Featured RETINA Paper: Comparison of Retrobulbar, Sub-tenon’s Anesthesia and Medial Canthus Episcleral Anesthesia for 25-gauge Posterior Vitrectomy

Summarized by:
Avni P. Finn MD, MBA
Assistant Professor, Vanderbilt Eye Institute
Nashville, TN

Original article by: Derri Roman-Pognuz, Giuseppe Scarpa, Gianni Virgili, Erik Roman-Pognuz, Giacomo Paluzzano, and Fabiano Cavarzeran

Vitreoretinal surgery has traditionally been performed under general anesthesia, but more recently there is an increase in the use and popularity of local anesthesia. Local anesthesia allows the rapid return to ambulation, the ability to perform outpatient surgery, avoids complications that may be associated with intubation and general anesthesia, and allows the patient to immediately position post-operatively. These authors compared the efficacy and safety of three methods of local anesthesia: retrobulbar anesthesia, sub-tenon’s anesthesia, and medial canthus episcleral anesthesia in patients undergoing 25-gauge pars plana vitrectomy.

This was a retrospective study of 90 patients who underwent surgery between November 2017 and June 2019 in Italy. The patients were matched by sex and age into the three local anesthesia groups. Patients were only included if they underwent surgery for epiretinal membrane, macular hole, or non-clearing vitreous hemorrhage. They were excluded if they had prior ocular surgery (other than cataract surgery), if the chart noted poor cooperation, or if they received any narcotic or amnestic agents during surgery.

5 mL of 2% mepivacaine hydrochloride was used for each type of block and the blocks were given as follows: a retrobulbar block (RB) was given with a 27-gauge 31 mm needle; sub-tenon’s anesthesia (STA) was given after an incision was made in the inferonasal quadrant and blunt dissection of sub-tenon’s layer was performed; and medial canthus episcleral anesthesia (MCEA) was given via a 26-gauge short bevel needle between the eyeball and semilunaris fold medially. For each block, 1000 mg/100 ml of paracetamol was also administered.

Figure shows the percentage of perfect akinesia by the technique and time after administration of anesthesia.

RB and STA showed similar globe akinesia at 2 and 5 minutes and outperformed MCEA at those timepoints. By 10 minutes, retrobulbar block outperformed both STA and MCEA. Ten minutes after anesthesia administration, the odds ratio of a complete block was 0.13 for MCEA and 0.18 for STA compared to a retrobulbar block. This was statistically significant for both comparisons. Both RB and STA blocks showed no statistically significant difference when comparing akinesia among the different rectus muscles. However, MCEA showed significant difference with limited akinesia of the lateral rectus compared to the superior, medial and inferior rectus muscles.

The three techniques did not have statistically significant difference in pain perception during the administration of anesthesia, although pain perception was somewhat more favorable among those receiving STA and MCEA compared to RB. RB outperformed MCEA when patients were asked about perioperative pain, (p=0.03). Sub-tenon’s anesthesia did not show a statistically significant different effect on pain compared to both RB and MCEA.

This retrospective study of local anesthesia techniques for vitrectomy surgery shows that all three block techniques allowed for safe surgery without the use of adjunctive intravenous narcotics or amnestics. However, retrobulbar blocks allowed for the greatest akinesia, followed by sub-tenon’s blocks. There was no significant difference in perioperative pain among STA and RB but RB block did outperform MCEA. This study is limited by its retrospective nature and the associated biases from the design and small sample size, which includes recall bias on the part of the patients as it relates to perioperative pain. Additionally, three different surgeons performed the blocks, allowing for some variation in technique. Further prospective randomized studies may be helpful to elucidate optimal routes of local anesthesia and dosage for vitrectomy surgery.