The use of intravenous magnesium sulfate on postoperative analgesia in orthopedic surgery: A systematic review of randomized controlled trials

Magnesium sulfate enhances the effect of the peripheral analgesic cocktail in total knee arthroplasty: a systematic review and meta-analysis of randomized controlled trials

Purpose

Although magnesium sulfate (MgSO4) is widely used as an analgesic adjuvant to peripheral analgesic cocktails, its efficacy in total knee arthroplasty (TKA) is still controversial. Therefore, we systematically reviewed and meta-analyzed the literature to assess the analgesic efficacy of MgSO4 as an adjuvant to the analgesic cocktail in TKA.

Methods

The PubMed, EMBASE, Web of Science, and Cochrane Library databases were searched. The meta-analysis was performed according to the PRISMA guidelines. Data were qualitatively synthesized or meta-analyzed using a random-effects model.

Results

Five randomized controlled trials involving 432 patients were included. Meta-analyses detected significant differences between the MgSO4 and control groups in the visual analog scale (VAS) pain scores (rest) at 6, 12, and 24 h postoperatively; VAS pain scores (motion) at 12, 24, and 48 h postoperatively; morphine consumption within 24 h, 24-48 h, and during the total hospitalization period; time to first rescue analgesia after TKA; and length of hospital stay. Regarding the functional recovery, the meta-analysis demonstrated significant differences between groups in terms of knee range of motion on postoperative day 1; daily mobilization distance on postoperative day 1; and daily mobilization distance. There was no significant intergroup difference in surgical complications.

Conclusion

The findings suggest that MgSO4 is a promising adjunct to the analgesic cocktail, achieving significant improvements in pain scores and total opioid consumption during the early postoperative period after TKA.

Effects of intra-operative magnesium sulfate infusion on orthognathic surgery: A prospective and randomized controlled trial

Purpose

To comprehensively understand the effects of intra-operative infusion of magnesium sulfate on patients who underwent orthognathic surgery, including remifentanil consumption, postoperative pain, postoperative nausea and vomiting (PONV), inflammatory response, and serum magnesium levels.

Methods

Seventy-five adult patients undergoing orthognathic surgery under general balanced anesthesia were randomly divided into two groups. One group (Group M) received 50 mg/kg of magnesium sulfate in 20 mL 0.9 % saline after intubation, followed by a continuous infusion at a rate of 15 mg/kg/h until 30 min before the anticipated end of surgery. The other group (Group C) received an equal volume of isotonic saline as a placebo. (Clinical trial registration number: chiCTR2100045981).

Results

The primary outcome was remifentanil consumption. The secondary outcomes included the pain score assessed using the verbal numerical rating scale (VNRS) and PONV assessed using a Likert scale. Remifentanil comsumption in Group M was lower than Group C (mean ± SD: 0.146 ± 0.04 μg/kg/min vs. 0.173 ± 0.04 μg/kg/min, P = 0.003). At 2 h after surgery, patients in Group C suffered more severe PONV than those in Group M (median [interquartile range, IQR]: 1 [3] vs. 1 [0], mean rank: 31.45 vs. 42.71, P = 0.040). At post-anesthesia care unit (PACU), postoperative pain in Group C was severe than Group M (3 [1] vs. 3 [0], mean rank: 31.45 vs. 42.71, P = 0.013). Changes in haemodynamics and surgical field scores did not differ between the groups (all P > 0.05). The levels of cytokines (IL-4, IL-6, IL-8, IL-10, TNF-a, and MIP-1β) were not significantly different between the groups after surgery (all P > 0.05). Postoperative serum magnesium levels in Group C were lower than those in Group M (0.74 ± 0.07 mmol/L vs. 0.91 ± 0.08 mmol/L, P = 0.000) and the preoperative level (0.74 ± 0.07 mmol/L vs. 0.83 ± 0.06 mmol/L, P = 0.219).

Conclusions

In orthognathic surgery, magnesium sulfate administration can reduce remifentanil requirement and relieve PONV and postoperative pain in the early postoperative phase.

Analgesic Effects of Preoperative Combination of Oral Pregabalin and Intravenous Magnesium Sulfate on Postoperative Pain in Patients Undergoing Posterolateral Spinal Fusion Surgery: A 4-arm, Randomized, Double-blind, Placebo-controlled Trial

BACKGROUND

Multimodal perioperative pain management including nonopioid analgesia is a major pillar of enhanced recovery after surgery programs. The aim of this study was to investigate the analgesic efficacy of the preoperative combination of 2 nonopioid drugs, oral pregabalin and intravenous magnesium sulfate, in patients undergoing posterolateral lumbar spinal fusion.

METHODS

This 4-arm, randomized, double-blind, placebo-controlled trial included 104 patients randomly allocated to receive: magnesium sulfate and pregabalin (MP), magnesium sulfate and oral placebo (M), 0.9% saline and oral pregabalin (P), and 0.9% saline and oral placebo (C). The study drugs were administered 1 hour preoperatively. The primary outcome was the cumulative morphine consumption on postoperative day 1. Secondary outcomes included visual analog scale scores for leg pain at rest and with movement, and postoperative nausea and vomiting (PONV) in the first 48 hours after surgery.

RESULTS

Cumulative morphine consumption on postoperative day 1 was lower in group MP (19.6±8.0 mg) compared with group M (32.6±9.5 mg; P <0.001), group P (28.9±9.4 mg; P =0.001), or group C (38.8±10.3 mg; P <0.001). Multiple linear regression demonstrated a significant association between group MP and cumulative morphine consumption (B=-5.4 [95% CI, -7.1, -3.7], P <0.001). Visual analog scale scores for leg pain at rest and with movement were lower in group MP compared with other groups ( P =0.006 and <0.001). The incidence of PONV was also lowest in group MP ( P =0.032).

CONCLUSIONS

Preoperative administration of oral pregabalin and intravenous magnesium sulfate resulted in reduced morphine consumption and greater analgesic effect than the use of each drug individually or placebo in patients undergoing posterolateral lumbar spinal fusion.

Effect of Intraoperative infusion Magnesium Sulfate Infusion on Postoperative Quality of Recovery in Patients Undergoing Total Knee Arthroplasty: A Prospective, Double-Blind, Randomized Controlled Trial

Background

Magnesium sulfate, an intravenous adjuvant, has recently attracted immense attention in multimodal analgesia. Previous studies confirmed the crucial role of magnesium sulfate in postoperative pain and nociceptive hypersensitivity. However, the effect of magnesium sulfate in multimodal analgesia on the quality of recovery (QoR) for elderly patients has not been thoroughly studied. Therefore, the present experiment aimed to investigate the effect of continuous intravenous magnesium sulfate on the quality of postoperative recovery in elderly patients undergoing total knee arthroplasty (TKA).

Patients and Methods

In this study, a total of 148 patients scheduled to undergo unilateral total knee arthroplasty were randomized into a magnesium sulfate group (Group M, n=68) and a control group (Group C, n=66) using a double-blind, randomized controlled trial. Before induction of anesthesia, Group M received intravenous magnesium sulfate (40 mg/kg) for 15 min, followed by a continuous infusion (15 mg/kg) until the end of the procedure. In the same manner, Group C received an infusion of the same amount of isotonic saline using the same method as the Group M.

Results

Compared with Group C, Group M had significantly better QoR-15 scores on postoperative day 1(POD1) than Group C (P <0.05). Analysis of the dimensions of QoR-15 scores indicated that Group M exhibited notably reduced levels of pain, and higher levels of emotional state and physical comfort than Group C (P <0.05). Furthermore, Group C had significantly higher numerical rating scale (NRS) scores at POD1 than Group M (P <0.05).

Conclusion

For elderly patients undergoing knee arthroplasty, magnesium sulfate can be used as an adjuvant in a multimodal analgesic regimen to reduce early postoperative pain and improve the quality of early postoperative recovery.

Efficacy of memantine premedication in alleviating postoperative pain- A systematic review and meta-analysis

Many premedication agents with opioid-sparing properties have been used in patients undergoing various elective surgeries. Memantine is an N-methyl-D-aspartate (NMDA) receptor antagonist that has been used by many researchers as an opioid-sparing strategy. Various databases like PubMed, Scopus, Cochrane Library, and clinicaltrials.gov were searched after registering the review protocol in PROSPERO for randomized-controlled trials (RCTs) that investigated the efficacy and safety of memantine premedication in adult patients undergoing various elective surgeries. The risk of bias (RoB-2) scale was used to assess the quality of evidence. From the 225 articles that were identified after a database search, 3 studies were included for a qualitative systematic review and a quantitative meta-analysis. The pooled analysis revealed that the use of memantine provided better pain scores at 2nd (mean difference: -0.82, 95% CI: -1.60, -0.05, P = 0.04) with significant heterogeneity (P = 0.06; I² =71%), and 6 hours postoperatively (mean difference: -1.80, 95% CI: -2.23, -1.37, P < 0.00001), but not at 1 hour. The sedation scores at 1 hour were higher in the memantine group but comparable in the 2nd hour. The number of doses of rescue analgesia and nausea/vomiting in the postoperative period was comparable in both groups. The results of this review suggest that memantine premedication could provide better pain scores in the immediate postoperative period with acceptable adverse effects. However, the current evidence is insufficient to suggest the routine use of memantine as a premedication before elective surgeries.

Intra-Operative Adjunctive Magnesium Sulfate in Pain Management of Total Knee Arthroplasty; a Systematic Review and Meta-analysis

Introduction

There has been growing interest in the potential role of adjunctive magnesium sulfate in improving pain management. This systematic review and meta-analysis aimed to assess the effect of intra-operative adjunctive magnesium sulfate on pain management and opioid consumption in total knee arthroplasty (TKA).

Methods

A comprehensive search was conducted in Medline, Embase, Scopus, Web of Science, and Cochrane Library databases, covering studies up to April 2023. The extracted data included pain management outcomes, opioid consumption, and adverse effects from the selected studies. Standardized mean differences (SMDs) were calculated for continuous outcomes, while risk ratios (RRs) were calculated for dichotomous outcomes. Meta-analysis was conducted employing random-effects models in STATA 17.

Results

In this meta-analysis of 8 randomized controlled trials involving 536 patients, adjunctive magnesium sulfate in TKA was found to significantly reduce opioid consumption during the first 24 hours after operation (SMD: -1.88, 95% confidence interval (CI): [-3.66 to -0.10]; p = 0.038). It also resulted in lower pain scores at rest 24 hours after surgery (SMD: -1.53, 95% CI: [-2.70 to -0.37]; p = 0.010). There were no significant differences in time to first rescue analgesic and adverse effects between the groups. The included studies were assessed to have low to high levels of risk of bias.

Conclusion

This study presents evidence at low to moderate levels supporting the use of intra-operative adjunctive magnesium sulfate in TKA for improved pain management and reduced opioid consumption. However, further research is needed to address the heterogeneity and to explore optimal dosing regimens and routes of administration to maximize the benefits of magnesium sulfate in TKA.

Comparative Efficacy of Adjuvant Nonopioid Analgesia in Adult Cardiac Surgical Patients: A Network Meta-Analysis

OBJECTIVES

To compare the relative efficacy of adjuvant nonopioid analgesic regimens in adult cardiac surgical patients.

DESIGN

This frequentist, random-effects network meta-analysis (NMA) was prospectively registered on PROSPERO (CRD42021282913) and conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analyses for Network Meta-Analyses (PRISMA-NMA). The risk of bias (RoB) and confidence of evidence were assessed by RoB 2 and Confidence in Network Meta-Analysis, respectively. Relevant databases were searched from inception to October 9, 2021.

SETTING

A total of 124 (N = 26,257) randomized controlled trials were included, of which 110 were analyzed.

PARTICIPANTS

Trials enrolling adults (≥18 years of age) undergoing cardiac surgery that compared nonopioid analgesics against other nonopioid analgesics, placebo, or no additional treatment, as adjuvants to standard analgesic management, and reported at least 1 of the outcomes of interest.

MEASUREMENT AND MAIN RESULTS

Outcomes of interest included resting postoperative pain scores at 24 hours. Compared with standard care and/or placebo, pain scores were reduced significantly by 10 different regimens, including acetaminophen (N = 176; mean difference [MD] -0.66 points, 95% CI -1.16 to -0.15 points; high confidence), magnesium (N = 323; -0.05 points, 95% CI -0.07 to -0.02 points; high confidence), gabapentin (N = 96; MD -0.40 points, 95% CI -0.71 to -0.09; moderate confidence), and clonidine (N = 64; MD v0.38 points, 95% CI -0.73 to v0.04 points; moderate confidence). Indomethacin, diclofenac, magnesium, and gabapentin significantly reduced 24-hour opioid consumption. Four regimens significantly decreased the intensive care unit length of stay. Hydrocortisone, dexmedetomidine, and clonidine significantly decreased the duration of mechanical ventilation. Magnesium decreased, while methylprednisolone significantly increased, the risk of myocardial infarction.

CONCLUSIONS

Given the increasing emphasis on enhanced recovery after surgery(ERAS) protocols and the eventual goal of limiting opiate prescriptions postoperatively, the authors' data suggested far greater use of nonopioid adjuncts to minimize pain and enhance recovery following cardiac surgery.

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.

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.

Impact of intraoperative intravenous magnesium on spine surgery: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

The effectiveness and safety of intraoperative intravenous magnesium (IIM) on spine surgery remain uncertain, as recent randomized controlled trials (RCTs) yielded conflicting results. The purpose of this study was to determine the impact of IIM on spine surgery.

METHODS

A literature search was performed on multiple electronic databases, ClinicalTrial.gov and Google Scholar on July 12th 2021, and reference lists were examined. We selected RCTs comparing the effects of IIM with placebo treatment on spine surgery. We calculated pooled standard mean difference (SMD) or risk ratio (RR) with 95% confident interval (CI) under a random-effect model. We assessed risk of bias using Cochrane risk-of-bias tool and Jadad score was applied to assess the quality of each included trial. Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) was used to determine the confidence in effect estimates. Sensitivity analysis was conducted by omitting each included study one by one from the pooled analysis. PROSPERO Registration: CRD42021266170.

FINDINGS

Fourteen trials of 781 participants were included. Low- to moderate-quality evidence suggested that IIM reduces postoperative morphine consumption at 24 h (SMD: -1·61 mg, 95% CI: -2·63 to -0·58) and intraoperative remifentanil requirement (SMD: -2·09 ug/h, 95% CI: -3·38 to -0·81). High-quality evidence suggested that IIM reduces the risk of postoperative nausea and vomiting compared with placebo (RR: 0·43, 95% CI: 0·26 to 0·71). Besides, moderate-quality evidence suggested that recovery orientation time in the IIM group is longer than control group (SMD: 1·13 min, 95% CI: 0·83 to 1·43).

INTERPRETATION

IIM as adjuvant analgesics showed overall benefits on spine surgery in terms of reducing analgesic requirement and postoperative nausea and vomiting; however, potential risks of IIM, such as delayed anesthetic awakening, should not be ignored. Future evidence will inform the optimal strategy of IIM administration for patients undergoing spine surgery.

FUNDING

This study was funded by Beijing Municipal Natural Science Foundation (Grant No :7212117).

Opioid-free anaesthesia for laparoscopic surgeries - A prospective non-randomised study in a tertiary care hospital

Background and Aims:

Opioids have nowadays become superfluous because of their adverse effects involving post-operative recovery of the patients. So, we aimed at comparing opioid-free anaesthesia with opioid-based technique for post-operative pain relief in laparoscopic surgeries. The primary objective was to assess the pain scores in the post-operative period using visual analogue scale (VAS) for 24 h, and the secondary objective was to compare intraoperative haemodynamic parameters, duration of postoperative analgesia and total analgesics consumed in the first 24 h.

Methods:

This study was conducted in 60 patients aged between 20 and 70 years, belonging to the American Society of Anesthesiologists physical class I and II posted for laparoscopic surgeries. Anaesthetic doses of lidocaine, magnesium and paracetamol in combination with fascial plane block for post-operative pain relief were given for 30 patients, and the other 30 patients received the conventional opioid-based anaesthesia. Mann–Whitney test was used for VAS scores, and Friedman test was used for repeated measures comparison.

Results:

VAS scores were higher in the conventional group as compared to the opioid-free group at 0, 2, 4, and 6 h during rest and at 0, 2, 4, 6, 24 h during movement and were statistically significant (P-value < 0.05). The duration of analgesia for the conventional group was 13.8 + 6.7 h, and for opioid-free anaesthesia was 6.7 + 2.2 hours. Intraoperative haemodynamic parameters did not show a statistically significant difference except for systolic blood pressure which was higher in the opioid-free group but was clinically insignificant. (P-value 0.013).

Conclusion:

Opioid-free anaesthesia along with erector spinae plane block provides better post-operative pain relief when compared to conventional opioid anaesthesia.

Intravenously injected lidocaine or magnesium improves the quality of early recovery after laparoscopic cholecystectomy: A randomised controlled trial

BACKGROUND

Previous data show that lidocaine or magnesium has unique characteristics of stress inhibition and antiinflammation.

OBJECTIVE

We aimed to observe the effects of lidocaine or magnesium on the quality of recovery (QoR) after laparoscopic cholecystectomy.

DESIGN

Single-centre, prospective, randomised, double-blind study.

SETTING

The Affiliated Hospital of Xuzhou Medical University from March 2019 to October 2019.

PATIENTS

One hundred and fourteen patients scheduled for laparoscopic cholecystectomy.

INTERVENTION

The enrolled patients were randomly divided into three groups. Lidocaine (group L), magnesium sulphate (group M) or 0.9% saline (group C) was administered intravenously 10 min before induction.

MAIN OUTCOME MEASURES

The quality of recovery 15 (QoR-15) score, the Hospital Anxiety and Depression Scale (HADS), and the Numerical Rating Scale (NRS) score were selected. The usage of propofol and remifentanil, haemodynamic parameters, anaesthesia recovery parameters and adverse events were also evaluated.

RESULTS

The QoR-15 scores for group L (132.0) and group M (134.0) were 6 and 8 points higher than that of group C (126.0) on POD1 (postoperative day 1) (adjP < 0.05). However, the decrease of QoR-15 in Group L is less than the minimal clinically important difference (8).The NRS scores on POD1 in group C 3, were higher than other two groups (adjP < 0.05). The dosage of remifentanil in group L was lower than other two groups (adjP < 0.05).The physical independence of group L and group M and physical comfort of group M were improved compared with group C.

CONCLUSION

The results show that magnesium sulphate improved the QoR through improving physical comfort and physical independence in patients after laparoscopic cholecystectomy. However, lidocaine had limited effects on QoR under current conditions.

TRIAL REGISTRATION

ChiCTR1800019092 (www.chictr.org.cn).

CLINICAL TRIAL NUMBER AND REGISTRY URL

The study was registered in the Chinese Clinical Trials Register (ChiCTR1800019092) https://www.chictr.org.cn.

Intravenous magnesium sulfate for postoperative analgesia after abdominal hysterectomy under spinal anesthesia: a randomized, double-blind trial

Background and objectives

Abdominal Hysterectomy (AH) is associated with significant inflammatory response and can result in moderate to severe postoperative pain. This study aimed to evaluate the efficacy of magnesium infusion in reducing postoperative pain and analgesic consumption after AH under spinal anesthesia with Intrathecal Morphine (ITM).

Method

Eighty-six patients were included in this clinical, controlled, randomized, double-blind study. Patients received in Group Mg, MgSO₄ 50 mg kg⁻¹ for 15 minutes followed by 15 mg kg⁻¹ h⁻¹ until the end of the surgery; and in Group C, (control) the same volume of isotonic saline. Both groups received 100 μg of ITM. All patients received dipyrone + ketoprofen intraoperatively and postoperatively, and dexamethasone intraoperatively only. We evaluated the intensity of pain, tramadol consumption, and adverse events 24 hours postoperatively.

Results

Serum magnesium concentrations were higher in Group Mg at the end, and one hour after the operation (p = 0.000). Postoperative pain scores were reduced in Group Mg at 6 hours at rest and on movement (p < 0.05). Tramadol consumption did not show a statistically significant difference between Group Mg and Group C (15.5 ± 36.6 mg and 29.2 ± 67.8 mg respectively, p = 0.53). Hemodynamic variables, the incidence of pruritus, nausea, and vomiting were similar in the two groups.

Conclusion

Infusion of MgSO₄ during AH undergoing spinal anesthesia with ITM reduced at 6 hours at rest and on movement. More studies should be performed to evaluate the potential antinociceptive effect of MgSO₄ in scenarios where a multimodal analgesia approach was employed.

Association between ionized magnesium and postoperative shivering

PURPOSE

Ionized magnesium (iMg) is considered to be the biologically active fraction of circulating total serum Mg (tMg). However, only the relationship between tMg and postoperative shivering has been studied. To our knowledge, hitherto no clinical studies have investigated the association between serum ionized magnesium concentration ([iMg]) and postoperative shivering. Therefore, we aimed to retrospectively examine this association, focusing on hypomagnesemia and depletion of [iMg].

METHODS

This retrospective study involved 421 patients who underwent pancreaticoduodenectomy under general anesthesia at our center from December 2012 to September 2019. Logistic regression analysis was performed to estimate the odds ratio (OR) for the incidence of postoperative shivering.

RESULTS

Postoperative shivering developed in 111 out of 421 patients. The post-surgical concentration of [iMg] was significantly associated with postoperative shivering in the non-adjusted model, but not in the multivariable-adjusted model. In multivariable-adjusted analysis, progressive decrease of [iMg] by 0.1 mmol/L significantly increased the risk of postoperative shivering (OR: 1.64, 95% CI 1.02-2.64, p = 0.04). The multivariable-adjusted OR for postoperative shivering was 3.65 (95% CI 1.25-13.55, p = 0.02) in subjects with post-surgical [iMg] less than 0.6 mmol/L and decrease in [iMg] during surgery compared with those with post-surgical [iMg] more than 0.6 mmol/L and constant or increased of [iMg] during surgery.

CONCLUSION

A decrease in the [iMg] during surgery was significantly associated with postoperative shivering. Subjects who had an [iMg] lower than 0.6 mmol/L post-surgery and decreased [iMg] during surgery had a significantly higher risk of postoperative shivering. Intraoperative depletion of [iMg] was significantly associated with shivering.

Ionized or Total Magnesium levels, what should we measure in critical ill patients?

Monitoring and measuring magnesium (Mg) values are essential to prevent the development of numerous complications in perioperative medicine and critically ill patients. Although previous studies suggest that measuring free ionized magnesium (iMg) is more useful for estimating Mg status, clinicians currently rely on measurement of total serum magnesium to determine if supplemental magnesium is needed. In this review, we analyzed the recent literature to decide whether it is better to measure ionized serum Mg or total serum Mg when assessing magnesium status, whether iMg predicts clinical outcome, and what are the difficulties in measuring serum iMg levels in intensive care patients and perioperative medicine.

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.

Effects of perioperative magnesium sulfate infusion on intraoperative blood loss and postoperative analgesia in patients undergoing posterior lumbar spinal fusion surgery: A randomized controlled trial

OBJECTIVE

Many studies have suggested the anti-nociceptive role for magnesium either as an adjunct for postoperative pain. Although several studies have been carried out to evaluate the anti-nociceptive effect of magnesium, there is still considerable uncertainty.

PATIENTS AND METHODS

Eighty patients who underwent posterior spinal fusion were randomly divided into two groups (magnesium and saline). Changes in cell count, magnesium concentration and coagulation status were assessed one hour after operation at both group and compared to baseline. At recovery room, their pain score was assessed according to 10 points visual analogue scale (VAS). Morphine consumption was evaluated at regular times after the surgery by patient controlled analgesia (PCA) device.

RESULTS

VAS scores were significantly lower in the magnesium group. Cumulative PCA morphine consumption after the surgery was significantly lower in the magnesium group. Pre and postoperative values for haemoglobin, platelet count, Prothrombin Time (PT), fibrinogen were not significantly different. There was a significant increase in activated Partial Thromboplastin Time (aPTT), International Normalized Ratio (INR), and bleeding time (BT), one hour after the operation in the magnesium group but intraoperative blood loss was similar in both groups.

CONCLUSIONS

Perioperative magnesium sulfate infusion improves the postoperative analgesia, decreases the amount of morphine consumption after the operation and does not change the intraoperative bleeding in patients undergoing posterior spinal fusion surgery.

Comparative evaluation of epidural bupivacaine alone and bupivacaine combined with magnesium sulfate in providing postoperative analgesia: a meta-analysis of randomized controlled trials

Background

The comparative efficacy of epidural bupivacaine alone and bupivacaine combined with magnesium sulfate in providing postoperative analgesia remains controversial.

Methods

We searched Mediline (OvidSP), EMBASE (OvidSP) and Cochrane Central Register of Controlled Trials (CENTRAL) to identify trials that compared epidural bupivacaine and magnesium sulfate combination (intervention) with bupivacaine alone (control). Grading of Recommendations, Assessment, Development and Evaluations (GRADE) framework was used to assess the quality of evidence.

Results

Eleven studies fulfilled our inclusion criteria after screening. We found that epidural bupivacaine combined with magnesium sulfate could prolong the time for first rescue analgesics (SMD 4.96; 95% CI [2.75, 7.17], P < 0.00001, I² = 98%), reduce the number of patients who need rescue analgesics (RR 0.38; 95% CI [0.20, 0.74], P = 0.004, I² = 75%) and requirement for rescue analgesics (SMD -2.65; 95% CI [− 4.23, − 1.06], P = 0.001, I² = 96%).

Conclusions

Magnesium suifate as an adjuvant of epidural bupivacaine improved postoperative analgesia. However, we rated the quality of evidence to be very low because of high heterogeneity, imprecise of results and small sample sizes. Furthermore, further large high-quality trials are still needed to confirm the effects of magnesium sulfate on postoperative analgesia.