Exercise capacity as measured by VO2peak (peak oxygen uptake) is low in hemodialysis patients. The current study assesses the determinants of VO2peak in patients with chronic kidney failure who changed kidney replacement modality to either frequent hemodialysis or received a kidney transplant.
Cohort study with assessment at baseline and 6-months following modality change.
Setting & Participants
Participants included non-diabetic individuals receiving conventional hemodialysis who a) remained on conventional hemodialysis (n=13), b) changed to short daily hemodialysis (n=10), or c) received a transplant (n=5), and d) individuals who received pre-emptive transplant (n=15). Additionally, 34 healthy controls were assessed at baseline only.
Measurement & Outcomes
Exercise capacity, assessed from the physiologic components of the Fick equation (VO2 = cardiac output x a-vO2dif, where a-vO2dif is arterial to venous oxygen difference) was determined by measurement of VO2peak and cardiac output during symptom-limited exercise testing. Analysis of covariance was used to compare the differences in changes in VO2peak, cardiac output, heart rate, stroke volume, and a-vO2dif, at peak exercise between those who remained on hemodialysis and those who underwent transplant.
Transplant was the only modality change that was associated with a significant change in VO2peak, occurring as a result of increased peak cardiac output and reflecting increased heart rate without change in peak a-vO2dif, despite increased hemoglobin levels. There were no differences in those who changed to daily hemodialysis compared to those who remained on conventional hemodialysis.
Small, non-randomized study.
VO2peak increases significantly following kidney transplant but not with daily hemodialysis; this improvement reflects increased peak cardiac output via increased peak heart rate. Despite statistical significance, the increase in VO2peak was not clinically significant, suggesting the need for interventions such as exercise training to increase VO2peak in all patients, regardless of treatment modality.