Acute Normovolemic Hemodilution in the Pig Is Associated with Renal Tissue Edema, Impaired Renal Microvascular Oxygenation, and Functional Loss

Background: The authors investigated the impact of acute normovolemic hemodilution (ANH) on intrarenal oxygenation and its functional short-term consequences in pigs. Methods: Renal microvascular oxygenation (mu Po-2) was measured in cortex, outer and inner medulla via three implanted optical fibers by oxygen-dependent quenching of phosphorescence. Besides systemic hemodynamics, renal function, histopathology, and hypoxia-inducible factor-1 alpha expression were determined. ANH was performed in n = 18 pigs with either colloids (hydroxyethyl starch 6% 130/0.4) or crystalloids (full electrolyte solution), in three steps from a hematocrit of 30% at baseline to a Results: ANH with crystalloids decreased mu Po-2 in cortex and outer medulla approximately by 65% (P < 0.05) and in inner medulla by 30% (P < 0.05) from baseline to H3. In contrast, mu Po-2 remained unaltered during ANH with colloids. Furthermore, renal function decreased by approximately 45% from baseline to H3 (P < 0.05) only in the crystalloid group. Three times more volume of crystalloids was administered compared with the colloid group. Alterations in systemic and renal regional hemodynamic Conclusions: ANH to a hematocrit of 15% statistically significantly impaired mu Po-2 and renal function in the crystalloid group. Less tissue edema formation and an unimpaired renal mu Po-2 in the colloid group might account for a preserved renal function.