The effect of intravenous magnesium on postoperative morphine consumption in noncardiac surgery: A systematic review and meta-analysis with trial sequential analysis.
What this study found
Adjunctive intravenous magnesium reduced postoperative morphine consumption in the first 24 hours, with a pooled mean difference of -5.6 mg (95% CI -7.54 to -3.66; P < 0.001; I2 = 92%) across 18 trials and 899 active-arm participants, and it delayed time to first analgesia by 143 minutes (95% CI 103 to 183; P < 0.001) in 11 trials with 824 active-arm participants. It did not meaningfully improve postoperative pain scores (MD -0.30 on a 0 to 10 scale, 95% CI -0.69 to 0.09; P = 0.13) or postoperative nausea and vomiting (OR 1.01, 95% CI 0.75 to 1.37; P = 0.93). Magnesium lowered shivering…
- Study & population
- Systematic review and meta-analysis with trial sequential analysis of randomized trials in adults undergoing noncardiac surgery.
- Intervention
- Prophylactic intravenous magnesium was administered perioperatively as a bolus, an infusion, or a bolus followed by infusion, with regimens varying widely across trials.
- Key limitation
- The evidence was limited by substantial heterogeneity for several outcomes, including morphine consumption and serum magnesium concentration, and by risk of bias, indirectness, and imprecision.
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Open PDFOriginal abstract
BACKGROUND Several studies suggest that systemic magnesium reduces postoperative opioid consumption and the intensity of pain, but others report conflicting results. The efficacy and safety profile of intravenous magnesium in noncardiac surgery remain uncertain. OBJECTIVES The aim of this review was to investigate the effect of intravenous magnesium on the consumption of postoperative morphine in the first 24 h in adults undergoing noncardiac surgery. DESIGN Systematic review and meta-analysis with trial sequential analysis. DATA SOURCES MEDLINE, EMBASE, CENTRAL from their inception until January 2019. ELIGIBILITY CRITERIA All randomised clinical trials comparing intravenous magnesium versus placebo in noncardiac surgery were systematically searched in the databases. Observational studies, case reports, case series and nonsystematic reviews were excluded. RESULTS Fifty-one trials (n=3311) were included for quantitative meta-analysis. In comparison with placebo, postoperative morphine consumption at 24-h was significantly reduced in the magnesium group, with a mean difference [95% confidence interval (CI)] of -5.6 mg (-7.54 to -3.66, P < 0.001, I = 92%, level of evidence low). The trial sequential analysis for the effect of magnesium on postoperative morphine consumption was conclusive. Patients who received magnesium had a longer time to the first analgesia request [143 (103 to 183) min, P < 0.001, I = 99%, level of evidence low] and a lower incidence of shivering [0.26 (0.15 to 0.44), P < 0.001, I = 35%, level of evidence very low]. However, no significance differences were demonstrated in postoperative pain scores in the first 24 h (mean difference, 95% CI) -0.30 (-0.69 to 0.09, P = 0.13, I = 91%, level of evidence low), bradycardia (odds ratio, 95% CI) 1.13 (0.43 to 2.98, P = 0.80, I = 35%, level of evidence very low) and postoperative nausea and vomiting (odds ratio, 95% CI) 0.90 (0.67 to 1.22, P = 0.49, I = 25%, level of evidence moderate). CONCLUSION The current meta-analysis demonstrates that the use of intravenous magnesium as part of multimodal analgesia may reduce morphine consumption in the first 24 h after surgery and delay the time to the first request for analgesia in patients undergoing noncardiac surgery. However, the included studies were of low-quality with substantial heterogeneity. TRIAL REGISTRATION CRD42018086846.