cartner on environmental heat stress
DESCRIPTION
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.TRANSCRIPT
Environmental(HEAT)
BCC 2012. Michaela Cartner
MdS….Sahara Ultramarathon
Heat Production
• Humans are furnaces
• 1.1’ C hourly rise
• x20 with exercise
• 42’ C Core temp in trained athletes
Environmental Heat Transfer
4 Mechanisms
Environmental Heat Transfer: CONDUCTION
The transfer of heat by direct physical contact
Environmental Heat Transfer: CONVECTION
The transfer of heat to air and water molecules.
Environmental Heat Transfer: RADIATION
The transfer of heat via EMG waves. Up to 300kCl /hr
Environmental Heat Transfer: EVAPORATION
Dominant method of cooling. 1ml of sweat will cool the body by 0.58kcal *(BMR 100kcal/hr :. 200mls sweat)
PATHOPHYSIOLOGY
Predisposing factors for heat illness
Classic
Classic
Classic
Heat Strain Indexes
• Meterological– The wet bulb globe
temperature index.– WBGT= 0.7Tw +
0.2Tg +Ta
– In use by the Military and athletes
• “ 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)
Heat Illnesses
Davidatmds2012.weebly.com
“Once the brain started to ignore those repetitive pain signals, comfort levels generally became bearable” Perratt.me.uk
• 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
Heat Oedema
Heat Exhaustion
1 Saline drip = 2hr time penalty2 Saline drips = Disqualified
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.
Oral rehydration should include cool fluids with 7% carbohydrateAbsorbtion 30% FASTER THAN FREE WATER
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
Heat Stroke
• Rhabdomyolysis + altered LFTs
• Renal failure
• Sweating in 50%• Hypoglycaemia• Coagulopathy
• Hyponatraemia
• CNS- seizures in 75%
Paul Williams, Extreme Ironer MdS 2012
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
Heat Stroke…Treatment
Cooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507
Heat Stroke…Treatment
Cooling methods used in the treatment of exertional heat illness Br J sports med 2005, 39:503-507
ADF Health Vol 11 2010 pp 9-12
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
The End
Thank you
Samwestonsimonds.com