Magnesium moderately decreases remifentanil dosage required for pain management after cardiac surgery †

Pain management after cardiac surgery via median sternotomy: A systematic review with procedure-specific postoperative pain management (PROSPECT) recommendations

BACKGROUND

Pain after cardiac surgery via median sternotomy can be difficult to treat, and if inadequately managed can lead to respiratory complications, prolonged hospital stays and chronic pain.

OBJECTIVES

To evaluate available literature and develop recommendations for optimal pain management after cardiac surgery via median sternotomy.

DESIGN

A systematic review using PROcedure-SPECific Pain Management (PROSPECT) methodology.

ELIGIBILITY CRITERIA

Randomised controlled trials and systematic reviews published in the English language until November 2020 assessing postoperative pain after cardiac surgery via median sternotomy using analgesic, anaesthetic or surgical interventions.

DATA SOURCES

PubMed, Embase and Cochrane Databases.

RESULTS

Of 319 eligible studies, 209 randomised controlled trials and three systematic reviews were included in the final analysis. Pre-operative, intra-operative and postoperative interventions that reduced postoperative pain included paracetamol, non-steroidal anti-inflammatory drugs (NSAIDs), intravenous magnesium, intravenous dexmedetomidine and parasternal block/infiltration.

CONCLUSIONS

The analgesic regimen for cardiac surgery via sternotomy should include paracetamol and NSAIDs, unless contraindicated, administered intra-operatively and continued postoperatively. Intra-operative magnesium and dexmedetomidine infusions may be considered as adjuncts particularly when basic analgesics are not administered. It is not clear if combining dexmedetomidine and magnesium would provide superior pain relief compared with either drug alone. Parasternal block/surgical site infiltration is also recommended. However, no basic analgesics were used in the studies assessing these interventions. Opioids should be reserved for rescue analgesia. Other interventions, including cyclo-oxygenase-2 specific inhibitors, are not recommended because there was insufficient, inconsistent or no evidence to support their use and/or due to safety concerns.

Effect of intraoperative systemic magnesium sulphate on postoperative Richmond Agitation-Sedation Scale score after endovascular repair of aortic aneurysm under general anesthesia: A double-blind, randomized, controlled trial

Intraoperative magnesium has the effect of reducing postoperative opiate requirement, pain, and agitation. However, its effect on postoperative sedation and delirium is unclear. This study investigated the effect of magnesium on the postoperative Richmond Agitation-Sedation Scale (RASS) score and delirium following endovascular repair of aortic aneurysm (EVAR). Sixty-three consecutive patients diagnosed with abdominal (45) and thoracic (18) aortic aneurysm who underwent EVAR under general anesthesia were eligible. Patients were allocated randomly to the magnesium group (infusion of 30 mg•kg-1 magnesium in the first hour followed by 10 mg•kg-1 h-1 until the end of surgical procedure, targeting total 60 mg•kg-1) or the control group (0.9% saline at the same volume and rate). The primary outcome was whether magnesium had an effect on RASS score of patients at postoperative ICU admission. Secondary outcomes were effects on RASS score, numerical rating scale (NRS) score, Confusion Assessment Method for the Intensive Care Unit (CAM-ICU) until 24 h after postoperative ICU transfer, and length of ICU stay. At postoperative ICU admission, magnesium had no significant effect on the RASS score (0[-0.5 to 0] vs 0[0 to 0]; P = 0.114), but at 1 h the NRS score was statistically different, 2[0 to 4] vs 4[0 to 5] (P = 0.0406). However, other data (RASS score, NRS score, CAM-ICU and length of ICU stay) did not show a significant difference. Our results did not show that intraoperative magnesium of target total 60 mg•kg-1 affected postoperative RASS score for undergoing EVAR. Trial registration: The current study was registered according to WHO and ICMJE standards on 4 July 2018, under registration number the Japan Registry of Clinical Trials, iRCTs041190013.

Effect of intravenous magnesium on postoperative pain control for major abdominal surgery: a randomized double-blinded study

Background

This study aimed to evaluate the postoperative analgesic effect of magnesium sulfate during abdominal surgery.

Methods

This randomized double-blinded study involved 84 patients candidates for abdominal surgery into two same groups. In the magnesium group, at first 25 mg/kg/1 h magnesium sulfate; and then, 100 mg/kg/24 h was infused in the intensive care unit. The pain intensity (the primary outcome), was assessed using the numeric rating scale (NRS) every 3 h. If the NRS was > 3, morphine (as a secondary outcome) was used and evaluated. The results were analyzed using SPSS ver. 19 software, and statistical significance was set at P < 0.05

Results

Demographic parameters were similar between the groups. The pain intensity were similar at first and then at the third hour in both groups (P = 0.393 and P = 0.172, respectively), but thereafter between 6 and 24 h, the pain severity was significantly lower in the magnesium group (4.4 ± 1.3 in the control and 3.34 ± 1 in the magnesium group at 6th hour and P = 0.001). In addition, morphine intake in the first 24 h in the two groups had a significant difference, with 13.2 ± 5.7 mg in control group and 8 ± 3.5 mg in magnesium group (P = 0.001).

Conclusions

In this study, intravenous magnesium sulfate after abdominal surgeries for 24 h resolved the pain intensity after six hours and reduced morphine dosage.

Nonopioid Analgesics in Postoperative Pain Management After Cardiac Surgery

Opioid analgesia is still considered the standard of practice for cardiac surgery. In recent years, combinations of several nonnarcotic analgesics and regional analgesia have shown promise in restricting opioid use during and after cardiac surgery. Ketamine infusion, dexmedetomidine infusion, acetaminophen, ketorolac, and gabapentin are useful adjuvants in cardiac anesthesia practice and have opioid-sparing properties. The beneficial effects of nonnarcotic multimodal analgesia on intraoperative stress response, recovery profile, postoperative pain, and persistent opioid use after cardiac surgery are yet to be established, and further randomized clinical trials are required.

Efficacy of transforaminal epidural magnesium administration when combined with a local anaesthetic and steroid in the management of lower limb radicular pain

BACKGROUND

Lower limb radicular pain resulting from a herniated intervertebral disc is a cause of functional disability and could lead to increased consumption of opioids. We evaluated the efficacy of epidural magnesium combined with a local anaesthetic and steroid in the management of this pain.

METHODS

This was a prospective, case-control, randomized, double-blind study. Fifty patients each received 2 ml bupivacaine, 1 ml (40 mg) methylprednisolone and 1 ml saline (0.9%) (group C) or magnesium (200 mg) instead of saline (group M). The primary outcome measure was the improvement in the pain score (assessed using a visual analogue scale (VAS)), and the secondary outcome was the improvement in the functional ability (assessed using the Modified Oswestry Disability Questionnaire (MODQ)). The VAS and MODQ scores were assessed before and at 1 day, 1 week, 1 month and 3 months post-intervention.

RESULTS

The VAS and MODQ scores were significantly better in group M compared to those in group C at all times post-injection (p-value < 0.001). Comparisons within the same group showed that the VAS and MODQ scores were significantly better at all post-injection time points compared to the pre-injection scores in both group C and group M (p-values < 0.0001).

CONCLUSIONS

Adding magnesium to a local anaesthetic and steroid to be injected in the transforaminal epidural space could improve the pain and the quality of life in patients suffering from lower limb radicular pain due to lumbo-sacral disc herniation, and this improvement could last for up to 3 months.

SIGNIFICANCE

Magnesium is efficient when added to local anaesthetics and steroids for management of lower limb radicular pain.

Intraoperative Ketamine and Magnesium Therapy to Control Postoperative Pain After Abdominoplasty and/or Liposuction: A Clinical Randomized Trial

Purpose

This study aimed to compare the effects of ketamine and ketamine associated with magnesium on opioid consumption and pain scores in patients undergoing abdominoplasty and/or liposuction compared to standard treatment.

Patients and Methods

A total of 63 patients were included and randomized as follows: 21 patients in the Control group, 20 patients in the Ketamine group (Ket), and 22 patients in the Ketamine-magnesium group (KetMag). The KetMag group received an IV bolus of 0.3 mg/kg of ketamine and 50 mg/kg magnesium, followed by continuous infusion of ketamine (0.15 mg/kg/h) and magnesium (10 mg/kg/h) until extubation. The Ket group received the same bolus and infusion of ketamine, together with a bolus and continuous infusion of placebo instead of magnesium. The Control group received saline instead of ketamine and magnesium. The groups were compared in morphine consumption during the first 12h, body-postoperative pain and disability scale until the 90th day, the time until the first morphine request on the PCA pump, pain scores, and the adverse effects related to the use of study drugs.

Results

The KetMag group had a lower morphine consumption by almost 50% during the first 12h than the Control and the Ket groups. In addition, the KetMag group required the first dose of morphine later than the other two groups. There were no differences in the adverse effects of the proposed treatments. Finally, multiple linear regression and a nonlinear approach analysis indicated that the Control group experienced a higher degree of pain and increased morphine consumption per hour than Ket and KetMag groups.

Conclusion

Co-administration of intraoperative ketamine plus magnesium and ketamine alone are an effective and easy regime for reducing pain and opioid consumption in the postoperative period.

Preventive effect of oral magnesium in postmastectomy pain: protocol for a randomised, double-blind, controlled clinical trial

INTRODUCTION

Breast cancer affects 1 in 10 women worldwide, and mastectomy is a cause of chronic pain with neuropathic characteristics. N-methyl-D-aspartate receptor (NMDAR) antagonists such as ketamine, memantine, dextromethorphan or magnesium are used to treat refractory pain by blocking NMDAR. Oral memantine has been shown to prevent postmastectomy pain and cognitive impact and to maintain quality of life. Likewise, the present study is intended to assess the preventive effect of oral magnesium, administered ahead of mastectomy, on the development of neuropathic pain. As a physiological blocker of NMDAR, magnesium could be an interesting candidate to prevent postoperative pain and associated comorbidities, including cognitive and emotional disorders, multiple analgesic consumption and impaired quality of life.

METHODS AND ANALYSIS

A randomised double-blind controlled clinical trial (NCT03063931) will include 100 women with breast cancer undergoing mastectomy at the Oncology Hospital, Clermont-Ferrand, France. Magnesium (100 mg/day; n=50) or placebo (n=50) will be administered for 6 weeks, starting 2 weeks before surgery. Intensity of pain, cognitive and emotional function and quality of life will be assessed by questionnaires. The primary endpoint is pain intensity on a 0-10 numerical rating scale at 1 month postmastectomy. Data analysis will use mixed models; all tests will be two-tailed, with type-I error set at α=0.05.

ETHICS AND DISSEMINATION

The study protocol and informed consent form were approved in December 2016 by the French Research Ethics Committee (South East VI Committee). Results will be communicated in various congresses and published in international publications.

TRIAL REGISTRATION NUMBER

NCT03063931.

Analgesic effect and safety of single-dose intra-articular magnesium after arthroscopic surgery: a systematic review and meta-analysis

To examine the analgesic effect and safety of single-dose intra-articular (IA) magnesium (Mg) after arthroscopic surgery. Pubmed, Embase and Cochrane library were searched through in January 2016. Eight RCTs and eight experimental studies were included. The IA Mg exhibited a significantly lower pain score when compared with placebo (MD, -0.41, 95% CI, -0.78 to -0.05, p = 0.03). There was no significant difference between Mg and bupivacaine in terms of pain relief and the time to first analgesic request. Furthermore, statistically significant differences both in pain score (MD, -0.62, 95% CI, -0.81 to -0.42, p < 0.00001) and time to first analgesic request (MD, 6.25, 95% CI, 5.22 to 7.29, p < 0.00001) were observed between Mg plus bupivacaine and bupivacaine alone. There was no statistically significant difference among the various groups with respect to adverse reactions. Most of the included in vitro studies reported the chondrocyte protective effect of Mg supplementation. There were also two in vivo studies showing the cartilage protective effect of IA Mg. The single-dose IA Mg following arthroscopic surgery was effective in pain relief without increasing adverse reactions, and it could also enhance the analgesic effect of bupivacaine. In addition, Mg seemed to possess the cartilage or chondrocyte protective effect based on experimental studies.

Novel treatment in refractory tic douloureux

A patient with refractory trigeminal neuralgia (tic douloureux) was treated by intravenous magnesium sulfate successfully. Parenteral magnesium sulfate is an analgesic that expresses its analgesic effects through a noncompetitive blockade of the N-methyl-D-aspartate (NMDA) receptors, which in turns inhibits calcium entry into the cells.

Ketamine and magnesium association reduces morphine consumption after scoliosis surgery: prospective randomised double-blind study

BACKGROUND

Scoliosis repair is a major orthopaedic surgery associated with severe post-operative pain. Ketamine and magnesium have an established efficacy as morphine-sparing agents. Our purpose was to evaluate the morphine-sparing effect of both magnesium and ketamine given simultaneously compared with ketamine alone during scoliosis surgery.

METHODS

Fifty patients scheduled for posterior instrumentation were randomised in a prospective double-blind study. The Gr (K + Mg) received, after induction, an intravenous (IV) bolus of ketamine 0.2 mg/kg and magnesium 50 mg/kg, followed by continuous infusion of ketamine (0.15 mg/kg/h) and magnesium (8 mg/kg/h) until extubation. The Gr (K) received the same dose of ketamine associated with bolus and continuous infusion of normal saline. All patients received multimodal analgesia associated with IV morphine administered via patient-controlled analgesia pump. Morphine consumption, visual analogue scale (VAS) pain scores and occurrence of side effects were followed until 48 h post-operatively. Sleep quality and patient satisfaction were also followed. P < 0.05 was considered statistically significant.

RESULTS

The average cumulative morphine consumption was significantly lower in the Gr (K + Mg) compared with the Gr (K) at post-operative hours 4, 8, 12, 18, 30, 36 and 48. The relative difference in the post-operative morphine consumption was 29.5%: Gr (K + Mg) 51.53 mg vs. Gr (K) 73.16 mg. VAS scores were not statistically different between the two groups. However, qualities of sleep and satisfaction scores on the first night were significantly better in the Gr (K + Mg) (P = 0.027 and P = 0.016, respectively).

CONCLUSION

Ketamine and magnesium association reduces the post-operative morphine consumption after scoliosis surgery. It seems to provide a better sleep quality and improves patient satisfaction.

Perioperative Systemic Magnesium to Minimize Postoperative Pain

Background:

Systemic magnesium has been used to minimize postoperative pain with conflicting results by clinical studies. It remains unknown whether the administration of perioperative systemic magnesium can minimize postoperative pain. The objective of the current investigation was to evaluate the effect of systemic magnesium on postoperative pain outcomes.

Methods:

A wide search was performed to identify randomized controlled trials that evaluated the effects of systemic magnesium on postoperative pain outcomes in surgical procedures performed under general anesthesia. Meta-analysis was performed using a random-effect model. Publication bias was evaluated by examining the presence of asymmetric funnel plots using Egger regression.

Results:

Twenty randomized clinical trials with 1,257 subjects were included. The weighted mean difference (99% CI) of the combined effects favored magnesium over control for pain at rest (≤4 h, −0.74 [−1.08 to −0.48]; 24 h, −0.36 [−0.63 to −0.09]) and with movement at 24 h, −0.73 (−1.37 to −0.1). Opioid consumption was largely decreased in the systemic magnesium group compared with control, weighted mean difference (99% CI) of −10.52 (−13.50 to −7.54) mg morphine IV equivalents. Publication bias was not present in any of the analysis. Significant heterogeneity was present in some analysis, but it could be partially explained by the sole intraoperative administration of magnesium compared with the intraoperative and postoperative administration. None of the studies reported clinical toxicity related to toxic serum levels of magnesium.

Conclusion:

Systemic administration of perioperative magnesium reduces postoperative pain and opioid consumption. Magnesium administration should be considered as a strategy to mitigate postoperative pain in surgical patients.

Is magnesium sulfate by the intrathecal route efficient and safe?

The polypharmacological approach to the treatment of postoperative pain has become routine in an attempt to minimize the adverse side effects of opioids. Magnesium sulphate is a noncompetitive antagonist of the N-methyl-d-aspartate (NMDA) receptor and thus can modify nociceptive modulation. Intravenous administration of magnesium sulphate can improve postoperative analgesia and decrease the requirement for postoperative opiates, but the effects are inconsistent and have not been reliably accompanied by a reduction in the incidence of morphine-related adverse events. Several studies have shown that the administration of magnesium by the intrathecal route is safe and, in combination with opiates, extends the effect of spinal anaesthesia in both animal and human studies. The analysis of these studies justifies further investigation of the use of magnesium sulphate by the intrathecal route.

Controlled hypotension for middle ear surgery: a comparison between remifentanil and magnesium sulphate

BACKGROUND

This prospective, randomized study was designed to compare remifentanil and magnesium sulphate during middle ear surgery in terms of postoperative pain and other complications.

METHODS

Eighty patients undergoing middle ear surgery were enrolled in the study. Patients were randomized into two groups of 40 to receive remifentanil (Group R) or magnesium sulphate (Group M) infusion. Propofol 2 mg kg(-1) was administered to induce anaesthesia, which was maintained using sevoflurane. Group R received a continuous infusion of remifentanil titrated between 3 and 4 ng ml(-1) using target-controlled infusion, whereas Group M received an i.v. magnesium sulphate bolus of 50 mg kg(-1) followed by a 15 mg kg(-1) h(-1) continuous infusion to maintain a mean arterial pressure (MAP) between 60 and 70 mm Hg. Haemodynamic variables, surgical conditions, postoperative pain, and adverse effects, such as postoperative nausea and vomiting (PONV) and shivering, were recorded.

RESULTS

Controlled hypotension was well maintained in both groups. MAP and heart rate were higher in Group R than in Group M after operation. Surgical conditions were not different between the two groups. Postoperative pain scores were significantly lower in Group M than in Group R (P<0.05). Seventeen patients in Group R (43%) and seven patients in Group M (18%) developed PONV (P=0.01).

CONCLUSIONS

Both magnesium sulphate and remifentanil when combined with sevoflurane provided adequate controlled hypotension and proper surgical conditions for middle ear surgery. However, patients administered magnesium sulphate had a more favourable postoperative course with better analgesia and less shivering and PONV.

Controlled hypotension in adults undergoing choroidal melanoma resection: comparison between the efficacy of nitroprusside and magnesium sulphate

BACKGROUND AND OBJECTIVE

To determine whether magnesium sulphate could induce controlled hypotension, reduce choroidal blood flow, provide a 'dry' operative field and could be compared with sodium nitroprusside in the recently raised issue of the use of hypotensive anaesthesia in eye surgery, i.e. for choroidal tumour surgery as the choroid is the most fragile and vascular structure in the eye.

METHODS

Forty adult patients undergoing choroidal melanoma resection and anaesthetized with 2.5 mg kg(-1) propofol, followed by a constant infusion of 120 microg kg(-1) min(-1), and remifentanil 1 microg kg(-1), followed by a continuous infusion of 0.25 microg kg(-1) min(-1), were randomly assigned to two groups to receive either magnesium sulphate or sodium nitroprusside.

RESULTS

Controlled hypotension was achieved at the target systolic pressure of 80 mmHg within 107 +/- 16 and 69 +/- 4.4 s for magnesium sulphate and sodium nitroprusside, respectively. Choroidal blood flow decreased by 24 +/- 0.3% and 22 +/- 3.3% for magnesium sulphate and sodium nitroprusside, respectively. Controlled hypotension was sustained in both groups throughout surgery, and the surgical field rating decreased in a range of 80% in both groups. Sodium nitroprusside decreased pH and increased PaCO2. There were no postoperative complications in any of the groups.

CONCLUSION

Magnesium sulphate controlled hypotension, reduced intraoperative pressure and provided good surgical conditions for choroidal melanoma resection with no need for additional use of a potent hypotensive agent in adults.

Magnesium as an adjuvant to postoperative analgesia: a systematic review of randomized trials

BACKGROUND

Randomized trials have reached different conclusions as to whether magnesium is a useful adjuvant to postoperative analgesia.

METHODS

We performed a comprehensive search (electronic databases, bibliographies, all languages, to 4.2006) for randomized comparisons of magnesium and placebo in the surgical setting. Information on postoperative pain intensity and analgesic requirements was extracted from the trials and compared qualitatively. Dichotomous data on adverse effects were combined using classic methods of meta-analysis.

RESULTS

Fourteen randomized trials (778 patients, 404 received magnesium) tested magnesium laevulinate, gluconate or sulfate. With magnesium, postoperative pain intensity was significantly decreased in four (29%) trials, was no different from placebo in seven (50%), and was increased in one (7%); two trials (14%) did not report on pain intensity. With magnesium, postoperative analgesic requirements were significantly reduced in eight (57%) trials, were no different from placebo in five (36%), and were increased in one (7%). Magnesium-treated patients had less postoperative shivering (relative risk 0.38, 95% confidence interval 0.17-0.88, number-needed-to-treat 14). Seven trials reported on magnesium serum levels. In all, serum levels were increased in patients who received magnesium; in six, serum levels were decreased in those who received placebo.

CONCLUSIONS

These trials do not provide convincing evidence that perioperative magnesium may have favorable effects on postoperative pain intensity and analgesic requirements. Perioperative magnesium supplementation prevents postoperative hypomagnesemia and decreases the incidence of postoperative shivering. It may be worthwhile to further study the role of magnesium as a supplement to postoperative analgesia, since this relatively harmless molecule is inexpensive, and the biological basis for its potential antinociceptive effect is promising.

Autonomic effects of epidural and intravenous fentanyl

BACKGROUND

We tested the hypothesis that there is greater suppression of autonomic reflexes during general anaesthesia when fentanyl is administered epidurally than when it is given intravenously.

METHODS

Ten volunteers were anaesthetized with desflurane. Noxious stimuli of variable intensity were then delivered by tetanic electrical stimuli. Heart rate, arterial pressure, and pupillary dilation in response to these stimuli defined nociception. Seven of these volunteers participated twice using a crossover design: they received i.v. fentanyl on one study day and epidurally on the other. Autonomic responses to alternative tetanic stimuli at L4 and C5 dermatomes were measured every 5 min for 3 h after fentanyl administration.

RESULTS

After a brief redistribution period, plasma fentanyl concentrations were virtually identical on both days. After stimulation of the L4 dermatome only, block of pupillary reflex dilation was greater by 47 (22)% after epidural fentanyl compared with i.v. fentanyl. Time to maximal depression of reflex dilation after L4 stimulation was 41 (13) min. Arterial pressure and heart rate decreased after fentanyl by either route but there were no differences observed between L4 and C5 stimulations.

CONCLUSION

We conclude that during general anaesthesia, epidural fentanyl enhances antinociception by a spinal mechanism which can be detected by pupillary dilation but not by changes in arterial pressure or heart rate.