Study Summary

Eighty-six adults undergoing elective lower limb orthopaedic surgery under epidural anaesthesia were analysed after randomisation to receive epidural 0.5% bupivacaine with magnesium sulphate (Group M, n=29), bupivacaine with fentanyl (Group F, n=29), or bupivacaine with saline (control, Group C, n=28). The primary outcome was time to onset of sensory block at the T8 dermatome. Secondary outcomes included time to complete motor block (Bromage 3), duration of epidural anaesthesia (from injection to first top-up), time to a postoperative Numerical Rating Scale (NRS) pain score of 3, side-effect profile, and patient satisfaction. Outcomes were assessed intraoperatively and up to discharge from the recovery room (approximately 2–3 hours postoperatively). Overall, the results of the study revealed that magnesium as an epidural adjuvant produced the fastest sensory and motor block onset, the longest duration of anaesthesia and analgesia, and the highest patient satisfaction scores, without increasing haemodynamic instability or other complications relative to fentanyl or control. These findings suggest that epidural magnesium sulphate is a superior non-opioid adjuvant to bupivacaine for lower limb orthopaedic surgery.