Impact of Serum Magnesium Levels on Kidney and Cardiovascular Prognosis and Mortality in CKD Patients.

INTRODUCTION: In the general population, hypomagnesemia has been associated with cardiovascular events and hypermagnesemia with overall mortality. In chronic kidney disease (CKD) the evidence is not so strong. The objective of our study was to investigate the relationship between serum magnesium (SMg) concentration and cardiovascular morbidity and mortality, all-cause mortality, and the progression to kidney failure in a population with CKD. METHODS: Observational study of a cohort of 746 patients with CKD. Baseline characteristics and analytical profile were collected at the first visit, and patients were followed for a mean of 42.6 months. RESULTS: A cohort of 746 patients were analyzed, age 70 ± 13 years, 62.9% were male, 45.2% had CKD grade 3, and 35.9% grade 4. The mean SMg concentration was 2.09 ± 0.33 mg/dL, with a close correlation between SMg concentration and serum creatinine, phosphorus, and intact parathyroid hormone (iPTH) values. Use of calcitriol was associated with higher SMg (SMgH) concentration, while calcium supplements and proton pump inhibitors (PPIs) were associated with lower SMg concentration. For risk of cardiovascular events, patients with hypermagnesemia had an overall higher risk on a crude analysis (Log Rank 4.83, P = .28) and adjusted analysis (HR = 1.34, CI 1.02-1.77, P = .037). For risk of all-cause mortality, patients with hypermagnesemia had an overall higher risk on crude analysis (Log Rank 13.11, P > .001) and adjusted analysis (HR = 1.5424, IC = 1.002-2.319, P = .049). After performing a propensity score matching for SMg concentration, we achieved two comparable groups of 287 patients, finding again higher all-cause mortality in the hypermagnesemia group (LogRank 15.147, P < .001), that persisted in the Cox model adjusted for calcium, phosphorus, and iPTH. No association was found between SMg concentration and initiation of kidney replacement therapy (KRT). CONCLUSIONS: Magnesium concentration increases with decreasing kidney function. Hypermagnesemia predicts cardiovascular events and all-cause mortality in this same population. Thus, magnesium supplementation should be used with caution in these patients.

The effect of replacing aluminium hydroxide with calcium acetate/magnesium carbonate on serum phosphorus control in haemodialysis patients.

INTRODUCTION: Calcium acetate/magnesium carbonate (MgCO3) is a phosphorus binder with advantages in terms of cost, safety and tolerance and it has a similar efficacy to other drugs. The objective of the study is to assess the effects of replacing aluminium hydroxide [Al(OH3)] with MgCO3 on phosphorus and calcium metabolism in a cohort of haemodialysis patients. MATERIALS AND METHODS: We included 21 patients with phosphorus <5mg/dl, with Al(OH3) as the only binder. The conversion to MgCO3 was carried out without changing the number of pills. We recorded clinical-demographic characteristics, treatment for secondary hyperparathyroidism and laboratory parameters before conversion and every month for four months. RESULTS: Phosphataemia decreased from 4.52 ± 0.99 to 4.02 ± 1.07 mg/dl (p=.027), and there was a decrease in the calcium-phosphorus product from 40.20 ± 10.44 to 35.16 ± 11.06 mg2/dl2 (p=.037). We did not observe significant changes in levels of calcium, parathyroid hormone or 25-OH-vitamin D3. The daily number of pills prescribed was reduced from 3.33 ± 2.29 to 2.15 ± 2.21 (p=.020). Concomitant treatments were not altered. We observed an initial significant increase in magnesaemia from 2.21 ± 0.24 to 2.43 ± 0.39 mg/dl (p=.001), which subsequently remained stable. We found a decrease in serum aluminium from 14.91 ± 8.55 to 8.47 ± 3.98 µg/l (p=.004), with levels within the recommended range in all patients. CONCLUSIONS: MgCO3 allowed good control of serum phosphorus in haemodialysis patients who were previously well controlled with Al(OH)3, using fewer daily pills. There was a slight increase in serum magnesium, without short-term clinical significance. We do not know the effects of this increase in the longer term.

Factors related with the progression of chronic kidney disease.

BACKGROUND: Our aims were to determine the rate of progression of chronic kidney disease (CKD) and to identify predictors, with particular emphasis on bone and mineral metabolism. METHODS: Retrospective and observational study including 300 patients with advanced CKD (61.2% males, 33.1% diabetics; age 65.6±14 years). Mean follow-up time was 19.4±10.1 months. Baseline estimated glomerular filtration rate (eGFR) (MDRD-4) was 22.5±7.18 mL/min. To calculate the rate of decline in eGFR, we used the slope of the regression line between all determinations of eGFR and follow-up time. We calculated the mean values for proteinuria and serum phosphate, calcium, uric acid, and PTH, as well as 24-hour urinary excretion of urea nitrogen over time for each patient. Follow-up was at least 6 months and included at least 4 measurements of eGFR. RESULTS: The mean rate of decline eGFR (-1.64 mL/min/1.73 m²/year) was inversely correlated with serum phosphate levels (4.3±2.1 mg/dL, P<.001), PTH (256.3±193.7 ng/L, p<.001) and proteinuria (0.84±1.31 g/day, P=.004) and directly correlated with mean serum calcium (P<.001) and the presence of hypertension (P<.02). However, only serum phosphate, serum PTH, and proteinuria persisted as predictors in the multivariate analysis. Stable-GFR patients (positive slope) were older (P=.041) and had lower serum phosphate and PTH levels (P<.01 and P<.01 respectively) and lower proteinuria (P<.01). CONCLUSIONS: The rate of decrease in eGFR was correlated with serum phosphate and PTH levels and proteinuria. All of these factors can be modified with an adequate treatment.