Heat- Related Illnesses are the various manifestations of extreme heat and are increasing with increased global warming and heat waves. Periods of extreme heat that have an effect on human health are referred as heat waves. Climate change is leading to an increase in average temperatures and increased possibilities of severe heat waves. The impact of extreme summer heat on human health may be exacerbated by increase in humidity. Heat waves are an emerging public-health problem.
Extreme heat can lead to minor illnesses, such as heat rash (prickly heat), heat oedema, heat cramps, and tetany, as well as serious illnesses as heat syncope, heat exhaustion and heat stroke. Heat stroke is the most severe form of the heat-related illness. The mortality rate among heat stroke victims is as high as one-third, and one-fifth of the heat stroke survivors suffer neurologic damage.
Heat-related illnesses include:
Heat stroke is a medical emergency. Even with immediate treatment, it can be life-threatening or cause serious long-term problems.
Heat- related illness is a common problem in the tropics and with ever-increasing global warming its incidence is rising even in temperate climate. The highest incidence of heat illness of 45-1300/100000 persons is reported from Saudi Arabia.
In India, heat stroke (HS) occurs frequently in areas of northern and western India, and sporadic cases of exertional heat stroke (EHS) are reported in military recruits. In 2015, (April-June) recorded maximum temperature was 6°C to 8°C more than the average maximum temperature (mean daily maximum temperature) which resulted in 2422 human deaths due to heat wave. States of Andhra Pradesh, Telangana, Odisha, Gujarat, Rajasthan, Madhya Pradesh, Uttar Pradesh, Vidarbha region of Maharashtra, Bihar, Jharkhand and Delhi are mostly affected by heat wave season.
Children, elderly persons, chronically ill persons, outdoor workers, pavement and slum dwellers, street venders and rickshaw pullers are at greater risk of heat related illnesses.
Greater awareness about heat related illnesses will help in preventing, recognizing and treating these disorders at an early stage. Public education on heat illnesses, behavioural changes and restricted use of alcohol, enforced rests and fluid protocols, acclimatisation and ready availability of cooling facilities in hot areas will help in decreasing morbidity and mortality. Most heat-related illnesses can be prevented by keeping the body cool and by avoiding dehydration in hot environments.
Find more information:
“Guidelines for Preparation of Action Plan – Prevention and Management of Heat-Wave”, 2016 by National Disaster Management Authority, Government of India-
Mehta SR et al, Heat Stroke, MJAFI 2003; 59: 140-143, accessed from medind.nic.in/
symptoms of various heat related illnesses are-
As the body temperature increases, the body tries to maintain its normal temperature by transferring heat. Sweating and blood flow to the skin (Thermoregulation) help to keep body cool. A heat-related illness occurs when the body cannot transfer enough heat to keep the body cool. A high body temperature (hyperthermia) can develop rapidly in extremely hot environments.
Heat-related illnesses produce a high body temperature because the body cannot transfer heat effectively or because external heat gain is excessive.(High temperature caused by a fever is different from a high body temperature caused by a heat-related illness. A fever is the body's normal reaction to infection and other conditions).
Heat rash (Prickly heat) develops when the sweat ducts become blocked and swell. It is attributed to heavy sweating during hot and humid weather.
Heat oedema develops when heat causes the blood vessels to expand (dilate) and body fluid moves into the hands or legs by gravity. If salt loss is less than normal, the increased salt level draws fluid into the hands and legs. Older adults have an increased risk of heat oedema, especially if they have other medical conditions that affect their circulation. People visiting hot climates from colder climates may also have an increased risk of heat oedema.
Heat syncope occurs when heat causes the blood vessels to expand (dilate) in order to keep body cool; as a result blood flow to the brain is reduced causing fainting. Heat Syncope can also be caused as a result of blood collecting in the legs if an individual is standing for an extended period of time in the hot sun or as a result of doing rigorous physical activity for an extended amount of time out in the sun.
Heat exhaustion occurs when body loses body fluids and salts (sweating), when exposed to high temperatures for long periods of time. It can develop when person works or exercises in hot weather and doesn't drink enough liquids to replace the fluids lost from sweating.
Heat stroke results when the body fails to regulate its own temperature, and body temperature continues to rise. Heat stroke is the most serious heat-related disorder. It occurs when the body fails to regulate its own temperature, the body's temperature rises rapidly, the sweating mechanism fails, and the body is unable to cool down. The body temperature can rise to 106 degrees Fahrenheit (41.1 degree Celsius) or higher within 10 to 15 minutes. Heat stroke can cause death or permanent disability if prompt medical treatment is not given.
There are two forms of heat stroke:
Risk factors for heatstroke include male sex, sleep deprivation, obesity, poor physical conditioning, lack of acclimatization, diuretic therapy, dehydration, febrile illness, alcohol abuse, skin diseases that affect sweating, heavy protective gear, drugs impairing normal thermoregulatory response, and a past history of HS.
Mehta SR et al Heat Stroke, MJAFI 2003; 59: 140-143, accessed from medind.nic.in/
In most cases diagnosis is made clinically. This involves taking the temperature and assessing the symptoms of heat exhaustion and heat stroke.
Baseline tests should include:
Blood test for:
Muscle function test- Creatinine kinase (CK), lactate dehydrogenase (LDH), aldolase, and myoglobin are released from muscles when muscle necrosis occurs.
Cerebrospinal fluid analysis- Cerebrospinal fluid (CSF) cell counts may show a nonspecific pleocytosis and CSF protein levels may be elevated.
Heat cramps-Treatment of heat cramps include rest, cooling the body, oral hydration, and stretching the muscles that are cramping. Medical attention should be sought if heat cramps are sustained for more than one hour.
Heat oedema- Treatment is not required as oedema usually subsides following acclimatization. Diuretics are not advised and avoid the heat as much as possible.
Heat syncope-The patient should rest in a cool place and be placed in a supine position with legs and hips elevated to increase venous return. Other serious causes of syncope need to be ruled out.
Heat related illnesses are preventable. A Heat-Health Action Plan (HHAP) may be constituted at state/district level according to local needs of the communities to reduce the morbidity and mortality due to heat waves.
National Disaster Management Authority (NDMC), Government of India has released “Guidelines for Preparation of Action Plan – Prevention and Management of Heat Wave” to prevent heat related illness during heat waves*.
HHAP may be formulated with incorporation of following activities:
Public awareness and community outreach activities: to communicate the risks of heat waves and measures to prevent heat-related deaths and illnesses.
Heat–Health Warning Systems (HHWSs): an early warning system with inter-sectoral coordination to alert communities/residents about predicted high and extreme temperatures.
Identification of Color Signals for Heat Alert (Ahmadabad Heat Action Plan 2015):
Red Alert Extreme Heat Alert for the Day
Orange Alert Heat Alert Day
Yellow Alert Hot Day
White Normal Day
Capacity building among health care professionals: to recognize and respond to heat-related illnesses.
Interventions for reducing heat exposure and providing supportive measures- access to potable drinking water, cooling spaces during day time in extreme hot days, open cooling centers to offer relief to people without proper shelter and urge the public to use them, mapping of high-risk areas of the city(urban heat islands*) and at-risk communities, collaboration with non-governmental organizations.
(*Urban heat island describes built up areas that are hotter than nearby rural areas. Heat islands can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, water quality, heat-related illness and mortality.
Long term measures: to reduce urban heat island effects:
To minimise the impact during the heat wave and to prevent serious heat related illnesses at community and individual level following DO’s and DONT’s are suggested:
Listen to Radio, watch TV, read News paper for local weather forecast to know if a heatwave is on the way.
Regularly drink water or other nonalcoholic fluids (homemade drinks like lassi, torani (rice water), lemon water, buttermilk, panna) and as often as possible, even if not thirsty.
People who have come from a cooler climate to a hot climate during the heat wave season are at risk for heat related illness. They should not move in open area for a period of one week till the body is acclimatized to heat and should drink plenty of water. Acclimatization is achieved by gradual exposure to the hot environment during heat wave.
Emergency kit –
If someone is suffering from the heat related illness: