Treatment with angiotensin II inhibitors and residual renal function in peritoneal dialysis patients.

BACKGROUND

Many studies have shown the renoprotective effect of angiotensin-converting enzyme inhibitors (ACEi) and angiotensin II receptor blockers (ARBs) in patients with chronic kidney disease stages I-IV. Two randomized controlled trials (RCTs) showed a positive effect of AII inhibitors on residual glomerular filtration rate (rGFR) in peritoneal dialysis (PD) patients. However, these studies were small and were performed in a highly selected group of PD patients. Our aim was to confirm the above findings in a larger number of prospectively followed PD patients.

METHODS

First we analyzed the time course of decline of rGFR in 452 incident PD patients that were not anuric at the start of dialysis and that had structured follow-up data, with measurements at 3, 6, 12, 18, 24, 30, and 36 months after the start of dialysis. Changes in rGFR over time were analyzed with a linear mixed model for repeated measures. In addition, Cox regression models were used to estimate the risk of developing anuria. In a second approach, we aimed to repeat the above analyses in a selected group of patients that theoretically could have been randomized and therefore resembled the population studied in the 2 mentioned RCTs. In this group the follow-up was restricted to 1 year.

RESULTS

201 patients were treated with ACEi/ARBs and 251 did not take these drugs at the start of PD. More patients from the treated group had diabetes and used more antihypertensive medications. The time course of decline of rGFR was not different between the 2 groups over the 3 years of PD treatment (p = 0.52). Less than 25% of patients from each group became anuric and there was no difference in time to development of complete anuria between the treated and untreated groups. In the second approach, 130 patients were included: 37 were treated with ACEi/ARBs and 93 were not. Again, no difference was found between the 2 groups with respect to the rate of decline of rGFR and time of anuria development.

CONCLUSION

Our findings are not in line with the results of previous RCTs. The biggest limitation of observational studies is the inability to avoid confounding by indication. However, a RCT in such a setting also does not give a reliable answer. Given all the benefits of ACEi/ARBs, the medications should not be withheld from PD patients. However, their renoprotective effects may often be overruled by other factors influencing the time course of rGFR.