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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Cartner on Environmental Heat Stress
- 5. Heat Production • Humans are furnaces • 1.1’ C hourly rise • x20 with exercise • 42’ C Core temp in trained athletes
- 6. Environmental Heat Transfer 4 Mechanisms
- 7. Environmental Heat Transfer: CONDUCTION The transfer of heat by direct physical contact
- 8. Environmental Heat Transfer: CONVECTION The transfer of heat to air and water molecules.
- 9. Environmental Heat Transfer: RADIATION The transfer of heat via EMG waves. Up to 300kCl /hr
- 10. Environmental Heat Transfer: EVAPORATION Dominant method of cooling. 1ml of sweat will cool the body by 0.58kcal *(BMR 100kcal/hr :. 200mls sweat)
- 11. PATHOPHYSIOLOGY Predisposing factors for heat illness
- 13. Heat Strain Indexes • Meterological – The wet bulb globe temperature index. – WBGT= 0.7Tw + 0.2Tg +Ta – In use by the Military and athletes
- 14. • “ I saved a gram by cutting the tags off my wind pants and an inch off the end of each drawstring” irunfar.com (Bryon Powell)
- 15. Heat Illnesses Davidatmds2012.weebly.com “Once the brain started to ignore those repetitive pain signals, comfort levels generally became bearable” Perratt.me.uk
- 16. • The Doc Trotters (52 members, 6000 painkillers and 150L Disinfectant) • Feet preparations include vet supplies/formalin/picric acid/ benzoin /alcohol /henna /curry Runningsahara.com/training/feet-the-ultimate-training–and-preparation
- 17. Heat Oedema
- 18. Heat Exhaustion 1 Saline drip = 2hr time penalty 2 Saline drips = Disqualified
- 19. Heat Exhaustion •Water depletion •Salt depletion “ Voluntary Dehydration” 2/3 of net water loss replaced •Treat with Saline if orthostatic •Replace with free water <2mOsm/hr.
- 20. Oral rehydration should include cool fluids with 7% carbohydrate Absorbtion 30% FASTER THAN FREE WATER
- 21. Heat Stroke “ While I was coherent, I saw some amazing sights.… Runners passing out at the top of the dunes and tumbling to the base - one elite runner broke his leg…” Perratt.me.uk Jackson Griffith
- 22. Heat Stroke • Rhabdomyolysis + altered LFTs • Renal failure • Sweating in 50% • Hypoglycaemia • Coagulopathy • Hyponatraemia • CNS- seizures in 75% Paul Williams, Extreme Ironer MdS 2012
- 23. Heat Stroke- Treatment • It does not take long either to boil an egg or cook neurons. D. Hamilton The Immediate Treatment of Heatstroke Anaesthesia 1976; 31:270-272
- 24. Heat Stroke…Treatment Cooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507
- 25. Heat Stroke…Treatment Cooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507
- 26. ADF Health Vol 11 2010 pp 9-12
- 27. Heat Stroke…Treatment • Adjuncts – ICE PACKS – Cooling blankets – Lavage – CPB - BZD - Discontinue cooling when 39’C • Fluids – Relative not absolute – Evidence of RHF Cooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507
- 28. The End
Editor's Notes
- 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