Antithrombotic Properties of Heparin in a Neonatal Piglet Model of Thrombin-Induced Thrombosis

SummaryThe relative deficiency of antithrombin III (AT III) in neonatal plasma results in lower recovery of heparin in some assay systems. It is uncertain whether low AT III levels also limit the antithrombotic effects of heparin in this age group. We therefore compared the antithrombotic properties of heparin in mature pigs and newborn piglets, whose coagulation and inhibitor system closely resembles that of the human neonate. Animals were pretreated with saline, 10 or 25 U/kg heparin (n ≥16 per age group and dose). Following an injection of 100 U/kg thrombin, systemic 125I-fibrinogen consumption and local 125I-fibrinogen incorporation into jugular venous stasis thrombi were measured. Significantly more 125I-fibrinogen was consumed in piglets than in pigs systemically (p