Cartner on Environmental Heat Stress


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Michaela Cartner, an Intensivist and ED physician from Queensland's Gold Coast, gives a fascinating talk on environmental heat stress. The Marathon des Sables provided a perfect backdrop to discuss this important topic.

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  • Tougest foot race in the world 6 marathons in 6 days 250kms longest stage 97kms. Carry everthything on yr back exept water and a tent
  • Loose fitting clothing maximizes convective and evaporative heat loss. When air temp exceeds mean skin temp heat transfer is reversed average temp is 55C to 5’ at night
  • We make 100kcal/hr
  • We make 100kcal/hr
  • The automotive analogy Exertional heat stroke
  • Temperature wind chill radiation Physiological ones as well the army uses it for accclimatised and non acclimatised
  • Why would you use a wet globe when you are running with fanatics likje these??
  • Say it takes between 5-60days to toughen up you feet
  • Aldostrone increases and percieved central volume deficit Minimal and self resolves. Usually eldery and long periods of sitting and standing Hydorstatic pressusse cutaneous vasodilation and orthostatic pooling
  • Stomach cramps and delay absorbtion No elevation of body temp and CNS is clear 1/3 to half
  • 100 out of 600 rescued. 2000 amazingly no casualties this year 2 in total
  • LFTs not up then the diagnosis should be rethought
  • Cartner on Environmental Heat Stress

    1. 1. Environmental(HEAT)BCC 2012.Michaela Cartner
    2. 2. MdS….Sahara Ultramarathon
    3. 3. Heat Production• Humans are furnaces• 1.1’ C hourly rise• x20 with exercise• 42’ C Core temp intrained athletes
    4. 4. Environmental Heat Transfer4 Mechanisms
    5. 5. Environmental Heat Transfer: CONDUCTIONThe transfer of heat by direct physical contact
    6. 6. Environmental Heat Transfer: CONVECTIONThe transfer of heat to air and water molecules.
    7. 7. Environmental Heat Transfer: RADIATIONThe transfer of heat via EMG waves. Up to 300kCl /hr
    8. 8. Environmental Heat Transfer: EVAPORATIONDominant method of cooling. 1ml of sweat will cool thebody by 0.58kcal *(BMR 100kcal/hr :. 200mls sweat)
    9. 9. PATHOPHYSIOLOGYPredisposing factors for heatillness
    10. 10. ClassicClassicClassic
    11. 11. Heat Strain Indexes• Meterological– The wet bulb globetemperature index.– WBGT= 0.7Tw +0.2Tg +Ta– In use by the Militaryand athletes
    12. 12. • “ I saved a gram by cutting the tags off mywind pants and an inch off the end of eachdrawstring” (Bryon Powell)
    13. 13. Heat“Once the brain started toignore those repetitive painsignals, comfort levelsgenerally became bearable”
    14. 14. • The Doc Trotters (52 members, 6000 painkillers and 150L Disinfectant)• Feet preparations include vet supplies/formalin/picric acid/ benzoin /alcohol /henna/curry–and-preparation
    15. 15. Heat Oedema
    16. 16. Heat Exhaustion1 Saline drip = 2hr time penalty2 Saline drips = Disqualified
    17. 17. Heat Exhaustion•Water depletion•Salt depletion“ Voluntary Dehydration”2/3 of net water lossreplaced•Treat with Saline if orthostatic•Replace with free water<2mOsm/hr.
    18. 18. Oral rehydration should includecool fluids with 7% carbohydrateAbsorbtion 30% FASTER THANFREE WATER
    19. 19. Heat Stroke“ While I was coherent, Isaw some amazingsights.…Runners passing out atthe top of the dunesand tumbling to thebase- one elite runner brokehis leg…” Jackson Griffith
    20. 20. Heat Stroke• Rhabdomyolysis + altered LFTs• Renal failure• Sweating in 50%• Hypoglycaemia• Coagulopathy• Hyponatraemia• CNS- seizures in 75%Paul Williams, Extreme Ironer MdS 2012
    21. 21. Heat Stroke- Treatment• It does not take long either to boil an eggor cook neurons.D. HamiltonThe Immediate Treatment of Heatstroke Anaesthesia 1976; 31:270-272
    22. 22. Heat Stroke…TreatmentCooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507
    23. 23. Heat Stroke…TreatmentCooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507
    24. 24. ADF Health Vol 11 2010 pp 9-12
    25. 25. Heat Stroke…Treatment• Adjuncts– ICE PACKS– Cooling blankets– Lavage– CPB- BZD- Discontinue coolingwhen 39’C• Fluids– Relative not absolute– Evidence of RHFCooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507
    26. 26. The End
    27. 27. Thank