Neurotoxic effects of intrathecal magnesium sulphate

The analgesic effects of magnesium in veterinary patients: a qualitative evidence synthesis

OBJECTIVE

To perform a qualitative evaluation of the analgesic effects of magnesium in domestic animals, including its anaesthetic sparing effects.

STUDY DESIGN

All database searches were made using PubMed and Google Scholar. Studies published after 1990, evaluating the use of magnesium and reporting information on analgesia, in dogs, cats, horses, cows, goats and sheep were selected (last search in August 2023). A reference check in the selected papers was performed to identify any study which was omitted. The CERQual (Confidence in Evidence from Reviews of Qualitative research) approach was used to assess confidence and analyse the evidence.

RESULTS

A total of 20 studies relevant to the analgesic effects of magnesium in veterinary patients and two reviews were included. All were published after 2006. Of the 20, five studies provided information about analgesia in the postoperative period in dogs with heterogenous results. Magnesium added epidurally increased the duration of the sensory block in several species. Motor block was also observed when added to spinal analgesia. Results regarding volatile agents sparing effect were conflicting. Occasional moderate adverse effects were reported in dogs, such as nausea and vomiting, when administered as a bolus in conscious animals, and hypotension when administered intraperitoneally. Collapse was reported in horses after epidural administration.

CONCLUSIONS AND CLINICAL RELEVANCE

The evidence of an analgesic effect of magnesium in veterinary patients remains scarce considering the paucity and low quality of published data. Further research may be helpful to establish the efficacy and indications of magnesium in multimodal analgesia in animals.

The effects of magnesium sulfate added to epidurally administered local anesthetic on postoperative pain: a systematic review

BACKGROUND

This study evaluated the efficacy of epidurally administered magnesium associated with local anesthetics on postoperative pain control.

METHODS

The study protocol was registered in PROSPERO as CRD42021231910. Literature searches were conducted on Medline, Cochrane, EMBASE, CENTRAL, and Web of Science for randomized controlled trials comparing epidural administration of magnesium added to local anesthetics for postoperative pain in elective surgical adult patients. Primary outcomes were the time to the first Postoperative (PO) Analgesic Request (TFAR), 24-hour postoperative opioid consumption, and Visual Analog Scale (VAS) scores at the first six and 24 postoperative hours. Secondary outcomes included Postoperative Nausea and Vomiting (PONV), pruritus, and shivering. Quality of evidence was assessed using GRADE criteria.

RESULTS

Seventeen studies comparing epidural were included. Effect estimates are described as weighted Mean Differences (MD) and 95% Confidence Intervals (95% CI) for the main outcomes: TFAR (MD = 72.4 min; 95% CI = 10.22-134.58 min; p < 0.001; I² = 99.8%; GRADE: very low); opioid consumption (MD = -7.2 mg (95% CI = -9.30 - -5.09; p < 0.001; I² = 98%; GRADE: very low). VAS pain scores within the first six PO hours (VAS) (MD = -1.01 cm; 95% CI = -1.40-0.64 cm; p < 0.001; I² = 88%; GRADE: very low), at 24 hours (MD = -0.56 cm; 95% CI = -1.14-0.01 cm; p = 0.05; I² = 97%; GRADE: very low).

CONCLUSIONS

Magnesium sulfate delayed TFAR and decreased 24-hour opioid consumption and early postoperative pain intensity. However, imprecision and inconsistency pervaded meta-analyses, causing very low certainty of effect estimates.

Could soluble minerals be hazardous to human health? Evidence from fibrous epsomite

From a toxicological point of view, particulates and fibres with high solubility in water and/or in biological environments have not been considered in detail and the knowledge to date in this area is very scarce. In this study, the water-soluble natural epsomite fibres from Perticara Mine (Italy) were investigated using SEM-EDS, XRPD, ICP-AES and alpha spectrometry measurements which were combined and integrated to characterise the fibres' morphology, crystal chemistry and mineralogy. The morphological and morphometric results showed that most of the fibres are of inhalable size (D_ae 5.09 μm) and can be potentially adsorbed from all parts of the respiratory tract. Chemical analysis reveals significant amounts of toxic elements (As, Co, Fe, Mn, Ni, Sr, Ti, Zn) and surprisingly high contents of radioactive isotopes (²¹⁰Po and ²²⁸Th) in epsomite crystals, making the inhalation of these fibres potentially hazardous to human health. Through this study, we want to focus on soluble minerals, such as epsomite, which can be present in both natural and anthropic environments and have never been considered from the point of view of their potential hazard.

The Options for Neuraxial Drug Administration

Neuraxial drug administration, i.e., the injection of drugs into the epidural or intrathecal space to produce anesthesia or analgesia, is a technique developed more than 120 years ago. Today, it still is widely used in daily practice in anesthesiology and in acute and chronic pain therapy. A multitude of different drugs have been introduced for neuraxial injection, only a part of which have obtained official approval for that indication. A broad understanding of the pharmacology of those agents is essential to the clinician to utilize them in a safe and efficient manner. In the present narrative review, we summarize current knowledge on neuraxial anatomy relevant to clinical practice, including pediatric anatomy. Then, we delineate the general pharmacology of neuraxial drug administration, with particular attention to specific aspects of epidural and intrathecal pharmacokinetics and pharmacodynamics. Furthermore, we describe the most common clinical indications for neuraxial drug administration, including the perioperative setting, obstetrics, and chronic pain. Then, we discuss possible neurotoxic effects of neuraxial drugs, and moreover, we detail the specific properties of the most commonly used neuraxial drugs that are relevant to clinicians who employ epidural or intrathecal drug administration, in order to ensure adequate treatment and patient safety in these techniques. Finally, we give a brief overview on new developments in neuraxial drug therapy.

Pharmacological and clinical implications of local anaesthetic mixtures: a narrative review

Various techniques have been explored to prolong the duration and improve the efficacy of local anaesthetic nerve blocks. Some of these involve mixing local anaesthetics or adding adjuncts. We did a literature review of studies published between 01 May 2011 and 01 May 2021 that studied specific combinations of local anaesthetics and adjuncts. The rationale behind mixing long- and short-acting local anaesthetics to hasten onset and extend duration is flawed on pharmacokinetic principles. Most local anaesthetic adjuncts are not licensed for use in this manner and the consequences of untested admixtures and adjuncts range from making the solution ineffective to potential harm. Pharmaceutical compatibility needs to be established before administration. The compatibility of drugs from the same class cannot be inferred and each admixture requires individual review. Precipitation on mixing (steroids, non-steroidal anti-inflammatory drugs) and subsequent embolisation can lead to serious adverse events, although these are rare. The additive itself or its preservative can have neurotoxic (adrenaline, midazolam) and/or chondrotoxic properties (non-steroidal anti-inflammatory drugs). The prolongation of block may occur at the expense of motor block quality (ketamine) or block onset (magnesium). Adverse effects for some adjuncts appear to be dose-dependent and recommendations concerning optimal dosing are lacking. An important confounding factor is whether studies used systemic administration of the adjunct as a control to accurately identify an additional benefit of perineural administration. The challenge of how best to prolong block duration while minimising adverse events remains a topic of interest with further research required.

Analgesic effect of perineural magnesium sulphate for sciatic nerve block for diabetic toe amputation: A randomized trial

Background and objectives

High concentrations of local anesthetics may be neurotoxic for diabetic patients. Additive perineural administration of magnesium was reported to decrease the consumption of local anesthetics for nerve block. It was hypothesized that MgSO₄ added to dilute ropivacaine was equianalgesic to more concentrated ropivacaine for toe amputations in diabetic patients.

Methods

Seventy diabetic patients were allocated into 3 groups: 1) perineural 200 mg MgSO₄ added to 0.25% ropivacaine, 2) 0.25% ropivacaine alone, and 3) 0.375% ropivacaine alone. All patients underwent popliteal sciatic nerve block that was guided by ultrasonography using the respective regimens. Time of onset, duration of motor and sensory block were recorded. Spontaneous and evoked pain score, worst pain score, additional analgesic consumption, satisfaction score and initial time of analgesic requirement of each patient were documented up to 48 hours postoperatively.

Results

In comparison with 0.25% ropivacaine alone, magnesium supplement prolonged the duration of sensory block (p = 0.001), as well as better evoked pain score at 6 hour postoperatively (p = 0.001). In comparison with evoked pain score (1.6/10) in group of 0.375% ropivacaine, magnesium plus 0.25% ropivacaine presented a little higher score (2.5/10) at 6 hour postoperatively (p = 0.001), while lower worst pain score (p = 0.001) and less postoperative total analgesic consumption (p = 0.002).

Conclusions

The regimen of adding 200mg MgSO₄ to 0.25% ropivacaine for sciatic nerve block yields equal analgesic effect in comparison with 0.375% ropivacaine. These findings have suggested that supplemental MgSO₄ could not improve analgesic quality except reducing the total amount of local anesthetics requirement in diabetic toe amputations with sciatic nerve blocks.

Adding magnesium sulfate to bupivacaine in transversus abdominis plane block for laparoscopic cholecystectomy: A single blinded randomized controlled trial

INTRODUCTION AND AIM

Use of transversus abdominis plane block (TAP) in the management of postoperative pain after the laparoscopic cholecystectomy (LC) has been a common anesthetic practice. This study evaluates the effect of adding magnesium sulfate to bupivacaine in TAP block in LC regarding postoperative analgesia and analgesic consumption.

PATIENTS AND METHODS

Ninety patients of American Society of Anesthesiologists I and II was divided into three groups: Control group (C group, n = 30), bupivacaine group (B group, n = 30), bupivacaine magnesium group (M group, n = 30).

RESULTS

M group showed better analgesic profile in the 1(st) postoperative day in the form of lower mean visual analog scale score (2.8 ± 0.6 for C group, 2.1 ± 0.5 for B group, 2.2 ± 0.5 for M group, P < 0.001), longer duration of analgesia (7 ± 2.8 h for C group, 16 ± 2.5 h for B group, 19 ± 2.2 h for M group, P < 0.006), lower morphine consumption (2 ± 0.1 mg for C group, 0.9 ± 0.1 mg for B group, 0.5 ± 0.1 mg for M group, P < 0.011). There was a significant lower incidence of postoperative nausea and vomiting (PONV) (32% for C group, 6% B group, 7% M group, P < 0.004).

CONCLUSION

Adding MgSo4 as an adjuvant to bupivacaine in TAP block; during anesthesia for LC; improved postoperative analgesia in the form of increased duration, decreased analgesic requirements and PONV.

Comparison of different doses of magnesium sulphate and fentanyl as adjuvants to bupivacaine for infraumbilical surgeries under subarachnoid block

Background and Aims:

Spinal anaesthesia is used for many years for surgeries below the level of umbilicus. It has certain disadvantages such as limited duration of blockade and post-operative analgesia. This study was undertaken to evaluate the effects of additives fentanyl and magnesium sulphate along with bupivacaine during spinal anaesthesia for prolongation of analgesia and motor blockade.

Methods:

This randomised study was conducted in 120 patients of either sex of American Society of Anesthesiologists physical status I and II, posted for infraumbilical surgeries. Patients were randomly allocated to four groups and were given the following drugs intrathecally as per group distribution; group A - bupivacaine 15 mg (0.5% heavy) with fentanyl 25 μg, group B - bupivacaine 15 mg (0.5% heavy) with magnesium 100 mg, group C - bupivacaine 15 mg (0.5% heavy) with magnesium 50 mg and group D - bupivacaine 15 mg (0.5% heavy) with 0.5 ml normal saline. Parameters monitored were duration of analgesia along with haemodynamic parameters and side effects. Data were analysed using the Student's t-test for the continuous variables and two-tailed Fisher exact test or Chi-square test for categorical variables.

Results:

There was significant increase in duration of analgesia in group A (374.37 min) and B (328.13 min) as compared to group C (274.87 min) and D (246.03 min). In group A, all haemodynamic parameters decreased by more than 20%, compared to baseline parameters, which was clinically and statistically significant as compared to other groups. There was also increase in duration of motor blockade in groups A and B.

Conclusion:

Addition of magnesium sulphate at 100 mg dose or fentanyl 25 μg as adjuvants to intrathecal bupivacaine significantly prolongs the duration of analgesia, though in the given doses, magnesium provides better haemodynamic stability than fentanyl, with fewer side effects.

Accidental intrathecal injection of magnesium sulfate for cesarean section

Magnesium sulfate is used frequently in the operation room and risks of wrong injection should be considered. A woman with history of pseudocholinesterase enzyme deficiency in the previous surgery was referred for cesarean operation. Magnesium sulfate of 700 mg (3.5 ml of 20% solution) was accidentally administered in the subarachnoid space. First, the patient had warm sensation and cutaneous anesthesia, but due to deep tissue pain, general anesthesia was induced by thiopental and atracurium. After the surgery, muscle relaxation and lethargy remained. At 8-10 h later, muscle strength improved and train of four (TOF) reached over 0.85, and then the endotracheal tube was removed. The patient was evaluated during the hospital stay and on the anesthesia clinic. No neurological symptoms, headache or backache were reported. Due to availability of magnesium sulfate, we should be careful for inadvertent intravenous, spinal and epidural injection; therefore before injection must be double checked.