Effects of pyridoxalated polyhemoglobin and stroma-free hemoglobin on ADP-induced platelet aggregation

Although polyhemoglobin produced from homologous sources is not immunogenic when utilized in vivo (1), effects on hemostasis and thrombosis have not been documented. In this study, we use rat platelet rich plasma (PRP) and light transmission aggregometry to measure the possible influence of stroma-free hemoglobin (SFHb) and pyridoxalated polyhemoglobin (PP-PolyHb) on platelet aggregation in response to various levels of adenosine triphosphate (ADP) activation in vitro. Our study demonstrates that PP-PolyHb and SFHb solutions, when added to PRP in volumes and concentrations likely to be administered to patients requiring perfusant therapy, do not initiate or facilitate platelet activation. Both solutions induce similar levels of aggregation (and presumably activation) inhibition, but do so only at high or maximal levels of ADP activator stimulation, late in the aggregation sequence. The apparent inability of the purified hemoglobins to stimulate platelets is a necessary characteristic if such preparations are to be used as clinical perfusants in hemorrhagic emergencies.