Fentanyl versus midazolam as additive to local anesthetic mixture for peribulbar block during posterior segment surgery in adult patients a prospective randomized double-blind study

Objectives
To evaluate analgesic and hemodynamic outcome of fentanyl or midazolam as additives to local anesthetic mixture (LAM) for peribulbar block (PBB) during posterior chamber surgery.
Methods
One hundred thirty-two ASA status I to III adult patients aged 50–75 years scheduled for posterior segment surgery (intraocular foreign body and elective vitrectomy) were enrolled in this prospective, randomized, double-blind trial from which 12 patients were excluded. After signing a written fully informed consent for study participation, patients were grouped into 3 groups (40 patients in each group); group C received local anesthetic mixture plus 1 ml plain saline, group F received local anesthetic mixture plus 25 μg fentanyl in 1 ml saline and group M received local anesthetic mixture plus 1 mg midazolam in 1 ml saline. The primary outcome was the onset time of eyelid and globe akinesia. Also, the duration of the block was assessed in the three studied groups. Intraoperative and postoperative hemodynamic measures were assessed. Postoperative analgesia was hourly-assessed using Visual analogue scale (VAS) and rescue analgesia was provided at visual analogue score of > 3.
Results
The number of patients who had fast eyelid and globe akinesia was significantly higher with significantly lower total 15-min score in group F than the other groups. Intraoperative and postoperative hemodynamic measures were non-significantly different between studied groups. Duration of the block was significantly longer in groups F and M than group C with significantly longer duration in group F. The number of patients who required postoperative rescue analgesia was significantly lower with significantly lower number of requests in group F than the other groups.
Conclusion
Additives to local anesthetic mixture during peribulbar block provided satisfactory anesthetic outcome than local anesthetic mixture alone. Fentanyl was superior to midazolam in terms of significantly speed up onset, longer block duration with significantly longer postoperative analgesia and lesser consumption of rescue analgesia. Both additives provided adjusted hemodynamic measures comparable to the control group.
Trial registration
Pan African Clinical Trials Registry () registered 03/08/2017 retrospectively.