Sub‐Tenon's injection in equine cadaver eyes: <scp>MRI</scp> visualization of anesthetic fluid distribution and comparison of two different volumes

Stadler, Silvia; Dennler, Matthias; Hetzel, Udo; Chicca, Francesca Del; Hoey, Séamus; Spiess, Bernhard M.; Voelter, Katrin; Pot, Simon A.

doi:10.1111/vop.12452

Cited by 7 publications

(6 citation statements)

References 21 publications

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“…The volume that was used for injection in our study (2.5 mL) was lower than the volume typically used in other studies [ 15 , 16 , 28 ]. This lower volume was selected to produce a more trustworthy result in dissection and because US guidance would decrease the volume of anesthetic injection solution required for an adequate nerve block [ 6 ].…”

Section: Discussionmentioning

confidence: 75%

“…To avoid these complications, other techniques have also recently been described in horses, such as sub-Tenon’s injection and the US-guided peribulbar block [ 16 , 20 , 21 , 28 ].…”

Section: Discussionmentioning

confidence: 99%

“…In the sub-Tenon’s injection, a small conjunctival incision is made 5 mm from the limbus and a curved blunt sub-Tenon’s cannula is placed in a temporal-dorsal position following the equator of the globe and 7–10 mL of anesthetic is injected [ 28 , 29 ]. This is widely used in human patients and has also been described in dogs [ 29 , 30 ].…”

Section: Discussionmentioning

confidence: 99%

“…This is widely used in human patients and has also been described in dogs [ 29 , 30 ]. In horses (in an ex vivo design), this technique makes it possible to gain access to the sub-Tenon’s space and, as fluid distribution occurs in the posterior sub-Tenon’s space and intraconal, it might be a valid alternative to the RNB in horses [ 28 ]. Its disadvantages are the risk of chemosis and accidental globe puncture; experience with the injection technique seemed to be necessary to prevent the latter [ 28 ].…”

Section: Discussionmentioning

confidence: 99%

See 3 more Smart Citations

Comparing Blind and Ultrasound-Guided Retrobulbar Nerve Blocks in Equine Cadavers: The Training Effect

Hermans

Lloyd-Edwards

Sommeren

et al. 2022

Animals

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In standing ophthalmic surgery in horses, a retrobulbar nerve block (RNB) is often placed blindly for anesthesia and akinesia. The ultrasound (US)-guided RNB may have fewer complications, but the two techniques have only been compared once in equine cadavers. This study compares the techniques for success and complication rates and analyzes the effect of training on US guidance. Twenty-two equine cadavers were divided into three groups: blind RNBs were performed bilaterally in eight cadavers, US-guided RNBs were performed bilaterally in seven cadavers, and after US-guided training, blind RNBs were performed bilaterally in seven cadavers. All RNBs were performed by the same two inexperienced operators, and a combination of contrast medium (CM; 1.25 mL) and methylene blue dye (1.25 mL) were injected (2.5 mL total volume). Needle positioning in the periorbita and the distance of the CM to the optic foramen were assessed using computerized tomography (CT). Dye spreading was evaluated by dissection. In group 1, 37.5% of the injections were in the optimal central position in the periorbita; in group 2, 75% and in group 3, 71.4%. There was no significant difference between the groups regarding needle position (groups 1 and 2 p = 0.056; groups 1 and 3 p = 0.069, groups 2 and 3 p = 0.8). The mean CM distribution distance was not significantly different between all groups. Group 1 had 18.75% intraocular injections versus 0% in group 2 and 7.1% in group 3 (not significant). US guidance showed no significant increases in accuracy nor decreases in complications. However, the effects on accuracy showed a trend towards significant improvement, and larger scale follow-up studies might show significant training effects on US guidance.

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Section: Discussionmentioning

confidence: 75%

“…To avoid these complications, other techniques have also recently been described in horses, such as sub-Tenon’s injection and the US-guided peribulbar block [ 16 , 20 , 21 , 28 ].…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Comparing Blind and Ultrasound-Guided Retrobulbar Nerve Blocks in Equine Cadavers: The Training Effect

Hermans

Lloyd-Edwards

Sommeren

et al. 2022

Animals

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“…21 While the RB has been utilized clinically for many decades in horses, there have been no in vivo studies evaluating RB in horses. 22,23 The purposes of our study were to determine whether the use of local anesthesia (RB) would improve ease of image acquisition and image quality via SD-OCT of the cornea and retina in standing horses similar to that of horses under GA and to document clinical (physiologic) variables affected by and complications associated with RB. By measuring the time to loss of both sensory and motor reflexes, we aimed to determine the time of RB onset, thus allowing us to determine the optimal time to proceed with OCT imaging in sedated horses.…”

mentioning

confidence: 99%

Comparison of image quality of corneal and retinal optical coherence tomography using sedation and general anesthesia protocols with or without retrobulbar anesthesia in horses

Hefner

Lin

Cole

et al. 2022

ajvr

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OBJECTIVE To compare image quality and acquisition time of corneal and retinal spectral domain optical coherence tomography (SD-OCT) under 3 different sedation-anesthesia conditions in horses. ANIMALS 6 middle-aged geldings free of ocular disease. PROCEDURES 1 randomly selected eye of each horse was evaluated via SD-OCT under the following 3 conditions: standing sedation without retrobulbar anesthetic block (RB), standing sedation with RB, and general anesthesia with RB. Five regions of interest were evaluated in the cornea (axial and 12, 3, 6, and 9 o’clock positions) and fundus (optic nerve head). Three diagnostic scans of predetermined quality were obtained per anatomical region. Image acquisition times and total scans per site were recorded. Corneal and retinal SD-OCT image quality was graded on a subjective scale from 0 (nondiagnostic) to 4 (excellent). RESULTS Mean values for the standing sedation without RB, standing sedation with RB, and general anesthesia conditions were 24, 23, and 17, respectively, for total cornea scan attempts; 23, 19, and 19 for total retina-scan attempts; 14.6, 13.2, and 9.2 minutes for total cornea scan time; 19.1, 9.2, and 13.0 for total retina scan time; 2.0, 2.3, and 2.5 for cornea grade; and 2.7, 2.9, and 2.5 for retina grade. CONCLUSIONS AND CLINICAL RELEVANCE The RB facilitated globe akinesia and improved the percentage of scans in frame and region of interest accuracy for retinal imaging via OCT in horses. Retrobulbar blocks improved clinical image acquisition while minimizing motion artifact.

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Anesthetic Management for Ocular Interventions

Martins¹,

Martin‐Flores²

2022

Equine Anesthesia and Co‐Existing Disease

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

Cited by 7 publications

References 21 publications

Comparing Blind and Ultrasound-Guided Retrobulbar Nerve Blocks in Equine Cadavers: The Training Effect

Comparing Blind and Ultrasound-Guided Retrobulbar Nerve Blocks in Equine Cadavers: The Training Effect

Comparison of image quality of corneal and retinal optical coherence tomography using sedation and general anesthesia protocols with or without retrobulbar anesthesia in horses

Anesthetic Management for Ocular Interventions

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