The Effect of Different Sevoflurane Concentrations on Intraocular Pressure in Patients Undergoing Ocular Surgery Under General Anesthesia

One important goal in anesthetic management during ocular surgery is to provide adequate control of intraocular pressure (IOP). An increase in IOP may be catastrophic in patients with glaucoma or a penetrating open-eye injury. There is an ongoing debate over the effect of anesthetic agents on the IOP. Anesthetic regimens in this surgical field commonly consist of short-acting anesthetic agents, such as propofol and sevoflurane, usually combined with short-acting analgesics, such as remifentanil. Both propofol and sevoflurane are known to reduce the IOP. To this end there is no data in the literature to support or disprove this finding.

Study Hypothesis Variations in the end-tidal sevoflurane concentrations have no significant effect on the IOP.

One important goal in anesthetic management during ocular surgery is to provide adequate control of intraocular pressure (IOP). An increase in IOP may be catastrophic in patients with glaucoma or a penetrating open-eye injury. There is an ongoing debate over the effect of anesthetic agents on the IOP. Anesthetic regimens in this surgical field commonly consist of short-acting anesthetic agents, such as propofol and sevoflurane, usually combined with short-acting analgesics, such as remifentanil. Both propofol and sevoflurane are known to reduce the IOP. Previous studies have compared these two anesthetics protocols in order to determine which provides superior control of the IOP. Propofol produced significantly lower IOP measurements compared to sevoflurane (both combined with remifentanil), in cataract surgery, whereas in non-ophthalmic surgery propofol and sevoflurane caused a comparable decrease in IOP. Sevoflurane, an inhalational anesthetic, has a rapid onset of action faster recovery time and is also suitable for inhalation induction because it does not irritate the airway. A prospective randomized clinical trial compared the effects of ketamine and sevoflurane on IOP during the eight minutes after induction of anesthesia (in 2-minute intervals) in children with suspected or diagnosed glaucoma undergoing EUA. During these 8 minutes the IOP decreased significantly only in the sevoflurane group. This finding contradicted claims that measurements immediately after induction are relatively unaffected by anesthetics and suggested that variations in sevoflurane concentration do affect the IOP. Yoshitake et al showed that the remarkable reductions of IOP after inductions are probably caused by induction agents, suggesting that sevoflurane is a useful anesthetic for elderly patients receiving ophthalmic surgeries. To this end there is no data in the literature to support or disprove this finding.

Study Hypothesis Variations in the end-tidal sevoflurane concentrations have no significant effect on the IOP.

Eligibility Criteria:
Inclusion Criteria:

* The study will include both men and women over 18 years old undergoing elective surgery for strabismus correction or tear duct probing and irrigation under general anesthesia.

Exclusion Criteria:

* Patients with known allergies,
* adverse reaction or contraindication (of any other reason) to sevoflurane or remifentanil, or any other anesthetic drug,
* patients with pre-existing intra-ocular ophthalmic disease, or infection.