Abstract
In order to clarify the relationship between the blood flow rate (QB) and transmembrane pressure (TMP) during hemodialysis (HD) or pre-dilution on-line hemodiafiltration (OHDF), blood pressure was measured at the blood inlet (PBi), blood outlet (PBo), dialysate inlet (PDi), and dialysate outlet (PDo) of dialysis membranes. The QB was gradually increased from 100 mL/min to 250 mL/min, while the dialysate flow rate was kept at 500 mL/min. During pre-dilution OHDF, the substitution flow rate was 18 L/hour. TMP was calculated from PBi, PBo (or its mean) and PDi, or PDo (or its mean) using 5 different formulas. The calculated TMP values varied according to the formula used. In HD, TMP decreased as the QB increased, regardless of which formula was used. In pre-dilution OHDF, TMP increased in parallel with the QB when the PBi-based TMP formula was used, while it decreased as the QB increased when the other formulas were employed. Our findings suggest that the inclusion of PBi in formulas for calculating TMP could be essential for estimating the effect of QB on TMP, as increasing the QB caused a pressure loss across the blood side of the filter. In HD, increasing the QB might result in a greater shear rate, which could account for the observed reduction in TMP. In pre-dilution OHDF, the concentration of the cells and protein in blood might increase the TMP.
