Comparison of two bupivacaine delivery methods to control postoperative pain after enucleation in dogs.

OBJECTIVE: To compare the efficacy of a preoperative retrobulbar injection of bupivacaine to an intraoperative splash block of bupivacaine in controlling postoperative pain following enucleation in dogs. ANIMALS STUDIED: Prospective, randomized, double-masked clinical study of 31 client owned dogs with end-stage ophthalmic disease requiring enucleation. PROCEDURES: Dogs admitted for unilateral enucleation were randomly assigned to receive bupivacaine 0.5% (1 mL/kg) into the retrobulbar space either via an inferior-temporal palpebral (ITP) injection preoperatively or an intraoperative splash block. Pain was assessed prior to pre-anesthetic sedation and at 0, 0.25, 0.5, 1, 2, 4 6, 8, and 24 hours (H) after extubation by masked observers using a previously described subjective pain scoring system. Rescue analgesia was initiated if overall pain score was >9 or if the score in any category at any time point was >3. RESULTS: There were no adverse reactions. One of 15 dogs that received bupivacaine via a preoperative retrobulbar ITP injection required rescue analgesia. There was no significant difference between groups with regard to the need for rescue analgesia or pain scores at any time point or overall. CONCLUSIONS AND CLINICAL RELEVANCE: Pain control using an intraoperative orbital splash administration of bupivacaine is not significantly different to a preoperative retrobulbar injection of bupivacaine.