Comparison of butorphanol, lidocaine or butorphanol/lidocaine for local anesthesia in intraoperative pain management in sedated calves undergoing umbilical hernia repair

The aim of the study was to compare the analgesic effects of butorphanol and lidocaine administered locally, alone or in combination, during umbilical hernia repair in sedated calves [1]. Thirty calves were enrolled and divided into three groups: L group (n=10), B group (n=10) and LB group (n=10). All subjects were sedated with xylazine 0,3 mg/kg administered intramuscularly (IM). For the local analgesic protocol the L group received lidocaine 4,5 mg/kg, both by infiltration of the surgical planes and intraperitoneally, the B group received butorphanol 0,02 mg/kg by infiltration of the surgical planes and intraperitoneally and the BL group received lidocaine by infiltration of the surgical planes 4,5 mg/kg and butorphanol 0,02 mg/kg intraperitoneally. The drug dose was divided into two syringes, with the total dose shared in the B and L groups and the syringes differentiated by drug in the BL group. The individual syringes were then used for infiltration into the surgical plane and for intraperitoneal administration. To achieve greater diffusion, the volume of each syringe was increased to 40 mL with the addition of saline solution (0.9% sodium chloride). Infiltration in the umbilical region involved both skin and muscle planes, while intraperitoneal injection was performed in the hernia sac. Heart rate (HR), respiratory rate (RR), arterial pressure (SAP, MAP, DAP) and hemoglobin oxygen saturation (SpO2) were recorded. These parameters were recorded before sedation (T0), 15 min after xylazine administration (T1), 10 min after local drug administration (T2), then at 10 (T3), 15 (T4), 20 (T5), 25 (T6), 30 (T7), 35 (T8), 40 (T9) min and on awakening (T10). To assess the response to intraoperative noxious stimulation, we used a cumulative numerical scale that considered percentage changes in HR, RR and SAP compared to baseline (T0) according to the following procedure: (time point value – basal value)/ basal value x 100 = % change. Scores were assessed as follows: Score 0 = variation ≤ 0%; 1 = variation ≤ 10%; 2 = variation > 10% but ≤20%; 3 = variation > 20% but ≤30%; 4 = variation > 30%. Scores were assigned by the evaluators who were blinded to treatment. A final score ranging from a minimum of 0 to a maximum of 12 was obtained by summing the scores of the selected variables; if the score was 6 or higher (HR, RR and SAP increased by more than 20%), rescue analgesia was administered and the surgical area was infiltrated and sprayed intraperitoneally with 2 mg/kg lidocaine 2%. The intraoperative noxious stimulation response scale showed a significant reduction from T3 to T10 compared to baseline in the B and L groups (p<0.001). The Bl group showed a significant reduction from T3 to T7 (p<0.001). When comparing between groups, the B group showed significant differences with the L group at many time points (T1, T2, T4, T5, T6, T9, p<0.001), while the BL group only showed a difference only at T1 (p<0.05). The comparison between the L group and the BL group showed significant differences at T1 and T6 (p<0.001). The results obtained showed a change in the monitored parameters (HR, RR, SAP) that did not require rescue analgesia in any case. The time from the start of the surgery to the animals' return to the standing position was significantly different between the B, BL group and the L group (p = 0.000) and was as follows: 180 min (160/210; 185± 15,5) B group, 128 min (95/180; 131± 25,6) L group and 192 min (160/240; 196± 23,1) BL group. The assessment of the postoperative pain score using the UNESP-Botucatu Unidimensional Composite Pain Scale showed a significant variation in the B and BL groups at 4 h and 5 h (p < 0.001), remaining ≤4 throughout the observation period. In the L group, the UNESP-Botucatu showed changes from 2 h to 5 h (p < 0.001), with 4 subjects at 4 h and 5 subjects at 5 h requiring rescue analgesia by administration of 3.3 mg/kg intravenous flunixin meglumine (Finadyne, Schering-Plough Animal Health, Oss, The Netherlands). Comparison of the groups with regard to UNESP scores showed a significant difference between B and L (p < 0.001) and between BL and L (p < 0.001), as the scores of B and BL were lower than those of L throughout the postoperative period. The number of legally authorized anesthetics and analgesics for livestock, including calves, is limited. Therefore, it is necessary to propose therapeutic alternatives to veterinarians designed to ensure patient welfare, surgeon comfort and staff safety. The protocol used in this study consisted of intramuscular administration of xylazine followed by butorphanol or lidocaine, alone or in combination, along the incision lines and intraperitoneally [2]. This protocol provided adequate sedation and analgesia in calves undergoing umbilical hernia repair, with no clinically demonstrable adverse effects [3].. The combination of butorphanol and lidocaine administered locally gave a better effect on the monitored parameters than the same drugs used alone. Therefore, this combination could be proposed as a viable alternative in calves undergoing umbilical hernia repair.