Intraoperative magnesium infusion as an adjuvant to a bilateral single-injection thoracic paravertebral block for laparoscopic cholecystectomy

Background Magnesium has antinociceptive effects. This prospective randomized, double-blinded, controlled study was designed to examine whether an intraoperative administration of intravenous magnesium with a bilateral thoracic paravertebral block (PVB) enhances postoperative analgesia while reducing opioid consumption and opioid-related side effects. Methods Fifty-nine patients undergoing laparoscopic cholecystectomy were administered a bilateral single-injection PVB at the level of T5 with 25 ml bupivacaine 0.5% before induction of general anesthesia. Patients were assigned to two groups. Group M (magnesium group) received a loading dose of magnesium sulphate 30 mg/kg in 100 ml of normal saline over 10 min, followed by an infusion of 10 mg/kg/h till the end of surgery. The control group (group C) received the same volume of normal saline as a loading dose, followed by a continuous infusion. In both groups, postoperative pain was initially controlled by intravenous fentanyl titration and then fentanyl patient-controlled analgesia. Cumulative and patient-controlled analgesia fentanyl consumption, pain intensities, sedation scores, cardiovascular and respiratory variables and opioid-related adverse effects were recorded for 36 h after the operation. Results Compared with the control group, patients in the magnesium group required 23.6% less fentanyl during the first 36 h postoperatively, with significantly better visual analogue scale scores, less incidence of pruritis (6 vs. 15 patients, respectively; P= 0.0376) and longer time to first analgesic request [413 (56) min vs. 247 (46) min; P 0.001]. Fewer patients in group M experienced nausea and vomiting than those in group C (7 vs. 18 patients, respectively; P= 0.0116). Conclusion A continuous intravenous magnesium infusion may be a useful adjuvant to PVB for patients undergoing laparoscopic cholecystectomy.