Effects of crystalloids and colloids on microcirculation, central venous oxygen saturation, and central venous-to-arterial carbon dioxide gap in a rabbit model of hemorrhagic shock

Abstract

The effects of hydroxyethyl starch (HES) on microcirculation, central venous oxygen saturation (ScvO2), and the central venous-to-arterial carbon dioxide gap (dCO2) are studied in a rabbit model of hemorrhagic shock for elucidating the advantages and drawbacks of resuscitation with HES compared with crystalloids. An ear chamber and sublingual mucosa were used to examine blood vessels by intravital microscopy. Hemorrhagic shock was induced by removing nearly half of the blood volume. Twenty-two rabbits received 20mL of HES by intravenous infusion immediately after bloodletting. Additional HES was then administered intravenously to a total volume of 100mL. The other 22 rabbits (control) were intravenously given 40mL of normal saline solution (NSS), followed by additional NSS to a total volume of 200mL, administered under the same conditions as HES. After the infusion, the vessel density and perfusion rate of the sublingual microcirculation recovered in the HES group. The arteriolar diameter, blood flow velocity, and blood flow rate of the ear microcirculation were maintained in this group, and microcirculatory failure did not develop. In the NSS group, however, all 5 of the aforementioned measured variables were significantly smaller than those in the HES group after the completion of infusion. The recovery of ScvO2 and dCO2 to the respective baseline values was significantly better in the HES group than in the NSS group. Intravenous infusion of HES effectively maintains adequate tissue oxygenation and perfusion in hemorrhagic shock.