Blood flow does not limit peritoneal transport

Abstract

Objective: We investigated the assumption that blood flow to the microvessels underlying the peritoneum does not limit solute or water exchange between the blood and the dialysis fluid. Design: Small plastic chambers were affixed to the serosal side of the liver, cecum, stomach, and abdominal wall of anesthetized rats. Solutions that contained labeled solutes or that were made hypertonic were placed into the chambers, which restricted the area of transfer across the tissue to the base of the chamber and which permitted calculation of mass or water transfer rates on the basis of area. The local blood flow was monitored continuously with a laser Doppler flowmeter during three periods of observation: control, after 50%-70% reduction of the blood flow, and postmortem. Results: Urea transfer across all serosa, except for the liver, showed no difference in mean mass transfer coefficient (cm/min) between control (0.0038-0.0046) and after 70% flow reduction (0.0037-0.0040), but demonstrated a significant decrease with blood flow equal to zero (0.0020). These tissues demonstrated small but insignificant decreases in osmotic water flow into the chamber (0.7-0.9 μL/min/cm2 under control conditions versus 0.4-0.7 μL/min/cm2 with reduced blood flow). The liver demonstrated limitations in water and solute transport with a 70% decrease in blood flow. Conclusion: Because the liver makes up a small part of the peritoneal area, we conclude that large drops in blood flow do not limit overall solute or water transfer across the peritoneum during dialysis, and therefore acute peritoneal dialysis may be an appropriate modality for ICU patients in shock and renal failure.