Coagulation responses of human plasma after hemodilution with hemoglobin solution in-vitro

To assess the potential for interference of Hb with the normal coagulation mechanism, we performed in-vitro hemodilution tests. Platelet rich plasma (PRP) was prepared from citrated blood samples of 5 normal volunteers diluted 3:1, 1:1, and 1:3 volume ratio with human stroma-free hemoglobin solution (SFH) or human albumin (HSA). Coagulation kinetics and clot strength were assessed with a thrombelastograph (TEG). Extrinsic and intrinsic coagulation factors were assessed measuring prothrombin time (PT) and activated partial thromboplastin time (aPTT) with an optical coagulation timer. Statistical significance was assessed using ANOVA and Neuman-Keuls tests at p < 0.05. At all dilutions, SFH diluted plasma showed significantly prolonged initial rate of clot formation compared to undiluted control or HSA (p < 0.05). However, there was no difference in formed clot strength between SFH and HSA. At high Hb concentrations Hb seems to interfere with the optical measurements of coagulation times (particularly aPTT). SFH appears to interfere with the initial phase coagulation mechanism in human plasma in-vitro; further study is needed to clarify the cause. In measuring coagulation times of plasma containing Hb a non-optical instrument should be considered.