Comparison of Bupivacaine Plus Magnesium Sulfate and Ropivacaine Plus Magnesium Sulfate Infiltration for Postoperative Analgesia in Patients Undergoing Lumbar Laminectomy: A Randomized Double-blinded Study

AIM: The objective of this study was to assess and compare the analgesic duration of local infiltration of bupivacaine plus magnesium sulfate and ropivacaine plus magnesium sulfate for postoperative analgesia in patients undergoing lumbar laminectomy. STUDY DESIGN: A randomized, prospective, double-blinded single hospital, comparative study. METHODS: Sixty adult patients of the American Society of Anesthesiologists physical Status I and II were randomly allocated into two Groups BM and RM, comprising 30 and 31 patients. Postlumbar laminectomy, the study drug was locally infiltrated into the paravertebral muscles on either side before skin closure. Group BM was given 20 ml of 0.25% bupivacaine combined with 500 mg of magnesium sulfate (constituted with normal saline [NS]), and Group RM was given 20 ml of 0.25% ropivacaine combined with 500 mg of magnesium sulfate (constituted with NS). Postoperative visual analog scale pain score was assessed hourly for the first 24 h postoperatively. Duration of postoperative analgesia, rescue analgesia consumption and side effects were also recorded. STATISTICAL ANALYSIS: Comparison of data between the groups was done with SPSS 21.0© using independent t-test, Chi-square test, and Mann–Whitney U-test accordingly. P<0.05 was considered statistically significant. RESULTS: Time to first analgesic consumption was significantly longer in Group BM (7.3 ± 0.46 h) compared to Group RM (6.6 ± 0.69 h) (P < 0.05). The consumption of nalbuphine rescue analgesic was significantly higher in Group RM (15.33 ± 5.07 mg) compared to Group BM (12 ± 4.07 mg) (P < 0.05). CONCLUSION: Wound infiltration with bupivacaine and magnesium sulfate compared to ropivacaine and magnesium sulfate provided longer duration of postoperative analgesia and significantly reduced postoperative opioid consumption in patients undergoing lumbar laminectomy.