Blood gas analyses
The pH level was maintained above 7.35 in the HbV and RBC/PPP groups via respiratory compensation throughout the experiment, whereas the pH level in the HES group was significantly decreased below 7.35 at 45 and 60 min owing to a lack of haemoglobin (p <0.01) (Figure 3C). There were no significant differences in the base excess levels, the values of PaO2 and PaCO2 among all groups throughout the experiment, indicating that the respiratory function of the animals was well-preserved throughout the experiment (Figure 3D, Figure S2A, B). During the initial 30 min, the CtO2 (i.e. the sum of oxygen bound to haemoglobin) decreased to approximately 6.5 vol% in all the three groups. RBC transfusion or HbV infusion restored the CtO2 to 7.0-8.0 vol% in the RBC/PPP and HbV groups. In contrast, the CtO2 decreased to unmeasurable values at 60 min in the HES group (Figure 3E). Hence, lactate levels were maintained at approximately 3.0 mmol/L throughout the experiment in the HbV and RBC/PPP groups, whereas the lactate level in the HES group critically increased to 6 mmol/L at 60 min, which was significantly higher than that in the other groups (p <0.05) (Figure 3F). At the end of the experiment, the HCO3- level was higher in RBC/PPP group than in the other groups (p <0.05) (Figure S2C).