Enhanced Peritoneal Diffusion Capacity of ⁵¹Cr-EDTA during the Initial Phase of Peritoneal Dialysis Dwells: Role of Vasodilatation, Dialysate ‘Stirring’, and of Interstitial Factors

Abstract

Mass transfer area coefficients (PS) to small solutes are usually markedly increased during the first 0–15 min of peritoneal dialysis (PD) dwells. This phenomenon may be due to, for example, initial arteriolar vasodilatation and, hence, recruitment of capillary surface area. Other possibilities are an initial discharge (or saturation) of solutes from (in) the interstitium or an increased mixing, i.e., ‘macrostirring’ caused by the exchange procedure per se. We have investigated these possibilities during acute PD in rats, by assessing PS for ⁵¹Cr-EDTA as a function of time [PS(t)]. The discharge effect was studied by saturating the peritoneal interstitium with ⁵¹Cr-EDTA by intravenous tracer infusion prior to each dwell and the results compared to those obtained in rats when tracer infusion and dwells were started simultaneously. The potential effect of initial vasodilatation was studied by adding isoproterenol to the dialysis fluid. Finally, the potential influence of an increased interstitial ‘microstirring’, induced by high glucose concentrations, was investigated by comparison of results for 1.36% Dianeal^® with those for 3.86% Dianeal. In nonvasodilated rats there was a significant drop in PS(t) between 2.5 and 15 min regardless of whether the rats were preloaded with tracer or not. However, there were no significant changes in PS(t) within the isoproterenol-treated group, indicating that vasodilatation plays a crucial role for the high PS initially. Furthermore, there was no difference in overall PS for ⁵¹Cr-EDTA among 1.36 and 3.86% Dianeal dwells. In conclusion, we have found that vasodilatation, but not interstitial discharge (or loading), may explain the inflation of PS occurring during the initial part of PD dwells. In addition, ‘macrostirring’, induced by the exchange procedure per se, may also be important.

Physiological Properties of the Peritoneum in an Adult Peritoneal Dialysis Population over a Three-Year Period

“…The area parameter (A 0 /Δx) reflects the amount of capillaries available for exchange. Initially during a dwell, there is vasodilatation and recruitment of capillaries (32). Studies in patients on automated PD revealed that this transient vasodilatation is pronounced (15).…”

Glycine improves peritoneal vasoreactivity to dialysis solutions in the elderly

“…20–22 Carlsson and Rippe proposed that PDS-induced vasodilation is a plausible explanation for the observed increase in the mass transfer area coefficient of small solutes during the initial phase (2–15 minutes) of the dwell compared to the transport rate during the subsequent dwell time. 23 However, PDS-mediated dilation is not restricted to the initial phase of the dwell, and it is sustained for as long as the peritoneal tissue is in contact with PDS. Therefore, variations in small solute transport during the dwell time are also subjected to different concentration gradients during the dwell time.…”

The Peritoneal Microcirculation in Peritoneal Dialysis

“…A marked increase in blood flow usually occurs at the start of the dialysis dwell, as has been measured in the most superficial part of the peritoneum using microsphere techniques (27). The practical consequences of this initial vasodilatation during peritoneal dialysis is that solute transport is usually enhanced (by 50% to 70%) during the first half hour of the dialysis period (10,65,88). The initial hyperemia may be explained by the vasodilatory effect of the hyperosmolality of conventional dialysis fluids, their low pH, and particularly, the presence of high concentrations of lactate used as a dialysate buffer (52,63).…”