Effects of viscogenic plasma expander on cardiac and vascular function

Lowering the amount of red blood cells (RBCs) caused by blood losses or anemia leads to the reduction of tissue oxygenation and anaerobic metabolism, ultimately inducing multi-organ dysfunction. Plasma expanders (PEs) and blood are used sequentially to treat volume deficit. Recently, the systemic and microscopic recovery has been proposed to be related to the restoration of the viscosity of circulating blood to values prevailing during normovolemic conditions. Studies in an awake hamster window chamber showed that the viscosity of PE plays a role in microvascular function. High viscosity PEs (HVPEs) have been tested in conditions of hemorrhagic shock resuscitation and acute hemodilution, supporting the contention that the restoration of blood viscosity to normal value is beneficial in studies made in awake animals. Recent studies, in awake animals, have shown that polyethylene glycol conjugated to human serum albumin (PEGHSA) can achieve the similar results caused by HVPEs. However, the effects of increasing plasma viscosity on the heart performance are insufficiently explored. The hypothesis of this study was that cardiac and vascular function is enhanced when plasma viscosity is increased even though the amount of RBCs decreases. Hemorrhagic shock resuscitation and acute hemodilution protocols were performed to test this hypothesis. Cardiac function was assessed in the left ventricle with a pressure volume conductance catheter. As the modulation of plasma viscosity, the effects of shear stress-induced vasodilator, nitric oxide (NO), on cardiac function was examined. Furthermore, the effect of interaction of PE with endothelial glycocalyx on cardiac function was investigated. The results showed that HVPE and PEG-HSA demonstrated the beneficial effects on cardiac function in acute hemodilution by increased cardiac output, lowered systemic vascular resistance and sustained cardiac contractility. However, HVPE did not show any enhancement on cardiac function in hemorrhagic shock resuscitation. There was a contribution of increased NO to the beneficial effects on cardiac function as observed in the acute hemodilution with low viscosity PE. It also revealed that PEG-HSA and HVPE interacted with endothelial glycocalyx with different mechanism but they showed similar results in cardiac function, implying an important role of endothelial glycocalyx in cardiac and vascular functio