Unilateral selective brain cooling.

In species with a carotid rete the arterial blood flowing to the brain can be cooled by passing the carotid rete. The mechanism is termed selective brain cooling (SBC). The aim of the study was to evaluate whether SBC could be induced unilaterally. 27 experiments were performed in 2 conscious goats which were prepared with carotid loops to manipulate the blood temperature of the left and right carotid artery independently of each other. The temperature of the left and right hemisphere of the brain was controlled by means of extracorporeal heat exchangers acting on the carotid blood while trunk temperature was clamped at 39.5 degrees C by a heat exchanger in an arteriovenous shunt. Unilateral warming of the brain induced ipsilateral SBC only, and was accompanied by a bilateral increase of the ear skin temperature. The results demonstrate the precise control of brain temperature by SBC since even unilateral temperature deviations of the brain can be reduced by SBC. In conclusion SBC regulates the temperature of single hemispheres rather than the mean brain temperature.