Influence of hemodialysis duration per week on parameters of dialysis adequacy and cardiovascular morbidity

INTRODUCTION: The optimal length of dialysis is still under debate and current regimen of 12 hours a week is medically acceptable. The aim of this observational study was to confirm the relationship between different length of dialysis per week and the parameters of dialysis adequacy and cardiovascular morbidity. MATERIAL AND METHODS: The study included 206 patients (128 man and 78 females) who were on maintenance hemodialysis for more than 6 months. They were classified into three groups according to the length of dialysis per week: group I (12 hours), group II (15 hours) and group III (≥17.5 hours). RESULTS: Index of dyalysis adequacy values did not differ among the groups (group I, II, III = 1.32 vs. 1.51 vs. 1.42; p>0.05); however, the patients from group III had the best bicarbonate level (group I, II and III = 22.7; 21.4; 17.6 mmol/L; p<0.001). In comparison with group I (12 hours), longer dialysis duration was associated with significantly higher hemoglobin values (12.2 vs. 11.4 vs. 10.5 g/dL), less frequent use of erythropoietin stimulating agents (26.9% vs. 65% vs. 86.3%), lower stimulating agents weekly dose (median in group I, II, III = 2000 vs. 5000 vs. 4000 I.J.), lower stimulating agents resistance index (4.9 vs. 7.8 vs. 8.8), significantly higher level of serum albumin (42.3 vs. 40.7 vs. 38.2 g/dL), total cholesterol (5.1 vs. 4.7 vs. 4.5 mmol/L) and serum calcium level (2.38 vs. 2.42 vs. 2.28 mmol/L), less frequent use of phosphate binders (53.8% vs. 85% vs. 84.4%) and calcitriol (19.2% vs. 65% vs. 50.6%) and lower intact parathyroid hormone level (336 vs. 363 vs. 446 pg/ml). In addition, longer dialysis duration was associated with lower cardiovascular morbidity score (0.52 vs. 1.05 vs. 1.26). CONCLUSION: Duration of dialysis per week above the current standard positively correlates with parameters of hemodialysis adequacy.