Hemoglobin solution: a potential oxygen transporting plasma volume expander

The potential of a 6% stroma-free human hemoglobin solution (WXb8326) as a plasma volume expander with oxygen transport capabilities was evaluated in barbiturate-anesthetized spontaneously breathing dogs. WXb8326 compared favorably with dextran-70 and 5% albumin solution as a plasma volume expander. Serial phlebotomies to a blood pressure of 35 mm Hg and immediate replacement with the above colloid expanders showed that only WXb8326-exchanged dogs survived acute reductions in hematocrit to critical levels of smaller than or equal to 5%. After several exchanges with WXb8326 to levels as low as 1%, it was possible to demonstrate acute survival. With less drastic reductions in the hematocrit (between 5 and 10%) all dogs survived acutely regardless of the type of plasma volume expander used; however, subacute survival rates varied. Oxygen transport characteristics during isovolumic hemodilution (phlebotomy and simultaneous replacement with WXb8326) were studied in a separate series of spontaneously breathing dogs in which hematocrit was reduced to approximately 50% of control. Oxygen content of erythrocytic hemoglobin (EHb) and extraerythrocytic hemoglobin (EEHb) resulting from infusions of WXb8326 was studied in arterial and venous blood at different levels of hemodilution. WXb8326 did not interfere with the arterial oxygen saturation of EHb in the pulmonary vascular bed and EEHb was oxygenated as efficiently as EHb. Oxygen delivery to tissues differed between EHb and EEHb. Erythrocytic hemoglobin met oxygen demands under basal conditions while EEHb contributed oxygen to tissues during conditions of high oxygen extraction. It is concluded that WXb8326 is an attractive condidate as a plasma volume expander with the capacity to transport oxygen to tissues.