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Duration of Effect of Liposomal Bupivacaine in an Induced Equine Lameness Model
07 August 2019 (online)
Introduction: Liposomal bupivacaine can provide analgesia for 72 hours postoperatively in dogs at 5.2 mg/kg; its use in horses has not been reported. We hypothesized that at milligram equivalent doses, liposomal bupivacaine in abaxial nerve blocks would not have a significantly longer duration of effect when compared with bupivacaine HCL in an equine induced-lameness model.
Materials and Methods: Eight horses were examined for lameness; two were eliminated from the main study for lameness. Abaxial nerve blocks were performed in the eliminated horse’s lame legs using either 10 mg (0.75 mL) or 27 mg (2 mL) liposomal bupivacaine. Neither horse showed adverse reaction. The remaining six horses had forelimb lameness induced in a single limb using a hoof-clamp model modified from Swaab, reported in 2015. Lameness was objectively evaluated using a body mounted inertial sensor system. An abaxial nerve block was then performed with either 10 mg of liposomal bupivacaine or 10 mg (2 mL) bupivacaine HCL. A successful block obliterated skin sensation at 30 minutes postinjection. Each horse was trotted every 30 minutes until the return of 85% of lameness. After at least 3 days, treatment and leg was crossed over.
Results: No horse showed adverse reaction to injection. The liposomal bupivacaine eliminated 85% of lameness for an average of 3.5 hours; bupivacaine HCL eliminated 85% of lameness for an average of 2.9 hours.
Discussion/Conclusion: Further investigations utilizing larger volumes of liposomal bupivacaine are warranted to determine if a longer duration of action can be achieved.
Acknowledgment: Funding provided by the Iowa State VCS Research Incentive grant.