Comparative efficacy of low-volume retrobulbar anesthesia using three commercial local anesthetics in adult horses.

OBJECTIVE: To compare the efficacy of low-volume (5-mL) locoregional retrobulbar anesthesia ("retrobulbar block") by use of 3 commercial local anesthetic formulations. ANIMALS: 8 healthy adult mares. METHODS: A block-randomized, masked, controlled design was used. A single ultrasound-guided retrobulbar block was performed with 2% lidocaine, 2% mepivacaine, or 0.5% bupivacaine (n = 5 eyes/group). Contralateral eyes served as untreated controls. End points performed at baseline and time intervals up to 24 hours postblock included the following: assessment of neurophthalmic reflexes/responses, intraocular pressure, and vertical pupil diameter measurement, corneal and periocular esthesiometry, and observation for adverse effects. RESULTS: Low-volume block did not result in increased intraocular pressure or other adverse effects at any time point in any treatment group. Statistically significant corneal anesthesia (P < .001) was observed 1 minute after block in all groups, persisting through 4 hours after lidocaine or mepivacaine block and through 24 hours after bupivacaine block. Clinically significant periocular anesthesia was not observed in any group. Significant vertical pupil diameter increase (P < .05) was observed for up to 4 hours after lidocaine or mepivacaine block and 6 hours after bupivacaine block. CLINICAL RELEVANCE: Low-volume retrobulbar block with any of the 3 local anesthetic drugs evaluated was not associated with adverse effects. In terms of efficacy, mepivacaine block showed no clinical advantage over lidocaine block. However, bupivacaine block induced comparatively rapid and sustained corneal anesthesia. In comparison to published findings using a larger injection volume, low-volume retrobulbar block with lidocaine produced clinically comparable corneal anesthesia. However, periocular soft tissue anesthesia was not achieved with any local anesthetic drug at low volume.

Comparison of preoperative retrobulbar bupivacaine and postoperative subcutaneous liposome-encapsulated bupivacaine on postoperative analgesia in dogs undergoing enucleation.

OBJECTIVE: To compare the effectiveness of preoperative bupivacaine inferotemporal retrobulbar blocks to postoperative liposome-encapsulated bupivacaine (Nocita) line blocks for analgesia following enucleation. ANIMALS: 39 client-owned dogs (40 eyes) presenting to the Ophthalmology Service for enucleation. METHODS: Dogs were randomly assigned to receive either a preoperative inferotemporal retrobulbar block with 0.5% bupivacaine or a peri-incisional line block with liposome-encapsulated bupivacaine (Nocita) at closure. Patients underwent unilateral enucleation and were hospitalized for 24 hours after surgery. Pain scores were performed by a masked observer with the Glasgow Composite Measure Pain Scale and the University of Wisconsin Ocular Pain Scale at 0.25, 0.5, 1, 2, 4, 6, 8, and 24 hours following surgery. Intraoperative use of blood pressure and anesthetic support mediations as well as need for rescue pain control were recorded and compared between groups. RESULTS: There was no significant difference in rescue rates between treatment groups. When comparing the use of medical intraoperative heart rate, blood pressure, or anesthetic plane support, there were no significant differences in use between groups. CLINICAL RELEVANCE: Use of preoperative bupivacaine retrobulbar blocks and postoperative Nocita line blocks were equally effective at postoperative pain control with similarly low complication rates.

Retrospective analysis of complications associated with retrobulbar bupivacaine in dogs undergoing enucleation surgery.

OBJECTIVE: To investigate complications associated with, and without, bupivacaine retrobulbar local anesthesia in dogs undergoing unilateral enucleation surgery. STUDY DESIGN: Retrospective, observational study. ANIMALS: A total of 167 dogs underwent unilateral enucleation surgery via a transpalpebral approach. METHODS: Records from 167 dogs that underwent unilateral enucleation surgery that did (RB) or did not (NB) include retrobulbar bupivacaine anesthesia were reviewed, including anesthetic record, daily physical examination records, surgery report, patient discharge report and patient notes within 14 days of the surgery. Specific complications and severity were compared between RB and NB using the Wilcoxon rank-sum test. A 'complication burden' (0-5) comprising five prespecified complications was assigned and tested using rank-sum procedures. Statistical significance was set to 0.05. RESULTS: Group RB included 97 dogs and group NB 70 dogs. Dogs in NB had a 17.0 percentage points (points) greater risk for a postoperative recovery complication (38.6% versus 21.6%; 95% confidence interval: 3.0-30.6 points; p = 0.017). There was inconclusive evidence that dogs in group RB had a lower risk of requiring perioperative anticholinergic administration (12.4% versus 22.9%; 10.5 points; p = 0.073). Other complications were similar between groups RB and NB with risks that differed by <10 points. The risk of hemorrhage was similar between groups RB (22.7%) and NB (20.0%) with no significant difference in the level of severity (p = 0.664). CONCLUSIONS AND CLINICAL RELEVANCE: In this retrospective study, the use of retrobulbar bupivacaine for enucleation surgery in dogs was not associated with an increased risk of major or minor complications.