Umbilical artery catheterization in newborns. III. Thrombosis--a study of some predisposing factors.

Thrombosis following umbilical artery catheterization is a relatively frequent complication. Low fibrinolytic activity in the vessel walls, high factor VIII and low antithrombin III (AT III, Heparin cofactor activity) in blood are factors known to favour the formation of thrombosis. In 30 newborns who died and in 2 foetuses the fibrinolytic activity determined in the aorta and the femoral vessels was in the normal 'adult' range except for a few very immature infants and the foetuses. The five cases with arterial thrombosis were not associated with low fibrinolytic activity. The various factor VIII activities (VIII:C, VIIIR:Ag, and VIIIR:RCF) ant AT III were studied in 30 sick newborns and in 20 healthy newborns. The sick exhibited increased levels of various factor VIII activities (VIIIR:Ag and VIIIR:RCF mainly) and markedly reduced levels of AT III. The high factor VIII activities and the low AT III found will add to the existing risk of thrombosis due to the presence of a foreign material. AT III substitution is suggested as a possible prophylactic.