Retrobulbar dexmedetomidine decreases the MLAC of ropivacaine in vitreoretinal surgery in children.

Abstract

Dexmedetomidine can prolong the duration of local anesthetics, but the effect of retrobulbar dexmedetomidine on the potency of ropivacaine for retrobulbar block has not been investigated. Our study was designed to determine the effect of retrobulbar dexmedetomidine on ropivacaine for retrobulbar block in children. A group of 90 children aged 10-16 years scheduled for vitreoretinal surgery who received retrobulbar block were randomly assigned to 1 of 3 groups: group L (retrobulbar ropivacaine), group LD1 (ropivacaine plus 0.5 µg.kg-1 dexmedetomidine), or group LD2 (ropivacaine plus 1 µg.kg-1 dexmedetomidine). The minimum local anesthetic concentration (MLAC) was determined according to a Dixon-Massey protocol. The primary endpoint of the study was MLAC. Secondary outcomes were duration of postoperative analgesia, postoperative pain scores, dexmedetomidine side effects, and time to hospital discharge. The MLAC values of retrobulbar ropivacaine were 0.314%, 0.259%, and 0.246% in groups L, LD1, and LD2, respectively. The median (interquartile range) durations of analgesia in the postoperative period were 66 (54-117), 89 (40-157), and 168 (120-194) minutes in groups L, LD1, and LD2, respectively (L vs LD1 or LD2, p<0.05). Wake-up time was significantly increased in groups LD1 and LD2. Retrobulbar dexmedetomidine reduces the MLAC values of ropivacaine and improves postoperative analgesia in children without any neurologic side effects.