Hypervolemia suppresses dilutional anaemic injury in a rat model of haemodilution.

Background and Objectives: Haemodilution leads to complications in clinical practice. It is exactly unknown whether this damage is caused by the fluid or by the stretching of the vascular bed. We aimed to compare two different haemodilution techniques at the same anaemic level. Methods: Normovolemic or hypervolemic haemodilution was performed on twelve adult male Wistar rats. In the normovolemic procedure, blood was withdrawn and instantaneously administered with similar amounts of 6% hydroxyethyl starch (HES 130/0.4). Fluid was administered without withdrawing blood in the hypervolemic procedure. In both models, a 25% haematocrit level was targeted and kept at this level for 90 min to deepen the anaemia effect. Besides haemodynamics measurement, renal function (creatinine, blood urea nitrogen) and injury (tissue norepinephrine, malondialdehyde) were evaluated. Also, systemic hypoxia (lactate), oxidative stress (malondialdehyde, ischaemia-modified albumin), inflammation (tumour necrosis factor-alpha [TNF-α]), osmotic stress, adrenal stress (norepinephrine, epinephrine), and vascular stretching (atrial natriuretic peptide [ANP]) were assessed. Results: Arterial pressure in the normovolemic group was lower than in the hypervolemic group. Serum creatinine, blood urea nitrogen, and lactate levels were higher in the normovolemic group. Tissue norepinephrine and malondialdehyde levels were higher in the normovolemic group. Serum ANP, malondialdehyde, ischaemia-modified albumin, free haemoglobin, syndecan-1, and TNF-α were higher in both groups compared to respective baseline. Conclusions: Normovolemic haemodilution may lead to hypoxic kidney injury. The hypervolemic state may be advantageous if fluid is to be administered. Thus, the effect of the fluid itself can be relatively masked.