Sunstroke
Sunstroke is a life-threatening
condition in which the body's heat-regulating system fails, due to exposure to
high temperatures.
Sunstroke can occur when the body's
mechanisms to rid itself of excess heat are overwhelmed by a very hot or humid
environment, or strenuous physical activity.
People particularly susceptible to
sunstroke are young children, the elderly, individuals not used to physical
activity and concomitant excessive sun exposure (such as overseas visitors
walking in the mountains in Africa), people suffering from certain chronic
medical conditions, and those involved in certain sporting activities.
Symptoms
of sunstroke include elevated body temperature; hot, dry skin; hyperventilation;
mental confusion; and eventual unconsciousness.
The primary treatment goal for
sunstroke is to lower the elevated body temperature rapidly in a controlled
fashion.
Sunstroke can
be prevented by drinking plenty of water and avoiding overtaxing the body in hot
weather and while exercising.
Alternative names
Heatstroke
What is sunstroke?
(heatstroke) is an acute, life-threatening condition in which
the body's heat-regulating system fails, due to prolonged exposure to high
temperatures, excessive production of heat or commonly a combination of the two.
The body is unable to lose heat adequately in order to return to its normal
temperature. Body temperature rises to very high levels, which can damage major
organs.
Sunstroke can be preceded by heat exhaustion, when excess loss of fluids and
salt in sweat results in marked weakness. Heat exhaustion becomes sunstroke when
your body can no longer maintain a normal body temperature.
Heat
exhaustion may be accompanied by heat cramps: sudden painful muscle spasms in
the arms or legs, and sometimes the abdomen.
What causes sunstroke?
In a hot environment, your body rids itself of excess heat through
increasing blood flow to the skin, sweating and breathing out warmed air. These
mechanisms can sometimes be overwhelmed, however, leading to heat-related
symptoms, which, if left untreated, can lead to sunstroke.
When
blood temperature rises above its normal range, a control centre in the brain
(the hypothalamus) signals the circulatory system to increase blood flow and
enlarge the blood vessels, particularly those in the skin. As more blood flows
through the enlarged vessels, excess heat from the blood passes into the cooler
air. If this is not sufficient to cool the blood, the sweat glands begin to
produce sweat, which cools the skin as it evaporates. If the air temperature is
very high, however, the blood may not cool down enough as it circulates through
the skin. Also, when you lose too much fluid, the blood volume decreases, and
body temperature increases. If the body continues to generate heat faster than
you can lose it, the core temperature (central body temperature) may rise to
dangerous levels, causing heat exhaustion or sunstroke.
Sunstroke usually occurs after exposure to high temperatures, for example from
working in an extremely hot environment, especially one to which you are unused;
exercising too strenuously, particularly in summer; or when you have a high
fever associated with illness. Humid weather also renders the cooling mechanism
of sweating less effective. Overdressing, overeating and drinking too much
alcohol can be contributing factors.
The
primary cause of symptoms is loss of sodium and chloride (which make up salt),
rather than the amount of water.
Who gets sunstroke and who is at risk?
Anyone exposed to high temperatures is at risk of sunstroke, but the
following groups are at particularly high risk and must take special precautions
to avoid hot, poorly ventilated places and exertion in hot weather:
Young children
Elderly
people
People
with certain chronic conditions such as:
Arteriosclerosis and congestive heart
failure
Diabetes mellitus
Alcoholism
Skin disorders that may impede heat
loss such as ectodermal dysplasia, congenital absence of the sweat glands, or
severe scleroderma.
People taking certain medications that
may interfere with temperature regulation. Some such medications include:
gastrointestinal drugs containing atropine (e.g. Donnatal); antidepressants or
antipsychotics (e.g. Thorazine, Haldol, Prozac); antihistamines (e.g. Benadryl);
certain cardiovascular medications including betablockers (e.g. Blocadren) and
diuretics (e.g. Diuril); and Parkinson's disease medications.
People
taking part in certain types of sporting activities, such as long-distance
running or cycling.
People known to be susceptible to the
effects of extreme heat.
Symptoms and signs of sunstroke
Symptoms of sunstroke may include:
Hot,
dry skin
No
sweating (usually)
Skin
is first flushed, then pale or purple
Hyperventilation
(rapid, shallow breathing)
Rapid, bounding pulse (alternates
between a higher intensity than normal, then disappears quickly)
Body temperature rises rapidly to 40°C
or higher
Headache
Muscle
cramps
Dilated
pupils
Signs of mental disorder may include
incoherent speech, disorientation, confusion, aggressive speech or behaviour,
agitation and hallucinations.
Lethargy
or stupor (reactions become extremely slow and sluggish)
Convulsions
Loss of consciousness
Symptoms of heat
exhaustion may include:
Weakness and fatigue
Tense
or aching muscles
Nausea and vomiting
Pale,
clammy skin
Weak, rapid pulse
Confusion
Normal
body temperature (usually)
Heat
cramps
Heavy
sweating
Dizziness or lightheadedness
Fainting
Dark
yellow or orange urine
Headache
Diarrhoea
How is sunstroke
diagnosed?
The doctor will review your symptoms and take blood pressure and
temperature readings. Rectal temperature is used rather than temperature in the
mouth. He or she may also take a sample of your blood and urine for testing.
How is sunstroke treated?
Treatment of heat-related illness depends on its severity.
Emergency treatment of sunstroke
Heat stroke is a medical emergency. If you think someone has
sunstroke, call an ambulance or take the person to hospital immediately. The
primary treatment goal is to lower the elevated body temperature as quickly as
possible. So, while you're waiting for medical help, give first aid as follows:
Remove the person's clothing
and immerse the body in a cold water bath. If this is not possible, cover the
body with a wet sheet or towels, sponge down the body with cool water or rub the
limbs with ice-cubes. If your water supply is limited, cooling the head and neck
becomes the priority. Place ice packs (if available) at the neck, armpits and
groin. Fan the person with a newspaper, towel or electric fan to increase air
flow and evaporation.
After
the bath, move the person to a cool place.
Elevate
the feet to direct blood back toward the head.
Massage
the extremities (arms and legs) to encourage the return of cool blood to the
brain and the core of the body.
If the person is conscious,
encourage him or her to sip water or a soft drink. If the mental state is
impaired, it may be impossible to get the person to drink. Continue with
external cooling in the hope that the person will recover sufficiently to begin
drinking.
While cooling the body down,
take the person's temperature rectally every 10 minutes and do not allow it to
fall below 38.5°C. Only immerse the person in a cold bath until their
temperature falls to 39.4°C. If you don't have a thermometer, continue with
first aid until the body feels cool to the touch. Resume cooling if the body
starts to heat up again.
Hospital care for sunstroke
More careful control measures are used in hospital, with better
temperature measurement and regulation. Core temperature is monitored
continuously to avoid hypothermia. Blood tests are used to determine salt and
electrolyte levels and fluid therapy is started to correct imbalances.
Careful
observation for signs of fluid and salt imbalances, and complications such as
kidney failure, will be required for several weeks after the initial episode.
Temperature changes may be expected for several weeks following the episode.
Treatment of heat exhaustion and heat cramps
Heat exhaustion and cramps can usually be resolved with home
treatment. Have the person lie down in a cool place, loosen or remove clothing
and sponge the body with cold water, or apply wet towels or ice packs.
You can
also fan them to increase cooling through evaporation. Offer a cool salty drink,
for example a teaspoon of salt dissolved in a litre of water, sipped slowly over
an hour. You can add a tablespoon of sugar or a sweet drink powder as an energy
boost. If the person is elderly or cannot keep the salty liquid down, he or she
should be taken to hospital.
Heat
cramps can be relieved by stretching and massage. Firm pressure on the cramped
muscles and warm towels may help. Drinking a salty solution, as recommended for
heat exhaustion, should keep cramps from recurring.
Anyone
who has had heat exhaustion or cramps should rest for 24 hours afterwards.
What is the outcome of sunstroke?
Heat exhaustion is not life-threatening unless it is ignored, but
sunstroke can be fatal if not properly treated. Once the cooling mechanism
fails, the core temperature rises rapidly and death can occur in as little as 30
minutes. Some people die up to several weeks after the initial acute episode, as
a result of complications such as kidney failure or heart failure. Sunstroke
kills over 10% of its victims. Sunstroke may also cause permanent damage to
organs such as the liver.
Can sunstroke be prevented?
The following guidelines can help prevent heat-related illness,
including sunstroke:
Drink
plenty of water whenever you spend a lot of time in the sun or a hot
environment, and before, during and after exercise. Don't wait until you feel
thirsty to drink, and drink more than you need to satisfy your thirst -
particularly if you've been sweating.
Rest
during the hottest part of the day.
Take time to get used to a new
climate, or the start of the hot season, before being very active or staying in
the sun. Your temperature regulation system will become more efficient as it
becomes accustomed to the heat.
If
you are an endurance runner or cyclist you should train in hot conditions if you
know that you will race in these conditions. This allows your body to start to
get used to the heat. Take care to drink adequate fluids while training and
don’t overdo it when you first start acclimatising.
Limit
exposure to the sun.
Wear a hat or cap, preferably one with
a wide brim, especially if working in the sun - the head is particularly
sensitive to heat.
Wear
light-coloured, loose-fitting, lightweight clothing in hot weather. Cotton is
best, as it allows air to pass through and sweat to evaporate.
Open
windows, or use a fan to improve indoor air circulation.
Eat
light, small meals, and limit alcohol intake in hot weather. Avoid alcohol
before, during, and immediately after exercise. Alcohol causes you to lose more
fluid than you consume.
Limit
vigorous activity during hot or humid weather, especially during the middle of
the day.
If
you have to exercise in the heat, maintain a pace that allows your body to adapt
to the hot weather: start with short workouts and increase them gradually over
at least two weeks. Try to schedule vigorous exercise during cooler morning or
evening hours. Rest in the shade for five to ten minutes every half hour, and
reduce your pace if you start to feel symptoms of exhaustion.
Ask your doctor whether any
medications you are taking may interfere with your body's temperature
regulation. (See: Who gets sunstroke and who is at risk.) If you use any of
these medications, be especially careful to limit exertion and drink enough
water in hot weather.
Be able to recognise the danger signs
of heat-related illness. Remember that symptoms can develop over several days or
suddenly during strenuous activity.
Heat
oedema
and prickly heat are two conditions that signal that your body is
under heat stress. Heat oedema is swelling of the hands and feet when blood
vessels expand and cause fluid to pool under the skin. You may first notice this
when your shoes or rings feel too tight. Prickly heat is an irritating rash
caused by sweat pore blockage, usually under clothes. This may happen if you
dress too warmly or wear clothing that doesn't "breathe". These conditions are
not harmful, but indicate that you need to cool down to avoid a more serious
heat-related illness.
When to call the doctor
Sunstroke is a medical emergency. Seek immediate medical help if you
or someone else develops any of the following heat-related symptoms:
Confusion
Extreme fatigue
Agitation
Intense
muscle aches, feverishness or nausea
Convulsions or loss of consciousness
