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Heat Illness/Hyperthermia

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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  1. Heat Illness/Hyperthermia Victor Politi, M.D., FACP Medical Director – St. Johns University-Physician Assistant Program

  2. Risk factors for heat illness • ObesityFatigueDrugsAlcoholSunburnUnacclimatizedFluid deficitPrevious history of heat injuryMany medical conditionsFebrile illnessCystic fibrosisDiabetesMalnutrition

  3. Heat Illness Classification • Heat Rash • Heat syncope • Heat cramps • Heat exhaustion • Heat stroke

  4. 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

  5. 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

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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 !!

  11. 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

  12. Hyperthermia 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 !

  13. 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

  14. 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

  15. Hyperthermia Splanchnic vasoconstriction Thermal injury Rhabdomyolysis Disseminated intravascular coagulation Diminished renal blood flow Glomerular damage Myoglobinuria Hyperuricemia & urinary acidification Renal Failure

  16. A catastrophic life-threatening medical emergency --- HEAT STROKE

  17. 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

  18. 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

  19. 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

  20. Exertional Heat Stroke • Like classic heat stroke- occurs during hot,humid weather • Occurs sporadically - effecting young, healthy persons engaged in strenuous physical activity

  21. 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

  22. 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

  23. 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)

  24. Treatment of early complications of Heat Stroke • Shivering • Convulsions • Myoglobinuria • Acidosis • Hypokalemia • Hypocalcemia

  25. 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

  26. 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

  27. Heat Illness Prevention • Fluid intake is the most critical variable

  28. Questions ?

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