Low serum sodium is associated with protein energy wasting and increased interdialytic weight gain in haemodialysis patients

Background. Low serum sodium (Na) has been associated with decreased body mass index and increased cardiovascular mortality in haemodialysis (HD) patients. We examined the relationship between serum Na and selected nutritional parameters of protein energy wasting that are not affected from the hydration status in a cohort of HD patients. Methods. Triceps skinfold thickness (TSF), mid-arm circumference (MAC), mid-arm muscle circumference (MAMC), handgrip strength (HGS) and subjective global assessment (SGA) were assessed in maintenance HD patients using standard techniques. MAMC was calculated with the formula MAMC (cm) = MAC (cm) -3.142 x TSF cm. Pre-dialysis serum Na values from routine monthly laboratory measurements were averaged for the last 6 months prior to the nutritional assessment. Results. Altogether 172 patients with anthropometric data were included in the final analysis. Mean age was 66 +/- 14, females 62 (36%) and diabetics 48 (28.9%). Patients with pre-dialysis serum Na below the mean value (136.2 mEq/L) had lower MAMC, HGS, SGA scores and albumin levels (23.50 +/- 3.16 cm versus 24.58 +/- 3.71 cm, P = 0.048; 21.7 +/- 13.6 kg versus 28.0 +/- 12.4 kg, P = 0.030; 5.1 +/- 1.2 versus 5.7 +/- 1.0, P = 0.012 and 31.65 +/- 4.73 mg/L versus 32.25 +/- 3.91 mg/L, P = 0.022, respectively) and higher interdialytic weight gains. Pre-dialysis serum Na correlated positively with MAMC, handgrip and SGA (Pearson's correlation r = 0.165, P = 0.031, r = 0.237, P = 0.022 and r = 0.195, P = 0.011, respectively). Conclusion. This study demonstrates that low serum sodium is associated with protein energy wasting and increased interdialytic weight gain in HD patients.