Tuesday, 26 July 2011

Heat Disorders

Published in Panorama

Beating the heat wisely

Yet again we are trying to beat the heat even as temperatures soar and humidity levels are high. It’s hardly surprising that a lot of individuals are suffering heat stress and disorders of heat. It’s only wise and safe that we exercise caution while exposing ourselves to long hours in the irksome environment. Dr.Preeti S.Kamath, General Physician, Al Rafa Poly Clinic, Gardens, Jebel Ali, helps understand this phenomenon of heat stress, identify the disorders and delineates treatment modalities and prevention.

How does the body regulate the heat generated in the body? There’s a balance maintained between heat loss and heat production in the body, which is normally regulated by the hypothalamus in the brain. This helps to maintain the body temperature at a constant 98.6 degrees Fahrenheit. The body gains or loses heat in four ways:
Conduction: when individuals come in direct contact with objects that are colder or warmer than the body.

Convection: transfers body heat to or from air moving over the skin

Radiation: transfers heat to or from surrounding objects that are not in direct contact with the body.

Evaporation: causes cooling when air absorbs body moisture from the lungs or skin.
Almost 65% of the body heat is lost by radiation when the external or environmental temperature is lower than the body temperature; a minor percentage is lost by convection and the rest by evaporation. On the other hand when the external temperature rises above our body temperature, then evaporation becomes the main form of heat loss. But if the humidity is high and close to 100%, evaporation also becomes limited in enabling heat loss from the body. And that is when heat disorders develop, explains Dr.Preeti.

The amount of heat that remains stored in the body depends on the surroundings, type, time worked and level of physical activity of the individual and recovery time between work periods. On the other hand, the amount and speed with which heat is lost or gained, depends on the environmental temperature, air movement and humidity level.

75% of body heat is lost when at rest, through conduction, convection and radiation, from the blood vessels at the surface of the skin. But when the body heat rises as a result of work or high atmospheric temperature, the surface blood vessels get dilated. Since more blood is being pumped close to the skin for cooling, less blood goes to the brain. In addition, there is increased sweating leading to depletion of fluid and electrolytes. This brings on the heat disorders, the main forms of which are Heat Syncope, Heat Cramps, Heat Exhaustion and Heat Stroke, in order of increased severity, respectively.
Individuals can suffer from any of these forms of disorder to various degrees of severity depending upon the duration of exposure to heat, says Dr.Preeti.

The typical symptoms of Heat Syncope appear when the blood flow to the brain is decreased and the person develops cerebral hypotension ( low blood pressure ) following cutaneous vasodilatation. This causes dizziness or a momentary black out, resulting in the patient falling down. However, once the person lies down, blood flow improves and he gains consciousness very fast. However, his skin will still be cool and clammy which leads us to diagnose heat syncope.

Heat cramps are always a danger signal since they may occur alone or be combined with one of the other major heat stress disorders. This condition is mostly seen in workers who work for long durations in the sun, as construction and other manual laborers. They are exposed, both to increased physical activity and the heat, both of which reinforce one another in enhancing heat production in the body. Further, these individuals are unable to lose as much heat as their body produces; there’s an imbalance between body and environmental temperatures, leading to depletion of electrolytes in the form of sweat. This in turn leads to muscle cramps which commonly occur in the thigh and calf muscles. There may be a sudden onset of the symptoms with the skin feeling hot and moist. The body temperature may vary from normal to slightly higher than normal. The patient may feel a trifle giddy and have unbearable cramps.

Heat Exhaustion occurs when the body’s heat control mechanism is overactive but hasn’t broken down completely, explains Dr.Preeti. The individual may also be having heat cramps and there is high risk that such a person progresses to the most severe form of heat disorder – heat stroke. This is particularly so if the individuals are the elderly, obese, neo-nates and children below 10 years and individuals suffering from coronary artery disease and individuals who are on certain drugs – beta blockers, diuretics. Symptoms of heat exhaustion include profuse sweating, intense thirst from dehydration, cool, moist, clammy skin, weak and rapid pulse, low to normal blood pressure, fatigue, weakness, nausea, vomiting, giddiness and headache. The core body temperature is raised.

There is some amount of sweating in a person suffering from heat exhaustion as the body tries to compensate the temperature imbalance by evaporation. When this sweating ceases, then body temperature will rise further, beyond 41 degrees Celsius – this presents as Heat Stroke, explains Dr.Preeti. Heat stroke is a medical emergency which results from failure of the thermoregulatory mechanism requiring prompt attention. It could be catastrophic, even fatal, if there is no appropriate and timely medical intervention.

The early symptoms of heat stroke include high body temperatures, above 41 degrees C, absence of sweating, red, hot flushed skin that is dry, rapid pulse, labored breathing, headache, dizziness, nausea, vomiting, delirium, hallucinations, blurred vision and disorientation. If prompt action is not taken, the symptoms can progress to convulsions or seizures, loss of consciousness, collapse of the victim and even coma.

Dr.Preeti cautions, “We have to treat promptly in the case of heat stroke, in particular since it is attended with several complications including congestive cardiac failure, renal failure, liver necrosis and neurological damage besides damage to the brain and various other organs.”

How should the various forms of heat disorders be managed and treated?
In all forms of the conditions it is of utmost importance to first move the victim to cooler environment.
Loosen or remove clothing and footwear.
Cool the victim as soon as possible with tepid water, accompanied by fanning.
Have the victim’s legs in an elevated position.
Give the victim water to drink, preferably with salt added – 1/2-1 tsp salt to a litre of water.
If the victim is unable to take oral fluids, he has to be administered fluids intravenously, which can be done only in a clinic or hospital setup.
If the victim is suffering from heat exhaustion, it is absolutely necessary that he/she be examined by a qualified medical professional.

In the event of heat stroke, it is of great importance to recognize the symptoms and immediately rush the victim to the hospital after initiating the cooling process without any delay, emphasizes Dr.Preeti. “At the hospital, medical personnel will first identify if the condition is attended by any complications associated with it. This is done while we are trying to replenish the electrolyte and fluid balance and promote the heat loss from the body. At this juncture, the normal fever medicines will be of no use to the victim. There could be shivering which will further augment heat production in the body. We have to tackle this shivering with other drugs. Since various organs could be affected, we should see if the heart, liver and kidney, particularly are functioning normally. It is necessary to see if the minimal urine output is maintained, else the person could be heading to an acute renal failure. Sometimes, there will be muscle disintegration due to the high heat and this could also affect the kidneys. So in the hospital, we try to prevent these complications from setting in. On the other hand, if they have already set in, we take measures to manage and treat them and prevent their further progression.

How can heat disorders be prevented in the first place?
1. Limit the amount of heat exposure.
2. Take plenty of fluids, particularly water.
3. Increase physical activity only gradually.
4. Wear light and light-colored clothes which help evaporation and also absorb less heat.
5. Where you cannot control temperature or humidity as in an exposed or outdoor workplace, acclimatize yourself to the environment before rushing into work for long stretches of continuous hours or undertaking strenuous work in such environments. Alternate longer periods of work with rest in cooler atmosphere. Acclimatization allows the body’s thermoregulation mechanism to adjust to the high external temperatures.
6. Hot food directly adds to body heat. Also, heavy meals reduce the body’s ability to lose heat since they redirect blood flow to the digestive tract instead of the skin surface. Hence, it is better to have cool meals and light meals at lunch, while working in very hot climates.
7. Abstain from alcoholic beverages since alcohol dehydrates the body.

Does carrying an umbrella when out in the sun for long hours help to prevent conditions of heat disorders? Dr.Preeti is unequivocal: “Covering any exposed area will certainly reduce heat gain by the body. But this cannot prevent the heat disorders because the body itself is still in the hot environment.”


No comments:

Post a Comment