The nature of the neuromuscular block produced by magnesium

Pharmacokinetics and Pharmacodynamics of Intravenous Magnesium Sulfate in Pediatric Acute Asthma Exacerbations

Pediatric asthma exacerbations represent a significant cause of emergency department use and hospitalizations. Despite available treatment options, many children's exacerbations are refractory to standard therapies and require adjunct treatments. The Intravenous Magnesium: Prompt use for Asthma in Children Treated in the Emergency Department study investigated the pharmacology of intravenous magnesium sulfate (IVMg) in treating pediatric asthma exacerbations. Specifically, the objectives of the study included (1) externally validating a previously published population pharmacokinetic model and (2) linking serum magnesium concentrations with outcomes including asthma severity score (efficacy) and hypotension (safety). Data were obtained from 49 children prospectively treated with IVMg (placebo, 50 or 75 mg/kg) after presenting to the pediatric emergency department with an acute asthma exacerbation. Reductions in Pediatric Respiratory Assessment Measure scores were associated with both total and ionized serum magnesium area under the concentration-time curve (AUC0-2 h). Despite frequent study-specific blood pressure monitoring, hypotension was uncommon in IVMg-treated participants (n = 2/31), and no concentration dependence was observed. The findings signal that IVMg may be an efficacious and safe option for treating moderate-severe pediatric acute asthma exacerbations in the ED. Importantly, this study is the first to suggest a serum exposure target (total serum magnesium AUC0-2 h >63.1 mg h/L) reflective of effective IVMg dosing in pediatric acute asthma. While further study in a larger clinical trial is needed to refine and validate this exposure target, these findings support the continued study of IVMg therapy as an adjunct therapeutic option in the setting of pediatric asthma exacerbations.

Neurological manifestations of hypermagnesemia: a narrative review

Hypermagnesemia is a rare but potentially fatal electrolyte disorder. High serum magnesium levels have been associated with the development of neurological manifestations such as dysautonomia, muscle weakness, respiratory failure, and altered level of consciousness from drowsiness to coma. Although rare, some subjects, such as those with chronic renal failure and those taking magnesium supplements or medications, are at risk of developing this condition. Recognizing this electrolyte alteration promptly allows for an immediate initiation of a therapeutic strategy that is often resolutive when addressed in time. This paper aims to review the neurological complications associated with hypermagnesemia, their pathophysiology, and management.

Magnesium sulfate in oxidative stress-associated pathologies: clinical, cellular, and molecular perspectives

Magnesium sulfate (MgSO₄) is a therapeutically versatile agent used across various medical conditions. This review integrates experimental and computational findings to elucidate the clinical, cellular, molecular, and electronic mechanisms underlying MgSO₄'s therapeutic effects, focusing on its antioxidant properties. MgSO₄ remains the gold standard treatment for preeclampsia and eclampsia, preventing seizures and mitigating oxidative damage. In preterm birth, it offers fetal neuroprotection, although its efficacy as a tocolytic agent is limited. MgSO₄ also shows promise in treating respiratory conditions, notably severe asthma, where it acts as a bronchodilator. Its applications extend to anesthesia, pain management, and cardiac arrhythmias, reflecting its diverse pharmacological actions. Advanced computational methods, including molecular dynamics simulations and quantum chemistry calculations, have revealed how MgSO₄ interacts with cell membranes and neutralizes hydroxyl radicals. These studies suggest that MgSO₄'s antioxidant effects stem from its ability to stabilize membrane structures and modulate electron transfer processes. The therapeutic effects are mediated through multiple pathways, including calcium channel modulation, NMDA receptor antagonism, and anti-inflammatory mechanisms. Although generally safe, MgSO₄ requires careful monitoring due to its narrow therapeutic window. Future research should focus on precision dosing strategies, innovative delivery systems, and expanded therapeutic applications. A comprehensive understanding of MgSO₄'s molecular mechanisms and clinical applications will further optimize its therapeutic use.

Graphical abstract

Why is binding of a divalent metal cation to a structural motif containing four carboxylate residues not accompanied by a conformational change?

We earlier showed that Torpedo californica acetylcholinesterase (AChE) contains a cluster of four conserved aspartates that can strongly bind divalent cations, which we named the 4D motif. Binding of the divalent metal cations greatly increases its thermal stability. Here we systematically examined all available crystallographic structures of T. californica AChE. Two additional metal-binding sites were identified, both composed of acidic and histidine residues. Relative binding to the 4D and additional sites was studied using metadynamics simulations. It was observed that in crystal structures devoid of metal ions in the 4D site, the conformation of T. californica AChE is almost identical to that in structures in which it is occupied by a divalent metal ion. Closer examination of the 4D motif reveals that three of the four acidic residues form ion pairs with conserved basic residues surrounding them. We named this new motif the 4A/3B motif. Molecular dynamics with quantum potential simulations was used to quantify the 4D motif's binding strength compared with that of the metal-binding site in the protein fXIIIa, which consists of four aspartates, but is devoid of adjacent cationic residues. Whereas fXIIIa's 4D site, in the absence of a metal cation, expanded significantly in the simulation, that of Torpedo AChE displayed only minor periodic changes in size. Furthermore, the energy of metal ion unbinding from the two sites differs by ca. 10 kcal/mol. We identified several other proteins in the PDB that contain the 4A/3B motif, whose conformations are identical in the presence or absence of a metal ion. An animated Interactive 3D Complement (I3DC) is available in Proteopedia at https://proteopedia.org/w/Journal:Protein_Science:4.

Neuromuscular Transmission in a Biological Context

Neuromuscular transmission is the process by which motor neurons activate muscle contraction and thus plays an essential role in generating the purposeful body movements that aid survival. While many features of this process are common throughout the Animal Kingdom, such as the release of transmitter in multimolecular "quanta," and the response to it by opening ligand-gated postsynaptic ion channels, there is also much diversity between and within species. Much of this diversity is associated with specialization for either slow, sustained movements such as maintain posture or fast but brief movements used during escape or prey capture. In invertebrates, with hydrostatic and exoskeletons, most motor neurons evoke graded depolarizations of the muscle which cause graded muscle contractions. By contrast, vertebrate motor neurons trigger action potentials in the muscle fibers which give rise to all-or-none contractions. The properties of neuromuscular transmission, in particular the intensity and persistence of transmitter release, reflect these differences. Neuromuscular transmission varies both between and within individual animals, which often have distinct tonic and phasic subsystems. Adaptive plasticity of neuromuscular transmission, on a range of time scales, occurs in many species. This article describes the main steps in neuromuscular transmission and how they vary in a number of "model" species, including C. elegans , Drosophila , zebrafish, mice, and humans. © 2024 American Physiological Society. Compr Physiol 14:5641-5702, 2024.

Magnesium as an Adjuvant to Rocuronium to Improve Intubation Conditions and Shorten the Intubation Time: A Randomized Controlled Study

AIM AND OBJECTIVE

The purpose of the study is to compare the effects of rocuronium priming with the combined technique of magnesium pretreatment and rocuronium priming and to investigate whether this pretreatment could further accelerate the onset of neuromuscular blockade during intubation.

MATERIALS AND METHODS

 A double-blinded randomized controlled trial (RCT) clinical study was done on patients at a tertiary care center for six months after obtaining approval from the institutional ethical committee. A total of 150 patients were randomly allocated as Group MP (infusion of 50 mg/kg of MgSo4 over 10 min was given 10 mins prior to premedication and dose of rocuronium 0.06 mg/kg given three minutes), Group P (priming dose of rocuronium 0.06 mg/kg given three minutes before the intubating dose), and Group C (control group with the same volume of 0.9% saline and rocuronium bolus of 0.6 mg/kg on intubation). Parameters such as demographic and hemodynamical data, American Society of Anesthesiologists (ASA) score, Mallampati scoring, neuromuscular monitoring, intubation grading, and number of successful/failed attempts were recorded.

RESULTS

 Our results showed that Group MP had a rapid onset of action of rocuronium with 58.90 +/- 4.77 seconds and a longer duration of action of rocuronium with 54.92 +/- 10.39 minutes, which are statistically significant compared to Group P (onset of action of ROC 106.70 +/- 4.24 seconds and duration of action rocuronium 45.88 +/- 6.22 minutes) and Group C (onset of action of ROC 154.56 +/- 11.39 seconds and duration of ROC 40.56 +/- 3.96 minutes). The maximum number of patients in Group MP (33 patients) showed good intubation conditions compared to Group P (23 patients) and Group C (16 patients), which was statistically significant.

CONCLUSION

We conclude that magnesium sulfate pretreatment in combination with rocuronium priming (Group MP) considerably accelerates the onset of rocuronium action, increases the duration of action of rocuronium, and enhances the intubation procedure without any adverse effect of rocuronium and magnesium sulfate.

Movement Disorders and Other Neurologic Impairment Associated With Hypomagnesemia: A Systematic Review

Purpose of Review

The objective of this study was to explore the clinical spectrum of movement disorders and associated neurologic findings in hypomagnesemia and challenges in diagnosis and treatment.

Recent Findings

Sixty patients were identified in the literature for analysis. Movement disorders observed were postural tremor (23.3%, n = 14), resting tremor (8.3%, n = 5), intention tremor (10%, n = 6), ataxia involving the trunk (48.3%, n = 29) or limbs (25%, n = 15) and dysarthria (21.7%, n = 13), athetosis (8.3%, n = 5), myoclonus (6.7%, n = 4), and chorea (1.8%, n = 1). Symptoms may be accompanied by downbeat nystagmus, tetany, drowsiness, vertigo, and proximal muscle weakness. Residual deficits were noted in 16 (26.67%) patients. Serum magnesium was 1.3 mg/dL or lower in 53 patients (88.3%). Imaging findings include bilateral cerebellar (20%, n = 11) and vermis hyperintensities (9.09%, n = 5) and normal imaging. Proton pump inhibitors are the commonest etiology.

Summary

The movement disorders linked with hypomagnesemia can be associated with varied neurologic symptoms. A high degree of suspicion will enable early diagnosis to prevent residual deficits.

Role of Magnesium in the Intensive Care Unit and Immunomodulation: A Literature Review

Both the role and the importance of magnesium in clinical practice have grown considerably in recent years. Emerging evidence suggests an association between loss of magnesium homeostasis and increased mortality in the critical care setting. The underlying mechanism is still unclear, but an increasing number of in vivo and in vitro studies on magnesium's immunomodulating capabilities may shed some light on the matter. This review aims to discuss the evidence behind magnesium homeostasis in critically ill patients, and its link with intensive care unit mortality via a likely magnesium-induced dysregulation of the immune response. The underlying pathogenetic mechanisms, and their implications for clinical outcomes, are discussed. The available evidence strongly supports the crucial role of magnesium in immune system regulation and inflammatory response. The loss of magnesium homeostasis has been associated with an elevated risk of bacterial infections, exacerbated sepsis progression, and detrimental effects on the cardiac, respiratory, neurological, and renal systems, ultimately leading to increased mortality. However, magnesium supplementation has been shown to be beneficial in these conditions, highlighting the importance of maintaining adequate magnesium levels in the intensive care setting.

Recording cilia activity in ctenophores: effects of nitric oxide and low molecular weight transmitters

Cilia are the major effectors in Ctenophores, but very little is known about their transmitter control and integration. Here, we present a simple protocol to monitor and quantify cilia activity and provide evidence for polysynaptic control of cilia coordination in ctenophores. We also screened the effects of several classical bilaterian neurotransmitters (acetylcholine, dopamine, L-DOPA, serotonin, octopamine, histamine, gamma-aminobutyric acid (GABA), L-aspartate, L-glutamate, glycine), neuropeptide (FMRFamide), and nitric oxide (NO) on cilia beating in Pleurobrachia bachei and Bolinopsis infundibulum. NO and FMRFamide produced noticeable inhibitory effects on cilia activity, whereas other tested transmitters were ineffective. These findings further suggest that ctenophore-specific neuropeptides could be major candidates for signal molecules controlling cilia activity in representatives of this early-branching metazoan lineage.

Nitric oxide suppresses cilia activity in ctenophores

Cilia are the major effectors in Ctenophores, but very little is known about their transmitter control and integration. Here, we present a simple protocol to monitor and quantify cilia activity in semi-intact preparations and provide evidence for polysynaptic control of cilia coordination in ctenophores. Next, we screen the effects of several classical bilaterian neurotransmitters (acetylcholine, dopamine, L-DOPA, serotonin, octopamine, histamine, gamma-aminobutyric acid (GABA), L-aspartate, L-glutamate, glycine), neuropeptides (FMRFamide), and nitric oxide (NO) on cilia beating in Pleurobrachia bachei and Bolinopsis infundibulum . Only NO inhibited cilia beating, whereas other tested transmitters were ineffective. These findings further suggest that ctenophore-specific neuropeptides could be major candidate signaling molecules controlling cilia activity in representatives of this early-branching metazoan lineage.

Amino acids integrate behaviors in nerveless placozoans

Placozoans are the simplest known free-living animals without recognized neurons and muscles but a complex behavioral repertoire. However, mechanisms and cellular bases of behavioral coordination are unknown. Here, using Trichoplax adhaerens as a model, we described 0.02-0.002 Hz oscillations in locomotory and feeding patterns as evidence of complex multicellular integration; and showed their dependence on the endogenous secretion of signal molecules. Evolutionary conserved low-molecular-weight transmitters (glutamate, aspartate, glycine, GABA, and ATP) acted as coordinators of distinct locomotory and feeding patterns. Specifically, L-glutamate induced and partially mimicked endogenous feeding cycles, whereas glycine and GABA suppressed feeding. ATP-modified feeding is complex, first causing feeding-like cycles and then suppressing feeding. Trichoplax locomotion was modulated by glycine, GABA, and, surprisingly, by animals' own mucus trails. Mucus triples locomotory speed compared to clean substrates. Glycine and GABA increased the frequency of turns. The effects of the amino acids are likely mediated by numerous receptors (R), including those from ionotropic GluRs, metabotropic GluRs, and GABA-BR families. Eighty-five of these receptors are encoded in the Trichoplax genome, more than in any other animal sequenced. Phylogenetic reconstructions illuminate massive lineage-specific expansions of amino acid receptors in Placozoa, Cnidaria, and Porifera and parallel evolution of nutritional sensing. Furthermore, we view the integration of feeding behaviors in nerveless animals by amino acids as ancestral exaptations that pave the way for co-options of glutamate, glycine, GABA, and ATP as classical neurotransmitters in eumetazoans.

Postoperative residual neuromuscular block in a woman with severe preeclampsia treated with magnesium sulfate and nicardipine: A case report and literature review

Calcium channel blockers and magnesium sulfate are frequently used together, particularly in women with underlying chronic hypertension and pre-eclampsia. A review of the literature showed prolonged neuromuscular blockade after treatment with magnesium sulfate. Since magnesium and calcium have opposite effects on the neuromuscular junctions, muscle weakness may become a postoperative manifestation of magnesium sulfate and calcium antagonist treatment in the obstetric population; however, limited information is available regarding this postulation. Here, we report a case wherein rocuronium activity was markedly prolonged due to pretreatment with magnesium sulfate and nicardipine after general anesthesia during an emergency cesarean delivery.

Correlation Between Serum Magnesium Level and Acute Exacerbation in Patients With Chronic Obstructive Pulmonary Disease (COPD)

Introduction

Although chronic obstructive pulmonary disease (COPD) is preventable and treatable, it is a major public health problem. The mortality risks are higher in patients with exacerbations. Magnesium (Mg) is crucial in numerous physiological processes, including membrane stabilization. However, incomplete information is available regarding the effect of magnesium on the frequency of acute exacerbation of COPD.

Objectives

To determine the serum magnesium level in COPD patients and its correlation with acute exacerbation of COPD.

Materials and methods

This cross-sectional study included 100 patients diagnosed with acute exacerbation of COPD. The serum magnesium level was measured in all patients with acute exacerbation of COPD at admission. Serum Mg level <1.7 mg/dl was considered hypomagnesemia. The correlation between serum magnesium level and duration of hospital stay and patient outcome was studied. 

Results

In the present study, hypomagnesemia was reported in 57% of patients with acute exacerbation of COPD. The duration of hospital stay (more than seven days) among hypomagnesemia (80.7%) patients was significantly higher than that of the normomagnesemia patients (55.8%). Mortality in patients with hypomagnesemia was higher than in patients with normomagnesemia, although not statistically significant.

Conclusion

Hypomagnesaemia is a common finding in acute exacerbation of COPD. The level of magnesium found is related to the length of hospital stay, but it is not related to mortality among patients with acute exacerbation of COPD. Further studies with larger sample sizes and extended follow-up periods are required to validate the results.

Intravenous magnesium sulfate inducing acute respiratory failure in a patient with myasthenia gravis

A woman in her 90s with a background of myasthenia gravis and atrial fibrillation presented to hospital following a fall. While in the emergency department it was noted that she was in atrial fibrillation with a fast-ventricular response and as part of her management was given intravenous magnesium. Following this she developed acute respiratory failure and required intubation and ventilation. The patient recovered quickly and was extubated in the intensive care unit the next day. On subsequent days, the patient received two further doses of intravenous magnesium before the link was identified. On both of these occasions she again developed respiratory failure which were managed with non-invasive ventilation. This case highlights the importance of all members of the team being aware of the drugs that can induce a myasthenic crisis. It also stimulates further research into the development of a guide of how to safely treat symptomatic hypomagnesaemia in patients with myasthenia gravis.

Magnesium sulfate for acute exacerbations of chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a chronic and progressive disease, often punctuated by recurrent flare-ups or exacerbations. Magnesium sulfate, having a bronchodilatory effect, may have a potential role as an adjunct treatment in COPD exacerbations. However, comprehensive evidence of its effects is required to facilitate clinical decision-making.

OBJECTIVES

To assess the effects of magnesium sulfate for acute exacerbations of chronic obstructive pulmonary disease in adults.

SEARCH METHODS

We searched the Cochrane Airways Trials Register, CENTRAL, MEDLINE, Embase, ClinicalTrials.gov, the World Health Organization (WHO) trials portal, EU Clinical Trials Register and Iranian Registry of Clinical Trials. We also searched the proceedings of major respiratory conferences and reference lists of included studies up to 2 August 2021.

SELECTION CRITERIA

We included single- or double-blind parallel-group randomised controlled trials (RCTs) assessing magnesium sulfate in adults with COPD exacerbations. We excluded cross-over trials.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. Two review authors independently selected trials for inclusion, extracted data and assessed risk of bias. The primary outcomes were: hospital admissions (from the emergency room); need for non-invasive ventilation (NIV), assisted ventilation or admission to intensive-care unit (ICU); and serious adverse events. Secondary outcomes were: length of hospital stay, mortality, adverse events, dyspnoea score, lung function and blood gas measurements. We assessed confidence in the evidence using GRADE methodology. For missing data, we contacted the study investigators.

MAIN RESULTS

We identified 11 RCTs (10 double-blind and 1 single-blind) with a total 762 participants. The mean age of participants ranged from 62 to 76 years. Trials were single- or two-centre trials conducted in Iran, New Zealand, Nepal, Turkey, the UK, Tunisia and the USA between 2004 and 2018. We judged studies to be at low or unclear risk of bias for most of the domains. Three studies were at high risk for blinding and other biases.  Intravenous magnesium sulfate versus placebo Seven studies (24 to 77 participants) were included. Fewer people may require hospital admission with magnesium infusion compared to placebo (odds ratio (OR) 0.45, 95% CI 0.23 to 0.88; number needed to treat for an additional beneficial outcome (NNTB) = 7; 3 studies, 170 participants; low-certainty evidence). Intravenous magnesium may result in little to no difference in the requirement for non-invasive ventilation (OR 0.74, 95% CI 0.31 to 1.75; very low-certainty evidence). There were no reported cases of endotracheal intubation (2 studies, 107 participants) or serious adverse events (1 study, 77 participants) in either group. Included studies did not report intensive care unit (ICU) admission or deaths. Magnesium infusion may reduce the length of hospital stay by a mean difference (MD) of 2.7 days (95% CI 4.73 days to 0.66 days; 2 studies, 54 participants; low-certainty evidence) and improve dyspnoea score by a standardised mean difference of -1.40 (95% CI -1.83 to -0.96; 2 studies, 101 participants; low-certainty evidence). We were uncertain about the effect of magnesium infusion on improving lung function or oxygen saturation. For all adverse events, the Peto OR was 0.14 (95% CI 0.02 to 1.00; 102 participants); however, the event rate was too low to reach a robust conclusion.  Nebulised magnesium sulfate versus placebo Three studies (20 to 172 participants) were included. Magnesium inhalation may have little to no impact on hospital admission (OR 0.77, 95% CI 0.21 to 2.82; very low-certainty evidence) or need for ventilatory support (NIV or mechanical ventilation) (OR 0.33, 95% CI 0.01 to 8.20; very low-certainty evidence). It may result in fewer ICU admissions compared to placebo (OR 0.39, 95% CI 0.15 to 1.00; very low-certainty evidence) and improvement in dyspnoea (MD -14.37, 95% CI -26.00 to -2.74; 1 study, 20 participants; very low-certainty evidence). There were no serious adverse events reported in either group. There was one reported death in the placebo arm in one trial, but the number of participants was too small for a conclusion. There was limited evidence about the effect of magnesium inhalation on length of hospital stay, lung function outcomes or oxygen saturation. Included studies did not report adverse events.  Magnesium sulfate versus ipratropium bromide  A single study with 124 participants assessed nebulised magnesium sulfate plus intravenous magnesium infusion versus nebulised ipratropium plus intravenous normal saline. There was little to no difference between these groups in terms of hospital admission (OR 1.62, 95% CI 0.78 to 3.37), endotracheal intubation (OR 1.69, 95% CI 0.61 to 4.71) and length of hospital stay (MD 1.10 days, 95% CI -0.22 to 2.42), all with very low-certainty evidence. There were no data available for non-invasive ventilation, ICU admission and serious adverse events. Adverse events were not reported.  AUTHORS' CONCLUSIONS: Intravenous magnesium sulfate may be associated with fewer hospital admissions, reduced length of hospital stay and improved dyspnoea scores compared to placebo. There is no evidence of a difference between magnesium infusion and placebo for NIV, lung function, oxygen saturation or adverse events. We found no evidence for ICU admission, endotracheal intubation, serious adverse events or mortality. For nebulised magnesium sulfate, we are unable to draw conclusions about its effects in COPD exacerbations for most of the outcomes. Studies reported possibly lower ICU admissions and a lesser degree of dyspnoea with magnesium inhalation compared to placebo; however, larger studies are required to yield a more precise estimate for these outcomes. Similarly, we could not identify any robust evidence for magnesium sulfate compared to ipratropium bromide. Future well-designed multicentre trials with larger samples are required, including subgroups according to severity of exacerbations and COPD phenotypes.

Postoperative respiratory depression caused by iatrogenic hypermagnesaemia

Hypermagnesaemia is an uncommon electrolyte disorder which can be fatal if not recognised and treated promptly. The signs and symptoms of hypermagnesaemia are non-specific, making it an under-diagnosed cause of cardiovascular dysfunction, hypocalcaemia, and neurological and respiratory depression. Since magnesium homeostasis is handled almost exclusively by the kidneys, symptomatic hypermagnesaemia seldom occurs in the context of normal renal function; when it does, it is usually iatrogenic. Here, we report a case of iatrogenic hypermagnesaemia which presented as respiratory depression, preventing weaning from mechanical ventilation following cardiac surgery in a patient in the early stages of chronic kidney disease. On investigation he was found to have isolated severe hypermagnesaemia, following an intravenous bolus of magnesium sulphate administered intra-operatively to treat tachyarrhythmia. Before administering intravenous magnesium therapeutically, it is important for clinicians to assess renal function and baseline serum magnesium along with other possible risk factors for hypermagnesaemia, and to actively look for signs and symptoms of magnesium toxicity when the patient is receiving therapeutic magnesium.

The effects of nebulized ketamine and intravenous magnesium sulfate on corticosteroid resistant asthma exacerbation; a randomized clinical trial

BACKGROUND AND AIMS

Asthma exacerbation is defined as an acute attack of shortness of breath with more than 25% decrease in morning peak flow compared to the baseline on 2 consecutive days, which requires immediate standard therapy. The majority of asthmatic patients are considered to be steroid-sensitive; however, corticosteroid-resistant asthma is a subset of asthma with poor response to corticosteroids and is responsible for frequent hospital admissions. In this study we aimed to compare the effects of two enhancing strategies, the nebulized ketamine and IV magnesium sulfate, in treatment of severe steroid resistant asthma.

MATERIALS AND METHODS

This double-blind randomized clinical trial was conducted on patients who presented to a referral clinic in Alborz, Iran. Using random allocation, patients were divided into two groups. The first group was treated with nebulized ketamine and the second group was treated with intravenous magnesium sulfate. Peak expiratory flow rates were assessed before the intervention, 30 and 60 min after the intervention and compared with the aid of SPSS software.

RESULTS

The Peak expiratory flow rates before the intervention, 30 min and 60 min after the intervention was statistically significantly different in both ketamine and magnesium sulfate groups. Peak expiratory flow rates change between 0 and 60 min were 29.4 and 15.2% in the ketamine and magnesium sulfate group respectively. Although the ketamine group showed much higher increase in mean PEFR compared to the MgSO4 groups, there was no statistically significant difference across both groups.

CONCLUSION

Our study concluded that combined with standard therapy, both ketamine and IV magnesium sulfate are effective agents in the improvement of PEFR in patients with acute severe asthma that failed to respond to traditional therapies. However, there were no statistically significant difference between the two groups.

Chloride channel inhibition improves neuromuscular function under conditions mimicking neuromuscular disorders

AIM

The skeletal muscle Cl^- channels, the ClC-1 channels, stabilize the resting membrane potential and dampen muscle fibre excitability. This study explored whether ClC-1 inhibition can recover nerve-stimulated force in isolated muscle under conditions of compromised neuromuscular transmission akin to disorders of myasthenia gravis and Lambert-Eaton syndrome.

METHODS

Nerve-muscle preparations were isolated from rats. Preparations were exposed to pre-or post-synaptic inhibitors (ω-agatoxin, elevated extracellular Mg²⁺ , α-bungarotoxin or tubocurarine). The potential of ClC-1 inhibition (9-AC or reduced extracellular Cl^- ) to recover nerve-stimulated force under these conditions was assessed.

RESULTS

ClC-1 inhibition recovered force in both slow-twitch soleus and fast-twitch EDL muscles exposed to 0.2 µmol/L tubocurarine or 3.5 mmol/L Mg²⁺ . Similarly, ClC-1 inhibition recovered force in soleus muscles exposed to α-bungarotoxin or ω-agatoxin. Moreover, the concentrations of tubocurarine and Mg²⁺ required for reducing force to 50% rose from 0.14 ± 0.02 µmol/L and 4.2 ± 0.2 mmol/L in control muscles to 0.45 ± 0.03 µmol/L and 4.7 ± 0.3 mmol/L in muscles with 9-AC respectively (P < .05, paired T test). Inhibition of acetylcholinesterase (neostigmine) and inhibition of voltage-gated K⁺ channels (4-AP) relieve symptoms in myasthenia gravis and Lambert-Eaton syndrome, respectively. Neostigmine and 9-AC additively increased the tubocurarine concentration required to reduce nerve-stimulated force to 50% (0.56 ± 0.05 µmol/L with 9-AC and neostigmine) and, similarly, 4-AP and 9-AC additively increased the Mg²⁺ concentration required to reduce nerve-stimulated force to 50% (6.5 ± 0.2 mmol/L with 9-AC and 4-AP).

CONCLUSION

This study shows that ClC-1 inhibition can improve neuromuscular function in pharmacological models of compromised neuromuscular transmission.

Drugs That Induce or Cause Deterioration of Myasthenia Gravis: An Update

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder which is characterized by presence of antibodies against acetylcholine receptors (AChRs) or other proteins of the postsynaptic membrane resulting in damage to postsynaptic membrane, decreased number of AChRs or blocking of the receptors by autoantibodies. A number of drugs such as immune checkpoint inhibitors, penicillamine, tyrosine kinase inhibitors and interferons may induce de novo MG by altering the immune homeostasis mechanisms which prevent emergence of autoimmune diseases such as MG. Other drugs, especially certain antibiotics, antiarrhythmics, anesthetics and neuromuscular blockers, have deleterious effects on neuromuscular transmission, resulting in increased weakness in MG or MG-like symptoms in patients who do not have MG, with the latter usually being under medical circumstances such as kidney failure. This review summarizes the drugs which can cause de novo MG, MG exacerbation or MG-like symptoms in nonmyasthenic patients.

Effects of magnesium on the dose of rocuronium for deep neuromuscular blockade: A randomised controlled trial

BACKGROUND

Magnesium is known to enhance the effect of rocuronium, but the extent is not quantified.

OBJECTIVES

We aimed to quantify the effect of magnesium on the dose of rocuronium for deep neuromuscular blockade.

DESIGN

A randomised controlled study.

SETTING

A single tertiary care hospital.

PATIENTS

Seventy males scheduled to undergo robot-assisted laparoscopic prostatectomy, aged between 20 and 80 years with American Society of Anesthesiologists physical status classification 1 or 2, were enrolled.

INTERVENTIONS

Patients were randomised to either the magnesium group or control group. The magnesium group were infused with 50 mg kg-1 of magnesium, followed by a continuous intra-operative infusion at 15 mg kg-1 h-1 while the control group were infused with the same volumes of 0.9% saline. Deep neuromuscular blockade was maintained with a continuous infusion of rocuronium and was reversed using sugammadex.

MAIN OUTCOME MEASURES

The primary outcome was the dose of rocuronium administered to maintain deep neuromuscular blockade. The secondary outcomes were recovery time, defined as the time from the administration of sugammadex to train-of-four ratio 0.9, and the incidence of postoperative nausea and vomiting.

RESULTS

The dose of rocuronium administered to maintain deep neuromuscular blockade was significantly lower in the magnesium group (7.5 vs. 9.4 μg kg-1 min-1, P = 0.01). There was no difference in recovery time or the incidence of nausea and vomiting.

CONCLUSION

Magnesium reduced the dose of rocuronium required for deep neuromuscular blockade by approximately 20% without affecting the recovery time after administration of sugammadex.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT04013243.

Establishing low-density lipoprotein apheresis tolerability in patients with prior anaphylactoid reactions to lipoprotein apheresis using magnesium sulfate

BACKGROUND

Lipoprotein apheresis (LA) tolerability is a key factor for the utilization of this therapy. Common reactions to LA are hypotension and nausea. Serious reactions include severe hypotension and anaphylactoid reactions (0.13%-1.3% and 0.2%-0.4%, respectively). The bradykinin response drives these reactions and can worsen with the use of angiotensin-converting-enzyme inhibitors. Efforts to mitigate these reactions are necessary for the tolerability of LA with a dextran sulfate-adsorption (DSA) system.

MATERIALS AND METHODS

In an effort to increase apheresis tolerability, seven patients at The University of Kansas, Department of Clinical Pharmacology, who had prior anaphylactoid reactions (defined as general cutaneous flushing, nausea/vomiting, tongue swelling, lightheadedness, and hypotension) to the DSA despite pharmacologic intervention, were treated with pre-LA intravenous magnesium adapted from a protocol developed by co-author Eliaz. This protocol consists of 1.5 g of magnesium sulfate administered over 45 minutes. All seven patients were treated with intravenous magnesium sulfate immediately before LA.

RESULTS

No episodes of anaphylactoid reactions during LA have been reported to date.

CONCLUSIONS

Magnesium infusion before DSA can be utilized to establish tolerability in patients with prior anaphylactoid reactions to LA. Proposed mechanisms include temporary stabilization of the negative-positive interactions of the dextran sulfate filter leading to a reduction of circulating bradykinin, reduction of nitric oxide, and reduction of the sympathetic response to LA.

The ECG Characteristics of Patients With Isolated Hypomagnesemia

Background

Electrocardiographic (ECG) characteristics of patients with isolated hypomagnesemia are not well defined. We aimed to investigate these ECG characteristics in order to define clearly the features of isolated hypomagnesemia.

Hypothesis

Lower serum magnesium could affect ECG parameters after excluding potential confounders.

Methods

This retrospective study was of patients with low serum magnesium <0.65 mmol/L compared with the same patients after restoration to normal serum magnesium. Patients with hypokalemia, hypocalcemia and other electrolyte disturbances were excluded. ECG parameters manually determined and analyzed were P wave dispersion, PR interval, QRS duration, ST-T changes, T wave amplitude, T peak-to-end interval (Tpe), corrected Tpe (Tpec), QT, corrected QT (QTc), QT peak corrected (QTpc) and Tpe dispersion, Tpe/QT ratio.

Results

Two-hundred-and-fourteen patients with isolated hypomagnesemia were identified with 50 of them (56.9 ± 13.6 years; 25 males) being eligible for final analysis from 270,997 patients presenting April 2011–October 2017. In the period of isolated hypomagnesemia, P wave duration was found prolonged (p ≤ 0.02); as was QTc (439 ± 27 vs. 433 ± 22, p = 0.01). Tpec (122 ± 24vs. 111 ± 22, p = 0.000) and Tpe/QT ratio (0.29 ± 0.05 vs. 0.27 ± 0.05, p = 0.000) were increased. QTpc decreased during hypomagnesemia (334 ± 28 vs. 342 ± 21, p = 0.02). However, no significant differences were found in PR interval, QRS duration (85 ± 12 ms vs. 86 ± 12 ms, p = 0.122) and ST-T segments between the patients and their own controls.

Conclusions

In patients with isolated hypomagnesemia, P wave duration, QTc, Tpec, and Tpe/QT ratio suggesting atrial depolarization and ventricular repolarization dispersion were significantly increased compared with normal magnesium levels in the same patients after restoration to normal levels.

Increased Cholinergic Tone Causes Pre-synaptic Neuromuscular Degeneration and is Associated with Impaired Diaphragm Function

In vertebrates, muscle activity is dependent on acetylcholine (ACh) released from neuromuscular junctions (NMJs), and changes in cholinergic neurotransmission are linked to a variety of neuromuscular diseases, including congenital myasthenic syndromes (CMS). The storage and release of ACh depends on the activity of the Vesicular Acetylcholine Transporter (VAChT), a rate-limiting step for cholinergic neurotransmission whose loss of function mutations was shown to cause human congenital myasthenia. However, we know much less about increased VAChT activity, due to copy number variations, for example. Therefore, here we investigated the impact of increased VAChT expression and consequently ACh levels at the synaptic cleft of the diaphragm NMJs. We analyzed structure and function of nerve and muscles from a mouse model of cholinergic hyperfunction (ChAT-ChR2-EYFP) with increased expression of VAChT. Our results showed a significant increase of ACh released under evoked stimuli. However, we observed deleterious changes in synaptic vesicles cycle (impaired endocytosis and decrease in vesicles number), together with structural alterations of NMJs. Interestingly, ultrastructure analyses showed that synaptic vesicles from ChAT-ChR2-EYFP mice NMJs were larger, which might be related to increased ACh load. We also observed that these larger synaptic vesicles were less rounded in comparison with control. Finally, we showed that ChAT-ChR2-EYFP mice NMJs have compromised safety factor, possible due to the structural alterations we described. These findings reveal that physiological cholinergic activity is important to maintain the structure and function of the neuromuscular system and help to understand some of the neuromuscular adverse effects experienced by chronically increased NMJ neurotransmission, such as individuals treated with cholinesterase inhibitors.

Magnesium sulphate for treating acute bronchiolitis in children up to two years of age

BACKGROUND

Acute bronchiolitis is a significant burden on children, their families and healthcare facilities. It mostly affects children younger than two years of age. Treatment involves adequate hydration, humidified oxygen supplementation, and nebulisation of medications, such as salbutamol, epinephrine, and hypertonic saline. The effectiveness of magnesium sulphate for acute bronchiolitis is unclear.

OBJECTIVES

To assess the effects of magnesium sulphate in acute bronchiolitis in children up to two years of age.

SEARCH METHODS

We searched CENTRAL, MEDLINE, Embase, LILACS, CINAHL, and two trials registries to 30 April 2020. We contacted trial authors to identify additional studies. We searched conference proceedings and reference lists of retrieved articles. Unpublished and published studies were eligible for inclusion.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs, comparing magnesium sulphate, alone or with another treatment, with placebo or another treatment, in children up to two years old with acute bronchiolitis. Primary outcomes were time to recovery, mortality, and adverse events. Secondary outcomes were duration of hospital stay, clinical severity score at 0 to 24 hours and 25 to 48 hours after treatment, pulmonary function test, hospital readmission within 30 days, duration of mechanical ventilation, and duration of intensive care unit stay.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane. We used GRADE methods to assess the certainty of the evidence.

MAIN RESULTS

We included four RCTs (564 children). One study received funding from a hospital and one from a university; two studies did not report funding sources. Comparator interventions differed among all four trials. Studies were conducted in Qatar, Turkey, Iran, and India. We assessed two studies to be at an overall low risk of bias, and two to be at unclear risk of bias, overall. The certainty of the evidence for all outcomes and comparisons was very low except for one: hospital re-admission rate within 30 days of discharge for magnesium sulphate versus placebo. None of the studies measured time to recovery, duration of mechanical ventilation, duration of intensive care unit stay, or pulmonary function. There were no events of mortality or adverse effects for magnesium sulphate compared with placebo (1 RCT, 160 children). The effects of magnesium sulphate on clinical severity are uncertain (at 0 to 24 hours: mean difference (MD) on the Wang score 0.13, 95% confidence interval (CI) -0.28 to 0.54; and at 25 to 48 hours: MD on the Wang score -0.42, 95% CI -0.84 to -0.00). Magnesium sulphate may increase hospital re-admission rate within 30 days of discharge (risk ratio (RR) 3.16, 95% CI 1.20 to 8.27; 158 children; low-certainty evidence). None of our primary outcomes were measured for magnesium sulphate compared with hypertonic saline (1 RCT, 220 children). Effects were uncertain on the duration of hospital stay in days (MD 0.00, 95% CI -0.28 to 0.28), and on clinical severity on the Respiratory Distress Assessment Instrument (RDAI) score at 25 to 48 hours (MD 0.10, 95% CI -0.39 to 0.59). There were no events of mortality or adverse effects for magnesium sulphate, with or without salbutamol, compared with salbutamol (1 RCT, 57 children). Effects on the duration of hospital stay were uncertain (magnesium sulphate: 24 hours (95% CI 25.8 to 47.4), magnesium sulphate + salbutamol: 20 hours (95% CI 15.3 to 39.0), and salbutamol: 24 hours (95% CI 23.4 to 76.9)). None of our primary outcomes were measured for magnesium sulphate + epinephrine compared with no treatment or normal saline + epinephrine (1 RCT,120 children). Effects were uncertain for the duration of hospital stay in hours (MD -0.40, 95% CI -3.94 to 3.14), and for RDAI scores (0 to 24 hours: MD -0.20, 95% CI -1.06 to 0.66; and 25 to 48 hours: MD -0.90, 95% CI -1.75 to -0.05).

AUTHORS' CONCLUSIONS

There is insufficient evidence to establish the efficacy and safety of magnesium sulphate for treating children up to two years of age with acute bronchiolitis. No evidence was available for time to recovery, duration of mechanical ventilation and intensive care unit stay, or pulmonary function. There was no information about adverse events for some comparisons. Well-designed RCTs to assess the effects of magnesium sulphate for children with acute bronchiolitis are needed. Important outcomes, such as time to recovery and adverse events should be measured.

Myasthenia gravis and pregnancy

Myasthenia gravis (MG) is an autoimmune disorder with bimodal age of presentation, occurring in young women of reproductive age and at an older age in men. Occasionally, MG is diagnosed during pregnancy. Management of MG includes symptomatic treatment with cholinesterase inhibitors and immunosuppressive therapy for controlling the disease activity. Treatment of MG in women of reproductive age, who may be contemplating pregnancy, requires discussion regarding the choice of medication as well as the understanding of risks/adverse effects involved with various treatments. During the peripartum period, it is essential to ensure careful monitoring of the disease state along with the well-being of the mother and fetus and to coordinate neonatal monitoring overseen by a multidisciplinary team comprising a high-risk maternal fetal medicine specialist, a neurologist familiar with these complex issues, and a neonatologist.

Pathomechanisms and Clinical Implications of Myasthenic Syndromes Exacerbated and Induced by Medical Treatments

Myasthenic syndromes are typically characterized by muscle weakness and increased fatigability due to an impaired transmission at the neuromuscular junction (NMJ). Most cases are caused by acquired autoimmune conditions such as myasthenia gravis (MG), typically with antibodies against the acetylcholine receptor (AChR). Different drugs are among the major factors that may complicate pre-existing autoimmune myasthenic conditions by further impairing transmission at the NMJ. Some clinical observations are substantiated by experimental data, indicating that presynaptic, postsynaptic or more complex pathomechanisms at the NMJ may be involved, depending on the individual compound. Most robust data exist for the risks associated with some antibiotics (e.g., aminoglycosides, ketolides, fluoroquinolones) and cardiovascular medications (e.g., class Ia antiarrhythmics, beta blockers). Apart from primarily autoimmune-mediated disorders of the NMJ, de novo myasthenic manifestations may also be triggered by medical treatments that induce an autoimmune reaction. Most notably, there is growing evidence that the immune checkpoint inhibitors (ICI), a modern class of drugs to treat various malignancies, represent a relevant risk factor to develop severe and progressive medication-induced myasthenia via an immune-mediated mechanism. From a clinical perspective, it is of utmost importance for the treating physicians to be aware of such adverse treatment effects and their consequences. In this article, we aim to summarize existing evidence regarding the key molecular and immunological mechanisms as well as the clinical implications of medication-aggravated and medication-induced myasthenic syndromes.

Magnesium sulfate for acute exacerbations of chronic obstructive pulmonary disease

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the effects of magnesium sulfate for acute exacerbations of chronic obstructive pulmonary disease in adults.

Magnesium sulfate reduces the rocuronium dose needed for satisfactory double lumen tube placement conditions in patients with myasthenia gravis

Background

Using a minimum dose of neuromuscular blockade (NMB) to achieve intubation condition is one of the goals in anaesthesia management of patients with myasthenia gravis (MG) for thoracoscopic (VATS) thymectomy. However, tracheal intubation with double lumen tube (DLT) could be challenging if intubation condition is not optimal. This double-blind randomised controlled study was designed to investigate whether magnesium sulfate would reduce the rocuronium dose needed for DLT intubation and improve the DLT placement condition for patients with MG who were scheduled for video-assisted thoracoscopic (VATS) thymectomy.

Methods

Recruited patients were randomly assigned to receive magnesium sulfate 60 mg.kg^− 1 or normal saline (control) prior to the administration of NMB. Titrating dose of rocuronium was administered to achieve train of four (TOF) ratio less than 10% before DLT intubation. The primary outcome was the rocuronium dose required to achieve TOF ratio less than 10%. The secondary outcome was intubation condition for DLT placement.

Results

Twenty-three patients had received magnesium sulfate and 22 patients had received normal saline before rocuronium administration. The required rocuronium dose [mean (standard deviation)] were 0.10 (0.05) mg.kg^− 1 and 0.28(0.17) mg.kg^− 1 in patients who had magnesium sulfate and normal saline respectively(P < 0.0001). With a similar depth of neuromuscular blockade and depth of anaesthesia, 100% of patients in the magnesium sulfate group and 72.7% of patients in the control group showed excellent intubation condition (P = 0.027) respectively. The patients in both groups had similar emergence characteristics.

Conclusions

Magnesium sulfate is associated with a decrease in rocuronium requirement for an optimal DLT intubation condition in patients with MG for VATS thymectomy.

Trial registration

Clinical Trial Registry of China (http://www.chictr.org.cn) identifier: ChiCTR-1800017696, retrospectively registered on August 10, 2018.

The effect of magnesium on the reversal of rocuronium-induced neuromuscular block with sugammadex: an ex vivo laboratory study

BACKGROUND

Magnesium dose-dependently potentiates the effect of non-depolarizing neuromuscular blocking agents. We investigated whether the potentiation of rocuronium-induced blockade by magnesium reduces the effect of sugammadex in an ex-vivo environment and how this influences the safety margin of reversal.

METHODS

Phrenic nerve - hemidiaphragm tissue preparations were isolated from male Wistar rats. The specimens were suspended in a tissue holder that allowed registering muscle contraction amplitude following electrical stimulation of the nerve. Concentration-response relationships were elucidated for magnesium, as well as for rocuronium and sugammadex.

RESULTS

The mean (95% confidence interval [CI]) half effective concentrations (EC₅₀) of rocuronium in the presence of magnesium 1 mM or 1.5 mM were 7.50 μM (6.97-8.07 μM) and 4.25 μM (4.09-4.41 μM), respectively (p < 0.0001). Increasing magnesium from 1 mM to 1.5 mM during reversal of rocuronium-induced block increased the mean (95% CI) EC₅₀ of sugammadex from 3.67 μM (3.43-3.92 μM) to 5.36 μM (5.18-5.53 μM), whereas mean (95% CI) effective concentrations for 95% effect (EC₉₅) were not significantly different at 7.22 μM (6.09-8.54 μM) and 7.61 μM (7.05-8.20 μM), respectively (p = 0.542). When rocuronium-induced block was reversed to a train-of-four (TOF) ratio > 0.9, but with still visible fade, increasing magnesium from 1 mM to 2 mM decreased the TOF ratio to below 0.9. If there was no visible fade after reversal, increasing magnesium concentration did not reduce the TOF ratio.

CONCLUSIONS

Magnesium potentiates the neuromuscular effect of rocuronium and shifts the concentration-response curve to the left. Magnesium decreases the safety margin of reversal of rocuronium-induced neuromuscular block with sugammadex.

Use Profile of Magnesium Sulfate in Anesthesia in Brazil

Objectives: The use of magnesium sulfate in the perioperative period has several benefits, including analgesia, inhibition of the release of catecholamines and prevention of vasospasm. The aim of this survey was to provide an overview of the use of magnesium sulfate in anesthesia. Method: This was a prospective descriptive cross-sectional study. An online questionnaire was sent to 9,869 Brazilian anesthesiologists and trainees. The questionnaire comprised closed questions mainly regarding the frequency, clinical effects, adverse events, and doses of magnesium sulfate used in anesthesia. Results: Of the 954 doctors who responded to the survey, 337 (35.32%) reported using magnesium sulfate in anesthesia. The most commonly cited clinical effects for the use of magnesium sulfate in anesthesia were (n/%): postoperative analgesia (245/72.70%), reduction of anesthetic consumption (240/71.21%) and prevention and treatment of preeclampsia and seizures in eclampsia (220/65.28%). The most frequently reported adverse events were hypotension (187/55.48%), residual neuromuscular blockade (133/39.46%), hypermagnesemia (30/8.90%), and intravenous injection pain (26/7.71%). The intravenous doses of magnesium sulfate used in most general anesthesia inductions were between 30 and 40 mg.kg-1. Conclusions: Magnesium sulfate is an important adjuvant drug in the practice of anesthesia, with several clinical effects and a low incidence of adverse events when used at recommended doses.

Effects of magnesium chloride on rocuronium-induced neuromuscular blockade and sugammadex reversal in an isolated rat phrenic nerve-hemidiaphragm preparation: An in-vitro study

BACKGROUND

Magnesium potentiates the effects of nondepolarising muscle relaxants. However, few studies have used magnesium chloride (MgCl2). Sugammadex reverses neuromuscular block by steroidal nondepolarising muscle relaxants.

OBJECTIVES

To assess the effects of MgCl2 on rocuronium-induced neuromuscular blockade and its reversal by sugammadex.

DESIGN

In-vitro experimental study.

SETTING

Animal laboratory, Asan Medical Center, Seoul, South Korea, from 20 March 2016 to 3 April 2016.

ANIMALS

Forty male Sprague Dawley rats.

INTERVENTION

Left phrenic nerve-hemidiaphragms from 40 Sprague Dawley rats were allocated randomly to four groups (1, 2, 3 and 4 mmol l MgCl2 group, n = 10 each). Rocuronium was administered cumulatively until the first twitch of train-of-four (TOF) disappeared completely. Then, equimolar sugammadex was administered.

MAIN OUTCOME MEASURES

The effective concentration (EC) of rocuronium was obtained in each group. After administering sugammadex, recovery of the first twitch height and the TOF ratio were measured for 30 min.

RESULTS

EC50, EC90 and EC95 significantly decreased as the concentration of MgCl2 increased (all P ≤ 0.001), except the comparison between the 3 and 4 mmol l MgCl2 groups. After administration of sugammadex, the maximal TOF ratio (%) was lower in the 4 mmol l MgCl2 group than the 1 mmol l MgCl2 group [median 91.7 interquartile range (83.4 to 95.8) vs. 98.3 interquartile range (92.2 to 103.4), P = 0.049]. The mean time (s) from sugammadex injection to achieving maximal first twitch was significantly prolonged in the 4 mmol l MgCl2 group vs. the 1 mmol l MgCl2 and 2 mmol l MgCl2 groups [1483.9 (± 237.0) vs. 1039.0 (± 351.8) and 926.0 (± 278.1), P = 0.022 and 0.002, respectively].

CONCLUSION

Increases in MgCl2 concentration reduce the ECs of rocuronium. In addition, administering sugammadex equimolar to the administered rocuronium shows limited efficacy as MgCl2 concentration is increased.

TRIAL REGISTRATION

The in-vitro study was not registered in a database.

Coupling the Structural and Functional Assembly of Synaptic Release Sites

Information processing in our brains depends on the exact timing of calcium (Ca²⁺)-activated exocytosis of synaptic vesicles (SVs) from unique release sites embedded within the presynaptic active zones (AZs). While AZ scaffolding proteins obviously provide an efficient environment for release site function, the molecular design creating such release sites had remained unknown for a long time. Recent advances in visualizing the ultrastructure and topology of presynaptic protein architectures have started to elucidate how scaffold proteins establish “nanodomains” that connect voltage-gated Ca²⁺ channels (VGCCs) physically and functionally with release-ready SVs. Scaffold proteins here seem to operate as “molecular rulers or spacers,” regulating SV-VGCC physical distances within tens of nanometers and, thus, influence the probability and plasticity of SV release. A number of recent studies at Drosophila and mammalian synapses show that the stable positioning of discrete clusters of obligate release factor (M)Unc13 defines the position of SV release sites, and the differential expression of (M)Unc13 isoforms at synapses can regulate SV-VGCC coupling. We here review the organization of matured AZ scaffolds concerning their intrinsic organization and role for release site formation. Moreover, we also discuss insights into the developmental sequence of AZ assembly, which often entails a tightening between VGCCs and SV release sites. The findings discussed here are retrieved from vertebrate and invertebrate preparations and include a spectrum of methods ranging from cell biology, super-resolution light and electron microscopy to biophysical and electrophysiological analysis. Our understanding of how the structural and functional organization of presynaptic AZs are coupled has matured, as these processes are crucial for the understanding of synapse maturation and plasticity, and, thus, accurate information transfer and storage at chemical synapses.

Hypomagnesemia in critically ill patients

BACKGROUND

Magnesium (Mg) is essential for life and plays a crucial role in several biochemical and physiological processes in the human body. Hypomagnesemia is common in all hospitalized patients, especially in critically ill patients with coexisting electrolyte abnormalities. Hypomagnesemia may cause severe and potential fatal complications if not timely diagnosed and properly treated, and associate with increased mortality.

MAIN BODY

Mg deficiency in critically ill patients is mainly caused by gastrointestinal and/or renal disorders and may lead to secondary hypokalemia and hypocalcemia, and severe neuromuscular and cardiovascular clinical manifestations. Because of the physical distribution of Mg, there are no readily or easy methods to assess Mg status. However, serum Mg and the Mg tolerance test are most widely used. There are limited studies to guide intermittent therapy of Mg deficiency in critically ill patients, but some empirical guidelines exist. Further clinical trials and critical evaluation of empiric Mg replacement strategies is needed.

CONCLUSION

Patients at risk of Mg deficiency, with typical biochemical findings or clinical symptoms of hypomagnesemia, should be considered for treatment even with serum Mg within the normal range.

Neuromuscular synapse degeneration without muscle function loss in the diaphragm of a murine model for Huntington's Disease

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease characterized by chorea, incoordination and psychiatric and behavioral symptoms. The leading cause of death in HD patients is aspiration pneumonia, associated with respiratory dysfunction, decreased respiratory muscle strength and dysphagia. Although most of the motor symptoms are derived from alterations in the central nervous system, some might be associated with changes in the components of motor units (MU). To explore this hypothesis, we evaluated morphofunctional aspects of the diaphragm muscle in a mouse model for HD (BACHD). We showed that the axons of the phrenic nerves were not affected in 12-months-old BACHD mice, but the axon terminals that form the neuromuscular junctions (NMJs) were more fragmented in these animals in comparison with the wild-type mice. In BACHD mice, the synaptic vesicles of the diaphragm NMJs presented a decreased exocytosis rate. Quantal content and quantal size were smaller and there was less synaptic depression whereas the estimated size of the readily releasable vesicle pool was not changed. At the ultrastructure level, the diaphragm NMJs of these mice presented fewer synaptic vesicles with flattened and oval shapes, which might be associated with the reduced expression of the vesicular acetylcholine transporter protein. Furthermore, mitochondria of the diaphragm muscle presented signs of degeneration in BACHD mice. Interestingly, despite all these cellular alterations, BACHD diaphragmatic function was not compromised, suggesting a higher resistance threshold of this muscle. A putative resistance mechanism may be protecting this vital muscle. Our data contribute to expanding the current understanding of the effects of mutated huntingtin in the neuromuscular synapse and the diaphragm muscle function.

The characteristics of patients with hypermagnesemia who underwent emergency hemodialysis

Aim

This study aimed to clarify the characteristics of patients who presented with severe hypermagnesemia and subsequently underwent emergency hemodialysis.

Methods

We investigated the age, gender, complications, clinical symptoms, causal drugs, electrocardiogram findings, and laboratory data of 15 patients.

Results

Magnesium oxide had been administered in all cases and 14 patients were over 65 years old. The male : female ratio was 6:9. Chief complaints included a disturbance of consciousness, hypotension, bradycardia, and respiratory failure. The median serum magnesium value before hemodialysis was 6.0 (3.7–18.6) mg/dL. The daily dosage of magnesium oxide was ≤ 2.0 g in 12 cases. The median serum creatinine value before hemodialysis was 5.39 (0.54–10.29) mg/dL. However, in two cases, the creatinine value was not elevated. Complications of acute kidney injury exacerbated the hypermagnesemia in nine cases.

Conclusions

We recommend that the serum magnesium value should be measured in older patients who are taking magnesium oxide and are showing signs and symptoms of a disturbance of consciousness, hypotension, bradycardia, and respiratory failure of an uncertain etiology, even if the serum creatinine value is not elevated or the dosage of magnesium oxide is within recommended levels.

Magnesium Sulfate-Induced Motor Evoked Potential Changes

Motor evoked potentials (MEPs) are commonly used during neurophysiologic intraoperative monitoring. Anesthetic, homeostatic, surgical, and technical factors can cause a change in MEPs. The authors describe a case in which a bolus of magnesium sulfate resulted in a loss of amplitude of MEPs. Responses returned to near baseline about 20 minutes later. The patient did not have any new postoperative deficits. When MEP changes occur, in addition to evaluating other causes, magnesium sulfate administration should be considered.

Inhaled magnesium sulfate in the treatment of acute asthma

BACKGROUND

Asthma exacerbations can be frequent and range in severity from mild to life-threatening. The use of magnesium sulfate (MgSO₄) is one of numerous treatment options available during acute exacerbations. While the efficacy of intravenous MgSO₄ has been demonstrated, the role of inhaled MgSO₄ is less clear.

OBJECTIVES

To determine the efficacy and safety of inhaled MgSO₄ administered in acute asthma.

SPECIFIC AIMS

to quantify the effects of inhaled MgSO₄ I) in addition to combination treatment with inhaled β₂-agonist and ipratropium bromide; ii) in addition to inhaled β₂-agonist; and iii) in comparison to inhaled β₂-agonist.

SEARCH METHODS

We identified randomised controlled trials (RCTs) from the Cochrane Airways Group register of trials and online trials registries in September 2017. We supplemented these with searches of the reference lists of published studies and by contact with trialists.

SELECTION CRITERIA

RCTs including adults or children with acute asthma were eligible for inclusion in the review. We included studies if patients were treated with nebulised MgSO₄ alone or in combination with β₂-agonist or ipratropium bromide or both, and were compared with the same co-intervention alone or inactive control.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial selection, data extraction and risk of bias. We made efforts to collect missing data from authors. We present results, with their 95% confidence intervals (CIs), as mean differences (MDs) or standardised mean differences (SMDs) for pulmonary function, clinical severity scores and vital signs; and risk ratios (RRs) for hospital admission. We used risk differences (RDs) to analyse adverse events because events were rare.

MAIN RESULTS

Twenty-five trials (43 references) of varying methodological quality were eligible; they included 2907 randomised patients (2777 patients completed). Nine of the 25 included studies involved adults; four included adult and paediatric patients; eight studies enrolled paediatric patients; and in the remaining four studies the age of participants was not stated. The design, definitions, intervention and outcomes were different in all 25 studies; this heterogeneity made direct comparisons difficult. The quality of the evidence presented ranged from high to very low, with most outcomes graded as low or very low. This was largely due to concerns about the methodological quality of the included studies and imprecision in the pooled effect estimates. Inhaled magnesium sulfate in addition to inhaled β₂-agonist and ipratropiumWe included seven studies in this comparison. Although some individual studies reported improvement in lung function indices favouring the intervention group, results were inconsistent overall and the largest study reporting this outcome found no between-group difference at 60 minutes (MD -0.3 % predicted peak expiratory flow rate (PEFR), 95% CI -2.71% to 2.11%). Admissions to hospital at initial presentation may be reduced by the addition of inhaled magnesium sulfate (RR 0.95, 95% CI 0.91 to 1.00; participants = 1308; studies = 4; I² = 52%) but no difference was detected for re-admissions or escalation of care to ITU/HDU. Serious adverse events during admission were rare. There was no difference between groups for all adverse events during admission (RD 0.01, 95% CI -0.03 to 0.05; participants = 1197; studies = 2). Inhaled magnesium sulfate in addition to inhaled β₂-agonistWe included 13 studies in this comparison. Although some individual studies reported improvement in lung function indices favouring the intervention group, none of the pooled results showed a conclusive benefit as measured by FEV1 or PEFR. Pooled results for hospital admission showed a point estimate that favoured the combination of MgSO₄ and β₂-agonist, but the confidence interval includes the possibility of admissions increasing in the intervention group (RR 0.78, 95% CI 0.52 to 1.15; participants = 375; studies = 6; I² = 0%). There were no serious adverse events reported by any of the included studies and no between-group difference for all adverse events (RD -0.01, 95% CI -0.05 to 0.03; participants = 694; studies = 5). Inhaled magnesium sulfate versus inhaled β₂-agonistWe included four studies in this comparison. The evidence for the efficacy of β₂-agonists in acute asthma is well-established and therefore this could be considered a historical comparison. Two studies reported a benefit of β₂-agonist over MgSO₄ alone for PEFR and two studies reported no difference; we did not pool these results. Admissions to hospital were only reported by one small study and events were rare, leading to an uncertain result. No serious adverse events were reported in any of the studies in this comparison; one small study reported mild to moderate adverse events but the result is imprecise.

AUTHORS' CONCLUSIONS

Treatment with nebulised MgSO₄ may result in modest additional benefits for lung function and hospital admission when added to inhaled β₂-agonists and ipratropium bromide, but our confidence in the evidence is low and there remains substantial uncertainty. The recent large, well-designed trials have generally not demonstrated clinically important benefits. Nebulised MgSO₄ does not appear to be associated with an increase in serious adverse events. Individual studies suggest that those with more severe attacks and attacks of shorter duration may experience a greater benefit but further research into subgroups is warranted.Despite including 24 trials in this review update we were unable to pool data for all outcomes of interest and this has limited the strength of the conclusions reached. A core outcomes set for studies in acute asthma is needed. This is particularly important in paediatric studies where measuring lung function at the time of an exacerbation may not be possible. Placebo-controlled trials in patients not responding to standard maximal treatment, including inhaled β₂-agonists and ipratropium bromide and systemic steroids, may help establish if nebulised MgSO₄ has a role in acute asthma. However, the accumulating evidence suggests that a substantial benefit may be unlikely.

Magnesium sulfate infusion for acute asthma in the emergency department

OBJECTIVES

To describe the role of intravenous magnesium sulfate (MgSO₄) as therapy for acute severe asthma in the pediatric emergency department (ED).

SOURCE

Publications were searched in the PubMed and Cochrane databases using the following keywords: magnesium AND asthma AND children AND clinical trial. A total of 53 publications were retrieved using this criteria. References of relevant articles were also screened. The authors included the summary of relevant publications where intravenous magnesium sulfate was studied in children (age <18 years) with acute asthma. The NAEPP and Global Initiative for Asthma expert panel guidelines were also reviewed.

SUMMARY OF THE DATA

There is a large variability in the ED practices on the intravenous administration of MgSO₄ for severe asthma. The pharmacokinetics of MgSO₄ is often not taken into account with a consequent impact in its pharmacodynamics properties. The cumulative evidence points to the effectiveness of intravenous MgSO₄ in preventing hospitalization, if utilized in a timely manner and at an appropriate dosage (50-75mg/kg). For every five children treated in the ED, one hospital admission could be prevented. Another administration modality is a high-dose continuous magnesium sulfate infusion (HDMI) as 50mg/kg/h/4h (200mg/kg/4h). The early utilization of HDMI for non-infectious mediated asthma may be superior to a MgSO₄ bolus in avoiding admissions and expediting discharges from the ED. HDMI appears to be cost-effective if applied early to a selected population. Intravenous MgSO₄ has a similar safety profile than other asthma therapies.

CONCLUSIONS

Treatment with intravenous MgSO₄ reduces the odds of hospital admissions. The use of intravenous MgSO₄ in the emergency room was not associated with significant side effects or harm. The authors emphasize the role of MgSO₄ as an adjunctive therapy, while corticosteroids and beta agonist remain the primary acute therapeutic agents.

Preparing for the unexpected: special considerations and complications after sugammadex administration

Sugammadex, a modified gamma-cyclodextrin, has changed clinical practice of neuromuscular reversal dramatically. With the introduction of this selective relaxant binding agent, rapid and reliable neuromuscular reversal from any depth of block became possible. Sugammadex can reverse neuromuscular blockade without the muscarinic side effects typically associated with the administration of acetylcholinesterase inhibitors. However, what remained unchanged is the incidence of residual neuromuscular blockade. It is known that sugammadex cannot always prevent its occurrence, if appropriate dosing is not chosen based on the level of neuromuscular paralysis prior to administration determined by objective neuromuscular monitoring. Alternatively, excessive doses of sugammadex administered in an attempt to ensure full and sustained reversal may affect the effectiveness of rocuronium in case of immediate reoperation or reintubation. In such emergent scenarios that require onset of rapid and reliable neuromuscular blockade, the summary of product characteristics (package insert) recommends using benzylisoquinolinium neuromuscular blocking agents or a depolarizing agent. However, if rapid intubation is required, succinylcholine has a significant number of side effects, and benzylisoquinolinium agents may not have the rapid onset required. Therefore, prior administration of sugammadex introduces a new set of potential problems that require new solutions. This novel reversal agent thus presents new challenges and anesthesiologists must familiarize themselves with specific issues with its use (e.g., bleeding risk, hypermagnesemia, hypothermia). This review will address sugammadex administration in such special clinical situations.

Cardiac Dysrhythmias and Neurological Dysregulation: Manifestations of Profound Hypomagnesemia

Magnesium is the second most common intracellular cation and serves as an important metabolic cofactor to over 300 enzymatic reactions throughout the human body. Among its various roles, magnesium modulates calcium entry and release from sarcoplasmic reticulum and regulates ATP pumps in myocytes and neurons, thereby regulating cardiac and neuronal excitability. Therefore, deficiency of this essential mineral may result in serious cardiovascular and neurologic derangements. In this case, we present the clinical course of a 76-year-old woman who presented with marked cardiac and neurological signs and symptoms which developed as a result of severe hypomagnesemia. The patient promptly responded to magnesium replacement once the diagnosis was established. We herein discuss the clinical presentation, pathophysiology, diagnosis, and management of severe hypomagnesemia and emphasize the implications of magnesium deficiency in the cardiovascular and central nervous systems. Furthermore, this case highlights the importance of having high vigilance for hypomagnesemia in the appropriate clinical setting.

Enhanced Dopamine Release by Dopamine Transport Inhibitors Described by a Restricted Diffusion Model and Fast-Scan Cyclic Voltammetry

Fast-scan cyclic voltammetry (FSCV) using carbon fiber electrodes is widely used to rapidly monitor changes in dopamine (DA) levels in vitro and in vivo. Current analytical approaches utilize parameters such as peak oxidation current amplitude and decay times to estimate release and uptake processes, respectively. However, peak amplitude changes are often observed with uptake inhibitors, thereby confounding the interpretation of these parameters. To overcome this limitation, we demonstrate that a simple five-parameter, two-compartment model mathematically describes DA signals as a balance of release (r/ke) and uptake (ku), summed with adsorption (kads and kdes) of DA to the carbon electrode surface. Using nonlinear regression, we demonstrate that our model precisely describes measured DA signals obtained in brain slice recordings. The parameters extracted from these curves were then validated using pharmacological manipulations that selectively alter vesicular release or DA transporter (DAT)-mediated uptake. Manipulation of DA release through altering the Ca(2+)/Mg(2+) ratio or adding tetrodotoxin reduced the release parameter with no effect on the uptake parameter. DAT inhibitors methylenedioxypyrovalerone, cocaine, and nomifensine significantly reduced uptake and increased vesicular DA release. In contrast, a low concentration of amphetamine reduced uptake but had no effect on DA release. Finally, the kappa opioid receptor agonist U50,488 significantly reduced vesicular DA release but had no effect on uptake. Together, these data demonstrate a novel analytical approach to distinguish the effects of manipulations on DA release or uptake that can be used to interpret FSCV data.

High-Dose Magnesium Sulfate Infusion for Severe Asthma in the Emergency Department: Efficacy Study

OBJECTIVE

To assess the efficacy of a high-dose prolonged magnesium sulfate infusion in patients with severe, noninfectious-mediated asthma.

DESIGN

Prospective, randomized, open-label study.

SETTING

Twenty-nine-bed pediatric emergency department located in a children's hospital in Asuncion, Paraguay.

PATIENTS

All patients of 6-16 years old who failed to improve after 2 hours of standard therapy for asthma.

INTERVENTIONS

Subjects were randomized to receive magnesium sulfate, 50 mg/kg over 1 hour (bolus) or high-dose prolonged magnesium sulfate infusion of 50 mg/kg/hr for 4 hours (max, 8.000 mg/4 hr). Patients were monitored for cardiorespiratory complications.

MEASUREMENTS AND MAIN RESULTS

Asthma severity was assessed via asthma scores and peak expiratory flow rates at 0-2-6 hours. The primary outcome was discharge to home at 24 hours. An analysis of the hospital length of stay and costs was a secondary outcome. Thirty-eight patients were enrolled, 19 in each group. The groups were of similar ages, past medical history of asthma, asthma score, and peak expiratory flow rate. There was a significant difference in the patients discharged at 24 hours: 47% in high-dose prolonged magnesium sulfate infusion (9/19) versus 10% (2/21) in the bolus group (p = 0.032) with an absolute risk reduction 37% (95% CI, 10-63) and a number needed to treat of 2.7 (95% CI, 1.6-9.5) to facilitate a discharge at or before 24 hours. The length of stay was shorter in the high-dose prolonged magnesium sulfate infusion group (mean ± SD in hr: high-dose prolonged magnesium sulfate infusion, 34.13 ± 19.54; bolus, 48.05 ± 18.72; p = 0.013; 95% CI, 1.3-26.5). The cost per patient in the high-dose prolonged magnesium sulfate infusion group was one third lower than the bolus group (mean ± SD: high-dose prolonged magnesium sulfate infusion, $603.16 ± 338.47; bolus, $834.37 ± 306.73; p < 0.016). There were no interventions or discontinuations of magnesium sulfate due to adverse events.

CONCLUSIONS

The early utilization of high-dose prolonged magnesium sulfate infusion (50 mg/kg/hr/4 hr), for non-infectious mediated asthma, expedites discharges from the emergency department with significant reduction in healthcare cost.

Admission serum magnesium levels and the risk of acute respiratory failure

BACKGROUND

The association between admission serum magnesium (Mg) levels and risk of acute respiratory failure (ARF) in hospitalised patients is limited. The aim of this study was to assess the risk of developing ARF in all hospitalised patients with various admission Mg levels.

METHODS

This is a single-center retrospective study conducted at a tertiary referral hospital. All hospitalised adult patients who had admission Mg available from January to December 2013 were analysed in this study. Admission Mg was categorised based on its distribution into six groups (less than 1.5, 1.5-1.7, 1.7-1.9, 1.9-2.1, 2.1-2.3 and greater than 2.3 mg/dl). The primary outcome was in-hospital ARF occurring after hospital admission. Logistic regression analysis was performed to obtain the odds ratio of ARF of various admission Mg levels using Mg of 1.7-1.9 mg/dl as the reference group.

RESULTS

Of 9780 patients enrolled, ARF occurred in 619 patients (6.3%). The lowest incidence of ARF was when serum Mg within 1.7-1.9 mg/dl. A U-shaped curve emerged demonstrating higher incidences of ARF associated with both hypomagnesemia (< 1.7) and hypermagnesemia (> 1.9). After adjusting for potential confounders, both hypomagnesemia (< 1.5 mg/dl) and hypermagnesemia (> 2.3 mg/dl) were associated with an increased risk of developing ARF with odds ratios of 1.69 (95% CI: 1.19-2.36) and 1.40 (95% CI: 1.02-1.91) respectively.

CONCLUSION

Both admission hypomagnesemia and hypermagnesemia were associated with an increased risk for in-hospital ARF.

Acute Respiratory Failure Induced by Magnesium Replacement in a 62-Year-Old Woman with Myasthenia Gravis

Magnesium is known to act at the neuromuscular junction by inhibiting the presynaptic release of acetylcholine and desensitizing the postsynaptic membrane. Because of these effects, magnesium has been postulated to potentiate neuromuscular weakness. We describe the case of a 62-year-old woman with myasthenia gravis and a metastatic thymoma who was admitted to our intensive care unit for management of a myasthenic crisis. The patient's neuromuscular weakness worsened in association with standard intravenous magnesium replacement, and the exacerbated respiratory failure necessitated intubation, mechanical ventilation, and an extended stay in the intensive care unit. The effect of magnesium replacement on myasthenia gravis patients has not been well documented, and we present this case to increase awareness and stimulate research. In addition, we discuss the relevant medical literature.

The physiology of artificial hibernation

Incomplete understanding of the mechanisms responsible for induction of hibernation prevent translation of natural hibernation to its artificial counterpart. To facilitate this translation, a model was developed that identifies the necessary physiological changes for induction of artificial hibernation. This model encompasses six essential components: metabolism (anabolism and catabolism), body temperature, thermoneutral zone, substrate, ambient temperature, and hibernation-inducing agents. The individual components are interrelated and collectively govern the induction and sustenance of a hypometabolic state. To illustrate the potential validity of this model, various pharmacological agents (hibernation induction trigger, delta-opioid, hydrogen sulfide, 5'-adenosine monophosphate, thyronamine, 2-deoxyglucose, magnesium) are described in terms of their influence on specific components of the model and corollary effects on metabolism. Relevance for patients: The ultimate purpose of this model is to help expand the paradigm regarding the mechanisms of hibernation from a physiological perspective and to assist in translating this natural phenomenon to the clinical setting.