Cold-promoted activation of factor VII: is It a problem under blood bank conditions?

Transfusion of blood or plasma kept at 4 degrees C for 12-14 h could be hazardous since about 15% of plasmas from healthy donors undergo cold activation of factor VII under such conditions. In this study we were unable to demonstrate in plasma from 209 healthy donors a significant rise in mean factor VII level after storage of plasma in the blood bank bags at 4 degrees C for 24 h. The blood bank unfavorable conditions for cold activation of factor VII were manifested in the plasma from a known cold activator whose plasma underwent cold activation in a plastic test tube while in the blood bank bag it did not. The lack of cold activation observed in blood bank versus laboratory conditions did not stem from differences in anticoagulant, in speed of centrifugation, in proportion anticoagulant-blood or in the plastic ware; it appeared to stem from differences in the ratio between plasma volume and surface of the containers used in the blood bank versus the laboratory. Since plasma factor VII from 3 out of 16 women taking contraceptives became activated in the cold even at relatively small surface exposure it seems advisable to separate and freeze as fast as possible plasma components from blood donated by women on contraceptives.