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Heat Illness/Hyperthermia PowerPoint PPT Presentation

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Heat Illness/Hyperthermia. Victor Politi, M.D., FACP Medical Director – St. Johns University-Physician Assistant Program. Risk factors for heat illness

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Heat Illness/Hyperthermia

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Heat illness hyperthermia l.jpg

Heat Illness/Hyperthermia

Victor Politi, M.D., FACP

Medical Director –

St. Johns University-Physician Assistant Program

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  • Risk factors for heat illness

    • ObesityFatigueDrugsAlcoholSunburnUnacclimatizedFluid deficitPrevious history of heat injuryMany medical conditionsFebrile illnessCystic fibrosisDiabetesMalnutrition

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Heat Illness Classification

  • Heat Rash

  • Heat syncope

  • Heat cramps

  • Heat exhaustion

  • Heat stroke

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Minor Heat Illness - Heat Cramps

  • Brief, intermittent, often severe muscular cramps typically occurring in muscles that are fatigued by heavy work

  • Usually occur after exertion

  • Copious hypotonic fluid replacement during exertion

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Minor Heat Illness - Heat Cramps

  • Related to salt deficiency

  • Victims exhibit -hyponatremia, hypochloremia, low urinary sodium and chloride levels

  • Usually rapidly relieved by salt solutions

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Minor Heat IllnessHeat Syncope

  • Individuals at risk should be warned to move frequently, flex leg muscles repeatedly whenever standing

  • Scintillating scotomata, tunnel vision, vertigo, nausea, diaphoresis, and weakness are prodromal symptoms of syncope

  • Adequate oral volume replacement may prevent some conditions

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Minor Heat Illness - Prickly Heat AKA miliaria rubra, lichen tropicus, heat rash

  • Acute phase -

    • Produces intensely pruritic vesicles on an erythematous base

    • Rash confined to clothed areas

    • Effected area completely anhydrotic

  • -

    • may persist for weeks

    • chronic dermatitis -frequent complication

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Heat Exhaustion - two types classically described

  • Water depletion heat exhaustion

    • inadequate fluid replacement by persons in heat “ voluntary dehydration”

    • weakness, fatigue, frontal headache, impaired judgement, vertigo, nausea/vomiting, occasional muscle cramps,sweating, body temperature near normal

    • orthostatic dizziness/syncope may occur

    • results in progressive hypovolemia

    • Untreated can progress to heat stroke

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Heat Exhaustion - two types classically described

  • Salt depletion heat exhaustion

    • takes longer to develop than water depletion form

    • systemic symptoms occur

    • hyponatremia, hypochloremia, low urinary sodium and chloride concentrations

    • Symptoms similar to water depletion type, body temperature remains near normal

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Heat Exhaustion: Diagnosis

  • Vague malaise, fatigue, headache

  • Core temperature often normal; if elevated less than 1040F

  • Mental function essentially intact; no coma or seizures

  • Tachycardia, orthostatic hypotension, clinical dehydration (may occur)

  • Other major illness ruled out

  • If in doubt, --- treat as heat stroke !!

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Heat Exhaustion - Treatment

  • Rest

  • cool environment

  • Assess volume status (orthostatic changes, BUN, hematocrit, serum sodium)

  • Fluid replacement

  • Consider admission if patient is elderly, has significant electolyte abnormalities or would be at risk of recurrence if d/c

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A patient presents to the ED with elevated body temperature -

1st thought ??

? Infectious etiologies/severe infection

but some patients with elevated temperature, including some with extreme pyrexia, do not have fever at all, they have hyperthermia !

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Fever versus Hyperthermia

  • Body temperature can become elevated through either of two very different processes

  • In fever, thermoregulation remains intact while hyperthermia represents thermoregulation failure

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Causes of Hyperthermia- Disorders of excessive heat production

  • Exertional hyperthermia

  • Heatstroke

  • Malignant hyperthermia of anesthesia

  • Neuroleptic malignant syndrome

  • Thyrotoxicosis / Pheochromocytoma

  • Salicylate intoxication / Delirium tremens

  • Cocaine, amphetamines, other drugs of abuse

  • Status epilepticus /Generalized tetanus

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Thermal injury


Disseminated intravascular



renal blood flow




Hyperuricemia &

urinary acidification

Renal Failure

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A catastrophic life-threatening medical emergency ---


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Heat Stroke Diagnosis

  • Exposure to heat stress, endogenous or exogenous

  • Signs of severe CNS dysfunction (coma, seizures, delirium

  • Core temperature usually 410C (105.80F) or more,

  • Dry, hot skin frequent,

  • Marked elevation of hepatic transaminases

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Classic Heatstroke

  • Occurs primarily in epidemics during summer heat waves

  • Most likely to effect the elderly and patients with serious underlying illnesses

  • Infants also at risk

  • Typical victim confined at home w/no fan or A/C

  • Dehydration - predisposing factor

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Classic Heatstroke

  • Other risk factors - obesity, neurologic or cardiovascular disease, use of diuretics, neuroleptics, or medications with anticholinergic properties that interfere with sweating

  • Alcohol use may be a risk factor

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Exertional Heat Stroke

  • Like classic heat stroke- occurs during hot,humid weather

  • Occurs sporadically - effecting young, healthy persons engaged in strenuous physical activity

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Initial Treatment of Heat Stroke

  • Immediate cooling

  • Protect airway (intubate if comatose or seizing)

  • IV line with 0.9% NaCl or Ringer’s lactate

  • CVP or Swan Ganz catheter in hypotensive patients

  • Foley catheter; monitor output

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Initial Treatment of Heat Stroke

  • Rectal probe - monitor temperature

  • Oxygen, 5-10L/min

  • ABGs

  • Labs - CBC, electrolytes, BUN, glucose, SGOT, LDH, CPK, calcium phosphate, lactate, PT/PTT, fibrin degradation products

  • Check glucose by dextrostix method & treate- administer D50 if hypoglycemia present

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Cooling Modalities to lower body temperature in heat stroke

  • Ice-water immersion

  • Evaporative cooling using large circulating fans and skin wetting

  • Ice packs

  • Peritoneal lavage

  • Rectal lavage

  • Gastric lavage

  • Cardiopulmonary bypass

  • Alcohol sponge baths (caution)

  • Phenothiazines (caution)

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Treatment of early complications of Heat Stroke

  • Shivering

  • Convulsions

  • Myoglobinuria

  • Acidosis

  • Hypokalemia

  • Hypocalcemia

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Heat Illness Prevention

  • A Crucial issue

  • Counsel persons with any risk factors regarding symptoms of heat stroke

    • Elderly persons

    • persons with chronic diseases

    • those on medications predisposing them to heat illness

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Heat Illness Prevention

  • Exertional heat stroke is most likely to strike young, healthy persons involved in strenuous physical activity

    • many of these people have risk factors for heat illness -commonly obesity,diarrhea,febrile illness

    • other variables to consider- hydration,salt intake, clothing, and climatic conditions

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Heat Illness Prevention

  • Fluid intake is the most critical variable

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Questions ?

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