Effects of intrathecal midazolam in spinal anaesthesia: a prospective randomised case control study

Subarachnoid block with local anaesthetics and adjuvants has been extensively used for surgery. Intrathecal midazolam produces antinociception and potentiates the effect of local anaesthetics. We compared intrathecal bupivacaine with and without midazolam to assess its effect on the duration of sensory block, motor block and pain relief.

A total of 100 patients scheduled for elective lower abdominal, lower limb and gynaecological procedures were selected to participate in this prospective, randomised, double-blind study. Patients were randomly allocated into two groups for intrathecal drug administration. Group B received 3 mL 0.5 percent bupivacaine with 0.4 mL saline, and group BM received 3 mL 0.5 percent bupivacaine and 0.4 mL (2 mg) midazolam mixture. The onset, duration of sensory/motor block, time to first rescue analgesia and side effects were noted.

Demographic profile and duration of surgery were comparable between the two groups. The onset of sensory (4.8 versus 4.6 min) and motor block (5.9 versus 6 min) was also comparable between the groups. The duration of sensory blockade was prolonged in the midazolam group (90.8 versus 115.8 min, p-value is 0.001), while the duration of motor blockade was comparable (151.8 versus 151.3 min, p-value is 0.51). The duration of effective analgesia was significantly longer in the midazolam group compared to the control group (121.3 versus 221.1 min, p-value is 0.001). Sedation score was comparable in the two groups.

The addition of preservative-free midazolam to bupivacaine intrathecally resulted in prolonged postoperative analgesia without increasing motor block.