title: Effects of modality change and transplant on peak oxygen uptake in patients with kidney failure.
abstract: BACKGROUND
  Exercise capacity as measured by peak oxygen uptake (Vo₂(peak)) is low in hemodialysis patients. The present study assesses determinants of VO₂(peak) in patients with chronic kidney failure who either changed kidney replacement modality to frequent hemodialysis therapy or received a kidney transplant.
  
  
  METHODS
  Cohort study with assessment at baseline and 6 months after modality change.
  
  
  METHODS
  Participants included nondiabetic individuals receiving conventional hemodialysis who: (1) remained on conventional hemodialysis therapy (n = 13), (2) changed to short daily hemodialysis therapy (n = 10), or (3) received a transplant (n = 5) and (4) individuals who underwent a pre-emptive transplant (n = 15). Additionally, 34 healthy controls were assessed at baseline only.
  
  
  METHODS
  Modality change.
  
  
  METHODS
  Exercise capacity, assessed using the physiologic components of the Fick equation (Vo₂ = cardiac output × a-vo₂(dif), where a-vo₂(dif) is arterial to venous oxygen difference) was determined using measurement of Vo₂(peak) and cardiac output during symptom-limited exercise testing. Analysis of covariance was used to compare differences in changes in Vo₂(peak), cardiac output, heart rate, stroke volume, and a-vo₂(dif) at peak exercise between participants who remained on hemodialysis therapy and those who underwent transplant.
  
  
  RESULTS
  Transplant was the only modality change associated with a significant change in Vo₂(peak), occurring as a result of increased peak cardiac output and reflecting increased heart rate without a change in peak a-vo₂(dif) despite increased hemoglobin levels. There were no differences in participants who changed to daily hemodialysis therapy compared with those who remained on conventional hemodialysis therapy.
  
  
  CONCLUSIONS
  Small nonrandomized study.
  
  
  CONCLUSIONS
  Vo₂(peak) increases significantly after kidney transplant, but not with daily hemodialysis; this improvement reflects increased peak cardiac output through increased peak heart rate. Despite statistical significance, the increase in Vo₂(peak) was not clinically significant, suggesting the need for interventions such as exercise training to increase Vo₂(peak) in all patients regardless of treatment modality.
authors.affiliation: University of Minnesota, Minneapolis, 55455, USA. tpainter@umn.edu
authors.forename: Patricia
authors.initials: P
authors.lastname: Painter
authors.forename: Joanne B
authors.initials: JB
authors.lastname: Krasnoff
authors.forename: Michael
authors.initials: M
authors.lastname: Kuskowski
authors.forename: Lynda
authors.initials: L
authors.lastname: Frassetto
authors.forename: Kirsten L
authors.initials: KL
authors.lastname: Johansen
mesh_terms: D000328:Adult; D001806:Blood Urea Nitrogen; D002302:Cardiac Output; D003404:Creatinine / Q000097:blood; D005080:Exercise Test; D017079:Exercise Tolerance; D005260:Female; D006339:Heart Rate; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood / Q000503:physiopathology* / Q000628:therapy; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D006435:Renal Dialysis / Q000379:methods*; D013318:Stroke Volume
chemical_list: D003404:Creatinine; D010100:Oxygen