Supplementation of retrobulbar block with clonidine in vitreoretinal surgery: effect on postoperative pain

Study Objective

To evaluate the effect of clonidine when added to local anesthetics on duration of postoperative analgesia during retrobulbar block.

Design

Prospective, randomized controlled trial.

Setting

Operating room and Postanesthesia Care Unit of a university-affiliated hospital.

Subjects

80 ASA physical status 1, 2, and 3 patients undergoing vitreoretinal surgery with or without scleral buckling.

Interventions

Patients in the control group (n = 40) received a retrobulbar block with 4.5 mL of lidocaine-bupivacaine and 0.5 mL of saline. Clonidine group patients (n = 40) received 4.5 mL of lidocaine-bupivacaine and 0.5 μg/kg of clonidine in a 0.5 mL volume.

Measurements

The time to first analgesic request, frequency of postoperative pain, and number of postoperative analgesic requests per patient were assessed.

Main Results

37 patients in the control group (92.5%) versus 24 patients (60%) in the clonidine group reported pain postoperatively (P = 0.001), with a shorter time to first analgesic request noted in the control group (4.9 ± 3 vs 11.9 ± 5.3 hrs; P < 0.001). The median number of postoperative analgesic requests per patient during the first 24 hours was higher in the control group than the clonidine group [2 (0-3) vs. 1 (0-3); P < 0.001].

Conclusions

The addition of clonidine 0.5 μg/kg to the local anesthetics of a retrobulbar block for vitreoretinal surgery decreases the frequency of postoperative pain and prolongs the time of analgesia.