Monitoring of ionized magnesium in hemodialysis patients: A useful tool to allow a personalized prescription of dialysate composition.

BACKGROUND AND AIMS: The dialysate magnesium (Mg) concentration is a major determinant of Mg balance in hemodialysis. This study aimed to assess the systemic variations of total (tMg) and ionized Mg (iMg) during a dialysis session using acetate or citrate fluids and 0.5 or 0.75 mM Mg. MATERIALS AND METHODS: 134 patients in maintenance hemodialysis were assigned to a dialysis session with 4 different dialysates: acetate fluid with 0.5 mM Mg (1) or 0.75 mM Mg (2), citrate fluid with 0.5 mM Mg (3) or 0.75 mM Mg (4). Ionized form was measured by direct ion-selective electrode. RESULTS: A Mg loss was observed in both acetate (0.12 and 0.08 mmol/L) and citrate (0.13 and 0.14 mmol/L for tMg and iMg, respectively) fluid groups containing 0.5 mM Mg. The use of acetate and citrate dialysates with 0.75 mM Mg led to a significant median intra-dialytic increase of 0.15 and 0.08 mmol/L for tMg, respectively. A significant augmentation in iMg concentration with acetate (0.11 mmol/L) but not with citrate dialysate (0.02 mmol/L) was observed. CONCLUSION: While a dialysate Mg concentration at 0.5 mM leads to a negative balance, increasing the concentration to 0.75 mM significantly raises post-dialysis circulating Mg. Monitoring of iMg should allow a personalized prescription in dialysate Mg.

Sample stability and heparin interference in ionized calcium and ionized magnesium measurements in horses using the Stat Profile Prime Plus co-oximetry electrolyte analyzer.

BACKGROUND: The determination of iCa and iMg is important in veterinary medicine, but their immediate determination in whole blood is not always possible. Their stability in other sample types and the existence of interferences must be evaluated before its use. OBJECTIVES: We aimed to analyze the effects of storage time on the stability of iCa, iMg, and other analytes in whole blood, plasma, and serum samples in horses and assess the interference of heparin in these measurements. METHODS: Whole blood, heparin-plasma, and serum samples from 10 horses were stored at 4°C and analyzed 1, 2, 3, 4, 5, 6, 7, 8, 24, 48, and 168 hours after sample collection using the Stat Profile Prime Plus Vet equipment (Nova Biomedical, Waltham, MA, USA). Results were analyzed by ANOVA or mixed-effect models. RESULTS: The concentration of iCa, iMg, total calcium (tCa), total magnesium (tMg), and the ratios iCa/tCa and iMg/tMg did not differ up to 168 hours when compared to the initial time. Total Ca, iMg, and tMg were not significantly different among sample types, but iCa concentrations were slightly but significantly lower in plasma. Freezing at -20°C did not affect iCa, iMg, tCa, and tMg. The pH increased in serum and plasma after 8 hours, and a mild negative correlation existed between plasma iCa concentration and pH. A negative correlation was observed also between the ratios iCa/tCa or iMg/tMg and pH in plasma and serum. A significant decrease in iCa and iMg was detected when comparing homemade syringes at high heparin concentration (~200-300 U heparin/mL) and commercial lithium-heparin tubes (20-30 U/mL). CONCLUSIONS: Samples stored at 4°C can be used to determine iCa and iMg concentrations up to 7 days after collection. Other metabolites are stable for up to 8 hours; heparin interference should be taken into account if using homemade heparin syringes.

Incidence of ionized hypomagnesemia in adult patients undergoing noncardiac major surgery: a prospective observational trial

Background: The present study aimed to investigate the incidence of preoperative ionized hypomagnesemia and compare with that of total hypomagnesemia. Methods: This prospective observational study included 536 patients aged >20 years who were scheduled for elective surgery. Total and ionized magnesium levels were evaluated before and after the surgery. Based on these levels, patients were classified into the following groups: ionized hypo- (<0.42 mmol/L), normo- (0.42-0.59 mmol/L) and hypermagnesemia (>0.59 mmol/L), as well as total hypo- (<1.9 mg/dL[0.78 mmol/L]), normo- (1.9-2.7 mg/dL[0.78-1.11 mmol/L]) and hypermagnesemia (>2.7 mg/dL [1.11 mmol/L]). The primary objective was to establish the incidence of preoperative ionized hypomagnesemia. Results: There was a marked difference between the incidence of preoperative ionized and total hypomagnesemia (28% vs. 19%; p<0.001). The postoperative values of ionized magnesium, ionized calcium, and albumin were significantly lower than the respective preoperative values (p<0.001 for all three variables). Conclusion: The incidence of hypomagnesemia, determined by ionized magnesium concentration, was higher than that determined by total magnesium concentration.

Does Ionized Magnesium Offer a Different Perspective Exploring the Association between Magnesemia and Targeted Cardiovascular Risk Factors?

Evidence of the association of magnesium (Mg) with arterial stiffness has so far been conflicting. The interplay between hypertension and elevated body mass index (BMI), with hypomagnesemia, instead, has been described in the literature in a more consistent way. Our study aims at revisiting the correlations between blood Mg levels and hemodynamic and body composition parameters in the general population, exploring the sensitivity profile of ionized Mg (Ion-Mg) compared to total Mg (Tot-Mg). We collected data from 755 subjects randomly chosen from a Swiss population previously described and stratified our sample into four equivalent classes according to ionized (whole blood) and total (serum) magnesium. After correcting for age, statistically significant differences emerged between: (i) Tot-Mg ≤ 0.70 and 0.81 ≤ Tot-Mg ≤ 0.90 for cf-PWV (p = 0.039); (ii) Tot-Mg ≤ 0.70 and Tot-Mg ≥ 0.91 for o-PWV (p = 0.046). We also found a statistically significant difference among groups of Ion-Mg values for the 24 h extremes of systolic blood pressure (p = 0.048) and among groups of Tot-Mg for BMI (p = 0.050). Females showed significantly lower levels of total magnesium (p = 0.035) and ionized magnesium (p < 0.001) than males. The overall agreement between magnesium analysis methods was 64% (95%CI: 60.8−67.7%). Our results confirm that Ion-Mg compared with Tot-Mg offers a different profile in detecting both correlations with hemodynamic and body composition parameters and dysmagnesemias. Lower levels of magnesium were associated with worse arterial aging parameters, larger 24 h blood pressure excursions, and higher BMI. Ion-Mg was superior in detecting the correlation with blood pressure only. Considering Ion-Mg as a more specific marker of the magnesium status, and the partially contradictory results of our explorative cross-sectional study, to avoid confounding factors and misinterpretations, ionized magnesium should be used as reference in future studies.

Two Cases of Liver Transplantation With a High Ionized Magnesium to Total Magnesium Ratio.

Magnesium (Mg), an important cation, is involved in the activation of enzymes important for life support. The incidence of hypomagnesemia in critically ill patients admitted to the intensive care unit (ICU) is high and has been reported to be a factor in worsening prognosis. Ionized magnesium (iMg) is physiologically active, although total magnesium (tMg) is often used to evaluate the concentration of magnesium because of the limited availability of instruments that can measure iMg. However, the changes in tMg and iMg are not correlated in critically ill patients. We obtained considerable data on the simultaneous measurements of iMg and tMg in two patients with severe liver disease who underwent liver transplantation. In both patients, the iMg/tMg values were high, suggesting the influence of hypoalbuminemia associated with liver dysfunction. Mg correction using tMg as a guide may lead to overdose. Furthermore, when considering the data for each case, the correlation between iMg and tMg was very high, which suggested that the iMg/tMg ratio may be a value unique to each individual or disease. Investigating in a large-scale study the correlation between iMg levels and clinical symptoms and prognosis is necessary in the future.

Relationship Between Dietary Magnesium Intake and Incident Heart Failure Among Older Women: The WHI.

Background Women represent a large proportion of the growing heart failure (HF) epidemic, yet data are lacking regarding optimal dietary and lifestyle prevention strategies for them. Specifically, the association between magnesium intake and HF in a multiracial cohort of women is uncertain. Methods and Results We included 97 725 postmenopausal women from the WHI (Women's Health Initiative) observational studies and placebo arms of the hormone trial. Magnesium intake was measured at baseline by a 122-item validated food-frequency questionnaire and stratified into quartiles based on diet only, total intake (diet with supplements), and residual intake (calibration by total energy). Incident hospitalized HF (2153 events, median follow-up 8.1 years) was adjudicated by medical record abstraction. In Cox proportional hazards models, we evaluated the association between magnesium intake and HF adjusting for potential confounders. Analyses were repeated on a subcohort (n=18 745; median-follow-up, 13.2 years) for whom HF cases were subclassified into preserved ejection fraction (526 events), reduced ejection fraction (291 events) or unknown (168 events). Most women were white (85%) with a mean age of 63. Compared with the highest quartile of magnesium intake, women in the lowest quartile had an increased risk of incident HF, with adjusted hazard ratios of 1.32 (95% CI, 1.02-1.71) for diet only (P trend=0.03), 1.26 (95% CI, 1.03-1.56) for total intake, and 1.31 (95% CI, 1.02-1.67) for residual intake. Results did not significantly vary by race. Subcohort analyses showed low residual magnesium intake was associated with HF with reduced ejection fraction (hazard ratio, 1.81, lowest versus highest quartile; 95% CI, 1.08-3.05) but not HF with preserved ejection fraction. Conclusions Low magnesium intake in a multiracial cohort of postmenopausal women was associated with a higher risk of incident HF, especially HF with reduced ejection fraction.

Circulating Ionized Magnesium: Comparisons with Circulating Total Magnesium and the Response to Magnesium Supplementation in a Randomized Controlled Trial.

Ionized Mg (iMg) is considered the biologically active fraction of circulating total Mg (tMg). It is possible that iMg may be a more physiologically relevant marker than tMg. Using data from a double-blind pilot randomized controlled trial, we tested (1) whether oral Mg supplementation will increase iMg concentrations compared with placebo and (2) the relationship between iMg and tMg at baseline. Additionally, we evaluated the agreement between iMg measured in fresh whole blood versus stored samples. A total of fifty-nine participants were randomized 1:1 to oral Mg supplementation (400 mg/day, Mg Oxide) or placebo for 10 weeks. Fasting blood samples were obtained at baseline and follow-up. The analysis used linear regression and an intent-to-treat approach. Participants were generally healthy, the mean age was 62, and 73% were female. The baseline iMg and tMg were modestly and positively associated (r = 0.50). The ratio of baseline iMg to tMg was 64%. The mean supplement effect on iMg was 0.03 mmol/L (95% CI:0.01, 0.05) for Mg supplementation versus placebo. The supplement effect on iMg was not statistically significantly different according to baseline iMg status (above/below median). Compared to fresh blood, iMg was consistently higher in refrigerated and frozen samples by 0.14 and 0.20 mmol/L, respectively. In this relatively healthy adult population, Mg supplementation over 10 weeks resulted in increased iMg concentrations. Whether iMg is a more appropriate measure of Mg status than tMg, and the public health or clinical utility of measuring iMg remains to be determined.

Assessment of Serum Magnesium Fractions in Workers Exposed to Pb from Pb-Battery Plant.

BACKGROUND: Most of studies assessed the effect of Pb-exposure on serum total magnesium (tMg). The hypomagnesium condition depended on protein concentration in the sample and influence of lifestyle factors. This study assessed the effect of Pb- exposure on serum tMg, corrected Mg (cMg), ionized Mg (iMg), percentage of iMg from tMg, and percentage of iMg from cMg with contemplation of lifestyle factors. STUDY DESIGN: Case control study. METHODS: The serum magnesium fractions were assessed in 176 male Pb-exposed workers in the year 2015 at Tamil nadu in India and 80 control subjects with no occupational exposure of Pb. The serum tMg and albumin concentrations were estimated using diagnostic kit methods. Blood lead levels (BLLs) were estimated using atomic absorbtion spectrophotometer method. The fraction of cMg and iMg were calculated from serum tMg and albumin concentration among individual subjects. RESULTS: The BLLs was significantly (P<0.001) increased in the study group as compared to control. Serum tMg, cMg, iMg, % of iMg from tMg and % of iMg from cMg concentrations were not significantly decreased in the study group as compared to control. Pb-exposure was significantly associated with abnormal frequency distribution of serum iMg (P=0.048) and % of iMg from tMg (P=0.016). Smoking habit was significantly associated with cMg (P=0.039) and % of iMg from cMg concentration (P=0.018). The alcohol consumption was significantly (P=0.049) associated with cMg. CONCLUSION: The Pb-exposure and lifestyle factor such as smoking and alcohol consumption were associated with alteration of serum magnesium fractions.

Quantitative imaging of magnesium distribution at single-cell resolution in brain tumors and infiltrating tumor cells with secondary ion mass spectrometry (SIMS).

Glioblastoma multiforme (GBM) is one of the deadliest forms of human brain tumors. The infiltrative pattern of growth of these tumors includes the spread of individual and/or clusters of tumor cells at some distance from the main tumor mass in parts of the brain protected by an intact blood-brain-barrier. Pathophysiological studies of GBM could be greatly enhanced by analytical techniques capable of in situ single-cell resolution measurements of infiltrating tumor cells. Magnesium homeostasis is an area of active investigation in high grade gliomas. In the present study, we have used the F98 rat glioma as a model of human GBM and an elemental/isotopic imaging technique of secondary ion mass spectrometry, a CAMECA IMS-3f ion microscope, for studying Mg distribution with single-cell resolution in freeze-dried brain tissue cryosections. Quantitative observations were made on tumor cells in the main tumor mass, contiguous brain tissue, and infiltrating tumor cells in adjacent normal brain. The brain tissue contained a significantly lower total Mg concentration of 4.70 ± 0.93 mmol/kg wet weight (mean ± SD) in comparison to 11.64 ± 1.96 mmol/kg wet weight in tumor cells of the main tumor mass and 10.72 ± 1.76 mmol/kg wet weight in infiltrating tumor cells (p < 0.05). The nucleus of individual tumor cells contained elevated levels of bound Mg. These observations have established that there was enhanced influx and increased binding of Mg in tumor cells. They provide strong support for further investigation of altered Mg homeostasis and activation of Mg-transporting channels in GBMs as possible therapeutic targets.

Estudio comparativo de la excreción urinaria de boro, calcio, magnesio y fósforo en mujeres posmenopáusicas con y sin osteoporosis / Comparative study of the urinary excretion of boron, calcium, magnesium and phosphorus in postmenopausal women with and without osteoporosis

Con el propósito de comparar la posible relación entre las concentraciones urinarias de boro y las concentraciones de calcio, de magnesio y de fósforo en suero y orina de mujeres posmenopáusicas con y sin osteoporosis, seleccionamos 45 mujeres posmenopáusicas con más de 47 años de edad, divididas en dos subgrupos: grupo I mujeres posmenopáusicas clínicamente sanas y grupo II mujeres posmenopáusicas con osteoporosis, sin enfermedades renales, hepáticas o diabetes mellitus. Se determinó el boro (B), el fósforo (P), el calcio total (Ca) y el magnesio total (Mg) en la orina de dos horas por espectroscopia de emisión atómica con plasma acoplado por inducción (ICPA-ES), el calcio y el magnesio total en suero por espectroscopia de absorción atómica en llama (FAAS) y el fósforo inorgánico en suero y la creatinina en suero y orina por espectroscopia de absorción molecular. Los resultados obtenidos sugieren preliminarmente una diferencia significativa (p<0,05) en las concentraciones de boro y de fósforo en la orina de dos horas entre los grupos estudiados. El análisis de regresión lineal aplicado, sugiere relación entre el índice boro/creatinina y los índices calcio/creatinina, magnesio/creatinina y fósforo/creatinina en la orina de las mujeres posmenopáusicas con osteoporosis.

In order to compare the possible relationship between urinary concentrations of boron, calcium, magnesium and phosphorus in serum and urine of postmenopausal women with and without osteoporosis, we selected 45 postmenopausal women over 47 years of age, divided into two groups: group I clinically healthy postmenopausal women and group II postmenopausal women with osteoporosis, without chronic kidney and hepatic diseases or diabetes mellitus. We determined the boron (B), phosphorus (P), total calcium (Ca) and total magnesium (Mg) in the urine of two hours, by atomic emission spectroscopy with induction-coupled plasma (ICPA-ES). Total calcium and total magnesium in serum were determined by atomic flame absorption spectroscopy (FAAS) and inorganic phosphorus in serum, and creatinine in serum and urine, by molecular absorption spectrometry. The preliminary results suggest the existence of a significant difference (p <0.05) in boron and phosphorus concentrations in the urine of two hours between the groups. The model of linear regression analysis used showed a relationship between urinary concentrations of boron/creatinine index and calcium/ creatinine, magnesium/creatinine and phosphorus/creatinine indexes in the urine of postmenopausal women with osteoporosis.

Changes in Ionized and Total Magnesium Concentration during Spinal Surgery / 대한마취과학회지

BACKGROUND: The incidence of postoperative hypomagnesemia in patients undergoing spinal surgery has been reported to be 70%. Ionized magnesium is considered to be the biologically active form, but until the early 1990s, only the total magnesium concentration could be measured. Currently, the ionized magnesium concentration as well as total magnesium concentration can be assessed due in part to the development of a selective electrode. The aim of this study was to more fully characterize the changes in the total and ionized magnesium concentrations in patients undergoing elective spinal fusion surgery. METHODS: The total and ionized magnesium, creatinine, albumin, urinary magnesium concentration, hematocrit, total amount of fluid administration, transfusion, blood loss, and urine output were evaluated both preoperatively and postoperatively in each patient. RESULTS: The total and ionized magnesium concentrations decreased from 0.783 mM/L and 0.529 mM/L preoperatively to 0.717 mM/L and 0.511 mM/L during the postoperative period, respectively. CONCLUSIONS: The incidence of total hypomagnesemia during spinal surgery was 15% but the incidence of ionized hypomagnesemia was only 3%.