HEMOGLOBIN-BASED OXYGEN-CARRYING SOLUTION STABILITY IN EXTRACORPOREAL-CIRCULATION - AN IN-VITRO EVALUATION AND IMPLICATIONS FOR CLINICAL USE

This study evaluated the stability of a hemoglobin based oxygen carryi ng (HBOC) solution during extracorporeal circulation. HBOC solution wa s diluted 1:1 with normal saline, 2 L of the resulting solution was ox ygenated in either a bubble oxygenator (n = 5) or membrane oxygenator (n = 5), and it was placed in extracorporeal circulation at a rate of 2 L/min for 5 hr at 37 degrees C. To assess the effect of added human blood, 500 mi of fresh human whole blood was added to 1.5 L of diluted HBOC solution, and circulated as described. Methemoglobin level, hemo globin integrity (percent of HBOC solution tetramer), and oxygen affin ity (PO2 at 50% hemoglobin saturation) were measured. Extracorporeal c irculation using the bubble oxygenator slightly altered (<1%) hemoglob in integrity compared with controls. Oxygen affinity decreased during extracorporeal circulation with both the membrane and bubble oxygenato rs; there was no significant difference between the oxygenators. Methe moglobin formation in controls and in extracorporeal circulation with either oxygenator was significant, with a slight advantage of the memb rane compared with the bubble oxygenator; however, the presence of blo od significantly decreased the rate of methemoglobin formation. In the presence of blood, HBOC solution remains structurally stable and effi cacious for oxygen delivery during extracorporeal circulation.