Hyperosmolality, acetate, and lactate: Dilatory factors during peritoneal dialysis

Abstract

Factors that alter peritoneal blood flow may influence the clearance of solutes during peritoneal dialysis. Arteriolar vasodilation, for instance, could increase the delivery of solutes to the capillaries and venules leading to an increase in solute transport into the peritoneal cavity. This study was designed to identify the vasoactive effects of several major components of McGaw and Dianeal peritoneal dialysis solutions to understand how the composition of these solutions may alter in vivo blood flow in the peritoneum. Because the major differences between these solutions and Krebs solution are a high osmolality, a high dextrose concentrations, and an acetate or lactate buffer system, we investigated the effects of these components. Rats were anesthetized with the combination of urethane and chloralose. The cremaster muscles, with the nerve and blood supplies from the rat still intact, was placed in a specially designed tissue chamber that was filled with Krebs solutions. A port permitted microscopic observations of the blood vessels. In vivo television microscopy observations was used to quantitate changes in small arteriole diameters induced by changes in the composition of the solution bathing the cremaster or by the addition of nitroprusside. Hyperosmolality produced by the addition of dextrose, sucrose, or sodium chloride to the Krebs solution induced a submaximal dilation of the small arterioles of the cremaster. The rate of dilation differed depending on the substance used to increase osmolality. A normal osmolality acetate (74 mM) or lactate (45 mM) solution produced a slow, submaximal dilation of the cremaster arterioles. Hyperosmolar acetate (37 or 74 mM) or lactate (45 mM) solutions produced a rapid, maximal dilation of these vessels. Because the rate of dilation and maximal effect produced by the commercial dialysis solutions were similar to these same parameters produced by the high-osmolality acetate or lactate solutions, the dilatory effects of McGaw and Dianeal solutions appear to be due to the combinations of high osmolality and the buffer anion acetate or lactate.

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

“…These factors are well-known vasodilators, expected to increase the 'effective' capillary exchange surface area early during the dwell [13]. The effects of PD fluid lactate and hyperosmolality on the microvasculature have been studied previously by Miller et al [14]. These authors found that the factors mentioned, especially lactate, indeed, acted as vasodilators.…”

Disparity in Osmolarity-Induced Vascular Reactivity

“…However, it seems that the magnitude of such reactivity is modified by the H ϩ concentration, ionic contents, and other vasoactive components of the solution such as lactate, as well as by the specific solute metabolic activity. Indeed, earlier intravital videomicroscopy studies of the rat's cremaster muscle have shown that the magnitude of arteriolar dilation evoked by hyperosmolar solutions of dextrose, sucrose, or sodium chloride was similar but that the dilation rate constant differs among the three hyperosmolar solutions (2). Other perfusion studies of the dog's forelimb (28) and cat's ileum (29) have found that both the magnitude and the time course of the dilatory effects of hyperosmolar dextrose and sodium chloride solutions differed significantly.…”

“…C onventional peritoneal dialysis solutions (PDS) dilate visceral and parietal microvasculature by mechanisms possibly related to hyperosmolality, low pH, and the buffer anion system of these solutions (1,2). Studies of hyperosmolar sodium solutions perfused into the intestinal lymph produced vasodilation of submucosal arterioles through a mechanism partially mediated by a hyperosmolality-induced nitric oxide (NO) release (3).…”

Recent Concepts in the Molecular Biology of the Peritoneal Membrane – Implications for More Biocompatible Dialysis Solutions

“…Conventional PD fluids possess vasoactive properties [70][71][72][73]. The causative mechanisms as well as the pathophysiologic consequences of this PD fluid-induced vasodilatation, in particular the potential acute effects on fluid and solute transport and long-term changes of peritoneal function and structure, are incompletely understood.…”