The effect of magnesium sulfate on postoperative pain in patients undergoing major abdominal surgery under remifentanil-based anesthesia

Unravelling the analgesic effects of perioperative magnesium in general abdominal surgery: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Prior research has established the effectiveness of magnesium in relieving postoperative pain. This article aims to evaluate magnesium sulfate for perioperative analgesia in adults undergoing general abdominal surgery under general anesthesia.

OBJECTIVE

The primary aim was to assess pain scores at 6 and 24 hours postoperatively in patients receiving magnesium sulfate vs. the control group. Secondary outcomes were postoperative opioid consumption, perioperative complications, and time to rescue analgesia.

METHODS

A comprehensive database search identified studies comparing magnesium sulfate with control in adults undergoing general anesthesia for general abdominal surgery. Using random-effects models, data were presented as mean ± Standard Deviation (SD) or Odds Ratios (OR) with corresponding 95% Confidence Intervals (95% CI). A two-sided p-value < 0.05 was considered statistically significant.

RESULTS

In total, 31 studies involving 1762 participants met the inclusion criteria. The magnesium group showed significantly lower postoperative pain scores at both early (within six hours) and late (up to 24 hours) time points compared to the control group. The early mean score was 3.1 ± 1.4 vs. 4.2 ± 2.3, and the late mean score was 2.3 ± 1.1 vs. 2.7 ± 1.5, resulting in an overall Mean Difference (MD) of -0.72; 95% CI -0.99, -0.44; p < 0.00001. The magnesium group was associated with lower rates of postoperative opioid consumption and shivering and had a longer time to first analgesia administration compared to the saline control group.

CONCLUSION

Magnesium sulfate administration was linked to reduced postoperative pain and opioid consumption following general abdominal surgery.

Effectiveness of Magnesium in Preventing Shivering in Surgical Patients: A Systematic Review and Meta-analysis

BACKGROUND

Clinical trials regarding the antishivering effect of perioperative magnesium have produced inconsistent results. We conducted a systematic review and meta-analysis with Trial Sequential Analysis to evaluate the effect of perioperative magnesium on prevention of shivering.

METHODS

We searched PubMed, EMBASE, Web of Science, Cochrane Central Register of Controlled Trials, and 2 registry sites for randomized clinical trials that compared the administration of magnesium to a placebo or no treatment in patients undergoing surgeries. The primary outcome of this meta-analysis was the incidence of shivering. The incidence of shivering was combined as a risk ratio with 95% CI using a random-effect model. The effect of the route of administration was evaluated in a subgroup analysis, and Trial Sequential Analysis with a risk of type 1 error of 5% and power of 90% was performed. The quality of each included trial was evaluated, and the quality of evidence was assessed using the Grading of Recommendation Assessment, Development, and Evaluation approach. We also assessed adverse events.

RESULTS

Sixty-four trials and 4303 patients (2300 and 2003 patients in magnesium and control groups, respectively) were included. The overall incidence of shivering was 9.9% in the magnesium group and 23.0% in the control group (risk ratio, 0.42; 95% CI, 0.33-0.52). Subgroup analysis revealed that the incidence of shivering was lower with IV (risk ratio, 0.29; 95% CI, 0.29-0.54; Grading of Recommendation Assessment, Development, and Evaluation, moderate), epidural (risk ratio, 0.24; 95% CI, 0.13-0.43; Grading of Recommendation Assessment, Development, and Evaluation, low), and intrathecal administration (risk ratio, 0.64; 95% CI, 0.43-0.96; Grading of Recommendation Assessment, Development, and Evaluation, moderate). Only trials with low risk of bias were included for Trial Sequential Analysis. The Z-cumulative curve for IV magnesium crossed the Trial Sequential Analysis monitoring boundary for benefit even though only 34.9% of the target sample size had been reached. The Z-cumulative curve for epidural or intrathecal administration did not cross the Trial Sequential Analysis monitoring boundary for benefit. No increase in adverse events was reported.

CONCLUSIONS

Perioperative IV administration of magnesium effectively reduced shivering and Trial Sequential Analysis suggested that no more trials are required to confirm that IV magnesium effectively reduces shivering.

The effects of magnesium sulfate infiltration on perioperative opioid consumption and opioid-induced hyperalgesia in patients undergoing robot-assisted laparoscopic prostatectomy with remifentanil-based anesthesia

BACKGROUND

Opioids not only exert an antinociceptive effect, but also modulate central N-methyl-D-aspartate (NMDA) receptors, resulting in hyperalgesia and acute opioid tolerance. This study was aimed to investigate the effect of the NMDA receptor antagonist, magnesium in preventing remifentanil-induced hyperalgesia.

METHODS

For this study, 75 patients scheduled for robot-assisted laparoscopic prostatectomy were randomly allocated into three groups of patients whose incision sites were infiltrated: Group M, with 25% magnesium sulfate 80 mg/kg; Group S, with the same volume of saline under remifentanil-based anesthesia, and Group D, with the same volume of saline under desflurane based anesthesia. All three groups were infiltrated into incision sites after pneumoperitoneum. Intraoperative evaluation included mean remifentanil dose, and postoperative evaluation included pain severity at time intervals of 30 min, 6, 12, 24 and 36 hours, time to first postoperative analgesic requirement, and analgesic dosage required during 24 hours.

RESULTS

Mean remifentanil doses during the intraoperative periods in group M were significantly lower than those in group S (P < 0.001). The time to first postoperative analgesic requirement in postoperative period in groups M and D was significantly longer than that in group S (P < 0.001). Visual analog scale scores for pain in groups M and D were significantly lower than those in group S for 12 hours after operation.

CONCLUSIONS

A relatively high dose and continuous infusion of remifentanil were associated with opioid induced hyperalgesia. Wound infiltration with magnesium sulfate decreased opioid consumption and reduces opioid induced hyperalgesia.

The Effects of Postoperative Brachial Plexus Block Using MgSO(4) on the Postoperative Pain after Upper Extremity Surgery

BACKGROUND

Although a brachial plexus block can be used to provide anesthesia and analgesia for upper extremity surgery, its effects using MgSO(4) on postoperative pain management have not been reported. The aim of this study was to evaluate brachial plexus block using MgSO(4) on postoperative analgesia.

METHODS

Thirty-eight patients who were scheduled to undergo upper extremity surgery were randomly allocated into two groups: patients receiving axillary brachial plexus block with 0.2% ropivacaine 20 ml and normal saline 2 ml (group S) or 0.2% ropivacaine 20 ml and MgSO(4) 200 mg (group M). Before extubation, the blocks were done and patient controlled analgesia was started, and then, the patients were transported to a postanesthetic care unit. The postoperative visual analogue scale (VAS), opioid consumption, and side effects were recorded.

RESULTS

The two groups were similar regarding the demographic variables and the duration of the surgery. No differences in VAS scores were observed between the two groups. There was no statistically significant difference in opioid consumption between the two groups. Nausea was observed in three patients for each group.

CONCLUSIONS

Axillary brachial plexus block using MgSO(4) did not reduce the level of postoperative pain and opioid consumption.