Clinical aspects of magnesium physiology in patients on dialysis

A multi-center study on the association between serum magnesium levels and allostatic load in hemodialysis patients

Objective: Serum magnesium (Mg²⁺) levels are associated with insulin resistance, hypertension, lipid abnormalities, and inflammation. However, limited studies have indicated the relationship between Mg²⁺ and multiple system indexes. The purpose of this study was to investigate the association between Mg²⁺ and allostatic load (AL) in hemodialysis patients.

Methods: A cross-sectional survey was conducted on hemodialysis patients from different centers in Anhui Province, China, between January and December 2020. A total of 3,025 hemodialysis patients were recruited. Their clinical data were measured before hemodialysis. Information was collected by an online self-reported questionnaire and medical record. Serum Mg²⁺ was divided into three groups by tertiles. A score of AL greater than or equal to 3 was defined as high AL. A binary logistic regression model was applied to examine the relationship between serum Mg²⁺ and AL.

Results: A total of 1,222 patients undergoing hemodialysis were included, 60% of whom were males (733/1,222). The mean (standard deviation) age of patients was 55.90 (12.75). The median level of serum Mg²⁺ was 1.22 mmol/L. The rate of high AL levels was 23.4%. Serum Mg²⁺ was negatively correlated with body mass index, fasting blood glucose (Glu), and C-reactive protein and positively correlated with high-density lipoprotein, low-density lipoprotein, total cholesterol, diastolic blood pressure (DBP), and serum phosphorus. After adjusting for gender, anxiety, diabetes, family residence, lipid-lowering agents, antihypertensive medications, albumin, and Glu, the binary logistic regression model showed that patients with lower levels of serum Mg²⁺ were more likely have high AL (OR for the T1 group of serum Mg²⁺:1.945, 95% CI: 1.365–2.773, and OR for the T2 group of serum Mg²⁺:1.556, 95% CI: 1.099–2.201).

Conclusion: Our data support the hypothesis that higher serum Mg²⁺ concentrations may contribute to lower health risk in hemodialysis populations. Further randomized controlled trials and cohort studies are warranted to verify whether Mg²⁺ supplementation could be part of routine examinations in hemodialysis populations.

Prevention of hypomagnesemia in critically ill patients with acute kidney injury on continuous kidney replacement therapy: the role of early supplementation and close monitoring

Hypomagnesemia is a common electrolyte disorder in critically ill patients and is associated with increased morbidity and mortality risk. Many clinical conditions may contribute to hypomagnesemia through different pathogenetic mechanisms. In patients with acute kidney injury (AKI) the need for continuous or prolonged intermittent kidney replacement therapy (CKRT and PIKRT, respectively) may further add to other causes of hypomagnesemia, especially when regional citrate anticoagulation (RCA) is used. The basic principle of RCA is chelation of ionized calcium by citrate within the extracorporeal circuit, thus blocking the coagulation cascade. Magnesium, a divalent cation, follows the same fate as calcium; the amount lost in the effluent includes both magnesium-citrate complexes and the free fraction directly diffusing through the hemofilter. While increasing the magnesium content of dialysis/replacement solutions may decrease the risk of hypomagnesemia, the optimal concentration for the variable combination of solutions adopted in different KRT protocols has not yet been identified. An alternative and effective approach is based on including early intravenous magnesium supplementation in the KRT protocol, and close monitoring of serum magnesium levels, especially in the setting of RCA. Thus, strategies aimed at precisely tailoring both dialysis prescriptions and the composition of KRT fluids, as well as early magnesium supplementation and close monitoring, could represent a cornerstone in reducing KRT-related hypomagnesemia.

Continuous Observation of Serum Total Magnesium Level in Patients Undergoing Hemodialysis

BACKGROUND

Magnesium is an indispensable cation and plays an important physiological role in the body. Most previous studies focused on the single measurement of serum magnesium in patients undergoing hemodialysis. However, scant studies focused on continuous observations of serum magnesium levels.

OBJECTIVE

To provide continuous observations of serum magnesium levels in patients on maintenance hemodialysis (MHD). The levels of magnesium in patients initiating hemodialysis are also recorded and analyzed in the present study.

METHODS

In this retrospective study, we serially investigated the measurements of serum total magnesium in MHD patients and patients initiating hemodialysis. Our data were followed up for one year. We provided real-time update on the levels of serum magnesium in patients on hemodialysis.

RESULTS

On January 1, 2019, a total of 356 end-stage renal disease patients were receiving hemodialysis in our hospital. On December 31, 2019, the number had increased to 383. We found that serum total magnesium levels were in the normal range before initiating hemodialysis. With the initiation of hemodialysis, the levels of serum total magnesium increased. In patients on MHD, hypermagnesemia was very common. Hypomagnesemia was rare when 0.5 mmol/L magnesium dialysate was used. We did not find proton pump inhibitor associated hypomagnesemia.

CONCLUSION

We find that serum total magnesium levels are in the normal range before initiating hemodialysis. However, in patients on MHD, hypermagnesemia is common when 0.5 mmol/L magnesium dialysate is used. Hypomagnesemia is very rare. Hypomagnesemia in patients on MHD is an indicator of poor condition.

Total serum magnesium in cats with chronic kidney disease with nephrolithiasis

OBJECTIVES

Magnesium has been 'the forgotten ion' for many years. Over the past decade, however, the role of magnesium in essential physiological functions and several illness conditions have been elucidated. Nevertheless, the investigation of magnesium in cats with chronic kidney disease (CKD) and nephrolithiasis is yet to be determined. The purpose of this study was to investigate whether CKD cats with nephrolithiasis have changes in total serum magnesium concentrations, and whether magnesium disorders may be associated with other electrolyte disturbances, as well as with prognosis. We also aimed to evaluate whether total serum magnesium concentration differs between CKD cats with and without nephrolithiasis.

METHODS

Total serum magnesium concentrations were assessed in 42 cats with CKD with stage 1-4 nephrolithiasis. The correlation between magnesium and other electrolytes, as well as Kaplan-Meier survival analysis, were performed. We also selected 14 control cats with CKD without nephrolithiasis age-matched with 14 cats with CKD with nephrolithiasis.

RESULTS

Hypermagnesemia was observed in 16/42 (38.1%) and hypomagnesemia in 6/42 (14.3%) cats. Serum magnesium abnormalities were observed in cats of all stages, and marked hypermagnesemia was noted in cats with stage 4 CKD with nephrolithiasis (P <0.001). There was a negative correlation between total serum magnesium and ionized calcium (r = -0.64; P <0.01), and a positive correlation between total serum magnesium and serum phosphorus (r = 0.58, P = 0.01). Cats with CKD with nephrolithiasis and hypomagnesemia or hypermagnesemia had higher mortality than those with normal total serum magnesium concentration (P <0.01), regardless of CKD stage. There was no difference in total serum magnesium concentration between CKD cats with and without nephrolithiasis.

CONCLUSIONS AND RELEVANCE

Cats with CKD with nephrolithiasis have magnesium abnormalities. Hypomagnesemia and hypermagnesemia were associated with an increase in mortality, and thus total serum magnesium abnormalities may be used as prognostic factors in these cases.

Hypomagnesemia is not an independent risk factor for mortality in Japanese maintenance hemodialysis patients

PURPOSE

It is unclear whether hypomagnesemia is an independent risk factor or innocent bystander for mortality in maintenance hemodialysis (MHD) patients. Thus, we studied associations between hypomagnesemia and all-cause as well as cardiovascular (CV) mortality in MHD patients.

METHODS

Baseline clinical characteristics and coronary artery calcium score (CACS) of 353 Japanese MHD patients were reviewed. Three-year survival rate and mortality risk factors were assessed.

RESULTS

Median (interquartile range) age, dialysis vintage, serum magnesium (Mg), serum albumin and CACS of the subjects were 68 (60-78) years, 75 (32-151) months, 2.4 (2.2-2.7) mg/dl, 3.6 (3.3-3.8) g/dl, and 1181 (278-3190), respectively. During the 3-year period, 91 patients died. Kaplan-Meier overall 3-year survival rates were 59.0% in in patients with Mg < 2.4 mg/dl (n = 136) and 82.3% in patients with Mg ≥ 2.4 mg/dl (n = 217), (P < 0.0001). In Cox regression models not incorporating serum albumin, Mg < 2.4 mg/dl was significantly associated with 3-year all-cause death, independent of age, dialysis vintage, average ultrafiltration, Log (CACS + 1), warfarin use, serum potassium, high-sensitivity C-reactive protein (hsCRP), phosphate, uric acid, and intact parathyroid hormone [Hazard ratio (HR) 95% confidence interval (CI): 2.82 (1.31-6.29), P = 0.0078], and CV death, independent of age, dialysis vintage, Log (CACS + 1), warfarin use, serum hsCRP, and uric acid [HR (95% CI): 4.47 (1.45-16.76), P = 0.0086]. Nevertheless, associations of Mg < 2.4 mg/dl with all-cause and CV mortality were all absent in models that included serum albumin.

CONCLUSIONS

Hypomagnesemia is not an independent risk factor for mortality but is associated with malnutrition in MHD patients.