THE EFFECTS OF ENFLURANE ON OCULAR BLOOD-FLOW

Although general anesthesia is frequently chosen for eye surgery or ex perimental studies of ocular blood flow, there are few data available describing its effects on ocular blood flow. In a previous study in ca ts, we reported that enflurane produced significant increases in prere tinal oxygen tension, indicating an increase in oxygen availability in the retina. To examine whether this effect was due to an increase in retinal or choroidal blood flow, we used radioactively labeled 15 mum microspheres of Ce 14 1, Sn 1 13, Ru 103, or Nb 95, to measure ocular blood flow in cats during enflurane anesthesia. In 10 adult cats, reti nal blood flow measured 75 +/- 13, 90 +/- 9 and 88 +/- 11 ml . 100 g-1 . min-1 (mean +/- S.E.M.) at 0.5, 1.0, and 1.5 MAC enflurane, respect ively (I MAC is the concentration at which 50% of subjects do not move in response to a standardized stimulus). Corresponding values for cho roidal blood flow were 1275 +/- 124, 876 +/- 106 and 843 +/- 102 ml . 100 g-1 . min-1 (mean +/- S.E.M.) at 0.5, 1.0, and 1.5 MAC enflurane, respectively. The decrease in choroidal blood flow was significant bet ween 0.5 and 1.0 MAC. These results differ from those in our previous investigation of the effects of halothane on ocular blood flow. With h alothane, retinal blood flow increased and choroidal blood flow decrea sed throughout the entire dose range (0.5, 1.0, and 1.5 MAC). We concl ude that inhalational anesthetic agents produce significant but differ ent effects upon ocular blood flow.