Transcript Slide 1
DISORDERS CAUSED BY HEAT
Dr Majid Golabadi
Occupational Medicine specialist
MEDICAL DISORDERS COUSED BY
EXCESSIVE EXPOSURE TO HOT ENVIRONMENTS
heat
stroke,
heat
exhaustion,
heat
cramps,
heat
syncope,
skin
disorders
THE TRANSFER OF HEAT BETWEEN SKIN AND
ENVIRONMENT
Convection
Conduction
Radiation
Evaporation
ACCLIMATIZATION
The scheduled and regulated exposure to
heated environments of increasing intensity
and duration allows the body to adjust to heat
Beginning to sweat at lower body temperatures,
Increasing the quantity of sweat produced,
Reducing the salt content of sweat,
Increasing the plasma volume, cardiac output,
and stroke volume while the heart rate
decreases.
HEAT STROKE
Life-threatening medical emergency
Thermal regulatory failure
Cerebral dysfunction with altered mental status
Core (rectal) temperature approaches 4l.l°C
(106°F)
Hyperventilation, respiratory alkalosis and
compensatory metabolic acidosis
Abnormal bleeding, renal failure, or
arrhythmias
Pathophysiology
Symptoms
Objective
findings
Laboratory
Heat Cramps
Heat Exhaustion
Heatstroke
Salt deficiency
Volume/electrolyte depletion
Thermoregulatory failure
Painful muscle cramps/
spasm
Weakness
Nausea
Vomiting
Weakness
Headache
Syncope
Nausea
Vomiting
Intense thirst (water
depletion)
Fatigue
Muscle cramps (salt
depletion)
Malaise
Irritability Confusion
Prodromal heat exhaustion
Collapse
Severe/sustained physical exertion
(exertional heat stroke) Psychotic
behavior
Core temperature < 38°C
(100.4°F)
Profuse sweating
Orthostatic vital signs
Tachycardia
Hyperventilation
Tetany
Core temperature >40°C(104°F)
Altered mental status—bizarre
behavior
Hot dry skin (classic heat stroke)
Moist skin (exertional heat stroke)
Coma
Hypotension/shock
Seizure
Tachycardia
Cyanosis
Rales
Euthermia
Elevated creatine
phospho-kinase (CPK), Oliguria
creatinuria
Hyperuricemia
CPK elevation
Dissemination intravascular
coagulation
Respiratory alkalosis
Hypokalemia
Thrombocytopenia
Myoglobinuria
Hypoglycemia
Transaminase elevation
THRESHOLD LIMIT VALUES FOR EXPOSURE TO
HEAT IN OCCUPATIONAL SETTINGS
wet-bulb globe temperature (WBGT)
Heat-index guidelines
IN OCCUPATIONS IN WHICH WORKERS
ARE EXPOSED TO EXCESSIVE HEAT
Medical evaluation to identify at risk
individuals for heat disorders
Training early signs and symptoms of heat
disorders
Advising of the importance of proper nutrition
and fluid intake.
Providing cool drinking water or electrolytecarbohydrate solutions and shaded rest areas
for workers
MANAGEMENT
Monitoring for hypovolemic and cardiogenic
shock,
Maintaining a patent airway, providing oxygen
Correcting fluid and electrolyte imbalances,
Supporting vital processes.
If hypovolemic shock is suspected, 500-1000 mL
of 5% dextrose in 1% or 0.5% normal saline
solution may be given intravenously without
overloading the circulation.
Fluid output should be monitored
Monitored for complications, including renal
failure (caused by dehydration and
rhabdomyolysis), hepatic failure, or cardiac
failure, respiratory distress, hypotension,
electrolyte imbalance (hypokalemia), and
coagulopathy.
PROGNOSIS
Elevated creatine phosphokinase (CPK)
Elevated liver enzymes,
Metabolic acidosis
are predictors of multiorgan dysfunction
Because hypersensitivity to heat continues
in some patients for prolonged periods
following
heat
stroke,
they
should
be
advised to avoid reexposure to heat for at
least 4 weeks.
HEAT EXHAUSTION
Etiology:
prolonged exposure to heat and insufficient salt
and water intake can cause heat exhaustion,
dehydration, and sodium depletion
Symptoms and signs:
weakness, nausea, fatigue, headache, confusion,
a core (rectal) temperature exceeding 38°C
(100.4°F), increased pulse rate, and moist skin,
Hyperventilation and respiratory alkalosis
HEAT EXHAUSTION
Treatment
Placing the patient in a cool and shaded
environment and providing hydration (1-2 L over
2-4 hours) and salt replenishment—orally if the
patient is able to swallow. Physiologic saline or
isotonic glucose solution should be administered
intravenously in more severe cases.
At least 24 hours' rest is recommended.
HEAT CRAMPS
Etiology
Result from dilutional hyponatremia caused by
replacement of sweat losses with water alone
Symptoms and signs:
Slow and painful muscle contractions and severe
muscle spasms that last from 1-3 minutes and
involve the muscles employed in strenuous work.
The temperature may be normal or slightly
increased
HEAT CRAMPS
Treatment
The patient should be moved to a cool
environment and given a balanced salt solution
or an oral saline solution. Salt tablets are not
recommended.
Rest for 1-3 days with continued salt
supplementation in the diet may be necessary
before returning to work.
HEAT SYNCOPE
Etiology
In heat syncope, sudden unconsciousness results
from volume depletion and cutaneous
vasodilatation with consequent systemic and
cerebral hypotension. Episodes occur commonly
following strenuous work for at least 2 hours.
Symptoms and signs:
The skin is cool and moist and the pulse weak.
Systolic blood pressure is usually under 100
mmHg
HEAT SYNCOPE
Treatment
Recumbency, cooling, and rehydration.
Preexisting medical conditions should be
monitored and treated if necessary
SKIN DISORDERS CAUSED BY HEAT
Miliaria (heat rash) is caused by sweat retention
resulting from obstruction of the sweat gland duct.
Erythema abigne ("from fire") is characterized by
the appearance of hyperkeratotic nodules following
direct contact with heat that is insufficient to cause a
burn.
Intertrigo results from excessive sweating and often
is seen in obese individuals. Skin in the body folds
(e.g., the groin and axillas) is erythematous and
macerated
Heat urticaria (cholinergic urticaria) can be
localized or generalized and is characterized by the
presence of wheals with surrounding erythema
("hives").