Effects of modality change and transplant on peak oxygen uptake in patients with kidney failure

Am J Kidney Dis. 2011 Jan;57(1):113-22. doi: 10.1053/j.ajkd.2010.06.026. Epub 2010 Sep 25.


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.

Study design: Cohort study with assessment at baseline and 6 months after modality change.

Setting & participants: 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.

Predictor: Modality change.

Measurement & outcomes: 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.

Limitations: 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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adult
  • Blood Urea Nitrogen
  • Cardiac Output
  • Creatinine / blood
  • Exercise Test
  • Exercise Tolerance*
  • Female
  • Heart Rate
  • Humans
  • Kidney Failure, Chronic / blood
  • Kidney Failure, Chronic / physiopathology*
  • Kidney Failure, Chronic / therapy
  • Kidney Transplantation*
  • Male
  • Middle Aged
  • Oxygen / blood
  • Oxygen Consumption*
  • Renal Dialysis / methods*
  • Stroke Volume


  • Creatinine
  • Oxygen