Intra-articular lidocaine plus bupivacaine in sheep undergoing stifle arthrotomy.

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.