Abstract: Objective  In clinical practice, a pre-charge volume has to be administered during the machine setup to prevent rapid blood pressure drop after blood drawing for hemodialysis (HD). The theoretical blood chamber volume varies among different dialyzer models, which poses a challenge for clinical assessment of pre-charge volume. This study aims to measure the pre-charge volume of different types of dialyzers used in HD and compare with the theoretical pre-charge volume to provide a reference for the dosage of pre-charge in clinical dialyzers.  Methods  The blood chamber volume and HD circuit volume of 9 types of dry membrane dialyzers commonly used in the Hemodialysis Division of Guangdong Provincial People's Hospital in June 2023 were tested.  Results  A total of 31 pre-charge data from 9 types of dry membrane dialyzers were collected, including 14 instances with cellulose acetate membrane and 17 instances with synthetic membrane. The physiological saline (NS) pre-charge volume required for the dialyzers with cellulose acetate membrane filters was 215.6(203.5～225.2) ml and that required for the dialyzers with synthetic membrane filters was 208.0 (192.2～217.6) ml. The amount of NS required for the internal wetting of synthetic membranes was statistically higher than that of cellulose acetate membranes [118.0(96.4, 141.0) ml vs. 33.8(23.7, 47.5) ml, Z=-9.181, P＜0.001]. Overall, there was a significant difference between the theoretical pre-charge volume and the measured pre-charge volume for dialyzers with both types of membranes, with the measured pre-charge volume significantly lower than the theoretical pre-charge volume (t=10.270, P＜0.001); the measured pre-charge volume for dialyzers with cellulose acetate membrane filter was significantly lower than the theoretical pre-charge volume (t=-14.429, P＜0.001), and the measured pre-charge volume for dialyzers with synthetic membrane was also significantly lower than the theoretical pre-charge volume (t=-13.339, P＜0.001).  Conclusion  The measured pre-charge volumes of the dialyzers used in this study were all less than the theoretical pre-charge volumes suggested in the manuals, and the NS volume required for internal wetting during pre-charge was higher for synthetic membranes than for cellulose acetate membranes. The conclusions of this study provide a theoretical basis for the precise management of volume in hemodynamically unstable HD patients who require pre-charge before blood drawing treatment.

Key words: Hemodialysis, Dialyzer, Priming volume