Heat Stroke and Heat Exhaustion

On a lazy Sunday afternoon, you may think of pursuing your hobby of gardening. Despite the unbearable, dry, and hot winds blowing, and the sun fiercely shining upon your head, you wear on your boots and start toiling the soil. Barely an hour into it, you feel weak, nauseated and extremely thirsty. If you still think you can continue it, think again. You may have heat exhaustion!

Regulation of body temperature

In human beings, it is vital to maintain body temperature within the range of 36.50C to 37.50C for normal functioning of the cells, and enzymes in the body even in unfavorable environmental conditions. The autonomic nervous system, the network of nerves that control certain bodily functions automatically independent of the brain, regulates the body temperature.

Hypothalamus, a part of the brain, receives the messages from the thermal receptors sensitive to the changes in the environmental heat via central nervous system (brain and spinal cord) and subsequently hypothalamus responds to these changes by sending proper signals to the peripheral nerves (nerves outside brain and spinal cord) for suitable action to be taken such as to conserve heat or to dissipate heat so that the body temperature is maintained within the “set-point” (36.50C to 37.50C).

Heat related illnesses

Heat exhaustion and heat stroke are both heat related illnesses which can be caused by excessive heat and humidity. Though they are similar, the symptoms they show differ. As the outside temperature rises, your body tries to keep cool by sweating, resulting in loss of water and salts. If this loss is not replenished, then it may result in high temperature, and eventually you become sick.

When you are exposed to excessive heat and lose water and electrolytes and become weak with frequent uneasy feeling in the throat and stomach and vomiting, then you are said to suffer from heat exhaustion.

When outside temperature is higher than your body’s temperature, your body responds with sweating as evaporation causes cooling. Along with water, electrolytes are also lost resulting in dehydration and salt-depletion. The core body’s temperature may or may not be elevated.

Heat exhaustion may be caused due to the failure of body’s cooling mechanism; depletion of body salts, replacement of only water but not salts and exposure to heat for a long time. The other causes could be alcohol consumption which can affect body’s ability to regulate temperature, and over dressing that may not allow proper sweating.

Another condition called heat stroke, occurs when body’s mechanism to control temperature fails. The body’s temperature rises up dangerously above 1040F or 400C and manifested by dry and hot skin and abnormalities of the central nervous system such as convulsions, confusion and coma.

The cause of heat stroke may be due to exposure to heat for too long period and over exercising or indulging in exercise not suitable for the age and condition.

Heat index

When it is hot outside and the presence of water vapor is also high (relative humidity) in the atmosphere, your body cannot sweat and cannot dissipate the heat which may lead to heat stroke.

The air temperature when taken along with the relative humidity is called heat index which is in simple terms indicates as to how hot it feels like in the shade. Heat index of 900F or above is considered as dangerous.

Some of the medications affect the way your body responds to heat and may cause heat stroke.

  • Antihistamines increase the susceptibility to heat stroke as they cause constriction of blood vessels, reduce sweating and may restrict dissipation of heat
  • The anti stress hormone medicines (beta blockers) block the production of stress hormones leading to the constriction of blood vessels thus may interfere in the regulation of heat in the body.
  • Illegal drugs and diet pills can dehydrate the body and/or increase metabolism and heat production increasing the risk of heat stroke.
  • Laxatives may cause excessive bowel movement resulting in dehydration and increase heat stroke risk.
  • Medications for mental illnesses interfere with the regulation of the temperature and may restrict sweating leading to rise in body temperature leading to heat stroke.
  • Water pills cause the body to lose water and as such may cause heat stroke.

Your doctor shall be able to guide you accurately as to which medications you should avoid so that there is no increased risk of suffering from heat stroke.

You should suspect a heat exhaustion if you have normal or above normal body temperature but not more than 1040F with a headache, and a feeling of exhaustion, tiredness and weakness the skin may feel moist, sweaty and dank.

You may feel irritated, and have an uneasy and unpleasant feeling in the stomach. Your urine output may be reduced.

You may feel giddy due to decreased blood pressure while standing. Heat exhaustion may cause abnormal sweating, enlarged pupils, abnormal breathing pattern, and irregular heartbeat.

The heat stroke symptom may be different in a heat stroke. The symptoms include:

  • Body temperature may rise above 1060F in a very short time
  • Dry and hot skin
  • Narrowed pupils
  • Deep and shallow breathing
  • Rapid and strong/weak heart beat
  • Initially high blood pressure subsequently lower than normal
  • Sensation of head swirling and uneasy sensation to vomit
  • Disorientation
  • Painful muscle contractions

Following are the things to be done when faced with a situation of heat stroke.

  • Call for medical emergency personnel
  • Keep the person who had heat stroke in a cool place away from sunlight or from the source of heat such as in an air-conditioned room or shade.
  • Remove unnecessary clothing from the body of the person with heat stroke and increase ventilation. Wet the skin of the person with cool water.
  • If possible, arrange for ice packs and keep them in the areas where blood vessels are closer to skin such as armpits, groin, neck and back.
  • Monitor the temperature

Get medical help immediately if you observe any of the following emergency signs:

  • Hot and dry but not sweaty skin
  • Unconscious
  • Severe vomiting
  • Breathing problems such as difficulty in breathing or shortness of breath

If you are treated for heat exhaustion or heat stroke you would probably recover in few hours to few days respectively. You may become more sensitive to heat subsequent to heat exhaustion or heat stroke. Try to avoid further exposure to heat and follow the advice of your doctor till return to your normal activities.

If the heat index is high, then it is advisable to stay indoors to prevent yourself from hat stroke. Engage in outdoor activities during cooler part of the day. If you need to go outside, then avoid heavy, tight fitting and dark colored cloths. Do not expose yourself to direct sunlight. May be you can wear a hat or umbrella. If possible, use a suitable sunscreen.

Ensure to take plenty of water as often as possible so as to avoid any loss of fluids. Try to avoid drinks that contain caffeine or other stimulants such as alcohol. While you carry out the outdoor activities, ensure to take water more often, say for every 15 minutes. Ensure to keep yourself properly hydrated all the time.

Incase if you have any other medical conditions and take medicines, discuss with your doctor as to how you can cope up with the high heat index and what steps you need to take.

Heat exhaustion and heat stroke are the two heat illnesses. Both need immediate medical attention. Though both are similar their symptoms differ. Heat exhaustion is body’s inability to retain body fluids and salts. Heat stroke, a bit different from heat exhaustion, is body’s inability to maintain the temperature regulatory mechanism.

If proper precautions are taken heat illnesses can be prevented. When occur, immediate attention is required and both can be treated effectively. Recovery may take from hours to days depending on the severity of the heat illness.