Effect of increasing doses of magnesium in experimental pulmonary hypertension after acute pulmonary embolism

Effect of magnesium sulfate on oxygenation and lung mechanics in morbidly obese patients undergoing bariatric surgery: a prospective double-blind randomized clinical trial

BACKGROUND

Respiratory mechanics are often significantly altered in morbidly obese patients and magnesium sulfate (MgSO4) is a promising agent for managing several respiratory disorders. This study aimed to examine the effects of MgSO4 infusions on arterial oxygenation and lung mechanics in patients with morbid obesity undergoing laparoscopic bariatric surgery.

METHODS

Forty patients with morbid obesity aged 21-60 years scheduled for laparoscopic bariatric surgery under general anesthesia were randomly allocated to either the control (normal saline infusion) or MgSO4 group (30 mg/kg lean body weight [LBW] of 10% MgSO4 in 100 ml normal saline intravenously over 30 min as a loading dose, followed by 10 mg/kg LBW/h for 90 min). The primary outcome was intraoperative arterial oxygenation (ΔPaO2/FiO2). Secondary outcomes included intraoperative static and dynamic compliance, dead space, and hemodynamic parameters.

RESULTS

At 90 min intraoperatively, the Δ PaO2/FiO2 ratio and the Δ dynamic lung compliance were statistically significantly higher in the MgSO4 group (mean ± SE: 16.1 ± 1.0, 95% CI [14.1, 18.1] and 8.4 ± 0.5 ml/cmH2O, 95% CI [7.4, 9.4]), respectively), and the Δ dead space (%) was statistically significantly lower in the MgSO4 group (mean ± SE: -8.0 ± 0.3%, 95% CI [-8.6, -7.4]) (P < 0.001). No significant differences in static compliance were observed.

CONCLUSIONS

Although MgSO4 significantly preserved arterial oxygenation and maintained dynamic lung compliance and dead space in patients with morbid obesity, the clinical relevance is minimal. This study failed to adequately reflect the clinical importance of these results.

Attenuating effect of magnesium on pulmonary arterial calcification in rodent models of pulmonary hypertension

OBJECTIVE

Vascular calcification has been considered as a potential therapeutic target in pulmonary hypertension. Mg2+ has a protective role against calcification. This study aimed to investigate whether Mg2+ could alleviate pulmonary hypertension by reducing medial calcification of pulmonary arteries.

METHODS

Monocrotaline (MCT)-induced and chronic hypoxia-induced pulmonary hypertension rats were given an oral administration of 10% MgSO4 (10 ml/kg per day). Additionally, we administered Mg2+ in calcified pulmonary artery smooth muscle cells (PASMCs) after incubating with β-glycerophosphate (β-GP, 10 mmol/l).

RESULTS

In vivo, MCT-induced and chronic hypoxia-induced pulmonary hypertension indexes, including right ventricular systolic pressure, right ventricular mass index, and arterial wall thickness, as well as Alizarin Red S (ARS) staining-visualized calcium deposition, high calcium levels, and osteochondrogenic differentiation in pulmonary arteries, were mitigated by dietary Mg2+ intake. In vitro, β-GP-induced calcium-rich deposits stained by ARS, calcium content, as well as the detrimental effects of calcification to proliferation, migration, and resistance to apoptosis of PASMCs were alleviated by high Mg2+ but exacerbated by low Mg2+. Expression levels of mRNA and protein of β-GP-induced osteochondrogenic markers, RUNX Family Transcription Factor 2, and Msh Homeobox 2 were decreased by high Mg2+ but increased by low Mg2+; however, Mg2+ did not affect β-GP-induced expression of SRY-Box Transcription Factor 9. Moreover, mRNA expression and protein levels of β-GP-reduced calcification inhibitor, Matrix GLA protein was increased by high Mg2+ but decreased by low Mg2+.

CONCLUSION

Mg2+ supplement is a powerful strategy to treat pulmonary hypertension by mitigating pulmonary arterial calcification as the calcification triggered physiological and pathological changes to PASMCs.

Magnesium Supplementation Attenuates Pulmonary Hypertension via Regulation of Magnesium Transporters

Pulmonary hypertension (PH) is characterized by profound vascular remodeling and altered Ca²⁺ homeostasis in pulmonary arterial smooth muscle cells (PASMCs). Magnesium ion (Mg²⁺), a natural Ca²⁺ antagonist and a cofactor for numerous enzymes, is crucial for regulating diverse cellular functions, but its roles in PH remains unclear. Here, we examined the roles of Mg²⁺ and its transporters in PH development. Chronic hypoxia and monocrotaline induced significant PH in adult male rats. It was associated with a reduction of [Mg²⁺]_i in PASMCs, a significant increase in gene expressions of Cnnm2, Hip14, Hip14l, Magt1, Mmgt1, Mrs2, Nipa1, Nipa2, Slc41a1, Slc41a2 and Trpm7; upregulation of SLC41A1, SLC41A2, CNNM2, and TRPM7 proteins; and downregulation of SLC41A3 mRNA and protein. Mg²⁺ supplement attenuated pulmonary arterial pressure, right heart hypertrophy, and medial wall thickening of pulmonary arteries, and reversed the changes in the expression of Mg²⁺ transporters. Incubation of PASMCs with a high concentration of Mg²⁺ markedly inhibited PASMC proliferation and migration, and increased apoptosis, whereas a low level of Mg²⁺ produced the opposite effects. siRNA targeting Slc41a1/2, Cnnm2, and Trpm7 attenuated PASMC proliferation and migration, but promoted apoptosis; and Slc41a3 overexpression also caused similar effects. Moreover, siRNA targeting Slc41a1 or high [Mg²⁺] incubation inhibited hypoxia-induced upregulation and nuclear translocation of NFATc3 in PASMCs. The results, for the first time, provide the supportive evidence that Mg²⁺ transporters participate in the development of PH by modulating PASMC proliferation, migration, and apoptosis; and Mg²⁺ supplementation attenuates PH through regulation of Mg²⁺ transporters involving the NFATc3 signaling pathway.

Intraoperative MgSO4 infusion protects oxygenation and lung mechanics in COPD patients during general anesthesia. A randomized clinical trial

BACKGROUND

The purpose of this study was to examine the effects of an intraoperative MgSO₄ infusion on arterial oxygenation and lung mechanics in patients with moderate COPD undergoing cancer larynx surgery under general anesthesia (GA). Our primary outcome was arterial oxygenation determined by the PaO₂ and PaO₂ /FiO₂ . The secondary outcomes were lung mechanics (peak airway pressure, airway plateau pressure, dead space, lung compliance, airway resistance) and postoperative complications.

METHODS

In this randomized controlled double-blinded trial, 40 patients with an ASA classifications II and/or III who were diagnosed with moderate COPD and who were scheduled for cancer larynx surgery under GA were randomly allocated into two equal groups, the target (Mg group) and control group (C group). In the Mg group, 30 mg/kg of 10% MgSO₄ solution was administered intravenously for over 20 minutes as the loading dose, followed by the continuous infusion of 10 mg/kg/hr In the C group, the same loading and maintenance infusion rates were administered using 0.9% saline.

RESULTS

Unlike the C group (baseline "T0" to post-infusion "T1" interval 294 ± 97 vs 238 ± 71 mm Hg, respectively, P = .04 ± SD), the Mg group exhibited preserved intraoperative PaO₂ (T0 to T1 interval 271 ± 89 vs 257 ± 53 mm Hg, respectively, P = .54 ± SD) and PaO₂ /FiO₂ (C group T0 to T1 interval 404 ± 81 vs 349 ± 84, P = .04 and Mg group 394 ± 91 vs 379 ± 95, P = .61, respectively), and these effects were modest. Further, compared to the C group, the Mg group exhibited lower airway resistance, dead space, airway plateau pressure, and peak airway pressure, and higher dynamic compliance. The postoperative PaO₂ and PaO₂ /FiO₂ were higher in the Mg group compared to the C group.

CONCLUSIONS

Intraoperative infusion of MgSO₄ in patients with moderate COPD undergoing laryngectomy surgery under GA produces mild perioperative protective effects on both arterial oxygenation and lung mechanics.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT03461328; registration date: 8 March 2018.

Serum magnesium and risk of incident heart failure in older men: The British Regional Heart Study

To examine the association between serum magnesium and incident heart failure (HF) in older men and investigate potential pathways including cardiac function, inflammation and lung function. Prospective study of 3523 men aged 60–79 years with no prevalent HF or myocardial infarction followed up for a mean period of 15 years, during which 268 incident HF cases were ascertained. Serum magnesium was inversely associated with many CVD risk factors including prevalent atrial fibrillation, lung function (FEV₁) and markers of inflammation (IL-6), endothelial dysfunction (vWF) and cardiac dysfunction [NT-proBNP and cardiac troponin T (cTnT)]. Serum magnesium was inversely related to risk of incident HF after adjustment for conventional CVD risk factors and incident MI. The adjusted hazard ratios (HRs) for HF in the 5 quintiles of magnesium groups were 1.00, 0.72 (0.50, 1.05), 0.85 (0.59, 1.26), 0.76 (0.52, 1.11) and 0.56 (0.36, 0.86) respectively [p (trend) = 0.04]. Further adjustment for atrial fibrillation, IL-6, vWF and FEV₁ attenuated the association but risk remained significantly reduced in the top quintile (≥ 0.87 mmol/l) compared with the lowest quintile [HR 0.62 (0.40, 0.97)]. Adjustment for NT-proBNP and cTnT attenuated the association further [HR 0.70 (0.44, 1.10)]. The benefit of high serum magnesium on HF risk was most evident in men with ECG evidence of ischaemia [HR 0.29 (0.13, 0.68)]. The potential beneficial effect of high serum magnesium was partially explained by its favourable association with CVD risk factors. Further studies are needed to investigate whether serum magnesium supplementation in older adults may protect from the development of HF.

Magnesium attenuates endothelin-1-induced vasoreactivity and enhances vasodilatation in mouse pulmonary arteries: Modulation by chronic hypoxic pulmonary hypertension

NEW FINDINGS

What is the central question of this study? The central goal of this study was to elucidate the role of magnesium in the regulation of pulmonary vascular reactivity in relationship to hypoxic pulmonary hypertension. What is the main finding and its importance? We found that magnesium is essential for normal vasoreactivity of the pulmonary artery. Increasing the magnesium concentration attenuates vasoconstriction and improves vasodilatation via release of nitric oxide. Pulmonary hypertension is associated with endothelial dysfunction resulting in the suppression of magnesium modulation of vasodilatation. These results provide evidence that magnesium is important for the modulation of pulmonary vascular function.

ABSTRACT

Pulmonary hypertension (PH) is characterized by enhanced vasoreactivity and sustained pulmonary vasoconstriction, arising from aberrant Ca²⁺ homeostasis in pulmonary arterial (PA) smooth muscle cells. In addition to Ca²⁺ , magnesium, the most abundant intracellular divalent cation, also plays crucial roles in many cellular processes that regulate cardiovascular function. Recent findings suggest that magnesium regulates vascular functions by altering the vascular responses to vasodilator and vasoactive agonists and affects endothelial function by modulating endothelium-dependent vasodilatation in hypertension. Administration of magnesium also decreased pulmonary arterial pressure and improved cardiac output in animal models of PH. However, the role of magnesium in the regulation of pulmonary vascular function related to PH has not been studied. In this study, we examined the effects of magnesium on endothelin-1 (ET-1)-induced vasoconstriction, ACh-induced vasodilatation and the generation of NO in PAs of normoxic mice and chronic hypoxia (CH)-treated mice. Our data showed that removal of extracellular magnesium suppressed vasoreactivity of PAs to both ET-1 and ACh. A high concentration of magnesium (4.8 mm) inhibited ET-1-induced vasoconstriction in endothelium-intact or endothelium-disrupted PAs of normoxic and CH-treated mice, and enhanced the ACh-induced production of NO in PAs of normoxic mice. Moreover, magnesium enhanced ACh-induced vasodilatation in PAs of normoxic mice, and the enhancement was completely abolished after exposure to CH. Hence, in this study we demonstrated that increasing the magnesium concentration can attenuate the ET-1-induced contractile response and improve vasodilatation via release of NO from the endothelium. We also demonstrated that chronic exposure to hypoxia can cause endothelial dysfunction resulting in suppression of the magnesium-dependent modulation of vasodilatation.