Aortic thrombosis in a neonate: failure of urokinase thrombolytic therapy.

Complete aortic occlusion at L2-L3 occurred in an 11-day-old male with hypernatremic dehydration. Attempted thrombolytic therapy using intraarterial urokinase was unsuccessful in inducing either a systemic hyperfibrinolytic state or lysis of the clot. The infant's plasma plasminogen level was low (50-75% of adult levels) and neither fresh frozen plasma nor cryoprecipitate infusion provided adequate plasminogen replacement. Thrombolytic therapy failure was due in part to inadequate generation of plasmin. Alternative means of lytic therapy will need to be devised for this age group.