Relationship between the serum parathyroid hormone and magnesium levels in continuous ambulatory peritoneal dialysis (CAPD) patients using low-magnesium peritoneal dialysate

Magnesium and Fracture Risk in the General Population and Patients Receiving Dialysis: A Narrative Review

Purpose of Review

Magnesium is an essential mineral for bone metabolism, but little is known about how magnesium intake alters fracture risk. We conducted a narrative review to better understand how magnesium intake, through supplementation, diet, or altering the concentration of dialysate magnesium, affects mineral bone disease and the risk of fracture in individuals across the spectrum of kidney disease.

Sources of Information

Peer-reviewed clinical trials and observational studies.

Methods

We searched for relevant articles in MEDLINE and EMBASE databases. The methodologic quality of clinical trials was assessed using a modified version of the Downs and Black criteria checklist.

Key Findings

The role of magnesium intake in fracture prevention is unclear in both the general population and in patients receiving maintenance dialysis. In those with normal kidney function, 2 meta-analyses showed higher bone mineral density in those with higher dietary magnesium, whereas 1 systematic review showed no effect on fracture risk. In patients receiving maintenance hemodialysis or peritoneal dialysis, a higher concentration of dialysate magnesium is associated with a lower concentration of parathyroid hormone, but little is known about other bone-related outcomes. In 2 observational studies of patients receiving hemodialysis, a higher concentration of serum magnesium was associated with a lower risk of hip fracture.

Limitations

This narrative review included only articles written in English. Observed effects of magnesium intake in the general population may not be applicable to those with chronic kidney disease particularly in those receiving dialysis.

Clinical Factors Associated with Serum Magnesium Concentration in Patients Undergoing Peritoneal Dialysis: A Single-Center Observational Study

Purpose

Magnesium (Mg) is an essential element that is associated with various physiological functions, such as maintenance of blood pressure, muscle contraction, and nerve function. In patients undergoing hemodialysis, hypomagnesemia is associated with cardiovascular and all-cause mortality. However, in patients undergoing peritoneal dialysis (PD), clinical factors associated with Mg have not been fully investigated.

Patients and Methods

Clinical factors including anthropometric data, comorbidities, laboratory data, medications, and dialysis methods were collected from the medical records of patients undergoing PD. The associations of these factors with the serum Mg concentration were investigated by univariate and multivariate analyses.

Results

Sixty patients undergoing PD were investigated. The univariate analysis showed that the serum Mg concentration was significantly associated with treatment by hybrid PD (daily PD + once-weekly hemodialysis) (β = 0.264, P = 0.04), administration of phosphate binders (β = 0.294, P = 0.02), the serum C-reactive protein concentration (β = -0.318, P = 0.01), the serum potassium (K) concentration (β = 0.451, P < 0.01), and the serum intact parathormone concentration (β = -0.333, P = 0.01). The multivariate analysis using these factors showed an independent association between the serum Mg and K concentrations (β = 0.333, P = 0.01).

Conclusion

The serum Mg concentration was independently associated with the serum K concentration in patients undergoing PD.

Hypomagnesemia Is a Risk Factor for Cardiovascular Disease- and Noncardiovascular Disease-Related Mortality in Peritoneal Dialysis Patients

PURPOSE

Recent research has shown that hypomagnesemia is associated with increased all-cause mortality in hemodialysis patients. However, the relationship between the long-term prognosis of peritoneal dialysis (PD) and the study is not yet clear. This study will analyze the effects of hypomagnesemia on all-cause, cardiovascular diseases (CVD), and non-CVD mortality in PD patients.

METHOD

In a retrospective cohort study, 1,004 samples were selected from 7 PD centers in China. Based on the baseline blood magnesium level at the beginning of stable dialysis, all patients were classified into blood magnesium <0.7 mmol/L group, 0.7-1.2 mmol/L group, and >1.2 mmol/L group (the end event was death). The Kaplan-Meier method was used to calculate the difference in cumulative survival rate; the Cox proportional hazard model was used to analyze the risk factors of all-cause, CVD, and non-CVD death causes.

RESULTS

Cox multiple regression analysis results (reference comparison of 0.7-1.2 mmol/L group): patients with serum magnesium <0.7 mmol/L have a higher risk ratio of all-cause mortality (HR = 1.580, 95% CI: 1.222-2.042, p = 0.001), and it is also obvious after correction by multiple models (HR = 1.578, 95% CI: 1.196-2.083, p = 0.001). Subgroup analysis of the causes of death was as follows: CVD risk (HR = 1.628, 95% CI: 1.114-2.379, p = 0.012) and non-CVD risk (HR = 1.521, 95% CI: 1.011-2.288, p = 0.044). Further analysis of the causes of infection-related death in non-CVD is also significant (HR = 1.919, 95% CI: 1.131-3.1257, p = 0.016). On the other hand, the serum magnesium>1.2 mmol/L group had lower all-cause mortality after correction (HR = 0.687, 95% CI: 0.480-0.985, p = 0.041), and subgroup analysis of the cause of death had no statistical significance (p > 0.05).

CONCLUSIONS

Hypomagnesemia (serum magnesium <0.7 mmol/L) during stable dialysis in PD patients is a risk factor for CVD- and non-CVD-related mortality, especially infection-related death causes.

Factors Affecting Bone Health in Kidney Transplant Recipients: Klotho Gene Single-Nucleotide Polymorphisms and Other Clinical Features

OBJECTIVES

Posttransplant bone diseases are a major cause of morbidity in kidney transplant recipients. We investigated the relationship between klotho gene single-nucleotide polymorphisms and bone diseases after kidney transplant. We also aimed to identify possible risk factors for development of bone disease.

MATERIALS AND METHODS

The study consisted of 251 kidney transplant recipients (164 men and 87 women) with minimum follow-up of 3 years after kidney transplant. Patients with prolonged immobilization, malignancy, parathyroidectomy, glomerular filtration rates less than 30 mL/min/1.73 m², hypo- or hyperthyroidism, and treatment with drugs that affect bone metabolism were excluded. We investigated the relationship between 6 single-nucleotide polymorphisms of the klotho gene (rs480780, rs211234, rs576404, rs211235, rs9536314, and rs1207568) and development of osteoporosis, avascular bone necrosis, and persistent hyperparathyroidism.

RESULTS

Longer dialysis treatment (odds ratio, 1.13; P = .002) and rs211235 single-nucleotide polymorphism in the klotho gene (odds ratio, 9.87; P = .001 for GG genotype) were significantly associated with persistent hyperparathyroidism. A higher magnesium level was detected as a protective factor from development of persistent hyperparathyroidism (odds ratio, 0.19; P = .009). Persistent hyperparathyroidism was defined as a risk factor for development of osteopenia/osteoporosis (odds ratio, 2.76; P = .003) and avascular bone necrosis (odds ratio, 2.52; P= .03). Although the rs480780 (odds ratio, 8.73; P = .04) single-nucleotide polymorphism in the klotho gene was defined as a risk factor for development of osteopenia/osteoporosis, none of the klotho single-nucleotide polymorphisms was found to be associated with development of avascular bone necrosis.

CONCLUSIONS

Persistent hyperparathyroidism could be an important indicator for development of bone disease in kidney transplant recipients. Also, some of the klotho gene single-nucleotide polymorphisms are associated with higher risk for bone disease after kidney transplant.

Relationship between Serum Magnesium, Parathyroid Hormone, and Vascular Calcification in Patients on Dialysis: A Literature Review

Secondary hyperparathyroidism is present in most patients with end-stage renal disease and has been linked to uremic bone disease, vascular calcification, and mortality. Current literature suggests an association between hypomagnesemia and cardiovascular disease in the general population. We reviewed all published studies on the relationship between serum magnesium and parathyroid hormone and the relationship between serum Mg and vascular calcification in dialysis patients. Of these, 10 of 12 studies of patients on hemodialysis and 4 of 5 studies of patients on peritoneal dialysis showed a significant inverse relationship between serum Mg and serum intact parathyroid hormone. Hyperparathyroidism develops in peritoneal dialysis patients dialyzed with a solution containing normal calcium (1.25 mmol/L) and low Mg (0.25 mmol/L), even though serum calcium is maintained at a normal level. Four of the hemodialysis studies and one of the peritoneal dialysis studies indicated that there is an inverse relationship between serum Mg and vascular calcification in these patients. Potential benefits have been attributed to magnesium carbonate as a phosphate binder and it may possibly be an effective, less toxic, less expensive phosphate binder. We believe that the role of Mg in secondary hyperparathyroidism and vascular calcification merits further investigation.

Serum Magnesium Abnormality and Influencing Factors of Serum Magnesium Level in Peritoneal Dialysis Patients: A Single-Center Study in Northern China

Background/Aims: Both hypomagnesemia and hypermagnesemia have been associated with cardiovascular diseases, bone diseases, and mortality in dialysis patients. We aimed to investigate the prevalence of and influencing factors for abnormal serum Mg levels in patients on peritoneal dialysis (PD). Methods: A cross-sectional study in Peking University People’s Hospital recorded the demographic information, clinical characteristics, and laboratory data. Data were assessed and compared with the results from 2 other studies in China. Results: Of 180 enrolled PD patients, the primary diseases were glomerulonephritis (38.3%) and diabetic nephropathy (38.3%). Mean serum Mg concentration was 1.02 ± 0.16 mmol/L; 67% had normal serum Mg concentrations, and 33% had hypermagnesemia. Conclusions: Hypermagnesemia is likely to occur in patients with higher serum phosphate, lower intact parathyroid hormone, and lower high-sensitivity C-reactive protein levels. Serum Mg level distributions in PD patients vary throughout China, may have different potential causes (such as geographical location and dietary habits) and should be further studied.

Clinical aspects of magnesium physiology in patients on dialysis

Magnesium balance is infrequently discussed in the dialysis population, and the clinical consequences of derangements in magnesium homeostasis are incompletely understood. There is an association between hypomagnesemia and adverse outcomes including increases in cardiovascular disease and mortality, while elevated magnesium levels have also been linked with complications such as osteomalacia. In this review, we discuss the features of magnesium physiology relevant to dialysis patients and provide an updated summary of the literature linking magnesium derangements with bone disease, cardiovascular disease, sudden cardiac death, and mortality.

Effects of different phosphate lowering strategies in patients with CKD on laboratory outcomes: A systematic review and NMA

BACKGROUND

Chronic kidney disease-mineral and bone disorder (CKD-MBD), a complication of chronic kidney disease, has been linked to reduced quality and length of life. High serum phosphate levels that result from CKD-MBD require phosphate-lowering agents, also known as phosphate binders. The objective of this systematic review is to compare the effects of available phosphate binders on laboratory outcomes in patients with CKD-MBD.

METHODS

Data sources included MEDLINE and EMBASE from January 1996 to April 2016, and the Cochrane Register of Controlled Trials up to April 2016. Teams of two reviewers, independently and in duplicate, screened titles and abstracts and potentially eligible full text reports to determine eligibility, and subsequently abstracted data and assessed risk of bias in eligible randomized controlled trials (RCTs). Eligible trials enrolled patients with CKD-MBD and randomized them to receive calcium-based phosphate binders (delivered as calcium acetate, calcium citrate or calcium carbonate), non-calcium-based phosphate binders (NCBPB) (sevelamer hydrochloride, sevelamer carbonate, lanthanum carbonate, sucroferric oxyhydroxide and ferric citrate), phosphorus restricted diet (diet), placebo or no treatment and reported effects on serum levels of phosphate, calcium and parathyroid hormone. We performed Bayesian network meta-analyses (NMA) to calculate the effect estimates (mean differences) and 95% credible intervals for serum levels of phosphate, calcium and parathyroid hormone. We calculated direct, indirect and network meta-analysis estimates using random-effects models. We applied the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach to rate the quality of evidence for each pairwise comparison.

RESULTS

Our search yielded 1108 citations; 71 RCTs were retrieved for full review and 16 proved eligible. Including an additional 13 studies from a previous review, 29 studies that enrolled 8335 participants proved eligible; 26 trials provided data for quantitative synthesis. Sevelamer, lanthanum, calcium, iron, diet and combinations of active treatments (calcium or sevelamer or lanthanum and combination of calcium and sevelamer) resulted in significantly lower serum phosphate as compared to placebo (moderate to very low quality of evidence). We found no statistically significant differences between active treatment categories in lowering serum phosphate. Sevelamer, lanthanum and diet resulted in lower serum calcium compared to calcium (moderate quality evidence for lanthanum and diet; low quality evidence for Sevelamer). Iron, sevelamer and calcium yielded lower parathyroid hormone levels as compared to lanthanum. Meta-regression analyses did not yield a statistically significant association between treatment effect and trial duration.

DISCUSSION/CONCLUSIONS

We found few differences between treatments in impact on phosphate and differences in parathyroid hormone. Relative to calcium, sevelamer, lanthanum and diet showed significant reduction in serum calcium from baseline. Treatment recommendations should be based on impact on patient-important outcomes rather than on surrogate outcomes. Systematic review registration: PROSPERO CRD-42016032945.

Why are serum magnesium levels lower in Saudi dialysis patients?

Objectives

Serum magnesium (Mg) levels are often altered in dialysis patients. This study was conducted to ascertain the trends in Mg levels in patients on dialysis treatment.

Methods

A retrospective study was performed in the Dialysis Unit of King Khalid University Hospital, King Saud University, Riyadh, on patients undergoing regular dialysis. Patient demographic data, including body mass index (BMI), serum calcium (Ca), Mg, parathyroid hormone (PTH), cholesterol, and triglycerides were documented.

Results

Of a total of 115 patients, 70 (60.9%) were on haemodialysis (HD), and 45 (39.1%) were on peritoneal dialysis (PD). Of these, 10 patients (8.7%) had Mg levels of <0.7 mmol/L, 13 (11.3%) had 0.7 mmol/L, 24 (20.9%) had 0.8 mmol/L, 26 (22.6%) had 0.9 mmol/L, 16 (13.9%) 1.0 mmol/L, and 26 (23.9%) showed levels of ≥1.1 mmol/L. Approximately 93.0% had increased PTH levels, 43 (37.4%) had decreased serum Ca, 24 (20.9%) had low serum cholesterol, and 60 (52.2%) had low serum triglyceride. PD patients had significantly lower Mg and higher PTH levels compared to HD patients.

Conclusion

Patients with chronic kidney disease are generally considered at risk of developing hypermagnesaemia due to reduced renal excretion. However, a considerable number of dialysis patients in our unit had hypomagnesaemia (or low levels) instead. In addition to other factors, PTH secretion is affected by serum Mg levels. We found a significant correlation between serum Mg and Ca as well as PTH levels. Consequently, optimizing Mg concentration in patients on dialysate is essential to reduce risk of dyslipidaemia, arrhythmias, hyperparathyroidism, or adynamic bone disease.

Hypomagnesemia Is Associated with Increased Mortality among Peritoneal Dialysis Patients

Objective

Hypomagnesemia has been associated with an increase in mortality among the general population as well as patients with chronic kidney disease or those on hemodialysis. However, this association has not been thoroughly studied in patients undergoing peritoneal dialysis. The aim of this study was to evaluate the association between serum magnesium concentrations and all-cause and cardiovascular mortalities in peritoneal dialysis patients.

Methods

This single-center retrospective study included 253 incident peritoneal dialysis patients enrolled between July 1, 2005 and December 31, 2014 and followed to June 30, 2015. Patient’s demographic characteristics as well as clinical and laboratory measurements were collected.

Results

Of 253 patients evaluated, 36 patients (14.2%) suffered from hypomagnesemia. During a median follow-up of 29 months (range: 4–120 months), 60 patients (23.7%) died, and 35 (58.3%) of these deaths were attributed to cardiovascular causes. Low serum magnesium was positively associated with peritoneal dialysis duration (r = 0.303, p < 0.001) as well as serum concentrations of albumin (r = 0.220, p < 0.001), triglycerides (r = 0.160, p = 0.011), potassium (r = 0.156, p = 0.013), calcium(r = 0.299, p < 0.001)and phosphate (r = 0.191, p = 0.002). Patients in the hypomagnesemia group had a lower survival rate than those in the normal magnesium groups (p < 0.001). In a multivariate Cox proportional hazards regression analysis, serum magnesium was an independent negative predictor of all-cause mortality (hazard ratio [HR] = 0.075, p = 0.011) and cardiovascular mortality (HR = 0.003, p < 0.001), especially in female patients. However, in univariate and multivariate Cox analysis, △Mg(difference between 1-year magnesium and baseline magnesium) was not an independent predictor of all-cause mortality and cardiovascular mortality.

Conclusion

Hypomagnesemia was common among peritoneal dialysis patients and was independently associated with all-cause mortality and cardiovascular mortality.

The relationship between proton pump inhibitor use and serum magnesium concentration among hemodialysis patients: a cross-sectional study

Background

Observational data suggest that serum magnesium (Mg) concentration is inversely related to vascular calcification and hyperparathyroidism among patients with end-stage renal disease (ESRD). In recent years, there have been several case reports of hypomagnesemia due to use of proton-pump inhibitors (PPI), with the hypomagnesemia attributed to inappropriate gastrointestinal (GI) Mg loss. We hypothesized that the tendency to GI Mg loss is more common than is currently reported. Since patients with ESRD have little to no renal Mg loss to affect serum Mg concentration, dialysis patients are an interesting population in whom to study the relationship between PPI use and serum Mg levels.

Methods

Using a single-center cross-sectional design, we studied 155 prevalent hemodialysis (HD) patients. Serum Mg concentration for each patient was determined based on the mean of 3 consecutive serum Mg levels drawn at 6 week intervals. PPI use at the time of the blood tests was documented. The relationship between PPI use and Mg concentration was determined in unadjusted analyses, as well as after adjustment for age, gender, race, cause of ESRD, diabetes, time on HD and dialysate Mg concentration.

Results

55 % of patients were on PPIs at the time of the study. The majority of patients (62 %) used a dialysate Mg (in mmol/L) of 0.5, and the remainder (38 %) used a dialysate Mg of 0.375. Serum Mg levels were significantly lower among PPI users vs. non-users (0.93 vs. 1.02 mmol/L, p < 0.001). This finding persisted after stratifying for dialysate Mg concentration, and after multivariable adjustment (p < 0.001). In addition, more PPI users vs. non-users had a Mg level < 1 mmol/L (79 % vs. 43 %) and a Mg level < 0.8 mmol/L (16 % vs. 4 %). There was a non-significant trend toward increased time on PPI being associated with lower serum Mg levels (p = 0.067).

Conclusion

Among HD patients, PPI users have lower serum Mg levels as compared with non-users. Further research is required to determine whether the magnitude of change in Mg levels among PPI users is associated with adverse outcomes.

Magnesium in chronic kidney disease Stages 3 and 4 and in dialysis patients

The kidney has a vital role in magnesium homeostasis and, although the renal handling of magnesium is highly adaptable, this ability deteriorates when renal function declines significantly. In moderate chronic kidney disease (CKD), increases in the fractional excretion of magnesium largely compensate for the loss of glomerular filtration rate to maintain normal serum magnesium levels. However, in more advanced CKD (as creatinine clearance falls <30 mL/min), this compensatory mechanism becomes inadequate such that overt hypermagnesaemia develops frequently in patients with creatinine clearances <10 mL/min. Dietary calcium and magnesium may affect the intestinal uptake of each other, though results are conflicting, and likewise the role of vitamin D on intestinal magnesium absorption is somewhat uncertain. In patients undergoing dialysis, the effect of various magnesium and calcium dialysate concentrations has been investigated in haemodialysis (HD) and peritoneal dialysis (PD). Results generally show that dialysate magnesium, at 0.75 mmol/L, is likely to cause mild hypermagnesaemia, results for a magnesium dialysate concentration of 0.5 mmol/L were less consistent, whereas serum magnesium levels were mostly normal to hypomagnesaemic when 0.2 and 0.25 mmol/L were used. While dialysate magnesium concentration is a major determinant of HD or PD patients’ magnesium balance, other factors such as nutrition and medications (e.g. laxatives or antacids) also play an important role. Also examined in this review is the role of magnesium on parathyroid hormone (PTH) levels in dialysis patients. Although various studies have shown that patients with higher serum magnesium tend to have lower PTH levels, many of these suffer from methodological limitations. Finally, we examine the complex and often conflicting results concerning the interplay between magnesium and bone in uraemic patients. Although the exact role of magnesium in bone metabolism is unclear, it may have both positive and negative effects, and it is uncertain what the optimal magnesium levels are in uraemic patients.

Hypomagnesemia in hemodialysis patients: role of proton pump inhibitors

BACKGROUND

Recent observations have associated hypomagnesemia with increased risk of cardiovascular morbidity and mortality in hemodialysis patients.

METHODS

We did a 3-month chart review of 62 chronic hemodialysis patients at a single US hospital. All were dialyzed using a dialysate [Mg] of 0.75-1.0 mEq/l. Patients were divided into two groups: hypomagnesemic (mean predialysis plasma [Mg] <1.5 mEq/l) and non-hypomagnesemic (mean predialysis plasma [Mg] ≥1.5 mEq/l).

RESULTS

All patients were male; mean age was 64.3 ± 8.7 years and the majority (73%) diabetic. 24 patients (39%) had hypomagnesemia and 38 (61%) were not hypomagnesemic. There were no significant differences between the two groups in age, diabetes status, blood pressure, duration of dialysis, plasma calcium, phosphorus, albumin, intact parathyroid hormone (PTH), dialysis adequacy (Kt/V), or dietary protein intake (as estimated by normalized protein catabolic rate, nPCR). However, use of proton pump inhibitors (PPIs) was significantly associated with hypomagnesemia (plasma [Mg] 1.48 ± 0.16 mEq/l in the PPI group vs. 1.65 ± 0.26 mEq/l in the non-PPI group, p = 0.007). Adjustment for age, diabetes status, duration of dialysis, plasma albumin, Kt/V, nPCR, and diuretic use did not affect the association between PPI use and hypomagnesemia.

CONCLUSIONS

Use of PPIs in patients dialyzed using a dialysate [Mg] of 0.75-1.0 mEq/l is associated with hypomagnesemia. We suggest monitoring plasma [Mg] in patients taking PPIs, with discontinuation of the medication if possible and/or adjustment of dialysate [Mg] to normalize plasma [Mg].

Lack of influence of serum magnesium levels on overall mortality and cardiovascular outcomes in patients with advanced chronic kidney disease

Background. Low serum magnesium has been associated with an increased cardiovascular risk in the general population and in dialysis patients. Our aim was to analyze the influence of serum magnesium on overall mortality and cardiovascular outcomes in patients with advanced CKD not yet on dialysis. Methods. Seventy patients with CKD stages 4 and 5 were included. After a single measurement of s-magnesium, patients were followed a mean of 11 months. Primary end-point was death of any cause, and secondary end-point was the occurrence of fatal or nonfatal CV events. Results. Basal s-magnesium was within normal range (2.1 ± 0.3 mg/dL), was lower in men (P = 0.008) and in diabetic patients (P = 0.02), and was not different (P = 0.2) between patients with and without cardiopathy. Magnesium did not correlate with PTH, calcium, phosphate, albumin, inflammatory parameters (CRP), and cardiac (NT-proBNP) biomarkers but correlated inversely (r = −0.23; P = 0.052) with the daily dose of loop diuretics. In univariate and multivariate Cox proportional hazard models, magnesium was not an independent predictor for overall mortality or CV events. Conclusions. Our results do not support that serum magnesium can be an independent predictor for overall mortality or future cardiovascular events among patients with advanced CKD not yet on dialysis.

Relationship between serum parathyroid hormone and trace elements (serum zinc and magnesium) in hemodialyzed chronic renal failure children

Secondary hyperparathyroidism and trace elements' metabolism disturbances are common, important, and treatable complications of chronic renal failure (CRF).The relation between parathyroid hormone (PTH) and some trace elements in CRF patients on hemodialysis is still not completely elucidated. The aim of this work is to determine the serum levels of PTH and the trace elements zinc (Zn) and magnesium (Mg) in children with CRF under hemodialysis. The relation between PTH and those trace elements will be investigated. The study included 24 children (15 males and nine females) with CRF on regular hemodialysis. Also, 15 healthy age-matched children were included as control group. Serum levels of PTH, zinc, and magnesium were determined in all cases and controls. PTH and magnesium levels in patients were significantly higher than controls. Serum zinc levels were significantly lower than controls. There was a significant negative correlation between serum levels of PTH and zinc as well as an insignificant negative correlation between PTH and serum magnesium in CRF patients. Elevated PTH may play a role in the pathogenesis of hypozincemia. However, this is another negative report on the relation between PTH and serum Mg in children with CRF.

Inverse correlation between serum magnesium and parathyroid hormone in peritoneal dialysis patients: a contributing factor to adynamic bone disease?

BACKGROUND

Secondary hyperparathyroidism (SHPTH) is present in many patients with end-stage renal disease (ESRD) and has been linked to uremic bone disease. Parathyroid hormone (PTH) levels are affected by calcium, vitamin D, and phosphorus. Recent data suggests that serum magnesium may also modulate PTH levels.

OBJECTIVE

The aim of this retrospective study was to investigate the impact of different calcium (Ca) and magnesium (Mg) concentrations of dialysis solutions on serum Mg and serum PTH levels in peritoneal dialysis (PD) patients.

PATIENTS AND METHODS

Two groups of PD patients-group A (n = 17) on "standard" Ca and Mg dialysis solution (SCa-MgD) (Ca: 1.62 mmol/l, Mg: 0.75 mmol/l and Lactate 35 mmol/l), and group B (n = 29) on "low" Ca and Mg dialysis solution (LCa-MgD) (Ca: 1.25 mmol/l, Mg: 0.25 mmol/l and Lactate 40 mmol/l), on PD for more than 6 months, were studied. Calcium carbonate (CaCO3) was used as the phosphate (P) binder in 87% (40/46) of the patients. Biochemical parameters were evaluated every 1-2 months over 6 months and the mean values were computed.

RESULTS

No significant differences were found between the two groups in all parameters except for serum Mg and PTH. Serum Mg was higher in SCa-MgD group compared to those in the LCa-MgD group (1.05 +/- 0.19 vs 0.90 +/- 0.23 mmol/l, respectively) and serum PTH was higher in LCa-MgD group compared to those in SCa-MgD group (72.3 +/- 64.2 vs 31.1 +/- 39.0 pmol/l, respectively) even though serum Ca was not different. There was a statistically significant inverse correlation between serum Mg and PTH levels (r = -0.357, p < 0.05).

CONCLUSION

Serum Mg is lower and serum PTH higher in patients dialyzed with lower Mg concentration dialysis solution compared to those with higher Mg concentration dialysis solution. Our study confirms previous reports that serum Mg may have a suppressive role on PTH synthesis and/or secretion, and thus may play a role in pathogenesis of adynamic bone disease that often develops in patients on chronic PD with high calcium and high magnesium concentrations.

Intradialytic changes of serum magnesium and their relation to hypotensive episodes in hemodialysis patients on different dialysates

Magnesium is a crucial mineral, involved in many important physiological processes. Magnesium plays a role of maintaining myocardial electrical stability in hemodialysis patients. Intradialytic hypotension is a common complication of dialysis and it is more common with acetate dialysate. The significance of the intradialytic changes of magnesium and their relation to parathyroid hormone (PTH) level and calcium changes during dialysis, and their relation to hypotensive episodes during dialysis are interesting. The aim of this work is to investigate the intradialytic changes of serum magnesium in chronic hemodialysis patients with different hemodialysis modalities and the relation to other electrolytes and to PTH, and also the relation to intradialytic hypotension. The present study was conducted on 20 chronic renal failure patients. All patients were on regular hemodialysis thrice weekly 4 hr each using acetate dialysate (group I). To study the effect of an acetate-based dialysate vs. a bicarbonate-based dialysate on acute changes of magnesium, calcium, phosphorus, and PTH during a hemodialysis session, the same patients were shifted to bicarbonate dialysis (group II). All patients were subjected to full history and clinical examination, predialysis laboratory assessment of blood urea nitrogen (BUN), serum creatinine, albumin, and hemoglobin, serial assessment of magnesium, calcium, phosphorus, and parathyroid hormone at the start of the hemodialysis session, 2 hr later, and at the end of the session, blood pH, and electrocardiogram (ECG) presession and postsession. All patients were urged to fix their dry weight, diet, and current medications. None of the patients had diabetes, neoplasia, liver disease, or cachexia, nor had they been recently on magnesium-containing drugs or previously parathyroidectomized. Hemodialysis sessions were performed by volumetric dialysis machines using the same electrolyte composition. Magnesium level significantly increased in the bicarbonate group at the end of dialysis (0 hr: 2.73+/-0.87, 2 hr: 3.21+/-1.1, and at 4 hr: 5.73+/-1.45 mg/dL, p value <0.01), while it significantly decreased in the acetate group (0 hr: 3.00+/-0.58, 2 hr: 2.26+/-0.39, 4 hr: 1.97+/-0.33 mg/dL, p value <0.01). Calcium level significantly increased in the bicarbonate group (p=0.024) but not in the acetate group. Phosphorus level significantly decreased in both acetate and bicarbonate groups. PTH level did not significantly change in either group, p value > or =0.05. Blood pH significantly increased, changing from acidic to alkaline pH, with both modalities of hemodialysis. ECG showed no significant changes during sessions with either type of dialysate. Hypotension was significantly higher in group I compared with group II (p=0.01), and this hypotension was positively correlated with a decrease in serum magnesium level in group I. Intradialytic changes in serum magnesium have no correlation with intradialytic changes in serum calcium or with PTH level. However, it was significantly correlated with hypotension during the dialysis session, especially with acetate dialysate. Further investigations are needed to determine whether or not this is true in patients using bicarbonate dialysis.