Equilibration of peritoneal dialysis solutions during long-dwell exchanges.

There is an increasing interest in CAPD for the treatment of chronic uremia. This technique uses long-dwell peritoneal exchanges lasting 4 hr or more. We have determined equilibration curves for multiple solutes during long exchanges with commercially available 1.5% and 4.25% dextrose dialysis solutions. For small solutes, rates of change of D/P ratios fall off dramatically after 3 hr of dwell time. For larger solutes, D/P ratios change more linearly. Some concentration gradients for net removal by diffusion persist well beyond 4 hr for all but the most highly diffusible solutes. Previously reported net sieving of sodium and chloride during hypertonic exchanges is still evident after many hours.