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Animals : an open access journal from MDPI2022; 12(2); 154; doi: 10.3390/ani12020154

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

Abstract: 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 = 0.056; groups 1 and 3 = 0.069, groups 2 and 3 = 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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Publication Date: 2022-01-09 PubMed ID: 35049776PubMed Central: PMC8772549DOI: 10.3390/ani12020154Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research compared the effectiveness and safety of two anesthesia techniques in horse eye surgery: a blind retrobulbar nerve block (RNB) and an ultrasound-guided RNB. The study also investigated how training can influence the accuracy of using ultrasound guidance. The results showed no significant difference in accuracies or complications between the techniques, but showed potential for improvement with further training in ultrasound guidance.

Details of the Research

  • The research was conducted on Twenty-two equine (horse) cadavers. The cadavers were divided into three groups: those that received blind RNBs, those that received ultrasound-guided RNBs, and those that received blind RNBs after ultrasound-guided training.
  • Each RNB was performed by the same two operators, who had no prior experience. A combination of contrast medium and methylene blue dye were injected. Needle positioning and the proximity of the contrast medium to the optic foramen were evaluated using Computerized Tomography (CT). Dissection was used to evaluate dye spreading.

Research Results

  • In the first group (blind RNBs without training), 37.5% of the injections were optimally placed in the central position of the periorbita, a section of the eye. In the second group (ultrasound-guided RNBs), this figure rose to 75%. In the final group (blind RNBs post-training), the figure was 71.4%.
  • There was no significant difference in needle position between the groups. Similarly, the average distribution distance of the contrast medium was not significantly different across all groups.
  • In the first group, there were 18.75% intraocular injections, compared to 0% in the second group and 7.1% in the third group. Despite the apparent trend, the differences were not statistically significant.
  • While no significant changes in accuracy or complication levels were seen with ultrasound guidance, there was a trend towards potentially significant improvements with additional training in this technique.

Implication of Results

  • The use of ultrasound-guided RNB compared to blind RNB did not significantly improve accuracy nor decrease complications in equine ophthalmic surgeries, according to the parameters of this study.
  • However, the process did show a non-significant trend towards improved results with ultrasound-guided training, which suggests that further large-scale studies might confirm the effectiveness of such training.

Cite This Article

APA
Hermans H, Lloyd-Edwards RA, Ferrão-van Sommeren AJH, Tersmette AA, Schouten JCM, Serra Bragança FM, van Loon JPAM. (2022). Comparing Blind and Ultrasound-Guided Retrobulbar Nerve Blocks in Equine Cadavers: The Training Effect. Animals (Basel), 12(2), 154. https://doi.org/10.3390/ani12020154

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 12
Issue: 2
PII: 154

Researcher Affiliations

Hermans, Hanneke
  • Department of Clinical Sciences, Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112-114, 3584 CM Utrecht, The Netherlands.
Lloyd-Edwards, Ralph A
  • Department of Clinical Sciences, Diagnostic Imaging, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 108, 3584 CM Utrecht, The Netherlands.
  • VetCT, St John's Innovation Centre, Cowley Road, Cambridge CB4 0WS, UK.
Ferrão-van Sommeren, Aukje J H
  • Diergeneeskundig Centrum Maas en Waal, Klepperheide 16, 6651 KM Druten, The Netherlands.
Tersmette, Anne A
  • Department of Clinical Sciences, Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112-114, 3584 CM Utrecht, The Netherlands.
Schouten, Jacobine C M
  • Department of Clinical Sciences, Anatomy and Physiology, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CM Utrecht, The Netherlands.
Serra Bragança, Filipe M
  • Department of Clinical Sciences, Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112-114, 3584 CM Utrecht, The Netherlands.
van Loon, Johannes P A M
  • Department of Clinical Sciences, Equine Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 112-114, 3584 CM Utrecht, The Netherlands.
  • Sporthorse Medical Diagnostic Centre (SMDC), Hooge Wijststraat 7, 5384 RC Bernheze, The Netherlands.

Conflict of Interest Statement

The authors declare no conflict of interest.

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Citations

This article has been cited 1 times.
  1. Marzok M, Almubarak A, Elkhidr RY, Elkawi MA, El-Sherif MW. Ultrasound-guided peribulbar block in dromedary camels: a descriptive cadaveric study. BMC Vet Res 2025 Jul 2;21(1):431.
    doi: 10.1186/s12917-025-04891-wpubmed: 40605014google scholar: lookup
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