Perioperative analgesic effect of epidural ropivacaine 0.5% in dogs undergoing total monolateral mastectomy

Total mastectomy causes considerable tissue damage and a marked perioperative pain response. This study aimed to evaluate the effectiveness of epidural administration of 0.5% ropivacaine on pain management for mastectomy in dogs. Twenty client-owned dogs were enrolled and divided in 2 groups: Epi-group (received a single dose of 0.5% ropicavaine epidurally) and Mor-group (received morphine IM). All dogs were premedicated with 0.3 mg kg 1 of morphine IM, anaesthesia was induced and maintained with propofol infusions. The volume of ropivacaine was calculated with a specific nomogram (Otero et al, 2010). Records of HR, fR, MAP, PE’CO2 and SpO2 were taken before and after epidural administration and throughout surgery. On recovery, dogs received 2 mg kg 1 of robenacoxib SC and were evaluated for pain score every hour, for 20 hours, using the Glasgow short form pain scale. Intraoperative rescue analgesia with fentanyl 2 lg kg 1 was administered if HR and MAP increased over 20% from previous values. Postoperative rescue analgesia (morphine 0.3 mg kg 1 IM) was administered with pain score higher than 5. Data were analysed with ANOVA tests and Tukey post hoc was used to evaluate data all over the time; a Friedmann test was used to compare pain scores. Values of p < 0.05 were considered significant. No differences were detected between groups for age, weight and surgery time. All the dogs of Mor-group and three dogs in Epi-group required intraoperative fentanyl. Postoperative pain score was significantly higher in Mor-group (p = 0.03) and the morphine requirement, over 20 hours, was significantly higher (p = 0.004) for Mor-group (1.4 0.43 mg kg 1) compared to Epi-group (0.76 0.42 mg kg 1). Epidural administration of ropivacaine 0.5% was a good analgesic option and the nomogram to calculate the injected volume appeared satisfactory for this procedure