Comparative evaluation of intrathecal midazolam and low dose clonidine: Efficacy, safety and duration of analgesia. A randomized, double blind, prospective clinical trial

Background: The study was planned to assess the comparative efficacy, safety and duration of analgesia produced by low-dose clonidine and midazolam when used as adjuvant for spinal anesthesia. Materials and Methods: This is a randomized, participant and observer blind, prospective, parallel group clinical trial. Fifty ASA grade I and II patients posted for lower abdominal surgery were randomly allocated into two groups. BC group received spinal clonidine 30 mu g and BM group received preservative-free midazolam 2 mg with 15 mg hyperbaric bupivacaine. Postoperative analgesia, analgesic requirement in 24 hours, onset and duration of block, hemodynamic stability and adverse effects were observed (P<0.05 - considered significant, P<0.01 considered highly significant). Results: The duration of postoperative analgesia was prolonged in BM group (391.64 +/- 132.98 min) than BC group (296.60 +/- 52.77 min) (P<0.01). The mean verbal rating pain score was significantly less in BM group than BC group (P<0.01). The number of analgesic doses in 24 hours were significantly less in BM group (P<0.05). Nine patients (36%) in BC group required additional analgesia as against none in BM group (P<0.01). The onset of sensory block and peak sensory level was significantly earlier in BM group as compared to BC group. Duration of sensory block was longer in BM group (P<0.05). Subjects in BC group(36%) had bradycardia as compared to none in BM group (P<0.01). Hypotension was observed in 44% patients in BC group as against 16% in BM group (P<0.05). Conclusion: Postoperative analgesia with clonidine is short lived with some bradycardia. Intrathecal midazolam provides superior analgesia without clinically relevant adverse effects.