Comparison of four peribulbar anaesthetic techniques: a preliminary study in equine cadavers.

The research investigated four different peribulbar anesthetic techniques using equine cadavers to see which methods were more likely to provide effective regional anesthesia. The preliminary results suggest that the method involving combined ventrolateral and dorsolateral peribulbar injections of 40 mL (VD-40) is more likely to achieve this result, but potential complications require further studies.

Research Context

• The research extends the knowledge of peribulbar anesthetic techniques, which are critical in ocular surgeries for ensuring pain-free and motionless conditions during operations. In this study, four different peribulbar anesthetic techniques were compared.

Methodology

• The researchers conducted a prospective experimental study on 12 equine cadaver heads and 24 eyes.
• Each of the 24 orbits underwent a different injection technique, with 6 orbits for each method. The techniques included 20 mL ventrolateral peribulbar injection (V-20), 20 mL dorsolateral peribulbar injection (D-20), combined ventrolateral and dorsolateral peribulbar injections of 10 mL each (VD-20), or 20 mL each (VD-40).
• The injected solution was a 1:4 mixture of a contrast medium and saline (CM).
• The researchers used computed tomography to assess and score the distribution of the CM at various locations including the base of the extraocular muscle cone (EOMC), within the EOMC, and around the optic nerve, before and after applying pressure on the periorbital area.
• The potential achievement of locoregional anesthesia was assessed based on two criteria and scored as ‘likely’, ‘possible’, or ‘unlikely’.
• The researchers used the Kruskal-Wallis analysis of variance to compare the CM distribution scores between the different injection techniques, while the Mann-Whitney U test was used for post hoc comparisons between groups when required.

Findings and Conclusion

• The results indicated that the possible CM distribution within the EOMC and around the optic nerve circumference could only be detected after pressure application in 7 out of the 24 orbits, and it was never considered ‘likely’, either before or after pressure application.
• CM distribution at the base of the EOMC was likely to provide regional anesthesia in 50% (V-20), 0% (D-20), 33% (VD-20), 100% (VD-40) and in 66% (V-20), 16% (D-20), 50% (VD-20), 100% (VD-40) before and after applying pressure, respectively.
• The study concluded that complete regional anesthesia is more likely to be achieved using the VD-40 technique. However, due to potential complications, the authors suggested exercising caution and called for further in vivo studies to evaluate the technique’s efficacy.