Timely initiation of dialysis: a urea kinetic approach

The traditional approach of initiating dialysis when the patient begins to manifest uremic symptoms may result in the development of significant malnutrition with detrimental effects on subsequent morbidity and mortality. The recently issued Dialysis Outcome Quality Initiative guidelines suggest that dialysis be initiated when the Kt/V from residual renal function decreases to less than 2.0. We have used the urea kinetic model to show how dialytic dose can be titrated to compensate for declining renal function while maintaining a constant total dose of delivered therapy (Kt/V = 2.0). For hemodialysis (HD), we show that initiating dialysis with once-weekly therapy may be a viable option only for a few months, being replaced by twice-weekly and subsequently with the more typical regimen of thrice-weekly HD. We recommend that the patient be directly initiated with twice-weekly HD to minimize wide swings in the serum concentrations of small-molecular-weight solutes. With continuous ambulatory peritoneal dialysis (CAPD), a hypothetical average-sized patient with high-average transport can be maintained for approximately 8 months with a single 2.5-L nocturnal exchange and from 8 to 17 months with two nocturnal exchanges of 2.5 L each. The use of nocturnal exchanges allows more normal daytime activities and is less intrusive on patient lifestyle. We have shown that both HD and CAPD regimens can be successfully adjusted to achieve a constant total Kt/V of 2.0 for 5 or more years, although CAPD may provide a smoother transition from no dialysis to a complete 10-L regimen.