The Effect of Phenobarbitone Anaesthesia on Blood Flow and Oxygen Consumption in the Rat Brain

The influence of phenobarbitone anaesthesia on blood flow (CBF) and oxygen consumption (CMR_o2) was evaluated in the rat brain, using a method that quantitatively measures CBF in mainly cortical areas. The data were compared to those obtained in animals under fentanyl citrate analgesia. Body temperature and arterial CO₂ tension were maintained close to normal values in all groups. With 50 mg/kg of phenobarbitone, CBF and CMR_O2 were reduced by about 20 %. With 150 or 250 mg/kg, further reductions in CBF and CMR_O2 were observed. At 250 mg/kg, CBF was reduced to one third, and CMR_O2 to about 50 % of normal. The results suggest that little further reduction in CBF or CMR_O2 can be expected if the dose of phenobarbitone is increased above 250 mg/kg.