Changes in circulating blood and plasma volume after hemoglobin-based oxygen carrier infusion and additional infusion of colloid solutions

The aim of this study was to investigate the changes in circulating blood volume (CBV) after infusions of Hemoglobin glutamer-200 (bovine; Hb-200) in combination with 6% hetastarch in an animal model of acute posthemorrhagic anemia. Fifteen rabbits with a mean body weight of 2.2 +/- 0.2 kg were studied. After determination of the circulating plasma volume (CPV) and CBV, one third of the CBV was withdrawn via an arterial catheter. An equal volume of Hb-200 was then infused in the 5 animals in study group 1. In the remaining 10 animals, the same volume of 6% hetastarch solution was infused. Fifteen minutes after completion of the infusion, an additional infusion of 6% hetastarch at a dose equal to one third of the baseline CBV was performed in study group 1 and the control group. In study group 2, equal volumes of Hb-200 were infused. CPV measurements were performed at baseline, after hemorrhage, 5 and 15 minutes after volume replacement, and 1 and 15 minutes after hypervolemic hemodilution using the Evans blue dye dilution technique. The mean baseline CPV value was 53.4 +/- 1.1 mL/kg. The mean CBV at baseline was 90.8 +/- 4.9 mL/kg. After one third of the CBV was withdrawn, no differences in CBV or CPV were observed between the three groups. Replacement of one third of the CBV with Hb-200 significantly increased the CPV (73.7 +/- 1.8 mL/kg) when compared with the baseline level (53.5 +/- 1.8 mL/kg; n = 5; P < 0.05). The difference between the groups was first observed 15 minutes after infusion. CPV was significantly higher in study group 1 (87.0 +/- 2.2 mL/kg) compared with the other groups (80.2 +/- 2.6 mL/kg in the control group and 79.5 +/- 3.6 mL/kg in study group 2). After a second transfusion, the differences between the groups became more prominent. Study group 2 demonstrated the highest CPV and CBV. The two study groups demonstrated a statistically significant increase in circulating volumes compared with the control group. The magnitude of this difference was lower than expected based on in vitro colloid osmotic pressure measurements.