Blood coagulation changes during effective thrombolysis using urokinase and heparin

Combined effects of urokinase and heparin on PTT values during thrombolytic therapy

The local infusion of urokinase may be complicated by hemorrhage. Except for maintaining fibrinogen levels above 100 mg/dL, no other criteria exist for titrating the dose of urokinase to avoid hemorrhagic complications. A retrospective examination of the fibrinolytic and coagulation states was performed on 11 patients receiving local high-dose urokinase (240,000 U/hr) and heparin for thrombolysis of acute occlusions to identify parameters other than fibrinogen levels that may correlate with bleeding complications. Five patients experienced bleeding complications, 3 of whom had partial thromboplastin time (PTT) values greater than 150 seconds. None of the five patients having hemorrhagic complications had fibrinogen levels below 100 mg/dL at any time. Urokinase began to enhance the effect of heparin on PTT values as a result of reducing fibrinogen levels. In 10 of 11 patients this effect caused PTT values to at least double when compared with heparin alone. This substantial rise in PTT occurred only after fibrinogen levels approached 200 mg/dL in 8 of 11 patients. Although the number of patients is small, these data suggest that when heparin is used during thrombolysis, closer PTT monitoring should be carried out as fibrinogen levels begin to decline, especially when they approach 200 mg/dL, to avoid excessive PTT elevations and subsequent bleeding.

A novel, stable high molecular weight urokinase: preliminary results

In this study, we successfully performed local thrombolysis in 6 patients with peripheral arterial occlusions by using a novel high-molecular-weight urokinase. Mean duration of recanalization was 12.8 hours, mean fibrinogen consumption was relatively low (42%), reptilase time was relatively long (mean increase by 47%). These findings would suggest that the substance is highly effective, though systemic adverse reactions are mild.

Protective activity of defibrotide against lethal acute myocardial ischemia in the cat

Defibrotide (D) is a natural polydeoxyribonucleotide from mammalian lungs with profibrinolytic and antithrombotic activities. D also has PGI2-stimulating and tissue plasminogen activator (TPA)-releasing activities, but has no anticoagulant properties. The protective effects of D were demonstrated very recently in a model for non-lethal ischemia in the cat. In the experiments reported here Defibrotide was tested in a model for acute myocardial ischemia leading to ventricular fibrillation (VF) and death of the cat. Occlusion of the coronary artery (LAD) at its origin induced VF and death in 17 of 20 control cats. When cats were treated with D (32 mg Kg-1, bolus i.v., + 32 mg Kg-1 h-1, i.v., after LAD occlusion) 19 of 20 animals survived until the end of experiments. D also prevented changes in plasma and myocardial CPK, hemodynamics and ECG. D was compared with a variety of pharmacological agents which are used clinically for specific cardiovascular diseases. The ability of D to promote considerable generation of PGI2 from vascular walls plus its ability to prevent the decreases in CPK-activity and ATP in the myocardial tissue may have roles in its beneficial effects against ischemic heart in the cat. However, the mechanism/s of the substantial protective effect of D against cardiac death has still to be clarified.

Effects of plasmin on von Willebrand factor multimers. Degradation in vitro and stimulation of release in vivo

von Willebrand factor (vWF), a multimeric protein that mediates platelet adhesion, circulates in association with the procoagulant Factor VIII (FVIII). In previous reports, plasmin was shown in vitro to inactivate FVIII and cleave the vWF subunit extensively, but to cause only a modest decrease in vWF platelet-agglutinating activity. In the present study, the digestion of vWF multimers by plasmin was analyzed by sodium dodecyl sulfate-agarose gel electrophoresis and radioimmunoblotting. In vitro, plasmin degraded the large vWF multimers to smaller forms that could be distinguished from the small multimers present before digestion only by a slightly increased electrophoretic mobility. These plasmin-cleaved "multimers" were composed of disulfide-linked fragments with no intact vWF subunits. Thus, many plasmin cleavages occur within disulfide loops. The slight increase in mobility of plasmin-digested vWF is in part explained by the early cleavage from the multimers of a 34,000-mol wt peptide, which was purified and partially sequenced. The amino-terminal sequence (33 residues) agrees with the previously reported sequence (15 residues) for the amino terminus of the intact vWF subunit. Analysis of plasmin-digested vWF allowed deduction of a model for the native vWF structure, including the approximate location of the interprotomer disulfide bond(s). To determine whether plasmin would digest vWF in vivo, plasmas from 12 patients and 2 normal volunteers who received intravenous streptokinase (SK) were analyzed. Rather than vWF digestion, a two- to threefold rise in vWF antigen and platelet-agglutinating activity occurred within 2 h after a single SK dose, and the increase was greatest among the largest multimers. In contrast, FVIII clotting activity dropped to 10-20% of pre-SK levels. Thus, although plasmin destroys FVIII, a pharmacologically induced fibrinolytic state is associated with significant release of vWF from endothelial cells, platelets, or some other storage pool.

Thrombolytic therapy of acute deep vein thrombosis of the lower limbs: choices, indications and limits

Thrombolytic agents are the treatment of choice of acute deep vein thrombosis of the lower limbs. Streptokinase and urokinase are equally effective. Occlusive and non-occlusive thrombi of the proximal veins should be treated as early as possible with streptokinase and urokinase given at fixed dosages for no less than three days. Hemostasis tests are not strictly necessary to monitor thrombolytic treatment or to predict its outcome.

[Fibrinolytic therapy of lower limb deep vein thrombosis with urokinase (author's transl)]

In 81 patients with deep vein thrombosis of the lower limb, urokinase therapy was performed in combination with heparin according to a new regimen at higher dosages. When urokinase was administered at an initial maintenance dosage of 1,000-2,000 IU/kg/h (loading dose 150,000-250,000 IU), phlebographically documented complete or partial recanalization could be observed in 68% of the cases. The higher dosage schedule induced a more pronounced deobliteration especially in treatment of iliac vein thromboses (67% recanalization) in comparison to the lower dosage regimen (only 43% recanalization). Nearly comparable therapeutic results could be achieved in therapy of popliteal or saphenous vein thromboses. The data suggest that the higher dosage schedule examined here is indicated in treatment of extensive and large volume thromboses. The dosage of urokinase was further adjusted to attain a reduction of fibrinogen to 50-100 mg/dl. The concentration should not fall below 50 mg/dl. Therapy with urokinase proved practicable. Serious side effects did not occur. 8.6% of the patients showed hematuria and 6% a decrease of the Hb by more than 2 g/dl. The high proportion of older thromboses and the only low rate of recanalization (23%) in these cases suggest the necessity of an early commencement of fibrinolyses in therapy of deep vein thrombosis.