Heatstroke causes, effects, symptoms, and first aid treatment.

Our body heat is generated by basal metabolic activity and muscle movement and lost by conduction (which is more effective in water than in air), convection, evaporation, and radiation (most important at lower temperatures when other mechanisms conserve heat). During outdoor activity, most of the people got affected due to heat stroke. That causes serious damage to the body, know profoundly about Heatstroke causes, effects, symptoms and, first aid treatment.

heat strokeBody temperature is controlled in the hypothalamus, which is directly sensitive to changes in core temperature and indirectly responds to temperature-sensitive neurons in the skin.

The normal temperature for the human body is regulated within 37 ± 0.5 °C, which is necessary to preserve all the normal function of many enzymes and other metabolic processes.

Balancing of the body heat production with heat loss which is achieved by a combination of physiological mechanisms (as peripheral vasodilatation or vasoconstriction, changes in heart rate, sweating or shivering) and behavioral mechanisms (increase or decrease in voluntary physical activity, seeking appropriate shelter, etc).

In addition, environmental conditions, viz. temperature, humidity and speed of air also greatly determine whether a person will be subjected to thermal stress.

What is Heatstroke?

Heatstroke causes, effects, symptoms, and first aid treatment.

Heat stroke occurs when the core body temperature rises above 40 °C and produces a life-threatening condition. It occurs due to body overheating which occurs due to continuous exposure or doing any physical exertion in high temperature. This mostly occurs in the summer seasons.

This condition requires emergency treatment as it can produce severe damage to other vital organs like brain, heart, kidneys, and muscles.

Situations in which heatstroke occurs

Adverse effects of heat stress are an important cause of morbidity and mortality not only in the developing countries but in the developed countries as well.


In India, 3,194 deaths due to heat stroke (HS) have been recorded over the 5-year period 1999 to 2003; the actual magnitude may be much more. The central and northern plains, western deserts and tropical forest areas of north-east have environmental conditions causing heat stress during the months of April to September.

heat stroke info

Persons who are at high risk of heat stroke

  • Extremes of age (<5 years or >65 years)
  • Pregnancy
  • Occupation—workers in military, agricultural, construction and industrial settings, laborers, sports-persons, and miners
  • Low level of physical fitness
  • Lack of acclimatization to environmental heat
  • Obesity
  • High ambient temperature, high atmospheric humidity, low air velocity
  • Alcohol use—acute and chronic
  • Skin diseases—extensive prickly heat, psoriasis, pyoderma
  • Sleep deprivation
  • Co-existing febrile illness, renal, thyroid, cardiovascular and metabolic diseases
  • Previous history of heat-illness
  • Use of drugs or habit-forming substances—phenothiazine, anticholinergics,
  • ACE-inhibitors, MAO-inhibitors, cocaine, amphetamines, antihistamines

How Heat Stroke affects the body?

As a part of thermo-regulatory process, even an increase of 1°C in the temperature of blood generates signals to the hypothalamic thermoregulatory centre in the brain due to which it causes an increase in heart rate and cardiac output, which in turn is connected with the sympathetic cutaneous vasodilatation and there is an increase in the skin blood flow.

Sweating is activated and its evaporation cools the body surface unless the air surrounding the body is fully saturated with water, i.e. having a relative humidity (RH) of 100%.

Increasing the movement of air in contact with the body also increases cooling by promoting evaporation of sweat. Sweating, however, leads to loss of water and salt, which may be as high as 2 liters per hour under conditions of high humidity and physical exertion.

Heat exhaustion

If the water and salt are not replaced adequately and concurrently, the fluid reserves would be depleted, even though the body core temperature may not be very high. This condition is called heat exhaustion’.


However, at times, the thermoregulatory response may be overwhelmed by the hot environment, even though the fluid and salt reserves of the body may be adequate.

Such thermo-regulatory failure, coupled with exaggerated acute phase response (increased production of inflammatory cytokines and endothelium-derived vasoactive factors and activation of coagulation process) and alterations in the expression of heat shock proteins (HSPs), leads to heat stroke’.

 For these reasons, a number of cases of heat exhaustion, if not properly managed, would also pass on to Heatstroke. Following Heat stroke, a multiple organ dysfunction syndromes (MODS) results from a complex interplay between the cytotoxic effects of heat and the inflammatory and coagulation responses of the host.

Serious complication due to heatstroke

The most serious complication of heatstroke is MODS, manifesting as hepatic failure, renal failure, cerebellar damage, cerebral oedema, and arrhythmias. Rhabdomyolysis and DIC are other serious complications.

Other adverse effects of Heatstroke:-

Heat Cramps:-

Patient in heat cramps complaints of spasms of muscles, especially lower extremity and shoulder, following heavy muscular exertion in a hot environment, with the associated intake of hypotonic oral fluids.

Treatment of heat cramps consists of oral administration of 0.1% to 0.2% salt solution. In case of severe or those with vomiting, the patient should be given intravenous normal saline.

Heat Tetany:-

Symptoms in heat tetany include carpopedal spasms and paraesthesia following short exposures to an excessively hot environment, leading to hyperventilation and respiratory alkalosis. Treatment

of heat, tetany consists of removing the patient to a cool environment and asking him to slow down the respiration.

Heat Syncope:-

This manifests as syncope following exposure to heat stress as a result of peripheral vasodilatation. For diagnosing of heat syncope one should exclude other serious causes of syncope. Treatment of heat syncope consists of removal of the patient to a cool environment and oral rehydration.

Heat Oedema:-

In heat Oedema, the patient will complaints of pitting edema of hands and feet, usually in the elderly people, following exposure to heat stress. For diagnosing other causes of edema should be excluded. Treatment of heat edema consists of reassurance, the elevation of affected limbs and if required, compression bandage.

Prickly Heat (Lichen Tropicus, Miliaria Rubra):-

The symptoms of prickly heat include erythematous, pruritic, maculopapular rash. If the condition is allowed to progress, extensive prickly heat that can progress to chronic dermatitis and superinfection can occur.

Prevention consists of regular baths with cool water after gently scrubbing the skin and wearing loose, lightweight clothing. In case of severe forms, local application of 1% salicylic acid cream and antibiotics for superinfection (usually Streptococcus aureus) should be given.

Symptoms of Heat Stroke

There are three main features of heatstroke.

  • Hyperpyrexia (increased body temperature) in which rectal temperature must be >40°C.
  • Central nervous system (CNS) dysfunction
  • Anhidrotic (diminished sweating in response to good stimulation)

Anhidrotic, however, is not a diagnostic requirement since it may appear later when volume depletion is severe.

Moreover, in cases which initially start as heat exhaustion or cases of heat stroke which occur among young people who have been exerting physically, the skin may be moist.

Brain dysfunction is usually severe (coma, stupor or delirium), but may sometimes be subtle, manifesting as inappropriate behavior or impaired judgments.

In fact, any person who develops irrational or confused behavior following exposure to heat stress either with or without a history of physical exertion should be treated as a potential heat stroke patient.

Other clinical features include evidence of

  • Dehydration
  • Shock
  • Convulsions
  • Mild icterus

Heat Stroke First-aid Treatment

Heatstroke causes, effects, symptoms, and first aid treatment.

Heatstroke should be treated as an acute emergency. Slight delay in the starting of the treatment for heatstroke may lead to death. So there are few minutes which can make difference between life and death. The treatment for the heatstroke include:-

  • Rapid cooling to bring down the core temperature to below 39°C and reducing it by approximately 0.2°C per minute
  • Rehydration and care of the comatose patient
  • To support the organ system function

Cooling measures should be stopped once core temperature falls below 39°C.

If you suspect that the person is having heat stroke than don’t be late for calling the emergency number for hospitalization of that person before it gets too late.

It the emergency comes you should start the first aid so that the condition can be under controlled so that the person can reach hospital and treatment can be initiated.

Remember not to use ice packs for:-

  • Older patients
  • Young children
  • Patients with chronic illness
  • In the case of that patient who has heat stroke without any vigorous exercise.

Management of Heatstroke in Hospital

  • Continue cooling measures.
  • Start monitoring the core temperature of the patient with a thermometer calibrated to measure high temperature (40°C to 47°C).
  • In case temperature is not reducing, immerse the patient in a tub containing cold or iced water, keep the head and neck outside the water surface.
  • In case the patient is shivering, give intravenous (IV) chlorpromazine 25 mg to 50 mg.
  • Incubate the patient, establish ventilator support, give oxygen inhalations.
  • Continue IV fluids; maintain mean arterial pressure at 60 mm Hg; if required, consider administering a vasopressor.
  • Frequently monitor blood electrolytes to guide IV fluid therapy.
  • In case there is evidence of shock, cerebral edema or adrenal insufficiency, administer IV hydrocortisone hemisuccinate 100 mg or betamethasone 4 mg to 8 mg.
  • If facilities exist, give a cold gastric lavage after incubating the patient.
  • Antipyretics do not seem to have any role.
  • Advice bed rest for about 7 days after recovery from heatstroke since temperature control mechanisms may remain labile after recovery.

Prevention of Heat Stroke:-

If the temperature of the outer environment is high than it is better to stay in an air-conditioned room. But if you have to go outside, then prevent yourself from the heatstroke by following these steps:-

Expose to sunlight

  • Try to avoid exposure to the outside environment during the summer, from 10 am to 5 pm unless it is very necessary.
  • If possible reschedule your program so as to avoid the sun. Keep the meeting or any activities at the coolest time of the day.
     Keep the children <5 years or the elderly >65 years away from the sun as far as possible. Never leave them in closed, parked cars in hot weather.

Water intake

  •  Keep drinking water regularly, especially if exerting. Drink 250 to 300 ml water after every half an hour even if you not thirsty.
  • Drink at least 5 to 6 liters cool water in a day and always carry a bottle of cool drinking water with you. Always remember that thirst is not a good indicator of dehydration, and hence, you should not wait for thirst to develop before starting to drink fluids.
  • Avoid taking too much salt. To replace it start drinking the fluids which contain an adequate amount of electrolyte in it. You can also drink sports beverages or fruit juices.


  • Put light-colored, loose and permeable clothes and prefer to wear cotton clothes in 1 to 2 layers only.
  • Put on a wide-brimmed hat of light color when going out.
  • Apply a sunscreen ointment of sun protection factor of at least 15 SPF when going out in sun.

Avoid drugs

  • Avoid alcohol, cocaine and other habit-forming drugs as these substances will make you lose more fluid from the body and will make you dehydrated.

Make it a habit

  • Acclimatize to heat by undertaking gradually increasing the intensity of physical exertion in a gradually increasing hot environment, for 80 to 100 minutes daily for 10 to 14 days.
  •  If feeling exhausted, too thirsty, confused or running out of memory/consciousness, move to a cool, shaded place, sit or lie down, drink cool water and seek help.

Along with these precautions, other strategies for preventing heat strokes are:-

  • Start monitoring the color of the urine. If there is alteration in color from yellow to the darker. This is the sign that the person is going in a dehydration state. So drink plenty of fluid.
  • Start monitoring the weight before and after physical activities. As loss of weight indicates how much fluid you needed to overcome the loss.
  • Make your room with good ventilation, open windows in the night. Keep the shades or dark curtain in the hottest part of the room and house so that rays of the sun cannot enter.

Types of Heatstroke

Heat-stroke is categorized under two forms

  • Classical heat stroke
  • Exertional heat stroke

To start with the treatment, it is important to diagnose which form of heat stroke the patient is actually suffering.

Difference between classical heat stroke and exertional heat stroke

CharacteristicsClassical heat strokeExertional stroke
Age groupElderly15-45 years
Previous health statusUsually compromisedHealthy
Concurrent activitySedentaryStrenuous activity
The habit of drug useOften presentUsually present
SweatingOften absentFrequently severe
SkinDryMaybe moist

Laboratory Investigation for Heat Stroke

Blood should always be drawn for a peripheral blood smear for malaria parasite as well as for other infectious causes of hyperpyrexia with CNS dysfunction.

Laboratory findings of Heatstroke include

  • Haemoconcentration
  • Mild leukocytosis
  • Elevation of blood urea
  •  In some patients of Exertional Heat Stroke
  • Hypoglycemia.
  • Impaired blood coagulation with lowered prothrombin,
  • Low platelet counts,
  • Hyperfibrinogenemia and
  • Features of disseminated intravascular coagulation (DIC)

Serum electrolyte studies generally show normal or high chlorides, hypokalemia, hypocalcemia, and hypophosphatemia.

Enzyme studies show an increase in creatine phosphokinase (CPK), serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) levels.

If rhabdomyolysis or acute renal failure (secondary to acute tubular necrosis) has set in, urine will show myoglobinuria, proteinuria, and hyaline and granular casts, and there will be an increase in blood urea nitrogen (BUN) levels.

How to differentiate Heat Stroke with other diseases

Heat stroke should be considered as a possibility in any patient who presents with elevated body temperature and altered mental functions.

Important and common diseases which need to be excluded are tropical infectious diseases like cerebral malaria, encephalitis, and meningitis.

Other diseases which need to be considered are thyroid storm, pheochromocytoma, status epilepticus, cocaine and amphetamine abuse, delirium tremens and cerebrovascular accident especially pontine hemorrhage.

The diagnosis of Heat stroke is usually one of exclusion and the typical history of exposure to a hot environment during the immediate past is an indication of heat stress hyperthermia.


Go to the doctor for the regular check-up and to increase the amount of liquid in the hot season for those people who are diagnosed with any kidney diseases, heart diseases, epilepsy, liver diseases, or any fluid retention diseases. As an increasing amount of water can be problematic for them.

If you have recovered from the heat stroke than there are more chances for you to get affected by the hot environment. So avoid going in the hot weather and stay in the cool places and don’t forget to consult your doctor regularly in summers so as to avoid all the fatal conditions which can be possible due to heat stroke.

Therefore, prevention and management of thermal stress disorders requires an understanding of these physiological, behavioral and environmental mechanisms and manipulating them appropriately.

Please give a review of this article”Heatstroke causes, effects, symptoms and, first-aid treatment”.

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