In a post hoc analysis of this study, an initial fall in GFR was found to predict better long-term Such acute changes in GFR are likely to reflect the hemodynamic changes that accompany initiation of RAAS blockade.88,428 However, since a reduction in GFR is not usually considered beneficial, observers have recently questioned the value of commencing or continuing BP- lowering regimens based on an ACE-I or ARB in elderly patients with advanced CKD and have specifically suggested that use of such agents in CKD 4 5 patients may compromise residual kidney function or even accelerate its rate of decline in both diabetic429 and non-diabetic patients.430 This opinion is based on uncontrolled observations and is contrary to the observations made from the RENAAL RCT in patients approaching renal replacement therapy.431 For example in one such observational study, discontinuation of ACE-Is and ARBs in 52 patients with CKD 4 5 was followed by a greater than 25% increase in the GFR in 61.5% of patients, and a greater than 50% increase in 36.5% of An RCT that specifically randomized patients with advanced CKD to benzapril or placebo did not support The study reported that 112 predominantly CKD 4 patients with a mean GFR of 26 ml/min/1.73 m2 receiving benzapril had a lower risk of doubling of SCr, kidney failure, or death compared with the same number of patients receiving placebo. A small study of 60 peritoneal dialysis patients showed better preservation of residual kidney function among patients randomized to ramipril as com- pared to no treatment.432 Thus, the current evidence does not support the discontinuing ACE-Is and ARBs in patients with advanced CKD in an effort to preserve residual kidney function, although hyperkalemia or hypotension may be a specific reason for discontinuation in some patients. 