Comparison of peribulbar and retrobulbar regional anesthesia with bupivacaine in cats

Abstract

Objective-To compare effectiveness and complications associated with peribulbar and retrobulbar anesthesia with bupivacaine in cats. Animals-6 healthy adult cats. Procedures-Cats were sedated with dexmedetomidine and received a peribulbar injection of 0.5% bupivacaine (1.5 mL), iopamidol (0.5 mL), and saline (0.9% NaCl) solution (1 mL) or retrobulbar injection of 0.5% bupivacaine (0.75 mL) and iopamidol (0.25 mL) in a crossover study with ≥ 2 weeks between treatments. The contralateral eye was the control. Injectate distribution was evaluated with CT. After atipamezole administration, periocular and corneal sensations, intraocular pressure (IOP), and ocular reflexes and appearance were evaluated for 24 hours. Results-All peribulbar and 3 of 6 retrobulbar injections resulted in CT evidence of intraconal injectate. Corneal sensation and periocular skin sensation were absent or significantly reduced relative to that for control eyes for 3 hours after peribulbar injection. Mean ± SD IOP immediately after injection was significantly higher for eyes with peribulbar injections (33 ± 12 mm Hg) than for control eyes or eyes with retrobulbar injections (both 14 ± 4 mm Hg) but 10 minutes later decreased to 18 ± 3 mm Hg. Exophthalmos, chemosis, and ptosis were evident in most injected eyes, and irritation was evident in 3 of 6 peribulbar-injected and 1 of 6 retrobulbar-injected eyes. All conditions resolved within 14 hours. Conclusions and Clinical Relevance-Peribulbar injection resulted in intraconal deposition of bupivicaine in a higher percentage of cats than did retrobulbar injection and induced notable anesthesia relative to that for the control eye; however, IOP increased temporarily.

Retrobulbar vs peribulbar regional anesthesia techniques using bupivacaine in dogs

“…Data from the present study support this as no change in corneal sensitivity was observed in those eyes, in which extraconal administration occurred. This was also reported in cats, where success rate of RBA was 50% (3 of 6) . The two successful RBA injections in the present study abolished corneal sensitivity for several hours following injection, which implies that when administered intraconally, 2 mL of bupivacaine is sufficient to produce corneal anesthesia in dogs up to (and maybe in excess of) 25 kg.…”

“…The periocular skin sensation was tested using a “pin‐prick” technique with pressure applied to the periocular skin using the tip of a ballpoint pen at the mid‐dorsal eyelid, mid ventral eyelid, and lateral and medial canthi. The response was considered positive when the dog closed the eyelids or moved the head . Lastly, corneal sensitivity and then IOP were assessed as described earlier.…”

“…Intraconal injectate distribution volume was scored as described: 0 = none, 1 = moderate, and 2 = large. The extent of contact between the injectate and the optic nerve was scored as: 0°, 90°, 180°, 270°, or 360° . Injectate distribution likely to produce partial anesthesia was defined as moderate intraconal distribution and optic nerve contact of 90‐180°, and distribution likely to produce successful anesthesia was defined as large intraconal distribution volume and optic nerve contact of 270‐360°.…”

Pharmacokinetics of bupivacaine after intraperitoneal administration to cats undergoing ovariohysterectomy

“…None of these aforementioned adverse effects were observed in the cats of the present study. The dose of bupivacaine used in this study was based on the veterinary literature, 34 results of experiments on IP administration of bupivacaine to humans, 15 and clinical experience with IP analgesia at the authors' institutions.…”

“…[34][35][36] In the present study, a final concentration of 0.25% was administered, and it is not known whether use of a higher concentration will increase the magnitude or duration of analgesia or cause adverse effects. The drug was diluted in saline solution to achieve a reasonable volume for anesthetic spread.…”