Sunday, June 17, 2001		Keeping fit

DURING the past fortnight, the temperature soared to 43°C in Chandigarh and 46°C in Amritsar. So unbearable was the heat the even a robust young man, who was exposed to the sun for five to six hours, became unconscious and had to be hospitalised. Last week in Ludhiana, a young man driving a motor cycle in the scorching heat fainted with a heat stroke on the road itself. Another 6’-3" tall BSF athlete who was undergoing rigorous training for the upcoming Asian Games, suffered from extreme weakness, lethargy and low blood pressure in the heat and could hardly stand without feeling giddy. Recently, two Army soldiers undergoing war-like exercises in a nearby area developed high fever, sore muscles and acute renal failure.

These four examples are manifestations of exposure to heat, resulting either in heat stroke, exhaustion and muscle damage with acute renal failure.

Environmental heat illness can result from a person’s inability to maintain the body homeostasis to keep the thermal regulation within limit, resulting in variable grades of ill health. This can lead to the commonly experienced heat cramps; heat exhaustion and heat stroke. A combination of heat and vigorous exercise can cause muscle damage and kidney failure.

The human body generates heat through metabolic (burning of the fuel) and neuromuscular activities. Heat is also absorbed from the environment depending upon the gradients. The body normally produces more heat than required to keep the body physiologically warm and, therefore, needs to lose heat except in a very cold environment. Heat is primarily lost by sweating and evaporation, but small amounts of heat may be lost by radiation, convection and through the lungs during respiration. The body temperature is regulated through a very sensitive mechanism in a centre located in the hypothalamus at the base of the brain.

To dissipate extra heat generated by the body, a process is initiated by the hypothalamus centre, increasing the activity of the sweat glands and dilatation of the skin vessels. With this mechanism we are able to lose as much as 600-700 kilo calories per hour. However, if the environmental humidity is high and there are other thermo-regulatory problems, enough heat is not lost, resulting in one of the problems mentioned above.

Heat cramps: This is the common problem with which most of us are familiar resulting from exposure to heat or physical activity in well-acclimatised persons. The replacement of salt and fluids usually takes care of the problem.

Heat exhaustion: Heat exhaustion results from a longer depletion of salt or water or both. Usually, it is a combination of the two. Pure water depletion can occur when fluids are not available and manifest itself as fatigue, weakness, thirst, anxiety and, if the condition deteriorates, it can lead to agitation, loss of coordination and extreme exhaustion, resulting in cramps. Obviously, the treatment is prompt cooling and replacement of fluids. If the main depletion is that of salt, which occurs when the loss is replaced only by water and there is relative shortage of salt, it results in weakness, fatigue, frontal headache, giddiness, loss of appetite, nausea, vomiting and muscle cramps. These people usually have low blood pressure and, therefore, feel giddy or faint on standing. The treatment is prompt replacement of salt as well as water by intravenous routes initially, followed by oral replacement of salt as well as fluids.

Heat stroke: This is the most catastrophic form of environmental heat illness. After a prolonged exposure to heat, with or without physical activity, there is a very high fever or rectal temperature of over 41°C. In this disorder, the body-regulating mechanisms fail and sweating is almost absent. This is an extreme emergency and unless treated promptly, the outcome can be fatal. It should be recognised by oncoming of extreme weakness, headache, giddiness, muscle cramps followed by neurological manifestations like agitation, confusion, delirium and coma. There may be convulsion. The skin is dry and hot and absence of sweat is characteristic. Blood pressure is low and there may be bleeding disorder and frank heart damage. If the heat stroke is preceded by high physical exercise, there is muscle damage, releasing a pigment, myoglobulin, which causes kidney damage and acute renal failure. The condition should be treated urgently in the hospital, but even before reaching there, the patient should be immersed in a tub of cold water or splashed with cold water bringing his temperature down as early as possible. In the hospital, he should be kept in an airconditioned environment, giving intravenous fluids and further cooling can be achieved by giving cold fluids in the stomach, by enema and the modern technique of peritoneal dialysis.

Although many people are exposed to the same hot environment, everybody does not suffer from a heat-related illness. There are certain predisposing factors for this:

«Extremes of age — very young and very elderly individuals — they are most vulnerable.

«Lack of acclimatisation to heat — a person newly arrived in a hot climate.

«Inadequate fluid and salt intake.

«Obesity — the surface area is relatively less than the body mass and thus cooling is insufficient.

«Various neurological and psychiatric illnesses.

«Systemic diseases like diabetes mellitus, heart failure, acute and chronic renal disease.

«Skin diseases which prevent adequate sweating.

«Drugs that impair sweating and adjustment to the environment.