Heatwave Hazards

Global warming has fuelled heat-related illnesses. Immediate action and increased awareness are crucial to mitigating the life-threatening risks posed by extreme hot weather conditions.
By Dr Suneela Garg & Dr Arvind Garg

Rising global temperatures, driven by increasing global warming, elevate both ambient temperature and humidity levels. This escalation significantly heightens the risk of heat-related illnesses, which are serious medical conditions arising from the body’s inability to cope with excessive heat. These illnesses include heat cramps, heat exhaustion, heat syncope (fainting or a temporary loss of consciousness and muscle strength), and heat stroke.

Understanding Heat Illness
Heat illness refers to a spectrum of conditions caused by the body’s failure to manage heat load effectively. This failure can lead to a range of symptoms and severities, from mild discomfort to life-threatening emergencies.
As per reports, with each degree of warming, atmospheric water vapour increases by approximately 6 to 7%, potentially pushing heat stress exposure beyond human tolerance in many areas. Human body temperature is maintained within a narrow range of 36.5–37.5°C (97.7–99.5°F) by balancing heat production from environmental exposure and metabolic processes with heat dissipation mechanisms.

Body temperature regulation involves complex physiological and behavioural mechanisms. When core body temperature rises, the autonomic nervous system, via the preoptic nucleus of the anterior hypothalamus, triggers increased sweating and cutaneous vasodilation to dissipate body heat. These mechanisms are crucial in maintaining thermal equilibrium, especially under conditions of extreme heat stress.

Impact of Heat-Related Illness
Humans must maintain their internal body temperature within a very narrow range around 98.6°F (37°C). Heat-related illness occurs when the body cannot shed excess heat quickly enough, losing its “heat balance.” This imbalance can lead to a cascade of physiological events.
When the body starts to overheat, blood vessels dilate, and the heart beats faster and harder. This increases blood flow to the skin’s surface from the body’s internal “core,” releasing heat into the cooler environment. If this process does not cool the body quickly enough, or if the outside air is warmer than the skin, the brain triggers sweating to cool the body. Sweat glands draw water from the bloodstream to produce sweat, which evaporates and releases heat.

During an hour of heavy work in hot weather, the body can sweat out up to one quart of water. Shifting blood to the outer body layers (the “shell”) reduces blood flow to the brain, muscles, and other organs (the “core”). Prolonged sweating can deplete the body of water and salts, leading to dehydration. Muscle cramps can occur as a result of the loss of essential salts needed for muscle function. The physiological strain from heat illness can cause dehydration, weakness, fatigue, and confusion.
As dehydration worsens, the body can no longer regulate its temperature within the normal range. Sweating stops, and severe heat illness can occur. In the case of heat stroke, the person’s body temperature rises rapidly, potentially damaging the brain, muscles, and vital organs, and can lead to death.

Types of Heat-Related Illnesses

1.Heat Cramps:
o Symptoms: Painful muscle cramps and spasms, particularly in the legs, often accompanied by flushed, moist skin.
o Cause: Intense exercise and sweating in high heat without adequate fluid replacement.
o Management: Rest in a cool place, drink water or electrolyte solutions, and gently stretch and massage the affected muscles.

2. Heat Exhaustion:
• Symptoms: Muscle cramps, pale and moist skin, fever over 100.4°F (38°C), nausea, vomiting, diarrhoea, headache, fatigue, weakness, anxiety, and faintness.
• Cause: Extreme heat and excessive sweating without sufficient fluid and salt replacement.
o Progression: If untreated, can lead to heat stroke.
• Management: Move to a cooler environment, hydrate with water or sports drinks, and apply cool, wet cloths to the skin. Rest and monitor for progression of symptoms.

3. Heat Syncope:
• Symptoms: Sudden dizziness or fainting, typically occurring after standing for a long time or suddenly rising from a sitting or lying position.
• Cause: Dehydration and lack of acclimatisation to hot environments.
• Management: Lie down in a cool place, elevate the legs, and hydrate with fluids.

4. Heat Stroke:
• Symptoms: High fever (usually over 104°F or 40°C), rapid heart rate, warm and dry skin, nausea, vomiting, headache, fatigue, confusion, agitation, lethargy, seizures, coma, and potential death.
• Cause: Overwhelming heat load exceeds the body’s cooling mechanisms.
• Emergency Response: Immediate medical attention is required. Move to a cool place, call emergency services, remove excess clothing, use cool cloths, and take cool drinks containing salt and sugar. Intravenous (IV) fluids should be administered, if necessary.

Prevention of Heat-Related Illnesses
• Hydration: Drink plenty of fluids during outdoor activities, especially on hot days. Water and sports drinks are recommended, while alcohol and caffeine should be avoided as they can cause dehydration.
• Appropriate Clothing: Wear light-coloured, lightweight, loose-fitting clothing to facilitate heat dissipation.
• Activity Scheduling: Schedule vigorous activities for cooler times of the day and take frequent rest periods in shady or cool areas to prevent overheating.
• Sun Protection: Use hats, sunglasses, and umbrellas to protect from direct sunlight. Apply sunscreen with at least SPF 15 to exposed skin.
• Acclimatisation: Gradually increase outdoor activity time to allow the body to adjust to the heat, thereby improving tolerance and reducing the risk of heat-related illnesses.
• Cooling Techniques: Encourage frequent drink breaks and use spray bottles to stay cool. Wetting down the body can help lower body temperature.
• Indoor Activities: Stay indoors as much as possible during very hot and humid days to minimise heat exposure.
• Exercise Precautions: Warm up and cool down before and after exercise to prevent sudden stress on the body.
• Medical Advice: Consult a doctor for advice on preventing heat-related illnesses, especially if you or your child have any medical conditions or are taking medications. Specific guidelines may be necessary to manage heat exposure effectively.

(The authors are Chair of the Programme Advisory Committee at NIHFW and Head of Paediatrics at Apollo Hospitals, Noida.)