Use of plasminogen activators in venous thrombosis

Recombinant tissue plasminogen activator treatment of pulmonary embolism also improves deep venous thrombosis

Anticoagulants are the standard form of treatment used in deep vein thrombosis (DVT). Thrombolytic therapy is another method to treat thromboembolism by using intravenous administration of streptokinase, urokinase and recombinant tissue plasminogen activator (r-tPA). We have investigated the effect of r-tPA, a systemic thrombolytic used for the treatment of pulmonary emboli, on DVT in the same patients. 130 patients who were diagnosed with both pulmonary embolism and DVT were included in this study. Lower extremity Doppler ultrasonography (DUS) was conducted on all of the patients upon admission and then on the 6th month. The patients were divided into two groups. Patıents in Group 1 were initially given 100 mg thrombolytic (r-tPA) intravenously and then standard anticoagulation therapy (enoxaparin sodium and warfarin). Patients in Group 2, however, were given only standard anticoagulation therapy (enoxaparin sodium and warfarin). In the 6th month DUS follow-up control for Group 1, out of 66 cases, the venous thrombosis of 54 patients were completely resolved, and the remaining 12 patients had residual vein occlusion (RVO). In Group 2, out of 64 cases, 41 patients were found to have complete resolution, while 23 patients continued to have RVO. This difference was statistically significant (p=0.029). OR was calculated to be 2.47. In other words, the risk of RVO was increased by 2.47 times in the patients who were not treated with r-tPA. Thrombolytic therapy of DVT should be considered more frequently to avoid complications of thrombosis, and DUS monitoring should be recommended before discontinuing anticoagulant therapy.

Comparison of TNK with wild-type tissue plasminogen activator in a rabbit embolic stroke model

BACKGROUND AND PURPOSE

Tissue plasminogen activator (tPA) is an effective treatment for stroke, but its utility is limited by fear of cerebral hemorrhage. Tenecteplase (TNK), a genetically modified form of wild-type tPA, exhibits a longer biological half-life and greater fibrin specificity, features that could lead to fewer cerebral hemorrhages than wild-type tPA in stroke patients.

METHODS

We injected radiolabeled blood clots into the cerebral circulation of New Zealand White rabbits. One hour later, we administered tPA (n=57), 0.6 mg/kg TNK (n=43), 1.5 mg/kg TNK (n=27), or vehicle control (n=37). A blinded observer examined the brains for macroscopic hemorrhage using a semiquantitative score. We estimated thrombolysis by assessing the amount of radiolabel remaining in the cerebral vessels postmortem.

RESULTS

Both wild-type tPA and TNK caused thrombolysis in most subjects. Hemorrhage was detected in 26% (6/23) of the control group, 66% (27/41) of the wild-type tPA group, 55% (16/29) in the 0.6-mg/kg TNK group, and 53% (9/17) in the 1.5-mg/kg TNK group (P:<0.05, chi(2) test). The tPA group was statistically significantly different from the control group, but the TNK and tPA groups did not differ from each other. Neither TNK nor tPA affected the size of the hemorrhages.

CONCLUSIONS

TNK shows comparable rates of recanalization compared with wild-type tPA in a model of embolic stroke. While tPA increases hemorrhage rate, the hemorrhage associated with TNK treatment is not statistically different compared with controls or the tPA group. These findings suggest that TNK shows promise as an alternative thrombolytic treatment for stroke, but we could not demonstrate improved safety compared with wild-type tPA.

Venous thromboembolism in neurosurgery and neurology patients: a review

Thromboembolism is a common problem in neurosurgery and neurology patients. Within this diverse population are subpopulations of patients with varying degrees of thromboembolic risk: low, moderate, and high. Patients at substantial risk for deep vein thrombosis and pulmonary embolism include those with spinal cord injury, brain tumor, subarachnoid hemorrhage, head trauma, stroke, and patients undergoing a neurosurgical operation. There are prophylactic strategies that can be applied to these various risk groups that will dramatically reduce the incidence of thromboembolism. The risk of pulmonary embolism or fatal pulmonary embolism typically exceeds the risk of severe or fatal bleeding from adequate prophylaxis, and these techniques should be applied on a routine basis. To adequately care for patients with deep venous thrombosis and pulmonary embolism, the physician requires a thorough understanding of the methods of diagnosis, the pharmacokinetics of heparin and warfarin, and a knowledge of their role in the treatment strategies that have proven efficacy and safety. In addition, an awareness of the low molecular weight heparins and heparinoids is becoming essential. These new agents have a potentially promising role in both the prophylaxis and treatment of patients with neurological disease. The principles concerning the prophylaxis, diagnosis, and clinical management of venous thromboembolic disease in neurosurgery and neurology patients are dealt with in this review.