The Effect of Low-Dose Dexmedetomidine as an Adjuvant to Levobupivacaine in Patients Undergoing Vitreoretinal Surgery Under Sub-Tenon's Block Anesthesia.

Abstract

This study evaluated the motor and sensory block durations and the postoperative analgesic effects of adding dexmedetomidine to levobupivacaine for sub-Tenon's block anesthesia in patients undergoing vitreoretinal surgery. Motor and sensory block durations were considered as a primary end point. Sixty ASA physical status I to III patients subjected to vitreoretinal surgery under sub-Tenon's block anesthesia were randomly divided equally into 2 groups, depending on the local anesthesia solution used, to receive 4 mL of 0.75% levobupivacaine plus 15 IU hyaluronidase diluted with 1 mL normal saline (group L) or 4 mL of 0.75% levobupivacaine plus 15 IU hyaluronidase and 20 μg dexmedetomidine diluted with 1 mL normal saline (group LD). The total volume of the local anesthesia solution used was 5 mL. Motor block and sensory block durations were evaluated until the return of normal motor and sensory functions. The sedation level was assessed during the surgery period and 24 hours postoperatively, together with the degree of postoperative pain. The total diclofenac consumption (milligrams) and the number of patients (%) who required tramadol were recorded. The sleep quality of the first postoperative night was assessed using the Consensus Sleep Diary. Dexmedetomidine provided significantly longer motor block duration (371.90 ± 48.10 vs 264.13 ± 41.48 minutes, P = 0.001) and significantly longer sensory block duration (499.10 ± 51.76 vs 344.33 ± 45.46 minutes, P = 0.001) compared with levobupivacaine alone. Furthermore, the patients in the dexmedetomidine group achieved significantly (P < 0.0001) greater levels of sedation during the surgery period and for 12 hours postoperatively together with significantly (P < 0.0001) lower values of verbal numeric rating scale of pain between the periods from 4 to 12 hours postoperatively compared with the patients in the levobupivacaine group. There was significantly (P = 0.001) less diclofenac consumed (mg) in the dexmedetomidine group. The patients in the dexmedetomidine group reported significantly higher rates of good sleep quality on the first postoperative night (70%) compared with those in the levobupivacaine group (30%; P < 0.0001). For patients undergoing vitreoretinal surgery, adding 20 μg of dexmedetomidine to levobupivacaine for sub-Tenon's block anesthesia in vitreoretinal surgery extended the motor and sensory block durations and provided more effective postoperative analgesia with improvement in the sleep quality in the first postoperative night compared with levobupivacaine alone.