Effects of a hemoglobin-based oxygen carrier (HBOC-201) and derivatives with altered oxygen affinity and viscosity on systemic and microcirculatory variables in a top-load rat model

• Top-load infusion of three polymerized hemoglobin-based oxygen carriers in rats
• Measured arterial pressure (MAP), arteriolar diameter and tissue oxygen tension (PO2)
• Explored effects of altered oxygen affinity (P50) and viscosity with HBOC derivatives
• Increasing doses of HBOC associated with increasing MAP and no change in diameter
• Interstitial PO2 unchanged except for decrease with high viscosity HBOC

The effects of a polymerized bovine hemoglobin-based oxygen carrier (HBOC) and two derivatives on arteriolar vasoactivity and tissue oxygen tension were explored by administering HBOC in a dose–response fashion to normovolemic rats. The effect of oxygen affinity (P50) and viscosity was also explored, where the P50 and viscosity of the parent compound (HBOC-201) and its modifications (MP50 and LP50A) were as follows: 40 mm Hg and 3.0 cP (HBOC-20 l); 18 mm Hg and 4.4 cP (MP50); and 17 mm Hg and 12.1 cP (LP50A). Anesthetized male Sprague–Dawley rats (N = 32) were randomized to receive one of the HBOC solutions, and were administered four infusions that increased in concentration for each dose (2, 22, 230 and 780 mg/kg, IV). Data were compared to rats receiving an equivalent volume for each of the four infusions (0.4, 0.4, 3.8, 13.1 ml/kg, IV) of iso-oncotic 5.9% human serum albumin (HSA). Increasing doses of either HBOC solutions or HSA were associated with increasing MAP. Doses 3 and 4 of HBOC-201, MP50 and HSA produced significant increases in MAP, whereas similar increases began at a lower dose (Dose 2) with LP50A. There were no significant changes in arteriolar diameters at any dose for any group. Interstitial partial pressure of oxygen (ISF PO2) remained unchanged for HBOC-201, MP50 and HSA, but LP50A caused a significant decrease in ISF PO2 compared to baseline after Doses 3 and 4. In conclusion, there was no evidence that HBOC-201 would perform better with increased oxygen affinity (40 to 18 mm Hg) or viscosity (3.0 to 4.4 cP).