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

3. 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

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

5. Classification 1- Hyperthermic Diseases A - Minor Y Cramps / Edema / Syncope / Prickly Heat B - Major YHeat Exhaustion YHeat Stroke 2- Hyperthermic Entities A - Malignant Hyperthermia B - Neuroleptic Malignant Syndrome 3- Febrile Illnesses

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

7. Hyperthermia vs Fever YHyperthermia… Thermoregulatory mecanism are surpassed … Peripherical mechanism dont suffice, The Hypothalamic « set point » is normal … YFever… Cytokins reaches Anterior Hypothalamus Resets the Thermostat... new « set point » Peripherical mechanism are intact...

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

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

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

11. 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

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

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

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

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

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

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

18. Heat Exhaustion « labs » YPossibly normal Y  Hematocrit Y  /  natremia YHypoglycemia ? Y  BUN / Creatinine YConcentrated urine

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

20. Differential Diagnosis Sepsis Meningitis Malaria Thyroid storm Status Epilepticus Cerebral Hemorrhage Malignant Hyperthermia Neuroleptic malignant syndrome Tetanus Toxicology ýASA / PCP / stimulants / Anticholinergic

21. Heat Stroke ClassicalExertionnal predisposing factorshealthy olderyounger sedentaryexercise anhidrosisdiaphoresis heat wavesporadic mild CPK  rhabdomyolysis mild coagulopathyDIC mild acidosismarked lactic acidosis oliguriaacute renal failure

22. Treatment

23. Heat Exhaustion « Treatment » YRest / Shade / Cooling methods YRehydration … Y PO … 0,1% NaCl solution Y IV … 0,9% NS ( modest to avoid overhydration) YPeds 20 cc/Kg YShivering & seizures: Benzos YDanger : Sodium levels

24. 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!”

25. « Mecca Body Cooling Unit »

26. Not this way ?

27. Heat Stroke « Complications » YRhabdomyolysis & Renal Failure YHypoglycemia /  Na /  K /  Ca YSevere Hepatocellular damage ý AST/ALT can be in the 1000 ’s < 24h YCoagulopathy / DIC / hemorrhage YRefractory Hypotension

28. Bad Prognosis YCoagulopathy YLactic Acidosis (classical) YT° > 42.2°C & prolonged hyperthermia YProlonged coma > 4 hrs YHypotension YAcute Renal Failure YHyperkalemia YAST > 1000 U/L

29. Hyperthermia Hepatic Clotting Fibrinolysis Endothelial Megakaryocyte damage factors damage damage Depletion DIC Thrombolysis Thrombocytopenia clotting factors Hemorrhage

30. Hypotension  CVP &  CVP &  CVP &  Cardiac Output  Cardiac Output  Cardiac Output Hypovolemic Hypodynamic Hyperdynamic Fluids Fluids & Pressors Cooling & fluids NS 250-500 cc then slowly (rarely) modest 300 cc/h NS correct BP > 90/60 or CVP N

31. 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 when you can

32. Summary

33. Malignant Hyperthermia YAutosomal Dominant condition ýSevere muscular hypermetabolism produced by excessive release of calcium from sarcoplasmic reticulum in response to anesthetic agents … YTreatment YDantrolene : 1-2 mg/Kg IV q 6h (max 10mg/Kg/24h) ý  calcium release from sarcoplasmic reticulum

34. Neuroleptic Malignant Syndrome Dopamine receptor blocade at Corpus Striatum  Muscular Spasticity & Dystonia   Heat Production  Target Organs (rhabdomyolysis, etc) YTreatment : ýDantrolene ýBromocriptine (Dopamine Agonist)

35. Points to remember... YIn doubt treat as « Heat Stroke » YASA & Acetaminophen = no place YDantrolene & Steroids = no place YKeep away from : ý Levophed (alpha-adrenergics) Yvasoconstriction & no benefit to cardiac output ý Atropine (anticholinergics) Yinhibition of sweating

36. Remember Y« Heat stroke victims should be cooled as rapidly as possible. The more rapid the cooling, the lower the mortality. » Y« It does not take long to either boil an egg or to cook neurons. » D Hamilton

37. Heat Related Illness Key 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

38. Questions ?