Heat stroke or heat hyperpyrexia is a condition characterized by rectal temperature greater than 41 degree celsius, and neurological disturbances, such as psychosis, delirium, stupor, coma and convulsions. The skin is dry, hot and flushed, with complete absence of sweating. Heat cramps are caused by a rapid dehydration of body through the loss of water and salt in the sweat. Heat syncope caused by cutaneous and muscular vasodilation redistributes intravascular volume to the periphery of the body. The patient's skin is cool and moist, the pulse is weak, and transient hypotension occurs. Heat exhaustion results from prolonged strenuous activity with inadequate water or salt intake in a hot environment. Heat exhaustion may progress to heat stroke if sweating ceases and mental status declines. Ref: Nemer J.A. (2013). Chapter 37. Disorders Related to Environmental Factors. In M.A. Papadakis, S.J. McPhee, M.W. Rabow (Eds), CURRENT Medical Diagnosis & Treatment 2013.