Magnesium Sulfate Reduced Opioid Consumption in Obese Patients Undergoing Sleeve Gastrectomy: a Prospective, Randomized Clinical Trial

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.

Is intravenous magnesium sulphate a suitable adjuvant in postoperative pain management? - A critical and systematic review of methodology in randomized controlled trials

A growing worldwide focus on opioid-free anaesthesia entails multimodal analgesic strategies involving non-opioids such as magnesium sulphate (MgSO4). Several systematic reviews have concluded there is beneficial analgesic effect of MgSO4 administration but do not take considerable heterogeneity among the studies into consideration. Medical literature published until June 2021 was searched in PubMed/Medline, Embase, Central and Web of Science: The final search yielded a total of 5,672 articles. We included only randomised controlled trials assessing the effect of intravenous MgSO4 on opioid consumption and acute postoperative pain when compared to either placebo or standardized analgesic treatment. The primary aim was to compare the homogeneity of essential variables and confounders. A post-hoc meta-analysis demonstrated a reduction in both postoperative morphine consumption (-6.12 mg) and pain score (-12.32 VAS points) in favour of the MgSO4-groups. Data for meta-analysis was missing from 19 studies (45%) on morphine consumption and 29 studies (69%) for pain score, the majority of which reports no effect for either morphine consumption or pain score. The calculated heterogeneity among the included studies was considerable for both outcomes; I 2=91% for morphine consumption and I 2=96% for pain score. Although we found a per se reduction in opioid consumption and pain score, methodological heterogeneity and clinical shortcomings of pre-, intra-, and post anaesthetic data precludes conclusions on clinical importance of intraoperative intravenous MgSO4. In addition, the reduction is likely less than what can be gained from using standardized analgesic treatment.

Oral application of magnesium-L-threonate enhances analgesia and reduces the dosage of opioids needed in advanced cancer patients-A randomized, double-blind, placebo-controlled trial

PURPOSE

To investigate the effects of oral administration of magnesium-L-threonate, a novel magnesium compound, on the analgesic effect of opioids in patients with advanced cancer.

METHODS

We performed a prospective, randomized, double-blind trial at a tertiary hospital in Shanghai, China. Eligible cancer patients who took opioids orally were assigned randomly to receive L-TAMS capsules (1.5 g or 2.0 g according to weight) or a placebo (starch capsules). The primary outcome was the increase in the daily oral dose of morphine in each of the two groups, measured at 7, 14, 21, 30, 60, and 90 days during this trial.

RESULTS

A total of 116 patients from the oncology and pain departments, including inpatients and outpatients, were screened; 83 were enrolled. The increases in daily morphine doses began to differ from day 30 (L-TAMS group 9.85 mg/d vs. Placebo group 20.49 mg/d, p < 0.05); the differences persisted on day 60 (L-TAMS group 15.96 mg/d vs. Placebo group 29.06 mg/d, p < 0.05) and on day 90 (L-TAMS group 21.20 mg/d vs. Placebo group 40.44 mg/d, p < 0.01).

CONCLUSIONS

L-TAMS outperforms a placebo in enhancing the analgesic effect of opioids and reducing the necessary opioid dosage. Moreover, L-TAMS can significantly relieve opioid-induced constipation. These advantages may be beneficial to patients with advanced cancer.

Strategy for Calculating Magnesium Sulfate Dose in Obese Patients: A Randomized Blinded Trial

Background. Magnesium sulfate has analgesic properties during the postoperative period. However, there is a knowledge gap in pharmacology related to the use of the real, ideal, or corrected ideal body weight to calculate its dose in obese patients. This trial compared postoperative analgesia using actual and corrected ideal body weight. Methods. Seventy-five obese patients scheduled to undergo laparoscopic gastroplasty or cholecystectomy under general anesthesia were randomly assigned to three groups. The patients in the control group did not receive magnesium sulfate; the other two groups received magnesium sulfate at 40 mg·kg−1 of actual body weight or corrected ideal body weight. Results. In patients with body mass index >30 mg·kg−2 (mean body mass index ranging from 32.964 kg·m−2 to 33.985 kg·m−2, according to the groups) scheduled for video laparoscopic cholecystectomy, there were no differences in the blood magnesium concentrations in the groups receiving magnesium sulfate throughout the study, regardless of whether the strategy to calculate its dose was based on total or corrected ideal body weight. Patients in the groups receiving magnesium sulfate showed a significant reduction in morphine consumption ( $p\le 0.001$ ) and pain scores ( $p=0.006$ ) in the postoperative period compared to those in the control group. There were no significant differences in morphine consumption ( $p=0.323$ ) or pain scores ( $p=0.082$ ) between the two groups receiving magnesium sulfate. There were no differences in the total duration of neuromuscular block induced by cisatracurium among the three groups ( $p=0.181$ ). Conclusions. Magnesium sulfate decreased postoperative pain and morphine consumption without affecting the recovery time of cisatracurium in obese patients undergoing laparoscopic cholecystectomy. Strategies to calculate the dose based on the actual or corrected ideal body weight had similar outcomes related to analgesia and the resulting blood magnesium concentration. However, as the sample in this trial presented body mass indices ranging from 30.11 kg·m−2 to 47.11 kg/m−2, further studies are needed to confirm these findings in more obese patients, easily found in centers specialized.

Effect of Perioperative Intravenous Magnesium Sulfate on Postoperative Pain After Iliac Venous Stenting

BACKGROUND

The aim of the present study was to evaluate the effect of perioperative intravenous (IV) magnesium sulfate (MS) on low back pain (LBP) severity after iliac venous stent implantation.

METHODS

The present study was a single-center retrospective study. A total of 97 patients who had undergone iliac venous stenting for post-thrombotic syndrome between January 1, 2019 and January 11, 2021 were considered for inclusion in the present study. The patients were divided into two groups: those who had received perioperative MS infusions (group M) and those who had not (control group; group C). Group M was given an IV bolus of 20 mg/kg before anesthesia induction and an IV MS infusion of 20 mg/kg/h during the procedure. Postoperative LBP severity was evaluated using the numerical rating scale at 1, 6, 12, and 24 hours after the procedure. The total tramadol consumption within 24 hours was measured with the help of a patient-controlled analgesia device. Moreover, additional analgesic needs and complaints of nausea and vomiting were evaluated.

RESULTS

A total of 97 patients were considered for inclusion in the present study. Of the 97 patients, 29 were excluded because of a lack of follow-up data, leaving 68 patients for the final analysis (group M, n = 36; group C, n = 32). The demographic data, body mass index, sedation time, procedure time, and stented side data were similar between the two groups (P > .05). The rates of atropine and ephedrine use during the procedure were similar between the two groups (P > .05). The numerical rating scale scores were significantly lower for group M at all follow-up periods (P < .001). The total tramadol consumption at 24 hours postoperatively was 191.94 ± 68.194 mg for group M and 378.75 ± 31.367 mg for group C (P < .001). Additional analgesics were used by 8 patients (22.2%) in group M and 17 patients (53.1%) in group C. Additional analgesic needs were significantly lower for group M (P = .008). Nausea and vomiting were observed in six (19.4%) and four (11.1%) patients in group M and eight (32%) and five (15.6%) patients in group C, respectively (P > .05).

CONCLUSIONS

For patients undergoing iliac venous stenting, perioperative MS infusion was an effective and safe treatment option that reduced LBP severity, opioid consumption, and the need for additional analgesics in the acute postoperative period.

Enhanced recovery after bariatric surgery: an Italian consensus statement

Background

Enhanced recovery after bariatric surgery (ERABS) is an approach developed to improve outcomes in obese surgical patients. Unfortunately, it is not evenly implemented in Italy. The Italian Society for the Surgery of Obesity and Metabolic Diseases and the Italian Society of Anesthesia, Analgesia, Resuscitation and Intensive Care joined in drafting an official statement on ERABS.

Methods

To assess the effectiveness and safety of ERABS and to develop evidence-based recommendations with regard to pre-, intra-, and post-operative care for obese patients undergoing ERABS, a 13-member expert task force of surgeons and anesthesiologists from Italian certified IFSO center of excellence in bariatric surgery was established and a review of English-language papers conducted. Oxford 2011 Levels of Evidence and U.S. Preventive Services Task Force Grade Definitions were used to grade the level of evidence and the strength of recommendations, respectively. The supporting evidence and recommendations were reviewed and discussed by the entire group at meetings to achieve a final consensus.

Results

Compared to the conventional approach, ERABS reduces the length of hospital stay and does not heighten the risk of major post-operative complications, re-operations, and hospital re-admissions, nor does it increase the overall surgical costs. A total of 25 recommendations were proposed, covering pre-operative evaluation and care (7 items), intra-operative management (1 item, 11 sub-items), and post-operative care and discharge (6 items).

Conclusions

ERABS is an effective and safe approach. The recommendations allow the proper management of obese patients undergoing ERABS for a better outcome.

Management of pain using magnesium sulphate: A narrative review

Pain is one of the most complex and unpleasant sensory and emotional human experiences. Pain relief continues to be a major medical challenge. The application of systemic opioid and regional analgesia techniques has facilitated a decrease in the occurrence and gravity of pain. Magnesium has an evolving role in pain management. Magnesium sulphate (MgSO4), the pharmacological form of magnesium, is a physiological voltage-dependent blocker of N-methyl-D-aspartate (NMDA)-coupled channels. In terms of its antinociceptive role, magnesium blocks calcium influx, which inhibits central sensitization and decreases preexisting pain hypersensitivity. These properties have encouraged the research of magnesium as an adjuvant agent for intra- and post-operative analgesia. Moreover, the mentioned magnesium impacts are also detected in patients with neuropathic pain. Intravenous magnesium sulphate, followed by a balanced analgesia, decreases opioid consumption. This review has focused on the existing evidence concerning the role of magnesium sulphate in pain management in situations including neuropathic pain, postherpetic neuralgia, trigeminal neuralgia, migraine, and post-operative pain. Additional studies are required to improve the use of magnesium sulphate for pain to increase the quality of life of patients.

Comparison of three intraoperative analgesic strategies in laparoscopic bariatric surgery: a retrospective study of immediate postoperative outcomes

Introduction and objectives

Multimodal Analgesia (MMA) has shown promising results in postoperative outcomes across a broad spectrum of surgeries, including bariatric surgery. We compared the analgesic effect immediately after Laparoscopic Bariatric Surgery (LBS) of the combined effect of MMA and methadone against two techniques that were based mainly on the use of high-potency medium-acting opioids.

Methods

Two hundred seventy-one patients were retrospectively reviewed. The primary outcome was postoperative pain score > 3/10 measured by the Verbal Numeric Scale (VNS) during the Postanesthetic Care Unit (PACU) stay. The three protocols of intraoperative analgesia were: (P1) sufentanil at anesthetic induction followed by remifentanil infusion; (P2) sufentanil at induction followed by dexmedetomidine infusion; and (P3) remifentanil at induction followed by MMA including dexmedetomidine, magnesium, lidocaine, and methadone. Only P1 and P2 patients received morphine toward the end of surgery. Poisson regression was used to adjust confounding factors and calculate Prevalence Ratio (PR).

Results

Postoperative VNS > 3 was recorded in 135 (49.81%) patients, of which 93 (68.89%) were subjected to P1, 25 (18.56%) to P2, and 17 (12.59%) to P3. In the final adjusted model, both anesthetic techniques (P3) (PR = 0.10; 95% CI [0.03–0.28]), and (P2) (PR = 0.42%; 95% CI [0.20–0.90]) were associated with lower occurrence of VNS > 3, whereas age range 20–29 was associated to higher occurrence of VNS > 3 (PR = 3.21; 95% CI [1.22–8.44]) in PACU. Postoperative Nausea and Vomiting (PONV) was distributed as follows: (P1) 20.3%, (P2) 31.25% and (P3) 6.77%; (P3 < P1, P2; p < 0.05). Intraoperative hypotension occurred more often in P3 (39%) compared to P2 (20.31%) and P1 (17.46%) (p < 0.05).

Conclusion

MMA + methadone was associated with higher incidence of intraoperative hypotension and lower incidence of moderate/severe pain in PACU after LBS.

The effect of intravenous magnesium on postoperative morphine consumption in noncardiac surgery: A systematic review and meta-analysis with trial sequential analysis

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.

Magnesium for Pain Treatment in 2021? State of the Art

Background: Magnesium (Mg) is commonly used in clinical practice for acute and chronic pain and has been reported to reduce pain intensity and analgesics consumption in a number of studies. Results are, however, contested. Objectives: This review aims to investigate randomised clinical trials (RCTs) on the effectiveness of Mg treatment on pain and analgesics consumption in situations including post-operative pain, migraine, renal pain, chronic pain, neuropathic pain and fibromyalgia. Results: The literature search identified 81 RCTs (n = 5447 patients) on Mg treatment in pain (50 RCTs in post-operative pain, 18 RCTs in migraine, 5 RCTs in renal pain, 6 RCTs in chronic/neuropathic pain, 2 RCTs in fibromyalgia). Conclusion: The level of evidence for the efficacy of Mg in reducing pain and analgesics consumption is globally modest and studies are not very numerous in chronic pain. A number of gaps have been identified in the literature that need to be addressed especially in methodology, rheumatic disease, and cancer. Additional clinical trials are needed to achieve a sufficient level of evidence and to better optimize the use of Mg for pain and pain comorbidities in order to improve the quality of life of patients who are in pain.

Magnesium and Pain

In terms of antinociceptive action, the main mode of action of magnesium involves its antagonist action at the N-methyl-d-aspartate (NMDA) receptor, which prevents central sensitization and attenuates preexisting pain hypersensitivity. Given the pivotal function of NMDA receptors in pain transduction, magnesium has been investigated in a variety of pain conditions. The oral and parenteral administration of magnesium via the intravenous, intrathecal, or epidural route may alleviate pain and perioperative anesthetic and analgesic requirements. These beneficial effects of magnesium therapy have also been reported in patients with neuropathic pain, such as malignancy-related neurologic symptoms, diabetic neuropathy, postherpetic neuralgia, and chemotherapy-induced peripheral neuropathy. In addition, magnesium treatment is reportedly able to alleviate fibromyalgia, dysmenorrhea, headaches, and acute migraine attacks. Although magnesium plays an evolving role in pain management, better understanding of the mechanism underlying its antinociceptive action and additional clinical studies is required to clarify its role as an adjuvant analgesic.

Perioperative care of the obese patient

Background

Obesity has become an increasing problem worldwide during the past few decades. Hence, surgeons and anaesthetists will care for an increasing number of obese patients in the foreseeable future, and should be prepared to provide optimal management for these individuals. This review provides an update of recent evidence regarding perioperative strategies for obese patients.

Methods

A search for papers on the perioperative care of obese patients (English language only) was performed in July 2019 using the PubMed, Scopus, Web of Science and Cochrane Library electronic databases. The review focused on the results of RCTs, although observational studies, meta-analyses, reviews, guidelines and other reports discussing the perioperative care of obese patients were also considered. When data from obese patients were not available, relevant data from non-obese populations were used.

Results and conclusion

Obese patients require comprehensive preoperative evaluation. Experienced medical teams, appropriate equipment and monitoring, careful anaesthetic management, and an adequate perioperative ventilation strategy may improve postoperative outcomes. Additional perioperative precautions are necessary in patients with severe morbid obesity, metabolic syndrome, untreated or severe obstructive sleep apnoea syndrome, or obesity hypoventilation syndrome; patients receiving home ventilatory support or postoperative opioid therapy; and obese patients undergoing open operations, long procedures or revisional surgery.

Effect of intravenous versus intraperitoneal magnesium sulfate on hemodynamic parameters and postoperative analgesia during laparoscopic sleeve gastrectomy-A prospective randomized study

Background and Aims:

Hemodynamic changes to pneumoperitoneum and postoperative pain can be detrimental in obese patients; we investigated whether intravenous (IV) or intraperitoneal (IP) magnesium sulphate (MgSo₄) administration could attenuate the hemodynamic stress response to pneumoperitoneum and improve postoperative pain control after laparoscopic sleeve gastrectomy (LSG).

Material and Methods:

In total, 120 patients scheduled for LSG were randomized to either, control group (Group C, IV and IP saline), Group I (IV 30 mg/kg MgSo₄), or Group P (IP 30 mg/kg MgSo₄). Outcome variables were mean arterial pressure (MAP), heart rate (HR), postoperative pain score, total analgesic consumption, and incidence of adverse events.

Results:

MAP and HR were significantly lower in Groups I and P than that in control group. Pain score was better in Groups I and P than in control group up to 2 h postoperative (P = 0.023, 0.010, respectively); it was significantly lower in Group P than other two groups at 4 h postoperative (P <0.001). Significantly, reduced postoperative analgesic consumption with delayed onset to first analgesic request were observed in magnesium groups compared to control (P = 0.001, respectively). Moreover, onset to first analgesic request was longer in Group P than Group I (P = 0.001). No serious side effects were noticed.

Conclusion:

The IV and IP administration of MgSo₄ significantly attenuated the circulatory response to pneumoperitoneum and reduced postoperative pain as well as opioid consumption as compared to controls in obese patients undergoing LSG with no serious adverse effects.