Use of intrathecal midazolam or fentanyl as an adjunct to spinal anaesthesia with bupivacaine for lower limb surgery: A randomised controlled study.

Background: Intrathecal adjuncts have been used to prolong the quality and duration of subarachnoid anaesthesia. Midazolam given intrathecally is reported to have antinociceptive properties. The purpose of this study was to compare intrathecal midazolam with fentanyl for pain relief and patient comfort.

Methods: In this prospective, double-blind, randomised controlled trial, 90 patients for lower limb surgeries were randomly allocated to three groups: "control group" (3 ml 0.5% heavy bupivacaine), "fentanyl group" (3 ml 0.5% bupivacaine + 10 mcg fentanyl) and "midazolam group" (3 ml 0.5% bupivacaine + 1 mg midazolam). Level, duration, and quality of blocks were compared along with the duration and quality of postoperative analgesia. Haemodynamic stability and any associated complications were also noted.

Results: Onset of block was fastest in Group C (28.5 ± 13.48 min) vis-a-vis other groups (35.5 ± 26.05 min for Group "F" and 28.5 ± 23.68 min for Group "M"; P = 0.51). Duration of block was comparable in all groups (130.5 ± 39.3 min Group "C"; 126.5 ± 44.0 min Group "F" and 129.5 ± 45.7 min Group "M"; P > 0.5).Addition of adjuncts did not significantly defer the appearance of pain. Intensity of pain was lower in Group "M". Average VAS scores were lower for Group "M" (3-4) than those for Group "C" (4-5) and Group "F" (4-6).Majority of patients required at least one dose of rescue analgesic; however, those receiving fentanyl reported better quality of postoperative analgesia than those in midazolam group.

Conclusion: Adjuvants improve quality of postoperative analgesia (fentanyl better than midazolam).