RESEARCH PAPER Total intravenous anesthesia with propofol and S(+)-ketamine in rabbits Fernando SF Cruz*, Adriano B Carregaro , Alceu G Raiser , Marina Zimmerman , Rafael Lukarsewski  & Renata PB Steffen  *Pharmacology Graduate Program, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil  Departamento de Clı ´nica de Pequenos Animais, Centro de Cie ˆncias Rurais, Universidade Federal de Santa Maria, Santa Maria, Rio Grande do Sul, Brazil Correspondence: Adriano B Carregaro, Departamento de Clı ´nica de Pequenos Animais, Centro de Cie ˆncias Rurais, Universidade Federal de Santa Maria, UFSM, Av. Roraima 1000, Santa Maria, Rio Grande do Sul, Brazil CEP 97105-900. E-mail: carregaro@smail.ufsm.br Abstract 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 lg 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 lg kg )1 minute )1 ) (PK100) or propofol (0.8 mg kg )1 minute )1 ) + S(+)-ketamine (200 lg kg )1 minute )1 ) (PK200). All animals received 100% O 2 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 respira- tory 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. Keywords intravenous anesthesia, propofol, rabbit, S(+)-ketamine. Introduction Rodents and lagomorphs are considered standard animals in biomedical research especially with regard to pharmacology, toxicology, surgery and genetics. Rabbits are the third most commonly anaesthetized species but have at least seven times more risks of anaesthetic-related death compared to dogs and cats (Brodbelt 2009). In relation to its 116 Veterinary Anaesthesia and Analgesia, 2010, 37, 116–122 doi:10.1111/j.1467-2995.2009.00513.x