Efficacy of intrathecal midazolam in potentiating the analgesic effect of intrathecal fentanyl in patients undergoing lower limb surgery.

Introduction: The intrathecal administration of combination of drugs has a synergistic effect on the subarachnoid block characteristics. This study was designed to study the efficacy of intrathecal midazolam in potentiating the analgesic duration of fentanyl along with prolonged sensorimotor blockade. Materials and Methods: In a double-blind study design, 75 adult patients were randomly divided into three groups: Group B, 3 ml of 0.5% hyperbaric bupivacaine; Group BF, 3 ml of 0.5% hyperbaric bupivacaine + 25 mcg of fentanyl; and Group BFM, 3 ml of 0.5% hyperbaric bupivacaine + 25 mcg of fentanyl + 1 mg of midazolam. Postoperative analgesia was assessed using visual analog scale scores and onset and duration of sensory and the motor blockade was recorded. Results: Mean duration of analgesia in Group B was 211.60 ± 16.12 min, in Group BF 420.80 ± 32.39 min and in Group BFM, it was 470.68 ± 37.51 min. There was statistically significant difference in duration of analgesia between Group B and BF ( P = 0.000), between Group B and BFM ( P = 0.000), and between Group BF and BFM ( P = 0.000). Both the onset and duration of sensory and motor blockade was significantly prolonged in BFM group. Conclusion: Intrathecal midazolam potentiates the effect of intrathecal fentanyl in terms of prolonged duration of analgesia and prolonged motor and sensory block without any significant hemodynamic compromise.