HEMICOOLING OF BRAIN BY CAROTID-CAROTID PERFUSION

Cooling of the brain by carotid-carotid perfusion was carried out in cats. As the brain temperature was lowered from 37 to 12 C, the arterial PO2 was increased and PCO2 decreased while there was no significant change in pH. There was no change in resting membrane potential of polarized elements in the cerebral cortex as the brain temperature was reduced to 11 C. The above observations suggest no anoxia of the brain tissue and probably no disturbance in differential distribution of ions in the extra- and intracellular compartments of the cortical tissue and no swelling of cortical cells. The spontaneous electrical activity of the cortex showed an increase at a temperature of 35-31 C and attaining a maximum at 34 C. Below 30 C, it rapidly decreased. At 20 C, in most instances, no activity was recorded. A similar phenomenon was also observed in spontaneous unit spike activity and evoked response to transcallosal stimulation. © 1968.