Stress-induced alterations in coagulation: assessment of a new hemoconcentration correction technique.

OBJECTIVE For the examination of psychological stress effects on coagulation, the Dill and Costill correction (DCC) for hemoconcentration effects has been used to adjust for stress-induced plasma volume changes. Although the correction is appropriate for adjusting concentrations of various large blood constituents, it may be inappropriate for time-dependent or functional coagulation assays. Two new plasma reconstitution techniques for correcting hemoconcentration effects on stress-induced changes in coagulation were compared with the DCC. METHODS Blood was collected from 31 men during baseline, the Trier Social Stress Test (TSST), and after 20-minute recovery. For the reconstitution techniques, TSST plasma samples were reconstituted with either baseline plasma or physiological saline equal to the amount of plasma lost during stress. RESULTS Uncorrected activated partial thromboplastin time (APTT) decreased, whereas fibrinogen, factor VIII clotting activity (FVIII:C), D-dimer and prothrombin time (PT%) increased significantly during the TSST. The DCC produced a significantly greater decrease in APTT during stress compared to uncorrected APTT, a significant decrease in PT% compared to uncorrected PT%, and stress D-dimer and fibrinogen and FVIII:C being no different than baseline. APTT, fibrinogen, D-dimer and PT% after saline reconstitution were not different from baseline, whereas FVIII:C after saline reconstitution remained elevated. APTT, PT%, fibrinogen and D-dimer after plasma reconstitution were no different from uncorrected values, whereas FVIII:C remained significantly elevated. CONCLUSIONS The observed changes in coagulation are likely in part a consequence of stress and hemoconcentration, but the DCC seems to be an inappropriate hemoconcentration correction technique of time-dependent assays. The saline reconstitution technique may be more biologically relevant when examining stress-hemoconcentration effects on coagulation.