[Fluid distribution abnormalities and influence of hemodialysis on fluid distribution in patients on maintenance hemodialysis].

OBJECTIVE: To study the fluid distribution abnormalities in patients on hemodialysis and fluid shift between intracellular and extracellular compartment during hemodialysis (HD).

METHODS: Eighty stable end stage renal disease patients on maintenance hemodialysis were selected. Conventional low flux dialyses at dialysate sodium concentration of 138 mmoL/L were performed for all of the patients. Fresenius polysulphons or Gambro hemophon dialyzers were used. All of the patients showed no clinical signs of over ultrafiltration during HD sessions and dry body weights were considered adequate. Intracellular water (ICW), extracellular water (ECW) and total body water (TBW) were measured and standardized by body weight (nICW, nECW, nTBW) before and after HD sessions. Sixty-seven cases of sex, age and body weight matched normal individuals were used as controls. Bio-impedance spectrum (BIS) analysis (Xitron, Technologies, San Diego, CA, USA) was used in body fluid measurement. Pre and post HD nICW, nECW, and nTBW were compared with these of the controls.

RESULTS: There were no differences in age, post-dialysis body weight and body mass index between patients on hemodialysis and the controls. Patients on hemodialysis had less nICW [male (0.28+/-0.05) vs (0.33+/-0.04), P<0.01; female (0.22+/-0.03) vs (0.27+/- 0.04), P<0.001], more nECW [male (0.28+/-0.02) vs (0.25+/-0.02), P<0.001; female (0.25+/-0.03) vs (0.23+/-0.01), P<0.05], and less nTBW [male (0.56+/-0.04) vs (0.58+/-0.05), P<0.05; female (0.47+/-0.05) vs (0.49+/-0.03), P<0.05] compared with the controls. The average ultra-filtration volume was (2.2+/-0.9)L. After dialysis, there was an increase in nICW [male (0.28+/-0.05) vs (0.30+/-0.05), P<0.001; female (0.22+/-0.03) vs (0.25+/-0.03), P<0.001), an decrease in nECW [male (0.28+/-0.02) vs (0.26+/-0.03), P<0.001; female (0.24+/-0.03) vs (0.21+/-0.03), P<0.001],and decrease of ECW/ICW ratio [male (1.06+/-0.30) vs (0.89+/-0.25) P<0.001; female (1.10+/-0.17) vs (0.88+/-0.17) P<0.001] which reached the levels of the normal individuals (0.79+/- 0.10 for male, 0.86+/-0.10 for female].

CONCLUSION: Our results show that (1) Before HD sessions, patients on HD had less nICW and more nECW; (2) During conventional low flux HD sessions at dialysate sodium concentration of 138 mmoL/L, fluid shifted from extracellular space to intracellular space.(3) nECW and ECW/ICW ratio from normal population are reasonable for evaluation of dry weight in patients on hemodialysis, but nTBW and nICW are not.