Postdialysis serum sodium changes and systolic blood pressure in patients undergoing online hemodiafiltration and high-flux hemodialysis

BACKGROUND Because hemodiafiltration (HDF) involves large amounts of ultra-filtration and substitution fluid infusion, its effects on serum electrolytes may be different from those of hemodialysis (HD). Serum sodium and blood pressures were compared between patients undergoing online HDF and high-flux HD (HFHD). METHODS Thirty-two of 101 patients on HFHD switched voluntarily to online HDF. Their pre- and postdialysis serum measurements were compared with those of the remaining 69 HFHD patients. RESULTS Online HDF patients had lower pre- and postdialysis systolic blood pressures (SBPs) than HFHD patients (predialysis, 136±21 vs. 145±19 mmHg, P<0.05; postdialysis, 129±22 vs. 142±25 mmHg, P<0.05). Pre- and postdialysis serum sodium concentrations were not significantly different between online HDF and HFHD (predialysis, 138±2 vs. 137±3 mEq/L; postdialysis, 134±2 vs. 134±2 mEq/L). However, the change in serum sodium concentration after dialysis was greater in online HDF than HFHD patients (-3.7±2.2 vs. -2.5±2.8 mEq/L, P<0.05). The change in serum sodium concentration was correlated with postdialysis SBP (r=0.304, P<0.005) and pulse pressure (r=0.299, P<0.005). Predialysis SBP (r = 0.317, P<0.005) and pulse pressure (r=0.324, P=0.001) were also correlated with the postdialysis serum sodium change. CONCLUSION Compared with HFHD, online HDF has a greater serum sodium lowering effect. This might contribute to the ability of online HDF to stabilize both pre- and postdialysis SBP.