MULTIFREQUENCY BIOIMPEDANCE IN ASSESSMENT OF DRY-WEIGHT IN HEMODIALYSIS

The use of multifrequency bioimpedance (MFB) for determination of dry weight (DW) in haemodialysis (HD) patients was evaluated in three stud ies. In Study 1, the fluid state [total body water (TBW) and extracell ular volume (ECV)] was measured by MFB in 82 normotensive patients, 41 hypertensive patients and in 30 healthy subjects. TBW and ECV were ex pressed as per cent of body weight (BW). In Study 2, DW of five hypert ensive HD patients was gradually decreased during 3 months and ECV (MF B) and blood pressure (48 h ambulatory blood pressure monitoring) were measured at the beginning and end of study. In Study 3, we measured t he fluid status repeatedly by RIFE and the diameter of the inferior ve na cava (DIVC) by ultrasound before, during and 2 h post-HD. In Study 1, the hypertensive patients had significantly greater TBW (P<0.05) th an the normotensive patients before (50.3 +/- 6.5% vs 47.6 +/- 5.8%) a nd after HD (48.8 +/- 7.8% vs 45.7 +/- 6.4%) and ECV (P < 0.001) befor e (29.3 +/- 3.6% vs 26.8 +/- 3.5% and after HD (27.0 +/- 4.0% vs 24.6 +/- 3.5%), Post-HD ECV in the normotensive patients was similar to tha t in the healthy subjects. In Study 2, more efficient ultrafiltration resulted in reduction of BW and ECV along with a decrease in blood pre ssure and need for antihypertensive medication. In Study 3, both ECV a nd DIVC decreased following the removal of fluid during HD. ECV mainta ined stable values during the post-HD period, unlike DIVC which increa sed significantly (P<0.005) due to refilling from the interstitial spa ce. We conclude that MFB is an appropriate noninvasive method for DW d etermination which is highly reproducible and technically simple to us e.