A method to test blood flow limitation of peritoneal-blood solute transport

Current transperitoneal transport models assume that effective blood flow to the microcirculation does not limit solute exchange with dialysate in the cavity. Despite evidence that gas transfer across the peritoneum (assumed to equal the effective blood flow) occurs at rates that exceed maximum urea transfer rates by a factor of two to three, the assumption has been strongly challenged. To address this problem at the tissue level, a technique to determine the effect of local blood flow on small-solute transport was developed in this study. Diffusion chambers were affixed to the serosal side of the anterior abdominal wall of rats, and solutions containing radiolabeled urea or mannitol were placed in the chambers. During each experiment, the local blood flow beneath the chamber was monitored with laser Doppler flowmetry and the disappearance of the tracer versus time was simultaneously measured under three conditions of blood flow: control, 30% of control, and zero blood flow. The results demonstrated no significant differences for either solute between control and the condition in which blood flow was reduced by 70%. However, there was a significant reduction in the rate of mass transfer with no blood flow. It was concluded that blood flow at > or = 30% of control values does not limit solute transfer across the abdominal wall peritoneum during dialysis.