The aim of this prospective, double-blinded, randomised study was to assess the efficacy of a preoperative administration of meloxicam in controlling postoperative pain relief in dogs undergoing ovariectomy. The analgesic efficacy and tolerance of meloxicam has already been demonstrated in dogs undergoing surgical procedures.
Each dog received meloxicam (Metacam ND, 0,2 mg/kg, IV) or saline (0.9% NACl) solution (0,04 ml/kg, IV) prior to induction. Pain was evaluated during recovery period 30 minutes, 1, 2, 4, 8, 12 and 20 hours after extubation using both a Visual Analogue Scale (=VAS) and a Numerical Rating Scale (=NRS). The VAS is a subjective assessment of pain whereas the NRS assigns numeric scores (from 0 to 3) to body temperature, heart rate, respiratory rate, salivation, pupils dilatation, external appearance, attitude regarding the surgical site, interactive behaviour, response to palpation-pressure of the surgical site, vocalization and gait. A Cumulative Pain Score (=CPS) was calculated by adding every parameters scores obtained at each examination time point. Data sets from all dogs for VAS and CPS were used to compare the two groups. Area Under the Curve (=AUC) values for VAS and CPS were compared. Differences were considered to be statistically significant if p <0.05.
66 bitches were finally kept for analysis (33 in the meloxicam group and 33 in the placebo group). Groups were comparable regarding age, body weight and duration of surgery. With regard to VAS, AUC values for changes from baseline, from 0 to 8 hours and to 20 hours after extubation, were 16.96 (+ 11.5) and 36.11 (+ 24.77) respectively in the meloxicam group and 23.29 (+ 13.08) and 50.96 (+ 31.76) respectively in the placebo group. These AUC values were statistically different in favor of meloxicam (p= 0.012 and p= 0.034 respectively). On the other hand, no significant difference was found between CPS for placebo and meloxicam at any examination time point. Corresponding area under the curve (AUC) values were 43.35 (+33.56) for meloxicam and 55.73 (+ 43.37) for placebo. The difference was non significant
Unlike the VAS, the CPS did not show significant difference between the two groups. The NRS used in this study for calculating CPS might have failed to show any difference due to inclusion of parameters with various sensitivity. In fact some parameters included in the CPS appeared clearly to be of minor importance. The major outcome of this study is that only sensitive parameters should be considered. Furthermore, score grading of various parameters in should be balanced when combined to a cumulative score. In this study the VAS proved to be more reliable to assess global recovery pain in dogs.
Finally, preoperative administration of meloxicam proved to be a safe and effective method of controlling pain for up to 20 hours in dogs undergoing ovariectomy.