We evaluated the frequency and severity of muscle cramps, and the effect of dialysate magnesium on muscle cramps in 62 stable ESRD patients on chronic hemodialysis. Each subject was surveyed twice within a 6-month period. A single nephrology fellow conducted all in-person surveys. During the first survey, the patients were dialyzed with dialysate magnesium of 0.75？meq/L (0.375？mmol/L). Prior to the second survey, the dialysate magnesium was increased to 1.0？meq/L (0.50？mmol/L). The severity of cramps was scored on a 1–10 scale, with 10 indicating maximal severity. The number of patients with muscle cramps was significantly lower with dialysate magnesium of 1.0？meq/L (0.50？mmol/L) (56% versus 77%, ). No significant difference was observed in interdialytic weight gain, intradialytic ultrafiltration, dry weight, or intradialytic hypotension. The mean ± SD severity score of muscle cramps decreased from to (). Seven of 31 (23%) patients in the group with low dialysate magnesium while 0/20 (0%) patients receiving high magnesium dialysate terminated hemodialysis early due to cramps (). Both the number of patients reporting muscle cramps and the severity score decreased with higher dialysate magnesium which contributed to better adherence to hemodialysis treatments. 1. Introduction Painful muscle cramps, usually in the lower extremities are common in patients receiving chronic hemodialysis (HD) . These cramps frequently occur toward the end of the dialysis sessions, sometimes precede hypotension, and are associated with higher fluid removal during HD . Recurrent muscle cramps frequently lead to noncompliance with the prescribed HD treatment  and impact patients’ quality of life . Varying the magnesium (MG) concentration to a low or no MG containing dialysate has been shown to increase the incidence of muscle cramps . Intravenous MG given during an episode of severe muscle cramping while on HD was shown to ameliorate the symptom . Previous therapies including quinine, vitamins C and E , L-carnitine , MG [7–9], and the use of sequential compression devices  have been investigated to ameliorate the frequency and intensity of muscle cramps with mixed efficacy. MG functions as a cofactor in the energy metabolism, nucleotide and protein synthesis, and as a regulator of sodium, potassium, and calcium channels . Severe hypomagnesaemia can cause muscle cramps, tremors, tetany, and cardiac arrhythmia . In patients on HD, the serum MG concentration parallels the dialysate MG level. MG readily crosses the dialysis membrane with its
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