Effect of Volume Used in Sub-Tenon’s Anesthesia on Efficacy and Intraocular Pressure in Vitreoretinal Surgery

Abstract

Purpose: To compare the effect of volumes used in sub- Tenon’s anesthesia on efficacy and intraocular pressure (IOP) in vitreoretinal surgery. Methods: A prospective clinical trial was conducted on patients undergoing sub-Tenon’s anesthesia for vitreoretinal surgery. Patients were randomized to receive either 3-, 5- or 7-ml volumes of anesthetic solution. IOP were measured immediately prior to injection, immediately after injection and at 2, 5 and 10 min after injection. Pain scores were assigned using a numerical visual analogue scale immediately after surgery, and again on postoperative day 1. Results: A total of 108 patients (119 eyes) were studied, including 35 eyes in the 3-ml group, 48 eyes in the 5-ml group, and 36 eyes in the 7-ml group. There were significant elevations in mean IOP following injection in all groups, and a trend for larger rises in IOP with larger volumes of anesthesia (p < 0.01). Mean IOP were elevated after injection, and reduced at all time intervals. However, the reduction in the 3-ml group took levels to preinjection amounts. There were no significant differences in patient-reported pain scores among the groups when assessed immediately after surgery or on postoperative day 1. The incidence of chemosis and high IOP elevations (≥40 mm Hg) were more frequent in the 7-ml group (p < 0.05). Conclusions: Sub-Tenon’s anesthesia is effective in vitreoretinal surgery. It would appear that a 3–5-ml volume of anesthetic is safe, when considering the associated complications.

Two-quadrant high-volume sub-Tenon's anaesthesia for vitrectomy: a randomised controlled trial

“…These differing responses in IOP might be due to the differing ethnic patient populations being investigated. Sohn et al suggested that their findings might in part be due to the smaller orbital volume and tighter orbital septum found more commonly among the Asian population 26. The reduction in IOP observed in our study and that of Alwitry et al may be a direct pharmacological effect of the local anaesthetic agent on ocular blood flow, or secondary to a reduction in aqueous production due to an effect on the ciliary ganglion, or possibly because of a reduction in extraocular muscle tone 17…”

“…IOP is known to rise with increasing volume of local anaesthetic agent used for peribulbar and retrobulbar anaesthesia techniques 24. There are few studies investigating the relationship between volume and IOP after sub-Tenon's anaesthesia 17 25 26. There are no comparative data observing the effect of injecting 10 ml of local anaesthetic into the sub-Tenon space on IOP in the current literature.…”

“…Alwitry et al used 5 ml of injectate via the inferonasal quadrant and also observed a small but insignificant rise in IOP followed by a significant reduction in IOP 17. Sohn et al , however, found significant rises in IOP with 3 ml, 5 ml and 7 ml of injectate injected via the inferonasal quadrant alone 26. These differing responses in IOP might be due to the differing ethnic patient populations being investigated.…”

Sub-Tenon's anesthesia: an update

“…A study by Sohn et al found that injectate volumes above 5 mL produced significant rises in IOP 14. Other work by Gil et al using a 2-quadrant technique with two 5 mL injections showed a prolonged duration of analgesia with no significant rise in IOP in comparison to a single 5 mL injection, although there was a higher incidence (52%) of chemosis 15…”

Effectiveness of single injection sub-Tenon’s block for Pars Plana Vitrectomy and associated procedures

“…However, there are inherent increased risk of morbidities related to higher volume of local anaesthetic agent and multiple injections such as changes in shape and gaze of the globe, myotoxicity, proptosed orbit, conjunctival scarring and increased intraocular pressure. 11 Rise in intraocular pressure can occur in patients with smaller orbital volume and tighter orbital septum -this commonly seen amongst the Asian population [21].…”