Trends in coronary artery calcification in peritoneal dialysis and transplant patients.

compensatory mechanisms and that a steady state of relative blood volume (RBV) may not have been attained during the brief period of exercise we employed. What we in fact suggested was that our findings may not extrapolate to older patients subjected to more prolonged or intense exercise at high ultrafiltration (UF) rates. We still think this is a reasonable caveat. We quoted evidence that exercise in the later stages of haemodialysis sessions employing UF may not be quite so well tolerated [1]. Indeed, Dasselaar et al. in their concluding remarks tacitly recognize this possibility stating that ‘patients who experience cardiovascular instability during intra-dialytic exercise may benefit from exercise programmes in the inter-dialytic interval’. Their second major point was that exercise-induced changes in the F-cell ratio provide a possible explanation for the discrepancy between the changes in haemoglobin and total protein concentrations we reported. We agree. We alluded to this possibility both in the paper’s introduction and in the discussion but concluded that ‘while it is not possible to exclude . . .an effect on RBV of haematocrit redistribution, we have not found any direct evidence. . .’. We still do not feel that the small differences we found justify a more definite conclusion. We wholeheartedly concur with Dasselaar et al.’s remarks that ‘exercise during haemodialysis should be promoted due to it positive effects. . .’. Our paper described haemodynamic responses during exercise on haemodialysis comparable with those seen during exercise in normal individuals. In our view, this enhances the case for intra-dialytic exercise.