SELECTIVE BRAIN COOLING IN HYPERTHERMIA - THE MECHANISMS AND MEDICAL IMPLICATIONS

We hypothesize that selective brain cooling (SEC) can occur in hyperth ermic humans despite the fact that humans have no carotid rete, a vasc ular structure that facilitates countercurrent heat exchange and that is located at the base of the skull in some mammals. We postulate that an increase in emissary and angular ocular venous flows contributes t o SEC. The efficiency of SEC is increased by evaporation of sweat on t he head and by ventilation through the nose. A body position that incr eases the intravenous pressure gradient across the skull increases emi ssary flows and hence enhances the efficiency of SEC. The validity of using tympanic temperature as an index of brain temperature is also po stulated.