Effects of graded doses of propofol for anesthesia induction on cardiovascular parameters and intraocular pressures in normal dogs

To determine the effects of graded doses of propofol on cardiovascular parameters and intraocular pressures (IOP) in normal dogs. Prospective, randomized, modified Latin square, cross-over experimental study. Eleven adult random-source dogs weighing 20.2 ± 5.7 kg. There were three treatment groups: propofol 8 mg kg−1 intravenous (IV) until loss of jaw tone (Group P), propofol until loss of jaw tone +20% (Group P20), and propofol until loss of jaw tone +50% (Group P50). Atracurium 0.1 mg kg−1 IV was administered in all treatments immediately after the propofol. All dogs received the three treatments in a randomized order, with at least a one week interval between treatments. Direct arterial blood pressure and IOP by applanation tonometry were obtained at baseline, after 5 minutes of pre-oxygenation (before induction), before, and after intubation. Blood gas samples were obtained at baseline, after pre-oxygenation, and before intubation. There was no significant difference in IOP readings at any time point among groups. The IOP was significantly higher before intubation versus before induction in all three groups. There was a significantly smaller change in systolic, mean (MAP), and diastolic (DAP) arterial pressures in the P50 group compared with the P group after intubation. There was a significantly smaller change in MAP and DAP in the P50 group compared with the P20 group after intubation. The increase in CO2 from before induction to before intubation was significantly greater in the P50 group than in the P or P20 groups. Graded doses of propofol did not affect the increase in IOP observed with propofol induction in normal dogs. Higher doses of propofol are of no apparent additional benefit in animals who cannot tolerate an abrupt increase in IOP but may be of benefit in dogs who cannot tolerate an abrupt increase in blood pressure accompanying orotracheal intubation.