Abstract: Objective This study aimed to explore the regularity of intracellular and extracellular water changes in maintenance hemodialysis (MHD) patients during dialysis. Methods We selected 55 MHD patients as the subjects and measured their total body water (TBW), intracellular water (ICW) and extracellular water (ECW) before dialysis and every hour during dialysis, i.e., a total of 5 measurements for a patient. Results ①Both ICW and ECW decreased during dialysis as compared with those before dialysis, and ICW decreased more than ECW. ② The ratio of ICW/ECW was 2:1 in the first two hours during the dialysis, without
significant difference with that before dialysis (t=- 5.620, P=0.580; t=- 2.048, P=0.053); the ratio increased slightly to 2.1:1 in the last two hours during the dialysis (t=-3.269, P=0.030; t=-4.696, P＜0.001). ③The ratios of ΔICW/ΔECW were 1.9, 1.8, 1.5 and 1.4 at the 1st, 2nd, 3rd and 4th hour respectively during the dialysis, and this ratio decreased significantly at the 4th hour as compared with that at the 1st hour (t=2.279, P= 0.036). ④After dialysis, the reduction rate of ICW and ECW were 5.4% and 8.4% respectively (t=3.994, P＜0.001). Conclusion ①Dialysis by ultrafiltration decreased the water retention in both extracellular and intracellular spaces, and the intracellular water decreased more than the extracellular water, resulting in slight increase of ICW/ECW ratio at the end of dialysis. ②The ratio of ΔICW/ΔECW decreased gradually along with the hour of the dialysis, and the reduction rate of ICW was less than that of ECW, suggesting that the excessive water in intracellular space moves to extracellular space through osmotic gradient and removes from the body with ECW during dialysis.

Key words: Hemodialysis, Intracellular water, Extracellular water, Bioelectrical impedance