Effect of low-dose (single-dose) magnesium sulfate on postoperative analgesia in hysterectomy patients receiving balanced general anesthesia

Adjuvant Analgesics in Acute Pain - Evaluation of Efficacy

PURPOSE OF THE REVIEW

Acute postoperative pain impacts a significant number of patients and is associated with various complications, such as a higher occurrence of chronic postsurgical pain as well as increased morbidity and mortality.

RECENT FINDINGS

Opioids are often used to manage severe pain, but they come with serious adverse effects, such as sedation, respiratory depression, postoperative nausea and vomiting, and impaired bowel function. Therefore, most enhanced recovery after surgery protocols promote multimodal analgesia, which includes adjuvant analgesics, to provide optimal pain control. In this article, we aim to offer a comprehensive review of the contemporary literature on adjuvant analgesics in the management of acute pain, especially in the perioperative setting. Adjuvant analgesics have proven efficacy in treating postoperative pain and reducing need for opioids. While ketamine is an established option for opioid-dependent patients, magnesium and α2-agonists have, in addition to their analgetic effect, the potential to attenuate hemodynamic responses, which make them especially useful in painful laparoscopic procedures. Furthermore, α2-agonists and dexamethasone can extend the analgesic effect of regional anesthesia techniques. However, findings for lidocaine remain inconclusive.

Magnesium Sulfate and Its Versatility in Anesthesia: A Comprehensive Review

In the field of general anesthesia, magnesium sulfate (MgSO4) has become a valuable adjunct because it provides a range of benefits that enhance and optimize conventional aesthetic procedures. This review highlights the various intra-anesthetic benefits of MgSO4 while examining its complex function in the treatment using anesthesia. Magnesium inhibits the release of acetylcholine at the motor endplate and blocks calcium channels at presynaptic nerve terminals. This reduces the amplitude of endplate potential and the excitability of muscle fibers, which increases the potency of a neuromuscular blockade by nondepolarizing neuromuscular blockers. This activity may lessen the need for primary muscle relaxants. Moreover, its capacity to potentially reduce the total amount of main aesthetic agents needed emphasizes its function in maximizing anesthesia dosage, ensuring sufficient depth while perhaps potentially reducing adverse effects linked with increased dosages. MgSO4's adaptable qualities present a viable path for improving anesthetic outcomes, possibly improving patient safety and improving surgical results.

Analgesic Effects of Magnesium Sulphate as an Adjuvant to Fentanyl for Monitored Anaesthesia Care During Hysteroscopy

BACKGROUND

Magnesium sulphate (MgSO4) is conventionally used in the treatment of eclampsia, refractive arrhythmias, asthma, etc. In our study, we aimed to study the analgesic effects of MgSO4 as an adjuvant to fentanyl and reduce the intraoperative opioid requirement to decrease their adverse effects.

METHODS

A total of 122 patients scheduled for hysteroscopy were randomly divided into two groups. Patients in the magnesium group (group A) received intravenous MgSO4 50 mg/kg in 100 ml of isotonic saline over 15 minutes before anaesthesia induction and then 15 mg/kg per hour by continuous intravenous infusion. Patients in the control group (group B) received an equal volume of isotonic saline as a placebo. All the patients were induced with fentanyl and propofol. Perioperative haemodynamic monitoring and postoperative assessment of pain were done.

RESULTS

Only 18% of the patients in group A required rescue analgesics as compared to 39.3% of patients in group B. The patients receiving MgSO4 displayed lower verbal numeric rating scale scores in the postoperative period. In addition, the intraoperative requirement of fentanyl (101 (21.33) vs. 144 (28.4) µg, mean (SD)) and propofol (121 (13.3) vs. 140 (16.5) mg, mean (SD)) was significantly lower in group A as compared to that in group B.

CONCLUSION

MgSO4, when administered as an adjuvant to opioids, provided effective postoperative analgesia thereby reducing the need for rescue analgesics. It also decreases intraoperative fentanyl consumption and its dose-related side effects.

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.

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.

Is Multimodal Anesthesia Effecting Postoperative Nausea and Vomiting in Laparoscopic Cholecystectomy?

Background: Multimodal anesthesia represents a technique that can improve analgesia and lower the occurrence of opioid side effects in the postoperative period, such as postoperative nausea and vomiting (PONV). It can be achieved by providing different types of medication during the intraoperative period which can decrease the need for opioids. PONV happens more often in patients who have received large amounts of opioids during laparoscopic cholecystectomy. In this study, our aim was to observe the occurrence of PONV between three different groups of patients who received lidocaine, ketamine and magnesium sulfate in combination with fentanyl in the intraoperative period. We also observed any additional nausea and vomiting in the three groups as well as the amount of fentanyl given to these groups during operation. Materials and methods: 120 patients aged 20-65 years old were included in this randomized and prospective study, ASA classification 1 and 2, scheduled for laparoscopic cholecystectomy. Patients were classified into three groups randomly: Group 1 (lidocaine group-LG), these patients received lidocaine at 1 mg/kg during induction to general anesthesia and 2 mg/kg/h after intubation in continuous intravenous infusion; Group 2 (ketamine group-KG) these patients received ketamine at 0.5 mg/kg during induction to general anesthesia; and Group 3 (magnesium group-MG) these patients received magnesium sulfate at 1.5 gr/hr as a continuous intravenous infusion after intubation. In all three groups, patients additionally received bolus doses of fentanyl. Postoperative nausea and vomiting were monitored in all three groups at 1, 4, 8, 12, and 24 hours after surgery as a primary objective, and if patients had complainant of vomiting, they were treated with 10 mg of metoclopramid. Between the five control time points, additional nausea and vomiting was recorded as well, as a secondary objective. The third objective was to measure of the total amount of fentanyl given in the intraoperative period. Results: Patients from the lidocaine group experienced less PONV and they received less fentanyl compared to patients of ketamine and magnesium groups. Patients from the ketamine group had more nausea than other groups. In the magnesium group, the rate of vomiting was higher, and they received higher amounts of fentanyl during surgery. Additional nausea and vomiting occurred in 3 patients in the LG, 2 in the KG, and 3 in the MG between the five control time points. The patients from the magnesium group received the highest dose of fentanyl during surgery (307.50 ± 130.4), followed by the patients from the ketamine group (292.50 ± 60.5), and then patients from the lidocaine group (258.75 ± 60.9). The doses of fentanyl that patients received during surgery in all three groups were not statistically significant. Conclusion: Multimodal anesthesia has been shown to lower PONV 24 hours after laparoscopic cholecystectomy and can lower need for opioids during laparoscopic cholecystectomy.

Pain and Multimodal Analgesia in Laparoscopic Cholecystectomy

Background: The administration of high doses of opioids during surgery can lead to higher postoperative pain scores at rest and when coughing. Multimodal analgesia may lower the need for opioids during surgery and the suffering of postoperative pain. Multimodal analgesia can be achieved by providing non-opioid drugs (lidocaine, ketamine, and magnesium sulfate), three different types of drugs. Each of these drugs as different analgesic effects and they belong to three different pharmacological groups. The aim of this study is to develop a better understanding of the effects of each drug (lidocaine, ketamine, and magnesium sulfate) on postoperative analgesia, the needs for rescue analgesics, and analyze the total amount of fentanyl during the intraoperative period in patients undergoing laparoscopic cholecystectomy. Methods: 120 patients were enrolled in this randomized controlled study. They were classified as ASA 1 and 2 and were scheduled for laparoscopic cholecystectomy. They were further divided into 3 groups. Group 1, or the lidocaine group, had received lidocaine at 1 mg/kg and a continuous intravenous infusion with lidocaine at 2 mg/kg/h. Group 2, or the ketamine group, received ketamine at 0.5 mg/kg. Group 3, or the magnesium sulfate group, received a continuous intravenous infusion of magnesium sulfate at 1.5 gr/kg. The intensity of postoperative pain was assessed using a VAS score at rest and when coughing, with evaluation at 1, 4, 8, 12, and 24 hours, postoperatively. Also, the needs for rescue analgesics and the total amount of fentanyl during the intraoperative period in all groups was also followed. Results: The patients from the lidocaine group had the highest scores of pain in the postoperative period at rest and when coughing, and the ketamine group had the lowest pain scores. Rescue analgesia was given the most to lidocaine group, and less so in the magnesium group. The magnesium group received the highest dose of fentanyl during surgery and the lowest dose was received by patients from the lidocaine group. Conclusion: Multimodal analgesia can lower the need for opioids in the intra- and postoperative period after laparoscopic cholecystectomy.

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.

The effect of preoperative oral magnesium oxide on the severity of postoperative pain among women undergoing hysterectomy

BACKGROUND

Magnesium sulfate has been reported to be effective in perioperative pain treatment and in blunting somatic, autonomic, and endocrine reflexes provoked by noxious stimuli. The pre-emptive analgesic effects of magnesium in reducing postoperative pain could be beneficial in abdominal and gynecologic surgeries.

OBJECTIVE

The aim of study was to compare the pre-emptive analgesic effects of oral magnesium oxide and naproxen for hysterectomy surgery.

METHODS

This study evaluated all patients who were candidates for hysterectomy in 2 months. The 64 patients were randomly divided into two groups using a random allocation sequence. The patients in the intervention and control groups received either magnesium oxide tablet (500 mg) or naproxen tablet (500 mg) orally half an hour before surgery, respectively. The severity of postoperative pain is assumed as a primary outcome which is evaluated using the visual analogue scale (VAS).

RESULTS

In this study, 64 patients were assessed. The results showed age, weight, systolic and diastolic blood pressure, and pulse rate of the patients in the two groups were not significantly different (p > 0.05). The mean score of pain intensity for these patients was significantly lower than the patients receiving naproxen (p-value: 0.03). Besides, more than one-quarter of patients in the magnesium oxide group (n = 9, 28.12%) received this analgesia with lower dose than the patients in the naproxen group (p-value: 0.03).

CONCLUSION

The results of this study showed that preoperative oral magnesium oxide had a significant effect on the severity of postoperative pain and consumption of postoperative analgesia.

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.

The Effect of Intraoperative Magnesium Sulphate Infusion on Emergence Agitation after Ambulatory Ophthalmic Surgery in Children

This study investigated whether intraoperative infusion of magnesium sulphate reduces the incidence of emergence agitation (EA) in paediatric patients who undergo ambulatory ophthalmic surgery using the Paediatric Anaesthesia Emergence Delirium (PAED) scale. Ninety-two paediatric patients who were scheduled for elective ophthalmic surgery were randomly allocated to two groups: control or magnesium. In the magnesium group, patients received an initial intravenous loading dose of 30 mg/kg of 10% solution of magnesium sulphate over 10 min and then a continuous infusion of 10 mg/kg×h during the surgery. In the control group, an equal volume of 0.9% isotonic saline was administered in the same way as in the magnesium group. The PAED scale was assessed at 15-min intervals until the PAED score reached below 10 at the postanaesthetic care unit. EA was defined as a PAED score of 10 or higher. Of the 86 patients recruited, 44 and 42 were allocated to the control and magnesium groups, respectively. The incidence of EA was 77.3% in the control group and 57.1% in the magnesium group (odds ratio, 0.392; 95% confidence interval, 0.154 to 0.997; p = 0.046). The intraoperative infusion of magnesium sulphate significantly reduced the incidence of EA.

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.

The Influence of Two Different Doses of Magnesium Sulfate on Intraocular Pressure Variations after Injection of Succinylcholine and Endotracheal Intubation: A Prospective, Randomized, Parallel Three-Arm, Double-blind, Placebo-controlled Clinical Trial

Background:

The use of succinylcholine for rapid sequence induction in patients with open globe injuries may be detrimental to the eye.

Aim:

The aim of this study is to determine if the premedication with magnesium sulfate (MgSO₄) could attenuate the increase in intraocular pressure (IOP) associated with succinylcholine injection and intubation.

Setting:

Operation theaters in a tertiary care University Hospital between December 2014 and July 215.

Design:

This was a prospective, randomized, parallel three-arm, double-blind, placebo-controlled clinical trial.

Participants:

One hundred and thirteen patients’ physical status ASA Classes I and II underwent elective cataract surgery under general anesthesia.

Patients and Methods:

These patients allocated into three groups: Group C (control group) received 100 ml normal saline, Group M1 received 30 mg/kg MgSO₄ in 100 ml normal saline, and Group M2 received 50 mg/kg MgSO₄ in 100 ml normal saline. IOP, mean arterial pressure (MAP), and heart rate (HR) reported at 5-time points related to study drug administration. In addition, any adverse effects related to MgSO₄ were recorded. Intragroup and between-groups differences were examined by analysis of variance test.

Results:

We noticed a significant decrease in IOP in M1 (n = 38) and M2 (n = 37) groups as compared with C group (n = 38) after study drugs infusion, 2 and 5 min after intubation, P < 0.001. While the difference between M1 and M2 groups was insignificant, P = 0.296 and P = 0.647, respectively. There was a significant decrease in MAP and HR in M1 and M2 groups as compared with C group 2 and 5 min after intubation, P = 0.01. While the difference between M1 and M2 groups was insignificant, P = 1.

Conclusion:

MgSO₄ 30 mg/kg as well as 50 mg/kg effectively prevented the rise in IOP, MAP, and HR associated with rapid sequence induction by succinylcholine and endotracheal intubation.

Magnesium in obstetric anesthesia and intensive care

Magnesium, one of the essential elements in the human body, has numerous favorable effects that offer a variety of possibilities for its use in obstetric anesthesia and intensive care. Administered as a single intravenous bolus dose or a bolus followed by continuous infusion during surgery, magnesium attenuates stress response to endotracheal intubation, and reduces intraoperative anesthetic and postoperative analgesic requirements, while at the same time preserving favorable hemodynamics. Applied as part of an intrathecal or epidural anesthetic mixture, magnesium prolongs the duration of anesthesia and diminishes total postoperative analgesic consumption with no adverse maternal or neonatal effects. In obstetric intensive care, magnesium represents a first-choice medication in the treatment and prevention of eclamptic seizures. If used in recommended doses with close monitoring, magnesium is a safe and effective medication.