Effects of nitrous oxide on IOP and pupillary diameter in dogs anesthetized with varying concentrations of desflurane

Objective The aim of the present study was to evaluate the effects of nitrous oxide on TOP and pupillary diameter (PD) of dogs anesthetized with varying desflurane concentrations.Animals studied Twenty adult Mongrel dogs were used.Methods They were anesthetized with propofol (10 mg/kg, IV) and maintained with varying concentrations of desflurane (1.6, 1.4, and 1.2 MAC diluted in 100% oxygen (G1) or in 70% nitrous oxide and 30% oxygen (G2) (30 mL/kg/min). TOP was measured by applanation tonometry and horizontal PD was taken with a caliper adjacent to the cornea. Mean arterial pressure (MAP), heart rate (HR), respiratory rate (RR), and end-tidal CO, (etCO(2)) were also measured. All parameters were measured at TO, T30, T45, and T60 time points. One-way repeated measures ANOVA and the t-test were used to assess statistical differences (P < 0.05).Results T30, T45, and T60 TOP measures were Within normal limits for both groups and TOP did not differ between groups at any time. There was a significant decrease in PD in G I between TO and T30, T45 and T60, and also between T30 and T60. PD did not differ between groups. All vital parameters were within normal limits throughout anesthesia.Conclusions Administration of nitrous oxide with desflurane results in maintenance of normal TOP and prevents a decrease in horizontal PD during anesthesia. Therefore, this may be a suitable protocol in dogs undergoing intraocular surgeries that require mydriasis and maintenance of normal TOP