Total intravenous anaesthesia with a combination of ketamine and propofol in cats undergoing ovariectomy : intra and post-operative evaluation

Ketamine/propofol constant rate infusion is intravenous (IV) combination used in humans and veterinary medicine (Ilkiw & Pascoe 2003). Intraoperative anaesthetic variables and postoperative analgesic and sedative effects were evaluated. Fifteen female cats undergoing ovariectomy, randomly allocated in two groups, received IV loading dose of ketamine/propofol (2 mg kg-1 each) (KP; n=8) mixed in the same syringe or ketamine/propofol added of dexmedetomidine (0.003 mg kg-1IV) (KPD; n=7), followed by IV infusion of ketamine/propofol mixture (10 mg kg-1h-1 each). Physiological parameters and venous blood gas analysis were monitored intraoperatively. Heinz-bodies count was performed before anaesthesia, at the end of the infusion and 1 and 5 days after surgery. Sedation degree, quality of recovery and pain assessment were evaluated for 24 hours postoperatively (Shaffran 2008; Belda 2008). Plasma concentrations of ketamine, norketamine and propofol were quantified in KP group by HPLC analysis and blood samples were collected during the infusion period and up to 24 h. Data were analyzed by ANOVA, Tukey test and Kruskal-Wallis test (P<0.05). Intraoperative HR was significantly higher (KP: 156,2 ±7,4; KPD 124,7 ±8,5) and time of extubation was significantly shorter in KP group (KP 7,13 ±2,53 min; KPD 29 ±6,,86 min). Blood gas analysis were not different among groups and infusion of propofol did not significantly increase oxidative damage to the red blood cells. Mean propofol, ketamine and norketamine half-life were respectively 6,8 ± 9,87 hours, 2,1 ±4,7 hours and 3,07 ±2,67 hours. Sedation degree was higher in KPD group; no cats needed rescue post-operative analgesia. Total intravenous anaesthesia (TIVA) with ketofol appeared to be effective in cats, with smooth recovery and adequate analgesia during postoperative period. Decrease HR in dexmedetomidine group resulted in a more stable haemodynamic state but prolonged recovery time. Ketofol infusion could represent a useful protocol for TIVA in cats undergoing moderately painful surgery