The Ability of Polyethylene Glycol Conjugated Bovine Hemoglobin (PEG-Hb) To Adequately Deliver Oxygen in Both Exchange Transfusion and Top-Loaded Rat Models

Abstract

The purpose of this study was to determine whether a six gram percent (g%) solution of the hemoglobin based oxygen carrier, polyethylene glycol conjugated bovine hemoglobin (PEG-Hb) could adequately deliver oxygen in both partial exchange transfusion and top-loaded rat models. This study measured tissue oxygen tension, circulatory retention and cardiovascular effects following both 30% exchange transfusion and 20 to 25 mL/kg top-loaded infusions of PEG-Hb. Oxygen delivery to rat tissues was determined using an oxygen dependant phosphorescence quenching method (Oxyspot®). Telemetric intravascular blood pressure probes monitored heart rate and mean arterial pressure. In both models, six g% PEG-Hb (P₅₀ - 15 torr) was shown to oxygenate tissue better than stroma-free bovine Hb (P₅₀ - 26 torr), cross-linked bovine Hb (P₅₀ - 48 torr) or simple plasma expanders. The mean circulatory half life of PEG-Hb was 15.0 ± 2.3 hours and 17.4 + 1.6 hours for exchange transfusion and 25 mL/kg top-loaded rat models, respectively. Mean arterial pressure (MAP) in PEG-Hb treated rats was insignificantly different from sham controls undergoing a 30% exchange transfusion or following a top-loaded infusion. In conclusion, the PEG conjugated form of bovine Hb with its relatively long vascular persistence may possess characteristics that facilitate tissue oxygenation in the rat.