EXPERIMENTAL-STUDY ON THE OPTIMUM FLOW-RATE AND PRESSURE FOR SELECTIVE CEREBRAL PERFUSION

The optimum now rate and pressure for selective cerebral perfusion during moderate hypothermia (25 degrees C) were investigated in 36 mongrel dogs. Cerebral perfusion was performed for 90 minutes at a now rate of 100% (the physiologic now rate), 50%, 25%, and 0%, or no now (cerebrocirculatory arrest). Somatosensory evoked potentials were monitored to assess brain function. An excess lactate level was considered an index of anaerobic cerebral metabolism, and histopathologic evaluation was performed. Somatosensory evoked potentials showed no abnormalities at now rates of 100% and 50%, but became abnormal in some dogs at 25% and in all dogs under no-flow conditions. The excess lactate level only increased at a no-now rate, but not significantly. Histopathologic evaluation showed no ischemic changes at now rates of 100% and 50%, but there were slight ischemic changes at 25% and severe ischemic damage at no now. The mean carotid arterial pressure was 63.1 +/- 5.9, 39.8 +/- 6.2, 24.9 +/- 6.0, and 11.3 +/- 3.5 mm Hg at a now rate of 100%, 50%, 25%, and no now, respectively These results suggest that the safe range of flow rates for cerebral perfusion during moderate hypothermia is more than 50% of the physiologic level with a carotid arterial pressure of about 30 mm Hg or more.