Last reviewed 01/2018
Heat exhaustion is the state of lethargy, faintness and thirst produced by water and salt depletion. Signs include hypotension and decreased urine output.
It may be one manifestation of the early stages of heat stroke, with which it is commonly confused. They share common aetiologies e.g. unaccustomed or excessive exposure to heat in the traveller, marathon running on hot and humid days.
Management entails rapid replacement of water and solute losses. Great care should be taken that it does not develop into potentially fatal heat stroke.