Key result
Intravenous magnesium significantly reduced postoperative morphine consumption at 24 hours compared to placebo (MD -5.6 mg; 95% CI -7.54 to -3.66; P<0.001).
Why the study?
Conflicting results exist regarding systemic magnesium for postoperative opioid consumption and pain intensity, leaving its efficacy and safety profile in noncardiac surgery uncertain.
Does intravenous magnesium reduce postoperative morphine consumption in the first 24 h in adults undergoing noncardiac surgery?
Meta-Analysis (n=3,311)
Does intravenous magnesium reduce postoperative morphine consumption in the first 24 h in adults undergoing noncardiac surgery?
Mean Difference: -5.6 (95% CI -7.54–-3.66)
p-value: p=< 0.001
Intravenous magnesium as part of multimodal analgesia significantly reduces morphine consumption and delays the first request for analgesia in the first 24 hours after noncardiac surgery.
IV magnesium may lower 24-h morphine use after noncardiac surgery; extends evidence for multimodal analgesia but needs larger confirmatory trials.
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.
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Ng et al. (2020) conducted a meta-analysis in noncardiac surgery (n=3,311). intravenous magnesium vs. placebo was evaluated on postoperative morphine consumption at 24-h (MD -5.6 mg, 95% CI -7.54 to -3.66, p=< 0.001). Intravenous magnesium significantly reduced postoperative morphine consumption at 24 hours compared to placebo (MD -5.6 mg; 95% CI -7.54 to -3.66; P<0.001).
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