Co-oximetry interference by hemoglobin-based blood substitutes

The blood substitutes now being developed from molecularly modified hemoglo bin interfere with a wide variety of clinical analyzers, but their effects on cooximeters are unknown. Therefore, we investigated the eff ec ts of fiv e hemoglobin-based blood substitutes on the measurements of eight different oximeters and cooximeters: the AVL Omni 6, the AVOXimeters 1000 and 4000, the Ciba Coming (now Bayer) CC270 CO-OximEter, the Instrumentation Laborato ry Synthesis 35, the IL482 and IL682 CO-Oximeters, and the Radiometer OSM3 Hemoximeter. The five blood substitutes in this study were obtained from Ap ex Bioscience (Research Triangle Park, NC), Baxter Healthcare Corp. (Deerfi eld, IL), Biopure Corp. (Cambridge, MA), Hemoglobin Therapeutics, and Hemos ol, Inc. (Etobicoke, Ontario, Canada). A cooximeter control was used to com pare the eight different instruments' measurements on unaltered human hemog lobin. The instruments yielded measurements of total hemoglobin concentrati on in undiluted blood substitutes that were generally not more variable tha n those on the control material. By contrast, when compared with readings o n controls, the test instruments yielded measurements of the fractional con centrations of oxy-, deoxy-, carboxy-, and methemoglobin that showed greate r instrument-to-instrument disparities and larger standard deviations about the all-instrument means. In some cases, the interference was even more ob vious: five of six cooximeters gave negative carboxyhemoglobin readings on one particular product. Our findings indicate that the instruments will giv e less accurate but clinically useful measurements in the presence of these hemoglobin-based blood substitutes.