Effect of isoflurane on brain tissue oxygen tension and cerebral autoregulation in rabbits.

Oxygen tension (PO(2)) was measured in rabbit whisker barrel cortex using oxygen sensitive electrodes to investigate the impact of isoflurane anesthesia on oxygen autoregulation. Responses to 90s episodes of 100% oxygen inspiration were obtained from rabbits before anesthesia, and then when the animals were anesthetized with 0.5% or 1.5% isoflurane. For each episode, ΔPO(2) (i.e., hyperoxic PO(2) minus baseline PO(2)) was computed. Compared to the conscious state, brain ΔPO(2) increased during anesthesia with 1.5% isoflurane (0.73 MAC) by an average of 116%, whereas 0.5% isoflurane produced an insignificant average increase of 31%. The results suggest that moderate levels of isoflurane impaired autoregulation of brain tissue oxygen tension.