Ionized magnesium level in whole blood of healthy Japanese children

Ionized Magnesium Correlates With Total Blood Magnesium in Pediatric Patients Following Kidney Transplant

Background

Abnormal serum magnesium (Mg) concentrations are common and associated with worse mortality in kidney-transplant recipients. Many kidney and transplant-related factors affect Mg homeostasis. The concentration of the active form, ionized Mg (iMg), is not measured clinically, and total Mg (tMg) and iMg correlations have conflicted. We hypothesized that iMg and tMg concentrations show poor categorical agreement (i.e., low, normal, and high) in kidney-transplant recipients but that ionized calcium (iCa) correlates with iMg.

Methods

We retrospectively evaluated hypomagnesemia in kidney-transplant recipients over a 2-yr period. We prospectively collected blood at 0-28 days post-transplant to measure correlations between iMg and iCa/tMg. iMg and iCa concentrations in the reference ranges of 0.44-0.65 and 1.0-1.3 mmol/L, respectively, were considered normal. Fisher's exact test and unweighted kappa statistics revealed category agreements. Pearson's correlation coefficients and linear regression measured correlations.

Results

Among 58 retrospective kidney-transplant recipients, 54 (93%) had tMg<0.66 mmol/L, 28/58 (48%) received Mg supplementation, and 20/28 (71%) had tacrolimus dose adjustments during supplementation. In 13 prospective transplant recipients (N=43 samples), iMg and tMg showed strong category agreement (P=0.0003) and correlation (r=0.71, P<0.001), whereas iMg and iCa did not (P=0.7; r=-0.25, P=0.103, respectively).

Conclusions

tMg and iMg exhibited strong correlation following kidney transplantation. However, iCa may not be an accurate surrogate for iMg. Determining the effect of Mg supplementation and the Mg concentration where supplementation is clinically necessary are important next steps.

Risk of low serum levels of ionized magnesium in children with febrile seizure

Background

Suboptimal intake of magnesium become prevalent due to the modern diet of processed food low in magnesium. Magnesium may modulate seizure activity by antagonizing excitatory calcium influx through the N-methyl-D-aspartate receptor. Although hyponatremia has been reported to be common in febrile seizures, the most common form of seizure, little is known about the status of serum ionized magnesium. We therefore investigated the status of serum ionized magnesium (iMg²⁺) in children with febrile seizures and compared with controls.

Methods

We included all patients from 1 to 6 years old who had presented with febrile seizure to the pediatric emergency department at the Korea University Guro Hospital from July 2016 to February 2017. The control group comprised patients admitted to the hospital with febrile respiratory tract infections, but with no history of febrile seizure. Clinical data, blood tests, and electroencephalogram (EEG) results were reviewed using the patients’ medical records.

Results

A total of 133 patients with febrile seizure and 141 control patients were analyzed in the present study. As a result, hypomagnesemia (< 0.50 mmol/L) was more common in patients with febrile seizure than in controls (42.9% vs. 6.9%, p < 0.001) and it was an independent risk factor for febrile seizure (OR, odds ratio = 22.12, 95% CI = 9.23–53.02, P < 0.001). A receiver operating curve analysis revealed that serum iMg²⁺ levels < 0.51 mmol/L predicted the presence of febrile seizures with a sensitivity of 45.1% and a specificity of 92.6% (AUC, area under the curve = 0.731, 95% confidence interval = 0.671–0.791). When the patients with febrile seizure were divided in terms of a serum iMg²⁺ concentration of 0.51 mmol/L, there was no difference in clinical features.

Conclusions

Hypomagnesemia was more common and serum iMg²⁺ level was lower in patients with febrile seizures than in controls. However, further evidence is needed for the causal relationship between low magnesium and febrile convulsions.

Skeletal morbidity in children receiving chemotherapy for acute lymphoblastic leukemia and its association with mineral homeostasis and duration of inpatient stay

BACKGROUND

Reduced activity, older age, and abnormal bone mineral status are considered as important determinants of poor bone health in children with acute lymphoblastic leukemia (ALL). The independent contribution of these factors toward skeletal morbidity (SM) requires further investigation.

AIM

The aim of this study was to investigate the influence of activity, age, and mineral status over the first 12 months of chemotherapy on subsequent SM.

PATIENTS AND METHODS

The medical records of 56 children presenting with ALL between 2003 and 2007 and treated on UKALL2003 were reviewed for the number of inpatient days over the first 12 months of chemotherapy as a surrogate marker of inactivity and lack of well-being. Data for serum Ca, albumin, Mg, and Pho were also collected over this period. SM was defined as any episode of musculoskeletal pain or fractures.

RESULTS

The median duration of inpatient days over the first 12 months of treatment in children with no SM was 58 days (40,100), whereas the median number of inpatient days during the first 12 months in those children with any SM, musculoskeletal pain only, or fractures only was 83 days (54,131), 81 days (52,119) and 91 days (59,158), respectively (P=0.003). Children with SM and fractures particularly had lower levels of serum Ca, Mg, and Pho compared with those without SM over the first 12 months of chemotherapy. There was a higher risk of SM in those who were diagnosed after the age of 8 years (P=0.001, odds ratio=16, 95% confidence interval: 3.80). Multiple regression analysis showed that the incidence of SM only had a significant independent association with age at diagnosis (P=0.001) and the number of inpatient days (P=0.03) over the first 12 months (r=23). All children who were diagnosed after the age of 8 years with an inpatient stay of more than 75 days, in the first 12 months of the chemotherapy (n,14) children had some form of SM (odds ratio=64).

CONCLUSIONS

The incidence of SM in children receiving chemotherapy for ALL is associated with a higher likelihood of being older and having longer periods of inpatient stay. The close link between age and changes in bone mineral status may be one explanation for the increased bone morbidity in ALL children.

Update on the assessment of magnesium status

Magnesium (Mg) is the fourth most abundant mineral in the body and the most abundant intracellular divalent cation, with essential roles in many physiological functions. Consequently, the assessment of Mg status is important for the study of diseases associated with chronic deficiency. In spite of intense research activities there is still no simple, rapid, and accurate laboratory test to determine total body Mg status in humans. However, serum Mg < 0.75 mmol/l is a useful measurement for severe deficiency, and for values between 0.75 and 0.85 mmol/l a loading test can identify deficient subjects. The loading test seems to be the gold standard for Mg status, but is unsuitable in patients with disturbed kidney and intestinal functions when administered orally. There is also a need to reach a consensus on a standardized protocol in order to compare results obtained in different clinical units. Other cellular Mg measurements, such as total or ionized Mg, frequently disagree and more research and systematic evaluations are needed. Muscle Mg appears to be a good marker, but biopsies limit its usefulness, as is the case with bone Mg, the most important but heterogeneous Mg compartment. The development of new and non invasive techniques such as nuclear magnetic resonance (NMR) may provide valuable tools for routinely analysing ionized Mg in tissues. With the development of molecular genetics techniques, the recent discovery of Transient Receptor Potential Melastatin channels offers new possibilities for the sensitive and rapid evaluation of Mg status in humans.

Variability within individuals of plasma ionic magnesium concentrations

BACKGROUND

With the invention of the ion-selective electrode (ISE), ionic magnesium (iMg) is a common blood assay. This could be advantageous, as iMg is the biologically active form of Mg. There is some evidence that iMg has considerable within subject variability.

RESULTS

Individual ranges averaged.08 mmol/L (range.05 to.14). Coefficients of variation (CV) ranged from 3% to 7% (mean 4%) while analytical variation was determined to be 2.3%. Biological variability thus accounts for almost half of the variability, which is clinically significant, as 9 of the 13 subjects recorded at least one value below a reference range of.46 -.60 mmol/L. A significant within-day variation (p <.001) was noted, with differences between 7:00 and 10:00 as well as 10:00 and 22:00. Between day variations were not significant (p =.56).

CONCLUSIONS

A plausible explanation of this data is that iMg has a circadian rhythm. Thus, cautious interpretation of single iMg values is warranted until future research determines the nature of iMg variability.