Comparison of body fluid distribution between chronic haemodialysis and peritoneal dialysis patients as assessed by biophysical and biochemical methods

Background. The control of extracellular volume is a key parameter for redu cing hypertension and the incidence of cardiovascular mortality in dialysis patients. In recent years bioimpedance measurement (BIA) has been proven a s a non-invasive and accurate method for measuring intracellular and extrac ellular fluid spaces in man, In addition. plasma atrial natriuretic peptide (ANP) and cyclic guanosine monophosphatase (cGMP) concentrations have been shown to reflect central venous filling. Using these methods. we compared body fluid status between stable patients on haemodialysis and peritoneal d ialysis. Methods. Thirty-nine chronic haemodialysis patients, 43 chronic peritoneal dialysis patients and 22 healthy controls were included in the study. Multi frequency BIA was performed using the Xitron BIS4000B device (frequencies f rom 5 to 500 kHz were scanned and fitted) in patients before and after haem odialysis. Peritoneal dialysis patients were measured after drainage of the dialysate. Plasma ANP and cGMP levels were measured in plasma using a I-12 5 solid phase RIA. Serum albumin concentrations and serum osmolality were m easured in all patients. The body fluid data were analysed in relation with the clinical findings. Results. Total body water (TBW) was 0.471 +/- 0.066 1/kg before haemodialys is and 0.466 +/- 0.054 1/kg after haemodialysis. Peritoneal dialysis patien ts had a TBW (0.498 +/- 0.063 1/kg) that was greater than the before and af ter dialysis values of haemodialysis patients. The extracellular body fluid ( Vf) was increased pre-haemodialysis. It was even greater in peritoneal d ialysis patients compared with patients both pre- and post-haemodialysis (p re 0.276 +/- 0.037 1/kg; post 0.254 +/- 0.034 1/kg; peritoneal dialysis 0.2 93 0.042 1/kg, P < 0.05). However, plasma ANP concentrations (representing intravascular filling) in peritoneal dialysis patients were comparable with post-haemodialysis values (284 +/- 191 pg/ml vs 286 +/- 144 pg/ml). The co rrelation coefficient between sysRR and V-ecf was r = 0.257 in haemodialysi s (P = 0.057) and r = 0.258 in peritoneal dialysis (P < 0.05). A significan t negative correlation was found between serum albumin and V-ecf,/TBW in pe ritoneal dialysis patients (r = -0.624). Conclusion. Body fluid analysis by BIA demonstrated that TBW and V-ecf were increased in peritoneal dialysis patients, and were comparable or even gre ater than values found before haemodialysis. However, plasma ANP levels ind icated that intravascular filling was not increased in peritoneal dialysis. The ratio of V-ecf to TBW was correlated to systolic pressure and negative ly to serum albumin in peritoneal dialysis patients.