The effect of intravenous magnesium sulfate infusion on reduction of pain after abdominal hysterectomy under general anesthesia: a double-blind, randomized clinical trial

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.

Intravenous magnesium sulphate in standing horses: effects on physiological parameters, plasma concentration of magnesium and nociceptive threshold tests

A bolus of 50 mg kg ^-1 MgSO₄ (treatment Mg) or the same volume of saline (treatment S) was infused over 15 minutes in 5 adult healthy horses. T0 was the end of the infusion. Physiological parameters were recorded throughout the study period. Measurements of electrical, thermal and mechanical nociceptive thresholds were performed at the pelvic limbs at baseline (before T0), and at specific timepoints. Blood samples were taken at fixed timepoints before, during and until 12 hours after the infusion. For statistical analysis, the 95% confidence intervals (CI's) for the differences in nociceptive thresholds between treatments were calculated. Physiological parameters were compared using a linear mixed model (global α = 0.05, with Bonferroni correction α = 0.0125). The concentrations of ions were also compared with baseline values at specific timepoints, using a linear mixed model. The Pearson's correlation coefficient was derived between the ion concentrations. The 95% CI's of thermal, mechanical and electrical thresholds were [-1; +2]°C, [0; +3] N and [-1; +1] mA (positive differences indicate higher thresholds for treatment Mg), respectively. Heart rate was significantly higher (p < 0.0001) and non-invasive systolic arterial pressure (p < 0.0001) and respiratory rate (p = 0.0002) significantly lower after treatment Mg compared to treatment S. Additionally, non-invasive systolic arterial pressure was significantly different at T45 (p < 0.001). Although mild changes in cardiovascular parameters and plasma concentrations were seen with intravenous administration of MgSO₄, no changes in nociceptive thresholds were detected in standing non-sedated horses.

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.

Pregabalin does not decrease acute pain or postoperative nausea and vomiting after hysterectomy: a meta-analysis

OBJECTIVE

Hysterectomy is associated with severe postoperative pain. The relative efficacy of pregabalin compared with other treatments for post-hysterectomy pain is unclear.

METHODS

We searched the PubMed, Cochrane Library, and Web of Science databases for studies that compared the use of pregabalin and placebo for reducing pain in patients undergoing hysterectomy.

RESULTS

This meta-analysis showed that pregabalin had limited pain-relieving effects at 2, 6, 24, and 48 hours after hysterectomy compared with placebo. Pregabalin significantly reduced postoperative nausea and vomiting. However, there was no significant difference in postoperative sedation or visual disturbances between patients treated with pregabalin and placebo.

CONCLUSIONS

Pregabalin is not clinically superior to placebo in terms of reducing pain intensity and morphine consumption in patients undergoing hysterectomy. However, the limitations of this meta-analysis mean that more high-quality randomized controlled trials are necessary to verify our pooled results.

Utilization of Magnesium for the Treatment of Chronic Pain

CONTEXT

The International Association for the Study of Pain (IASP) defines chronic pain as pain that persists or recurs for longer than 3 months. Chronic pain has a significant global disease burden with profound effects on health, quality of life, and socioeconomic costs.

EVIDENCE ACQUISITION

Narrative review.

RESULTS

There are several treatment options, including pharmacological therapy, physical rehabilitation, psychological therapies, and surgical interventions, for chronic pain management. Magnesium has been FDA-approved for several indications including hypomagnesemia, arrhythmia, prevention of seizures in eclampsia/preeclampsia, and constipation. Magnesium has been used for numerous off-label uses, notably for acute and chronic pain management. The mechanism of magnesium in pain management is primarily through its action as a voltage-gated antagonist of NMDA receptors, which are involved in pain transduction.

CONCLUSIONS

This narrative review will focus on the current evidence and data surrounding the utilization of magnesium as a treatment option for chronic pain.

Effects of magnesium sulfate administration in attenuating chronic postsurgical pain in rats

Chronic postsurgical pain (CPSP) is a serious issue for many postoperative patients. Though there are numerous treatment options for the prevention of CPSP, none of them is optimal as the mechanisms of the transition from acute to chronic postoperative pain have not been elucidated. Ketamine and opioids have been administered for chronic postoperative pain treatment but induce severe adverse reactions and/or physical dependency. Here, we examined whether pre-administration of the nonselective N-methyl-d-aspartate (NMDA) receptor antagonist magnesium sulfate attenuates CPSP behavior and alters the expression of glutamate ionotropic receptor NMDA type subunit 1a (Grin1 mRNA) in a rat skin/muscle incision and retraction (SMIR) model. We assessed the effects of a single subcutaneous magnesium sulfate injection on nociceptive behaviors including guarding pain, mechanical hyperalgesia, and heat hypersensitivity in rats after SMIR surgery. We used reverse transcription-quantitative PCR (RT-qPCR) to evaluate Grin1 mRNA expression in the dorsal horn of the spinal cord on postoperative day 14. Compared with the vehicle, magnesium sulfate administration before SMIR surgery reduced mechanical hyperalgesia for 17 d Grin1 gene expression was significantly higher on the ipsilateral side than the contralateral side (P = 0.001) on postoperative day 14. The magnesium sulfate injection prevented Grin1 mRNA upregulation in the spinal cord dorsal horn. A single magnesium sulfate injection mitigated SMIR-induced mechanical hyperalgesia possibly by modulating Grin1 expression. Preoperative magnesium sulfate administration could prove to be a simple and safe CPSP treatment.

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.

Pregabalin can decrease acute pain and postoperative nausea and vomiting in hysterectomy: A meta-analysis

BACKGROUND

Whether the preoperative administration of pregabalin plays a beneficial role in controlling acute pain after hysterectomy is unknown. We performed a systematic review and meta-analysis of randomized controlled trials (RCTs) to determine the efficacy and safety of the preoperative use of pregabalin to treat acute postoperative pain following hysterectomy.

METHODS

In April 2017, a systematic computer-based search was conducted in the PubMed, EMBASE, Web of Science, Cochrane Library, and Google databases. RCTs comparing pregabalin with placebo in patients undergoing hysterectomy were retrieved. The primary endpoint was the visual analog scale (VAS) score with rest or mobilization at 2 h, 4 and 24 hours and cumulative morphine consumption at 2, 4, 24, and 48 hours. The secondary outcomes were complications of nausea, vomiting, sedation, and dizziness. After tests for publication bias and heterogeneity among studies were performed, the data were aggregated for random-effects models when necessary.

RESULTS

Ten clinical studies with 1207 patients (pregabalin = 760, control = 447) were finally included in this meta-analysis. Preoperative administration of pregabalin was associated with a significant reduction of VAS with rest or mobilization at 2, 4, and 24 hours after hysterectomy. Further, the preoperative administration of pregabalin was associated with a reduction in total morphine consumption at 2, 4, 24, and 48 hours after hysterectomy. The occurrence of morphine-related complications (nausea and vomiting) was also reduced in the pregabalin group. However, the preoperative administration of pregabalin was associated with an increase in the occurrence of dizziness. There was no significant difference in the occurrence of sedation.

CONCLUSIONS

The preoperative use of pregabalin reduced postoperative pain, total morphine consumption, and morphine-related complications following hysterectomy. The doses of pregabalin were different, and large heterogeneity was the limitation of the current meta-analysis. Further studies should determine the optimal dose for controlling acute pain after hysterectomy.