By Peter Laird, MD
Several studies have conclusively shown that residual renal function (RRF) is an important factor in dialysis patient survival. Douglas Shemin, MD and his group followed 114 hemodialysis patients and categorized them according to the presence or absence of preserved residual function.
Residual renal function and mortality risk in hemodialysis patients
This prospective observational study of all 114 patients at a single community-based freestanding HD center is designed to examine the impact of residual renal function (defined as renal urea clearance and renal creatinine clearance derived from 24-hour urinary volumes) on mortality over a 2-year period. During that period, 50 deaths occurred in 114 patients. The presence of residual renal function was protective against mortality (odds ratio for death, 0.44; 95% confidence interval, 0.24 to 0.81; P [equals] 0.008), even after adjustment for duration of dialysis treatment, age, smoking, presence of diabetes, presence of cardiovascular disease, serum albumin level, and urea reduction rate. In conclusion, the presence of residual renal function, even at a low level, is associated with a lower mortality risk in HD patients.
There are several strategies to preserve residual renal function including starting first with peritoneal dialysis as PD has greater preserved RRF than conventional hemodialysis, ultra-pure dialysate and biocompatible membranes, ACE Inhibitors, ARB’s and calcium channel blockers, controlling ambulatory blood pressure, avoiding nephrotoxic drugs, and lastly to avoid hypotensive episodes and dehydration hemodialysis sessions.
Predictors of the rate of decline of residual renal function in incident dialysis patients
Conclusions: rGFR is better maintained in PD patients than in HD patients. The associated factors such as a higher diastolic blood pressure, proteinuria, dialysis hypotension and dehydration can either be treated or avoided.
Despite the clear survival advantage of preserving RRF, many patients continue to experience significant episodes of intradialytic hypotension which many rightly believe, in my opinion, avoidably contributes to rapidly declining residual renal function.
Europe has more stringent water quality standards supporting ultra-pure dialysate while America continues to largely ignore the positive outcomes with ultra-pure dialysate. NxStage utilizes their pureflow system which their published accounts show an ultra-pure dialysate level. An important aspect of residual renal function is whether more frequent dialysis with gentler ultrafiltration will positively impact RRF in the same magnitude that PD offers to patients. Studies are greatly needed in this area.
Patients on home hemodialysis should discuss the additional factors known to preserve residual renal function with their health care team and simply remind anyone that they encounter in a hospital setting that they need to offer treatments specifically designed to avoid further damage to their kidneys even though they are already on dialysis. Unfortunately, despite the known benefits, concerted efforts to preserve RRF are largely ignored even within the nephrology community, let alone among the many other physicians a dialysis patient will especially encounter in a hospital setting. In this instance, the dialysis patient and his care partners will need to remind each health care professional of the importance of designing a care plan around the central goal of preserving the residual renal function. It truly is a matter of life and death for dialysis patients.