiency heat exhaustion.
Heat syncope (fainting) occurs typically in the unacclimatized on first exposure to the heat. Due to circulatory instability during the early days, it occurs after prolonged standing or on the sudden change of posture. The ‘head-low‘ or lying position will return the blood to the brain. An hour or two of rest and graded exercise will soon banish the condition.