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Health
Effects of Heat Waves
Prolonged periods of unusually
high temperatures increase morbidity and mortality. Persons aged over 65 and
young children are at greater risk. The brain centres
that regulate body temperature attempt to keep core temperature within
healthy limits. At rest, this temperature is around 37 degree centigrade, but
with exercise, it can increase to 38-39 degree centigrade without harm to
health. To stay within the control range, the body needs to balance its heat
production and other possible heat gains with heat loss.
Classical heat illnesses
include, in order of increasing severity, skin eruptions, heat fatigue, heat
cramps, heat syncope, heat exhaustion and heat stroke. Most of these, except
skin eruptions and heat cramps, are symptoms of failure of thermoregulatory
system of the body of varying severity. The conditions that can make people
more vulnerable to failure of thermoregulatory system of body during a heat
wave include: dehydration due to reduced food and liquid intake, reduction of
sodium in the body due to excessive loss of liquids, use of drugs such as
diuretics, beta blockers, anticholinergics,
digitalis and barbiturates. The other common factors are acute diseases such
as diarrhea, fever, infections and skin burns.
Heat Syncope
This refers to the sudden loss
of consciousness by persons who are not acclimatized to hot weather. A
failure to keep up blood pressure and oxygen supply to the brain causes heat
syncope. As soon as the affected person is put in the lying down posture in
cool surroundings, the body systems recovers quickly. This should be followed
by rehydration.
Heat Stroke
What is heat stroke?
Heat stroke is the most severe form of heat illness
and is a life-threatening emergency. It is the result of long and severe
exposure to the sun, in which a person does not sweat enough to lower body
temperature. The elderly, infants, persons who work outdoors and those on
certain types of medications are most susceptible to heat stroke. It is a
condition that develops rapidly and requires immediate medical treatment.
What causes
heat stroke?
Our bodies produce a tremendous amount of internal
heat and we normally cool ourselves by sweating and radiating heat through
the skin. However, in certain circumstances, such as extreme heat, high
humidity or vigorous activity in the hot sun, this cooling system may begin
to fail, allowing heat to build up to dangerous levels.
If a person becomes dehydrated and cannot sweat
enough to cool his/ her body, the internal temperature may rise to
dangerously high levels, causing heat stroke. It results from a high heat
load with body temperature above 40.5 degree centigrade. If not reduced
quickly, it causes damage to the cellular structures and the thermoregulatory
system, with a high risk of death. Complications of heat stroke include adult
respiratory distress syndrome, kidney failure, and liver failure and
disseminated intravascular coagulation. Deadly heat strokes may be under-
reported because they are similar to other, more familiar causes of death,
particularly coronary or cerebral thrombosis.
What are
the symptoms of heat stroke?
The following are the most common symptoms of heat
stroke:
 headache
dizziness
disorientation, agitation or confusion
sluggishness or fatigue
seizure
hot, dry skin that is flushed but not sweaty
a high body temperature
loss of consciousness
rapid heart beat
hallucinations
How is heat
stroke treated?
It is important for the person to be treated
immediately since the heat stroke can cause permanent damage or death.
Immediate first aid measures that could be undertaken while waiting for help
to arrive are:
Get the person indoors.
Remove clothing and gently apply cool water to
the skin followed by fanning to stimulate sweating.
Apply ice packs to the groin and armpits.
Have the person lie down in a cool area with
the feet slightly elevated.
Intravenous fluids are often necessary to compensate
for fluid or electrolyte loss. Bed rest is generally advised and body
temperature may fluctuate abnormally for weeks after heat stroke.
How can
heat stroke be prevented?
There are precautions that can help protect you
against the adverse effects of heat stroke. These include the following:
Drink plenty of fluids during outdoor
activities, especially on hot days. Water and sports drinks are the drinks of
choice; avoid tea, coffee, soda and alcohol as these can lead to dehydration.
Wear lightweight, loose-fitting clothing in
light colors.
Schedule vigorous activity and sports for
cooler times of the day.
Protect yourself from the sun by wearing a
hat, sunglasses and by using an umbrella.
Gradually increase time spent outdoors to get
your body used to the heat.
During outdoor activities, take frequent drink
breaks and mist yourself with a spray bottle to avoid becoming overheated.
Try to spend as much time indoors as possible
on very hot and humid days.
If you live in a hot climate and have a chronic
condition, talk to your physician about extra precautions you can take to
protect yourself against heat stroke.
Dehydration and Heat Stroke
The danger of dehydration and heat stroke:
Dehydration and heat stroke are two very common
heat-related disorders that can be life-threatening if left untreated.
What is dehydration?
Dehydration can be a serious heat-related disorder,
as well as being a dangerous side-effect of diarrhea, vomiting and fever.
Children and persons over the age of 60 are particularly susceptible to
dehydration.
What causes
dehydration?
Under normal conditions, we all lose body water
daily through sweat, tears, urine and stool. In a healthy person, this water
is replaced by drinking fluids and eating foods that contain water. When a
person becomes so sick with fever, diarrhea and vomiting, or if an individual
is overexposed to the sun, dehydration occurs. The body loses water and
essential body salts such as sodium, potassium, calcium bicarbonate and
phosphate.
Occasionally, dehydration can be caused by drugs,
such as diuretics, which deplete body fluids and electrolytes. Whatever the
cause, dehydration should be treated as soon as possible.
What are
the symptoms of dehydration?
The following are the most common symptoms of
dehydration:
thirst
less-frequent urination
dry skin
fatigue
light-headedness
dizziness
dry mouth and mucous membranes
increased heart rate and breathing
In children, additional symptoms may include:
dry mouth and tongue
no tears when crying
no wet diapers for several hours
sunken abdomen, eyes or cheeks
high fever
listlessness
irritability
skin that does not flatten when pinched and
released
Treatment
for dehydration:
If suspected early, dehydration can often be treated
at home under a physician's guidance. In children, directions for giving food
and fluids will differ according to the cause of the dehydration, so it is
important to consult a pediatrician.
In cases of mild dehydration, simple rehydration is recommended by drinking fluids. Many
drinks available on the market effectively restore body fluids, electrolytes,
and salt balance.
The home based oral fluids such as butter milk,
water from tender coconut, rice water with salt and sugar, pulp of raw mango
meshed after roasting mixed with water, sugar and salt, can be very
effective in treating dehydration.
If diagnosed early enough, simple rehydration with home based oral rehydration
solutions as stated above supplemented with ORS preparations may be
effective. Cases of serious dehydration should be treated as a medical
emergency, and hospitalization, along with intravenous fluids, is necessary.
Immediate action should be taken.
How can
dehydration be prevented?
Take precautionary measures to avoid the harmful
effects of dehydration, including:
Drink plenty of fluids, especially when working
or playing in the sun.
Make sure you are taking in more fluid than
you are losing.
Try to schedule physical outdoor activities
for the cooler parts of the day.
Drink appropriate drinks to help maintain
electrolyte balance.
For infants and young children, solutions like
readymade oral rehydration packs available on the
market or from nearest health care facility, will help maintain electrolyte
balance during illness or heat exposure. Where these preparations are not
available, the home based Oral Rehydration
Solutions could be used after getting the briefing from a health care
provider about the quantity of sugar and salt to be used in them.
Heat Cramps
These cramps occur as a result of fluid and
electrolyte imbalance following strenuous exercise done in the heat. Cramps
tend to occur in the muscles that have been exercised most. They are common
in athletes who must perform in the heat or in workers in ‘hot’ industries.
This can be corrected with the help of oral rehydration
with proper electrolyte replenishment by using standard oral rehydration packs available from a health centre or the
market. In case the same are not handy, the home based oral rehydration should be provided under the guidance from a
trained health care worker.
References:
1. Fact Sheet from WHO,
EURO/ 04/ 03 Copenhagen, Rome, 29 September 2003, on Health effects
of Heat waves.
2. First Aid for Dehydration and heat stroke,
University of Maryland Medical Center (http://www.umm.edu/non_trauma/dehyrat.htm)
3. The Public Health Consequences of Disasters,
edited by Eric K. Noji, National Center for
Environmental Health, Centers for Disease Control and Prevention, New York,
Oxford University Press, 1997.
4. A revolution in the management of diarrhoea, Olivier Fontaine & Charlotte Newton,
Bulletin of the W H O, 2001, 79 (5).
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