Trabecular outflow facility and formation rate of aqueous humor during anesthesia with sevoflurane nitrous oxide or sevoflurane-remifentanil in rabbits

In the present study, we examined the effect of sevoflurane and remifentani l on intraocular pressure (IOP) and fluid dynamics. Twenty-eight rabbits we re anesthetized with halothane, and IOP was measured via a 25-gauge needle in the anterior chamber. Rabbits were then assigned to one of four groups, and halothane was replaced with sevoflurane 1% (n = 7), 2% (n = 7), 3% (n = 7), or 1% + remifentanil 0.65 mu g.kg(-1).min(-1) IV (n = 7). In all group s, a series of intraocular infusions was made into the anterior chamber, an d IOP, trabecular outflow facility, the rate of aqueous humor formation, an d intraocular compliance were determined. With sevoflurane only, intraocula r compliance decreased (55 +/- 14, 39 +/- 22, 31 +/- 17 nL/mm Hg; P < 0.05) as the concentration of sevoflurane increased. With sevoflurane 1% + remif entanil, intraocular compliance was significantly increased (100.1 +/- 30.5 nL/mm Hg; P < 0.05) compared with sevoflurane 1%, 2%, or 3%. Trabecular ou tflow facility, rate of aqueous humor formation, and IOP did not differ amo ng groups, and IOP was similar to values obtained during halothane anesthes ia. Implications: The dose-related effects of sevoflurane on intraocular co mpliance did not produce significant intraocular pressure differences. Addi ng remifentanil to sevoflurane increased intraocular compliance. Sevofluran e or sevoflurane + remifentanil causes a decrease in intraocular pressure c ompared with the average of previously reported values in awake rabbits, an d the magnitude of the decrease is similar to that previously reported in r abbits anesthetized with ethyl urethane, pentobarbital, or halothane alone or in combination with propofol, cocaine, or lidocaine.