disorders caused by heat dr majid golabadi occupational medicine specialist
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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
Heat CrampsHeat ExhaustionHeatstroke
PathophysiologySalt deficiencyVolume/electrolyte depletionThermoregulatory failure
SymptomsPainful muscle cramps/ spasmWeaknessNauseaVomiting
WeaknessHeadacheSyncopeNauseaVomitingIntense thirst (water depletion)FatigueMuscle cramps (salt depletion)Malaise
Irritability ConfusionProdromal heat exhaustion CollapseSevere/sustained physical exertion (exer tional heat stroke) Psychotic behavior
Objective findingsEuthermia
Core temperature < 38°C (100.4°F)Profuse sweatingOrthostatic vital signsTachycardiaHyperventilationTetany
Core temperature >40°C(104°F)Altered mental status—bizarre behaviorHot dry skin (classic heat stroke)Moist skin (exertional heat stroke)ComaHypotension/shockSeizureTachycardiaCyanosisRales
LaboratoryElevated creatine phospho-kinase (CPK), creatinuria
OliguriaHyperuricemiaCPK elevationDissemination intravascular coagulationRespiratory alkalosisHypokalemiaThrombocytopeniaMyoglobinuriaHypoglycemiaTransaminase 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 electrolyte-
carbohydrate solutions and shaded rest
areas for workers
MANAGEMENT Monitoring for hypovolemic and cardiogenic
shock, Maintaining a patent air way, 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, con
fusion, 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").
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