Quote Originally Posted by Mike T View Post
Terminology: the term Heat Exhaustion is rarely used in the current literature - it confuses the issue by making people think it is a different illness from Heat Stroke - whereas of course Exertional Heat Illness is a spectrum, with Exercise Associated Collapse at one end, and Exertional Heat Stroke at the other.

Exertional Heat Stroke - EHS - has 2 diagnostic criteria - 1/ a core temperature above 40 C and 2/ CNS dysfunction - this can be dizziness, collapse, confusion, fitting, aggression, hysteria, coma and so on. The skin can be anything from drenched to dry - there is a common misunderstanding that for EHS to be diagnosed sweating must be absent.

Like in cardiac arrest, where instant CPR is the gold standard treatment, by bystanders if need be, in EHS cooling by CWI - Cold Water Immersion - or rotating drenched towels to all skin - is the gold standard - before transport. Fans/cold packs to axillae/groin/neck are not good enough.

In the field of course the collapsed confused runner may have EHS, but the possibilities also include hypoglycaemia, a cardiac event, hyponatraemia, head injury, stroke - the list goes on - and the chances are a rectal temperature probe is not available. In EHS aggressive cooling is needed within minutes - maximum 10 - rotating drenched towels or clothing is the most likely available cooling method - a stream/tarn might be nearby but the risks with a combative/confused/comatose person are high. If someone develops EHS on the fell I just hope someone with knowledge of the various possibilities and how to treat them is involved in their care!



From the prevention point of view, whilst dehydration is to be avoided, so is over hydration, so drink to thirst applies. Acclimatisation to exercising in warm/hot conditions is also important, and has been shown to be helpful.



It would be interesting to know how many cases of EHS have occurred in fell running. I have seen a couple of cases of EAC - Exercise Associated Collapse - in my running career, on hot days (in UK terms). They recovered fairly quickly - half an hour or so - with rest/shade/drinks.
What about the dramatic decrease in physical performance, are reduced cardiac efficiency and shutting down of blood supply to the limbs to blame? Assuming of course that your energy and salt levels are ok, which they should be for a short race.