A comparison of retrobulbar and two peribulbar regional anesthetic techniques in dog cadavers

Yael Shilo-Benjamini; Peter J Pascoe; Erik R Wisner; Nili Kahane; Philip H Kass; David J Maggs

doi:10.1016/j.vaa.2017.02.009

A comparison of retrobulbar and two peribulbar regional anesthetic techniques in dog cadavers

Vet Anaesth Analg. 2017 Jul;44(4):925-932. doi: 10.1016/j.vaa.2017.02.009. Epub 2017 Apr 13.

Authors

Yael Shilo-Benjamini¹, Peter J Pascoe², Erik R Wisner², Nili Kahane³, Philip H Kass⁴, David J Maggs²

Affiliations

¹ Koret School of Veterinary Medicine, The Robert H Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Jerusalem, Israel. Electronic address: shilo.yael@gmail.com.
² Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California Davis, Davis, CA, USA.
³ Koret School of Veterinary Medicine, The Robert H Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Jerusalem, Israel.
⁴ Department of Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Davis, CA, USA.

PMID: 28716684
DOI: 10.1016/j.vaa.2017.02.009

Abstract

Objective: To compare injectate distribution and likelihood of regional anesthesia to the orbit following retrobulbar (RB) or peribulbar (PB) injections in dog cadavers.

Study design: Randomized, masked study.

Animals: Twenty-four dog cadavers (aged 5.5-17 years, 2.0-36.3 kg).

Methods: Orbits underwent one of three injection techniques with bupivacaine 0.5% and iohexol (1:1): ventrolateral RB injection (1-2 mL; 15 orbits), medial canthal PB injection (2-8 mL; PB-1; 16 orbits), or dorsomedial and ventrolateral PB injections (each 1-4 mL; PB-2; 16 orbits). The likelihood of successful regional anesthesia was estimated based on computed tomographic images scored for injectate volume of distribution at the base and within the extraocular muscle cone (EOMC), and injectate distribution around the optic nerve. Intraocular pressure (IOP) was measured before and after injections. Mixed-effects linear regression with post hoc Bonferroni contrast adjustments was performed. Significance was set at 0.05.

Results: A difference in injectate volume of distribution within or at the base of the EOMC was not detected among groups. The median optic nerve circumference of injectate distribution was significantly higher in the RB injected group than in the PB-2 group. Injectate distribution following RB, PB-1 and PB-2 injections was graded as likely to provide regional anesthesia within the EOMC in 40%, 19% and 31% of eyes, and at the EOMC base in 60%, 63% and 50% of eyes, respectively. The probability of likelihood to provide regional anesthesia was lower in dogs of higher body weights. The IOP was significantly higher than baseline following PB-1 (18 ± 14 mmHg) and in comparison with RB (2 ± 3 mmHg), but not different from PB-2 injection (10 ± 11 mmHg).

Conclusions and clinical relevance: None of the techniques reliably produced 'successful' injectate distribution based on this study's definitions; however, clinical assessment of anesthetic success is required.

Keywords: canine; peribulbar anesthesia; regional ocular anesthesia; retrobulbar anesthesia.

Publication types

Comparative Study
Randomized Controlled Trial

MeSH terms

Anesthesia, Conduction / methods
Anesthesia, Conduction / veterinary*
Anesthetics, Local / administration & dosage*
Animals
Dogs
Female
Injections / veterinary
Male
Orbit* / diagnostic imaging
Tomography, X-Ray Computed

Substances

Anesthetics, Local