Background and Goal of Study: Peribulbar block (PB) is a safe and easily performed regional anaesthetic tecnique. Some factors may influence the levels of akinesia in PB, namely the volume (V) of the local anaesthetic injected. On the other hand, large volumes may affect intra-ocular pressure. The goal of our study is to compare akinesia after PB with the volume of local anaesthetic, number and the site of injection and complications.
Materials and Methods: A prospective observational study was performed between May and October 2016. With 22mm needle, the PB was done with 1%ropivacaine or 1%ropivacaine+2%lidocaine with injection site at inferotemporal (IT), superonasal (SN), superotemporal (ST) and/or lacrimal caruncle (LC). A pressure of 30mmHg was applied for 5-10 min and akinesia of each rectus muscle was evaluated 15 minutes after injection as “0-total”, “1-partial”, “2-no akinesia”.
Results and Discussion: Sixty-seven patients were recorded, mean age of 72.52 years; 49.3% female; 68.7% ASA 2, 29.9% ASA 3 and 1.5% ASA 4. The surgical procedures were 14.9% vitrectomies (VPP), 76.1% phacoemulsification with intraocular lens implantation (PIL), 3% VPP and PIL, 4.5% trabulectomy and 1.5% ahmed valve revision. A mean of 2.13 injections were performed. The mean volume at SN was 1.79mL, IT 3.31mL, LC 1.02mL, ST 0.75mL and total volume (Tv) 5.23mL.
Internal akinesia 0 was found in 43,3%, 1 in 37,3% and 2 in 19,4%; external akinesia 0 in 38,8%, 1 in 43,3% and 2 in 17,9%; inferior akinesia 0 in 56,7%, 1 in 31,3% and 2 in 11,9%; superior akinesia 0 in 56,7%, 1 in 23,4% and 2 in 14,9% of all patients. For all quadrants, 0 was observed in 23.9%, 1 in 68.6% and 2 in 7.5%. 
With the univariate analysis we verify that, for the superior akinesia the IT volume was statistically significant (p 0.006), for the external akinesia the IT volume (p 0.0001) and the Tv (p 0.002) were statistically significant. For the type of procedure, the Tv (p 0.004), number of injections (p 0.001) and SN volume (p 0.003) had statistical significance. There were no block-related complications.
Conclusion(s): Our results show that the IT volume is important for superior and external akinesia and the Tv for external akinesia. About the type of procedure, the SN volume, the Tv and the number of injections affect the degree of akinesia. Multicenter studies with larger population and alternative techniques of PB are necessary to improve the degree of akinesia.

Peribulbar block with akinesia: how to do it?