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Heat Related Illness

Heat Related Illness . Richard Dionne MD Emergency Medicine – University of Ottawa March 2013. Heat Related Illness. Goals & Objectives Discuss the thermoregulation differences between hyperthermic entities and fever

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Heat Related Illness

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  1. Heat Related Illness Richard Dionne MD Emergency Medicine – University of Ottawa March 2013

  2. Heat Related Illness • Goals & Objectives • Discuss the thermoregulation differences between hyperthermic entities and fever • Discuss the differences between Heat Exhaustion and Heat Stroke and their target organ injuries • Identify the differential diagnosis and the proper investigation in the ER • Discuss the acute management in the ER

  3. Basics • Severe illness secondary to overwhelming heat stress • Dehydration – electrolytes – thermoregulation dysfunction – MOF • Increase temperature – increase O2 consumption and metabolism • Failure of OxydativePhosphorylation and certain enzymes > 42 °C

  4. Classification 1- HyperthermicDiseases A - Minor • Cramps / Edema / Syncope / PricklyHeat B - Major • Heat Exhaustion • HeatStroke 2- HyperthermicEntities A - MalignantHyperthermia B - NeurolepticMalignantSyndrome 3- FebrileIllnesses

  5. Hyperthermia« Auto-Regulation» Peripherical& Central Thermistors  Central Thermostat (Anterior Hypothalamus)  Modulation Response  Peripherical Adaptation Mechanism (vasodilation & sweating)

  6. Hyperthermia vs Fever • Hyperthermia… • Thermoregulatorymecanism are surpassed … • Periphericalmechanism dont suffice, • The Hypothalamic« set point »is normal … • Fever… • CytokinsreachesAnterior Hypothalamus • Resetsthe Thermostat... new « set point » • Periphericalmechanism are intact...

  7. Heat Exhaustion • Core T < 40° C • Fluid & electrolyte depletion • Thermoregulation is maintained • CNS function is preserved

  8. Heat Stroke • Core T > 40.5 C • Loss of thermoregulation, severe CNS dysfunction & MOF • Triad:Hyperthemia / CNS / Anhydrose • Classic • Exertional

  9. Heat Stroke • Classic Heat Stroke (non-exertional) • Compromised thermoregulation • (cannot remove from source) • Days • Severe dehydration • Warm & dry skin

  10. Heat Stroke • Exertional Heat Stroke • Younger / athletic with combined environmental & exertional heat stress • Internal heat production overwhelms dissipating mechanisms… • Sweating may be present at beginning

  11. Heat Cramps • Secondary to excessive sweating and sodium loss • Cramps in heavily exercised muscles • Primarily in lower extremities • During or after exercise

  12. Prickly Heat • Blockage of sweat glands leading to a maculopapular rash over clothed area …

  13. Heat Edema • Swelling of dependent areas of body (usually lower limbs) • Resolves with acclimatization & rest

  14. Etiology • Pre-existing conditions: • Age extremes • Dehydration • Cardiovascular disease • Obesity • Hyperthyroidism • Febrile Illness • Skin disease that interferes with sweating (psoriasis / eczema)

  15. Etiology • Pharmacologic: • Sympathomimetics • LSD / PCP • MAO inhibitors • Anticholinergics • Antihistamines • B-blockers • Diuretics • Drug & alcohol withdrawal

  16. Etiology • Physical / Environmental: • Prolonged exertion • Lack of mobility • Lack of air conditioning • Excessive humidity • Lack of acclimatization

  17. Heat Exhaustion « labs » • Possibly normal •  Hematocrit •  / natremia • Hypoglycemia ? • BUN / Creatinine • Concentrated urine

  18. Imaging • ECG: cardiac risks • CT-scan Head: r/o CNS primary • Chest X-ray: ARDS?

  19. DifferentialDiagnosis Sepsis Meningitis Malaria Thyroid storm Status Epilepticus Cerebral Hemorrhage Malignant Hyperthermia Neuroleptic malignant syndrome Tetanus Toxicology • ASA / PCP / stimulants / Anticholinergic

  20. Heat Stroke ClassicalExertionnal predisposingfactorshealthy olderyounger sedentaryexercise anhidrosisdiaphoresis heatwavesporadic mild CPKrhabdomyolysis mildcoagulopathy DIC mildacidosismarkedlacticacidosis oliguria acute renalfailure

  21. Treatment

  22. Heat Exhaustion« Treatment » • Rest / Shade / Coolingmethods • Rehydration … • PO … 0,1% NaCl solution • IV … 0,9% NS ( modest to avoidoverhydration) • Peds 20 cc/Kg • Shivering & seizures: Benzos • Danger : Sodium levels

  23. Cooling measures • Evaporative • Very effective • Spray with fine mist • Airflow with fans • Prevent shivering • Conductive • Ice pack groin / axilla & neck • Immersion not practical ad risk if seizures “Stop cooling at 39°C to risk hypothermia!”

  24. «Mecca Body Cooling Unit»

  25. Not thisway ?

  26. Heat Stroke« Complications » • Rhabdomyolysis & Renal Failure • Hypoglycemia /  Na /  K /  Ca • Severe Hepatocellular damage • AST/ALT can be in the 1000 ’s < 24h • Coagulopathy / DIC / hemorrhage • Refractory Hypotension

  27. Bad Prognosis • Coagulopathy • Lactic Acidosis (classical) • T° > 42.2°C & prolonged hyperthermia • Prolonged coma > 4 hrs • Hypotension • Acute Renal Failure • Hyperkalemia • AST > 1000 U/L

  28. Hyperthermia HepaticClottingFibrinolysisEndothelialMegakaryocyte damage factors damage damage DepletionDIC ThrombolysisThrombocytopenia clotting factors Hemorrhage

  29. Hypotension CVP &  CVP & CVP & Cardiac Output Cardiac Output Cardiac Output HypovolemicHypodynamicHyperdynamic FluidsFluids & PressorsCooling & fluids NS 250-500 cc thenslowly (rarely) modest 300 cc/h NS correct BP > 90/60 or CVP N

  30. Prevention 1- Rely not on thirst 2- Drink on schedule 3- Favor sports drinks 4- Monitor weight 5- Watch urine 6- No caffeine or alcohol 7- Key on meals 8- Stay cool whenyoucan

  31. Summary

  32. MalignantHyperthermia • Autosomal Dominant condition • Severemuscularhypermetabolismproduced by excessive release of calcium fromsarcoplasmicreticulum in response to anesthetic agents … • Treatment • Dantrolene : 1-2 mg/Kg IV q 6h (max 10mg/Kg/24h) • calcium release fromsarcoplasmicreticulum

  33. NeurolepticMalignant Syndrome Dopamine receptorblocadeat Corpus Striatum  MuscularSpasticity & Dystonia  Heat Production  Target Organs (rhabdomyolysis, etc) • Treatment: • Dantrolene • Bromocriptine (Dopamine Agonist)

  34. Points to remember ... • In doubttreat as «Heat Stroke » • ASA & Acetaminophen = no place • Dantrolene & Steroids = no place • Keepawayfrom: • Levophed (alpha-adrenergics) • vasoconstriction & no benefit to cardiacoutput • Atropine (anticholinergics) • inhibition of sweating

  35. Remember • «Heat stroke victimsshouldbecooled as rapidly as possible. The more rapid the cooling, the lower the mortality. » • « It does not take long to eitherboil an egg or to cookneurons. » D Hamilton

  36. Heat Related IllnessKey Concepts • Antipyretics are ineffective and should not be used • Diaphoresis is common in exertional heat stroke • Rapid (convective) cooling should be initiated rapidly • Heatstroke can cause right-sided cardiac dilation and elevated CVP, resembling Pulmonary Edema, but requires crystalloid resuscitation

  37. Questions ?

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