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Sub-Tenon's injection in equine cadaver eyes: MRI visualization of anesthetic fluid distribution and comparison of two different volumes


Stadler, Silvia; Dennler, Matthias; Hetzel, Udo; Del Chicca, Francesca; Hoey, Sèamus; Spiess, Bernhard M; Pot, Simon A (2016). Sub-Tenon's injection in equine cadaver eyes: MRI visualization of anesthetic fluid distribution and comparison of two different volumes. Veterinary Ophthalmology:Epub ahead of print.

Abstract

Objective: To compare the localization and distribution of two different anesthetic fluid volumes around equine cadaver eyes to determine an appropriate volume for a single sub-Tenon's injection in horses.
Procedure: A single sub-Tenon's injection of 2% lidocaine was performed in 10 equine cadaver heads (20 eyes) using two different volumes (7 mL on one side and 10 mL on the opposite side). The posterior circular distribution of the anesthetic was quantified in sagittal, dorsal, and transverse MRI (T2W-TSE) sequences and evaluated independently by three board-certified radiologists. The distribution of the two fluid volumes was compared via a paired Student's t-test. The interobserver reliability was evaluated via a Kruskal–Wallis test.
Results: Extension of the injection fluid was observed along the dorsal and temporal quadrants of the globe within the subconjunctival space, the anterior and posterior sub-Tenon's space, and into the muscle sheaths along the extraocular muscles. Accumulation of anesthetic fluid directly surrounding the optic nerve was detected in three of 20 cadaver eyes. Circular distribution of the 7 and 10 mL anesthetic volumes was not significantly different (P = 0.849). More retrograde leakage of the anesthetic was observed using the 10 mL volume. Evaluation of interobserver reliability revealed no significant differences between observers (P = 0.21–0.92).
Conclusions: Sub-Tenon's anesthesia can have potential as an alternative to retrobulbar anesthesia for ophthalmic surgeries in equines. A 7- to 10-mL injection volume should be appropriate based on the results of this study. The distribution of the anesthetic solution in live tissues, the clinical effects, and the potential for complications will have to be evaluated in vivo.

Abstract

Objective: To compare the localization and distribution of two different anesthetic fluid volumes around equine cadaver eyes to determine an appropriate volume for a single sub-Tenon's injection in horses.
Procedure: A single sub-Tenon's injection of 2% lidocaine was performed in 10 equine cadaver heads (20 eyes) using two different volumes (7 mL on one side and 10 mL on the opposite side). The posterior circular distribution of the anesthetic was quantified in sagittal, dorsal, and transverse MRI (T2W-TSE) sequences and evaluated independently by three board-certified radiologists. The distribution of the two fluid volumes was compared via a paired Student's t-test. The interobserver reliability was evaluated via a Kruskal–Wallis test.
Results: Extension of the injection fluid was observed along the dorsal and temporal quadrants of the globe within the subconjunctival space, the anterior and posterior sub-Tenon's space, and into the muscle sheaths along the extraocular muscles. Accumulation of anesthetic fluid directly surrounding the optic nerve was detected in three of 20 cadaver eyes. Circular distribution of the 7 and 10 mL anesthetic volumes was not significantly different (P = 0.849). More retrograde leakage of the anesthetic was observed using the 10 mL volume. Evaluation of interobserver reliability revealed no significant differences between observers (P = 0.21–0.92).
Conclusions: Sub-Tenon's anesthesia can have potential as an alternative to retrobulbar anesthesia for ophthalmic surgeries in equines. A 7- to 10-mL injection volume should be appropriate based on the results of this study. The distribution of the anesthetic solution in live tissues, the clinical effects, and the potential for complications will have to be evaluated in vivo.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Veterinary Clinic > Equine Department
05 Vetsuisse Faculty > Institute of Veterinary Pathology
05 Vetsuisse Faculty > Veterinary Clinic > Department of Small Animals
Dewey Decimal Classification:570 Life sciences; biology
630 Agriculture
Language:English
Date:2016
Deposited On:23 Dec 2016 10:13
Last Modified:29 Apr 2017 17:47
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:1463-5216
Publisher DOI:https://doi.org/10.1111/vop.12452
PubMed ID:28008696

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