Abstract: Cryoprecipitate for the production of factor VIII is extracted from frozen blood plasma by continuously circulating the plasma in a crushed state between the peripheral and central regions of an externally, steadily heated thawing zone, with thawed mixture of liquor and cryoprecipitate being removed from the lowermost region of the zone by way of a path including a weir configuration. Preferably: the zone is formed by an axially upright cylindrical vessel; circulation is effected by at least one helical blade coaxially rotatable in the vessel, which blade extends over the vessel heights, is radially narrow compared to the vessel, is close to the vessel wall, and scoops material upwardly; the outlet from the vessel is tangentially opposed to the blade rotation; and heating is by way of a liquid jacket with generally axial flow therethrough.

Abstract: The present invention relates to the reduction of the fibrinogen concentration in cryoprecipitate fraction formed during the fractionation of blood. This zinc-mediated decrease of fibrinogen increases the ratio of Factor VIII to total protein content.