The effect of increasing doses of rt-PA (Alteplase) in catheter relate
d thrombi in children was studied. The data suggest that optimal local
fibrinolytic treatment is realized at a systemic level of 0.80 ng/ml
of t-PA, which was reached with a dosis of 0.10 mg/kg hour directly in
fused via the affected catheter. After the introduction of rt-PA the l
evel of PAI-1 activity immediately fell below 2 IU/ml, whereas the amo
unt of PAI-1 antigen stayed at the same level throughout rt-PA treatme
nt.