Heat Stroke

Overview of heat stroke

With the aggressive growth of industrial development in the past decade, there has been a steady increase in the rate of global warming. This has adversely impacted the global population, especially the residents of urban and industrial areas in terms of health, money, and productivity. Among various ailments triggered by the increased temperature of Earth, “heat stroke” poses a potential threat to human existence. A recent survey by World Health Organization (2015) shows that strokes caused by heat waves kill more than 2000 people per year in tropical countries like India, Pakistan and a few more. Global health organizations are predicting an increase in the morbidity and mortality rates in the upcoming years unless adequate measures to control diseases due to excessive heat are not formulated.

What is heat stroke?

A heatstroke is basically a form of “Hyperthermia” which is a pathological condition of abnormally increased body temperature due to external heat sources.

Heatstroke causes numerous physiological complications.

At present, heatstroke is one of the leading causes of emergency medical conditions, in which the human body temperature rises above 40 degree Celcius due to prolonged and unprotected exposure to sources of heat.

In this condition, perspiration does not occur and the internal body temperature steadily increases due to lack of cooling. It affects the thermoregulation mechanism of the body adversely.

What causes heat stroke?

Heatstroke normally occurs as a continuation of existing heat-related disorders such as heat cramps or heat exhaustion. The generalized causes of heatstroke are listed below-

• Abrupt increase in internal body temperature (up to 105^o F)
• Lack of cooling (due to reduced perspiration)
• Sudden exposure to a source of heat
• Direct and prolonged exposure to ultraviolet radiations of sun
• Extremely hot weather with no breeze
• Extreme sensitivity of the body to elevated temperature
• Reduced adaptability of the body to change in temperature
• Wearing excessive clothing in a hot environment
• Occupational hazards (Eg: Factory workers are exposed to heat from blast furnace)
• Lack of ventilation
• Existing illnesses like heart diseases , high blood pressure or fever
• Medications like vasoconstrictors and beta-blockers which affect the thermoregulation capacity of the body
• Dehydration due to low intake of fluids
• Diet deficient in essential nutrients
• Excess alcohol or tobacco consumption which impedes the body’s thermoregulation capacity
• Electrolyte imbalance within the body (Eg: drop of sodium level)

Symptoms of heat stroke

The symptoms of heatstroke are often confused with cardiac arrest or other physiological disorders. A proper identification of the following symptoms is necessary to protect a person from the risks of heatstroke-

• Complete lack of sweating even at a very high temperature
• Extremely dry, heated up and reddened skin
• Rapid heart rate (palpitation)
• Increased respiratory rate
• Dizziness and convulsions
• A persistent and throbbing headache
• Confused and agitated mental state

Immediate hospitalization is necessary if the symptoms persist, to avoid serious consequences.

Clinical complications of heatstroke

Heatstroke in most cases does not limit itself to few superficial symptoms. Very often it leads to multisystem failure and attacks the vital organs of the body as well. The following clinical complications can be expected after heatstroke incidences-

• Central Nervous System is affected in 20% cases
• The muscular system is impacted due to Rhabdomyolysis which badly damages the muscular tissues
• Renal failure occurs in various instances due to the presence of excess protein (myoglobin) in urine
• Damage to liver cells occur, leading to Coagulopathy (impaired blood clotting) and Hepatitis
• Cardiac failure may occur due to myocardiopathy (damage to heart muscles)

Types of heat stroke

Depending on the etiological factor behind heatstroke, they may be classified into two main categories- (a) Exertional heatstroke and (b) Classic heatstroke

• Exertional heat stroke: Heat stroke caused due to prolonged physical exertion at extremely high temperatures (greater than 104^o F) is called exertional heatstroke. It is characterized by muscle cramps (heat cramps), extreme fatigue (heat exhaustion) and temporary unconsciousness due to a rapid drop in blood pressure (heat syncope). Few other features include diaphoresis (unusual sweating) and “altered sensorium” (impaired functioning of sense organs). Usually, people undergoing rigorous physical activities under extreme heat conditions are victims of this kind of heat stroke. Marathon athletes and factory workers (exposed to high temperature of a blast furnace) and firefighters usually fall into this category. This type of heatstroke usually stops manifesting itself once the physical activities in extreme environmental conditions are stopped. Exertional heatstroke can also occur due to excessive use of drugs such as cocaine or amphetamines which causes an abnormal increase in the rate of motor activities.
• Classic heatstroke: Classic heatstroke or Non-exertional heatstroke mostly occurs due to an abnormally elevated temperature of the surrounding for a long period of time. NEHS is characterized by hyperthermia, anhidrosis, and an altered sensorium, which develop suddenly after a period of prolonged elevations in ambient temperatures (ie, heat waves). Core body temperatures greater than 41°C are diagnostic, although heatstroke may occur with lower core body temperatures.

Numerous central nervous system (CNS) symptoms, ranging from minor irritability to delusions, irrational behavior, hallucinations, and coma have been described. Other possible CNS symptoms include seizures, cranial nerve abnormalities, cerebellar dysfunction, and opisthotonos.Anhidrosis due to the cessation of sweating is a late occurrence in heatstroke and may not be present when patients are examined.

Patients with NEHS initially may exhibit a hyperdynamic circulatory state, but, in severe cases, hypodynamic states may be noted.

Classic heatstroke most commonly occurs during episodes of prolonged elevations in ambient temperatures. It affects people who are unable to control their environment and water intake (eg, infants, elderly persons, individuals who are chronically ill), people with reduced cardiovascular reserve (eg, elderly persons, patients with chronic cardiovascular illnesses), and people with impaired sweating (eg, from skin disease or ingestion of anticholinergic or psychiatric drugs). In addition, infants have an immature thermoregulatory system, and elderly persons have impaired perception of changes in body and ambient temperatures and a decreased capacity to sweat.

Vulnerable groups

Anyone can suffer from heat-related illness, but those most at risk are:

• People over 65 years, particularly those living alone or without air conditioning
• Babies and young children
• Pregnant and nursing mothers
• People who are physically unwell, especially with heart disease, high blood pressure or lung diseases.

Treatment & Prevention

All the treatment methodologies designed to treat heat stroke aim to cool down the high body temperature to normal levels.

Treatment should be provided as quickly as possible so that the vital organs such as the brain don’t get damaged.

Immersing the patient’s body in ice cold water will help in rapidly decreasing the body’s core temperature.

Ice-cold showers can also help.

There are special cooling blankets available that help in protecting from heat strokes.Apply ice packs in certain areas of the body such as the armpits, back, neck, and groin to help in decreasing the body temperature.Certain home remedies such covering the patient with cold damp sheets can also help.

Drink plenty of fluids throughout the hot days to ensure that your core temperature is maintained as the homeostatic level.  Don’t provide caffeine or alcohol containing drinks to the person during an episode of heat stroke. During summers, wear loose-fitting and light-weight clothes.  Never sit inside a car when it’s parked in the hot sun. Never leave kids or pets unattended in such conditions.

References