Strategies to improve clinical outcomes in peritoneal dialysis patients: Delivered dose and membrane transport

For patients with end-stage renal disease treated with peritoneal dialysis, prospective cohort studies using multivariate statistical analysis have shown an association between greater urea clearance and a decreased relative risk for death. The recommended weekly Kt/V for urea is 2.0, with the corresponding creatinine clearance (CrCl) of 60 L/1.73 m2. This is considered adequate dialysis but fails to define optimum urea and CrCl targets. The assumption that renal and peritoneal clearances are equivalent has been challenged by circumstantial data and is probably untenable. The relative importance of these clearances requires definition. The suggestion that CrCl is a more important indicator of adequacy of dialysis is confounded by association with renal, rather than peritoneal, clearance and perhaps by the early referral and initiation of dialysis. Recent reports have shown an association between increased peritoneal membrane transport and an increased relative risk for technique failure and/or death. Patients with higher peritoneal transport should have greater clearance of urea and creatinine and better clinical outcomes. Possible explanations for this apparent contradiction include the adverse effects of increased glucose absorption, malnutrition, and fluid overload, the latter caused by decreased ultrafiltration. Available data suggest an important role for the failure of ultrafiltration among patients treated with continuous ambulatory peritoneal dialysis (CAPD). Strategies to improve the clearance of urea and creatinine include the preservation of residual renal function and increased peritoneal clearance. Loss of residual renal function may be delayed by the avoidance of nephrotoxic drugs and angiographic dye. Peritoneal clearance can be enhanced by a combination of increased volume and frequency of peritoneal dialysis cycles. Ultrafiltration failure, but not protein loss, can be addressed with shorter cycles with nocturnal peritoneal dialysis. Development of an alternative to glucose as an osmotic agent is an important strategy.