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.