title: Determinants and short-term reproducibility of relative plasma volume slopes during hemodialysis.
abstract: OBJECTIVE
  Hypervolemia is a major cause of morbidity, in part because of the lack of well characterized diagnostic tests. The hypothesis was that relative plasma volume (RPV) slopes are influenced by ultrafiltration rate, directly associate with improvement in arterial oxygen saturation, and are reproducible.
  
  
  METHODS
  RPV slopes were measured on three consecutive hemodialysis sessions. Various relationships were tested using mixed models. Reproducibility was assessed by the intraclass correlation coefficient.
  
  
  RESULTS
  RPV slopes averaged 1.37 ± 1.45% per hour. The mean RPV slopes were steeper on the first dialysis of the week, which correlated with a higher ultrafiltration rate; RPV slope and ultrafiltration rate were directly related. Increasing ultrafiltration rate quartiles were associated with similar change in RPV in the first 1 hour of dialysis but steeper changes in RPV subsequently. A direct relationship emerged between increasing RPV slopes and increasing arterial oxygen saturation slopes. The intraclass correlation coefficient for the relative plasma volume slope was 0.77.
  
  
  CONCLUSIONS
  Although ultrafiltration rate is a major determinant of RPV slope, similar ultrafiltration rates are associated with varying RPV between individuals. Because RPV is associated with little change by ultrafiltration rate during the first 1 hour of dialysis, probing dry weight during the earlier part of dialysis may be safer. RPV slopes are physiologically meaningful, because they are associated with parallel changes in arterial oxygenation saturation slopes. RPV slopes are reproducible, and therefore, RPV may serve as a useful marker to judge changes in volume status within an individual.
authors.affiliation: Division of Nephrology, Department of Medicine, Indiana University School of Medicine and Richard L Roudebush Veterans Administration Medical Center, Indianapolis, Indiana 46202, USA.
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Anand
authors.forename: Arjun D
authors.initials: AD
authors.lastname: Sinha
authors.forename: Rajiv
authors.initials: R
authors.lastname: Agarwal
mesh_terms: D000328:Adult; D005260:Female; D017583:Hemodiafiltration; D006801:Humans; D020896:Hypovolemia / Q000175:diagnosis; D007676:Kidney Failure, Chronic / Q000503:physiopathology / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D010953:Plasma Volume; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D010100:Oxygen