• Rebecca Cardigan, Katherine Philpot, Philip Cookson, and Roger Luddington.
• NHS Blood & Transplant, Long Road, Brentwood, Cambridge, UK. cardigan@nbs.nhs.uk
• Transfusion. 2009 Apr 1;49(4):696-703.

BackgroundMethylene blue (MB) treatment of plasma is known to reduce the activity of clotting factors, but its effect on thrombin generation and clot formation is not well documented.Study Design And MethodsIndividual clotting factors and inhibitors and global tests of thrombin generation and clot formation using rotational thrombelastometry (ROTEM) were assessed in a paired study of standard or MB plasma and cryoprecipitate (n = 20 each).ResultsMB treatment resulted in a 10 percent reduction in endogenous thrombin potential and 30 percent decrease in peak thrombin as well as the expected 20 to 35 percent loss of Factor (F)VIII, fibrinogen, and FXI activity. MB treatment had no effect on the rate of clot formation and increased the clot firmness by 20 percent as assessed by ROTEM. There were minimal further changes in either coagulation factor levels or thrombin generation when thawed plasma was stored for an additional 24 hours. FVIII and fibrinogen content of MB cryoprecipitate was reduced by 30 and 40 percent, respectively, but this was not associated with altered clot time or rate of clot formation by ROTEM and only an 8 percent decrease in clot firmness.ConclusionsIt is concluded that MB treatment is associated with a reduction in the thrombin-generating capacity of plasma, but has very little effect on the strength of clot formation as assessed by thrombelastometry. The thrombin-generating capacity of standard and MB plasma is relatively unaltered by subsequent storage of thawed plasma at 4 degrees C for 24 hours.

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