Epidural administration of tramadol does not provide sufficient intraoperative analgesia for elective ovariohysterectomy in healthy cats

Few studies today address trans-operative analgesia provided by tramadol without local anesthetics for intra-abdominal procedures. The objective of this study was to assess the efficacy of trans-operative analgesia provided by epidurally administered tramadol in cats undergoing elective ovariohysterectomy. For this purpose, 16 healthy queens were randomly assigned to participate in one of two groups: GC, control group, 0.9% NaCl at 0.3 mL/kg; and GT, tramadol group, tramadol 1 mg/kg in saline to the same final volume. Subjects received premedication with ketamine, xylazine and morphine and were anesthetized and maintained with a propofol infusion at 0.4-0.8 mg/kg/min until the end of surgery. Variables heart rate (HR), respiratory rate (F_R) and systolic blood pressure (SAP) were recorded before epidural injection (TB), 5 minutes after epidural injection (TAE), at surgical incision of the skin (TSI), at clamping of the first ovarian pedicle (TP1), at clamping of the second pedicle (TP2), at clamping of the uterine stump (TU), at the beginning of abdominal cavity closure (TC) and at the final suture of the skin (TFS). A bolus of fentanyl 2 μg/kg was administered IV in case of a 20% increase of physiologic variables during these times. At the end of the study, data was analyzed using ANOVA for repeated measures followed by Tukey test. The number of fentanyl boluses was compared between groups using Kruskal-Wallis followed by Dunn test. All analyses were performed under 5% significance. There were no significant differences in HR, F_R and SAP between groups. Only a mild difference was seen in HR in GT at times MP1, MP2, MU and MC compared to baseline (before epidural injections). There were no differences in number of fentanyl boluses between groups, with median (range) of 3 (1–5) in GC and 3 (1–4) in GT. In conclusion, tramadol given epidurally to cats undergoing elective ovariohysterectomy does not provide reliable intraoperative analgesia, and therefore other strategies are necessary to ensure intraoperative analgesia of healthy cats during elective ovariohysterectomy.