title: Volume excess in chronic haemodialysis patients--effects of treatment frequency and treatment spacing.
abstract: BACKGROUND
  The main objective of this study was to theoretically quantify the fluctuations of fluid volume excess for different modes of intermittent ultrafiltration schedules and to compare the prediction for the typical and asymmetric thrice-weekly schedule to clinical, physiological and biophysical markers of volume expansion in a group of stable haemodialysis patients.
  
  
  METHODS
  Overall volume excess (V(OVE)) was described as the sum of a time-independent (V(0)) and a time-dependent component (V). An exact relationship was developed to relate V to variable treatment frequency, treatment spacing and net volume accumulation rate. In a single-centre haemodialysis population, body mass profiling was combined with volume state evaluation by bioimpedance analysis, N-terminal pro-B-type natriuretic peptide (NT-pro BNP) levels, clinical signs, a volume questionnaire and blood pressure levels.
  
  
  RESULTS
  In 23 patients following the typical thrice-weekly schedule, the time-averaged volume excess (V) during the whole week (1.1 ± 0.5 L) was significantly larger than that during the midweek interval (0.9 ± 0.4 L) (P < 0.002) by a factor comparable to that of 1.21 obtained from the theoretical analysis. V(OVE) was 1.3 ± 1.7 L and significantly related to pre- (P < 0.001) and post-dialysis levels of NT-pro BNP (P < 0.001).
  
  
  CONCLUSIONS
  Asymmetric treatment spacing such as with the typical thrice-weekly treatment schedule leads to a significant increase in time-averaged volume excess. The theoretical analysis allows for comparison of time-averaged volume excess in treatments varying with regard to treatment frequency and regularity and could be helpful to prescribe post-treatment volume (target weight) for such variable treatment modes.
authors.affiliation: Institute of Physiology, Medical University of Graz, Graz, Austria.
authors.forename: Jakob
authors.initials: J
authors.lastname: Stockinger
authors.forename: Werner
authors.initials: W
authors.lastname: Ribitsch
authors.forename: Daniel
authors.initials: D
authors.lastname: Schneditz
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood*; D001834:Body Water / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D006435:Renal Dialysis / Q000379:methods*; D013997:Time Factors; D014462:Ultrafiltration / Q000379:methods*; D055815:Young Adult
chemical_list: D015415:Biomarkers