Intra- and post-operative analgesic effects of carprofen in medetomidine premedicated dogs undergoing ovariectomy

Intra- and post-operative analgesic effects of pre-operative administration of carprofen were investigated in 16 medetomidine-premedicated dogs undergoing elective ovariectomy. Dogs were randomly allocated into carprofen (n=8; 4 mg/kg, intramuscularly) or placebo group (n = 8). After medetomidine (1000 [xg/m2, intramuscularly) premedication, they were induced with propofol (1 mg/kg, intravenously) and maintained with isoflurane (FE'ISO 1.0 %) in 100% oxygen. During anaesthesia, the analgesia was assessed in terms of changes in heart rate, respiratory rate and arterial blood pressure as a response to the surgery. Assessments of post-operative sedation (simple numerical rating scale) and pain (multifactorial pain scale) were made at 15 minutes, 30 minutes, 1,2,3, 4, 5, and 6 hours after the surgery. In addition, pulse rate, respiratory rate and body temperature were measured at the same time. During anaesthesia, lower heart rate, respiratory rate and mean arterial blood pressure and higher tidal volume of respiration were observed in the carprofen group. Post-operative pain score was relatively low in both groups of dogs, however it was higher, but not significantly, in the placebo group. There was no difference between the groups in terms of respiratory and pulse rate after surgery. The post-operative sedation score was higher in the placebo group only in the early post-operative period most probably due to misinterpretation of pain behaviour. Carprofen together with other anaesthetic drugs provided sufficient intra-operative analgesia only until major painful surgical stimulus occurred, after which analgesia had to be supplemented with a subanaesthetic dose of ketamine. Comparing to that analgesia was insufficient in the placebo group throughout the procedure. The post-operative pain scoring system was probably not sensitive enough to detect the differences between the groups; however, the effects of other drugs that extended in the post-operative period may be responsible for a low postoperative pain score in both groups of dogs