Liposomal bupivacaine is both safe and effective when administered via local infiltration at surgical site and mesovarium for laparoscopic ovariectomy in mares.

Background: Liposomal local anaesthetic solutions may provide extended-duration analgesia postoperatively but have not been assessed following intra-peritoneal local infiltration in any species.

Objectives: To evaluate two doses of 1.33% liposomal bupivacaine (LB) versus 0.75% bupivacaine HCL (BHCl) for analgesia following laparoscopic ovariectomy in mares.

Study Design: Prospective cohort study.

Methods: Fifteen healthy Quarter Horse mares (age 2-20 years) with normal bilateral ovarian palpation and appearance were enrolled. Horses were restrained in standing stocks and administered an α-2 agonist, butorphanol, and flunixin meglumine, followed by a variable rate infusion of sedation with α-2 agonists. Bilateral paralumbar fossa ovariectomies were performed. Treatment with either 30 ml 0.75% BHCl followed by 20 or 40 ml LB 13.3% (LB20 and LB40) volume expanded with saline to 80 ml total (n = 6/group) or 80 ml BHCl alone (n = 3, BCHL) was infused around incision sites and each mesovarium (LB or BHCl) prior to ovariectomy. Horses were monitored for 72 h by physical examination, algometry, and pain scoring (composite pain scale by Bussieres et al., Horse Grimace Scale). Abdominocentesis with peritoneal fluid analysis was performed at 72 h.

Results: Analgesia achieved with all treatment protocols allowed completion of ovariectomy procedures. Pressure algometry scores were lower in BHCl-treated horses versus both LB groups overall. Pain scores were improved with LB-treated horses in a dose-dependent fashion (Horse Grimace Scale scores LB40 < LB20 < BHCL; composite pain scale scores LB40 < BHCL, LB20 < BHCL, BHCL, and LB20 did not differ). Peritoneal fluid total protein was lower in LB40 versus LB20 and BHCL horses. No complications from LB administration were appreciated.

Main Limitations: Small patient sample size, lack of follow-up past 72 h or histopathology.

Conclusions: Analgesia duration was extended and pain scores improved postoperatively with LB versus BHCl in a dose-dependent fashion. Further clinical evaluation of extended-duration local anaesthetics in horses for improved postoperative pain management is warranted.