Objective: To evaluate the effect of intra-articular (i.a.) lidocaine plus bupivacaine on post-operative pain in sheep undergoing stifle arthrotomy.
Study design: Randomized controlled experimental trial.
Animals: Sixteen adult Rambouillet-cross ewes.
Methods: Sheep were randomly assigned to one of two treatment groups. The lidocaine/bupivacaine group (L/B, n=8) received i.a. lidocaine (40 mg (2 mL)) prior to incision and i.a. bupivacaine (10 mg (2 mL)) post-closure, while the control group (n=8) received no i.a. injections. i.a. local anesthetics were an addition to the standard analgesic protocol of phenylbutazone (1 g orally, every 24 hours for 5 days) and transdermal fentanyl (equivalent to 15 mg), initiated 24 hours prior to surgery. A stifle arthrotomy was performed with the purpose of creating a full-thickness articular cartilage defect. Two observers blinded to treatment assessed sheep for total pain score using a numeric ranking scale that included: comfort, movement, and flock behavior. The first observation (T=0) was obtained the evening of surgery (3-7 hours post-operatively); subsequent observations occurred every 12 hours for 72 hours. Nonparametric statistical tests were used to evaluate differences between groups for total pain score.
Results: L/B sheep had significantly lower total pain scores at T=0 than control sheep (p<0.05). No significant differences between treatments were noted at any subsequent time periods. There were no differences attributable to the use of different observers.
Conclusions and clinical relevance: i.a. lidocaine plus bupivacaine provided analgesia at 3-7 hours post-operatively. Use of i.a. lidocaine and bupivacaine is a simple, effective, yet inexpensive perioperative analgesic protocol for joint surgery in sheep.