Total intravenous anesthesia with propofol and S(+)-ketamine in rabbits

Objective To evaluate total intravenous anesthesia with propofol alone or in combination with S(+)-ketamine in rabbits undergoing surgery. Study design Prospective, randomized, blinded trial. Animals Nine 6-month-old New Zealand white rabbits, weighing 2.5–3 kg. Methods Animals received acepromazine (0.1 mg kg−1) and buprenorphine (20 μg kg−1) IM, and anesthesia was induced with propofol (2 mg kg−1) and S(+)-ketamine (1 mg kg−1) IV. Rabbits received two of three treatments: propofol (0.8 mg kg−1 minute−1) (control treatment, P), propofol (0.8 mg kg−1 minute−1) + S(+)-ketamine (100 μg kg−1 minute−1) (PK100) or propofol (0.8 mg kg−1 minute−1) + S(+)-ketamine (200 μg kg−1 minute−1) (PK200). All animals received 100% O2 during anesthesia. Heart rate, mean arterial pressure, hemoglobin oxygen saturation and respiratory rate were measured every 5 minutes for 60 minutes. Blood-gas parameters were measured at zero time and 60 minutes. Additional propofol injections, if necessary, and recovery time were recorded. Results An increase in heart rate was observed in P and PK200 up to 10 minutes after induction of anesthesia. Blood pressure decreased from baseline values during the first 10 minutes in P and PK200, and during the first 15 minutes and between 45 and 55 minutes in PK100. A reduction in respiratory rate was observed after 5 minutes in all treatments. Respiratory acidosis was observed in all treatments. Six (2.8) [median (interquartile range)] further propofol injections were necessary in P, which differed statistically from PK100 [1 (0.2)] and PK200 [2 (0.6)]. Recovery time was shorter in P compared with PK100 and PK200, being [7.5 minutes (4.11)], [17.5 minutes (10.30)], and [12 minutes (10.30)], respectively. Conclusions and clinical relevance S(+)-ketamine potentiates propofol-induced anesthesia in rabbits, providing better maintenance of heart rate. All of these techniques were accompanied by clinically significant respiratory depression.