Thrombus removal

Temporary Endovascular Bypass and Thrombus Removal with "Stentrievers"... 

Small, W., Metzger, M. R, Wilson, T. S., Maitland, D. J. (2005a), Laser-activated shape memory polymer microactuator for thrombus removal following ischemic stroke Preliminary in vitro analysis, IEEE Journal of Selected Topics in Quantum Electronics, 11, 892-901. 

The effectiveness of catheter-based intra-arterial therapy to remove residual thrombus after IV rt-PA treatment is being tested in the Interventional Management of Stroke study (IMS-Ill). This study will randomize patients to 0.6 mg/kg IV rt-PA, followed by angiography with additional intra-arterial therapy as indicated, or IV full-dose rt-PA (0.9 mg/kg). A nonrandomized safety study suggested that intraarterial therapy, after 0.6 mg/kg IV rt-PA, could be accomphshed with acceptable rates of sICH. ° ... 

Venous thrombectomy may be performed to remove a massive obstructive thrombus in a patient with significant iliofemoral venous thrombosis, particularly if the patient is either not a candidate for or has not responded to thrombolysis. Full-dose anticoagulation therapy is essential during the entire operative and postoperative period. These patients need indefinite oral anticoagulation therapy targeted to an INR of 2.5 (range 2.0 to 3.0). 

The time interval until the thrombotic occlusion of the vessel occurs and the thrombus size (wet weight measured immediately after removal at the end of the experiment) are determined. 

Thrombus size (mg) = wet weight of the thrombus immediately after removal. 

The test agent is administered by gavage or as an intravenous injection at a defined time prior to initiation of thrombus formation. Thrombus formation is induced by the application of filter paper (2x5 mm), saturated with 25 % I cCIs solution, to the carotid artery. The paper is allowed to remain on the vessel 10 min before removal. The experiment is continued for 60 min after the induction of thrombosis. At that time, the thrombus is removed and weighed. 

Thrombus formation is induced by inserting the thrombosis catheter into the caval vein via the V. iliaca (7 cm). Then the copper wire is pushed forward 3 cm to liberate the cotton threads into the vessel lumen. At 150 min after thrombus initiation, the caval segment containing the cotton threads and the developed thrombus will be removed, longitudinally opened and the content blotted on filter paper. After weighing the cotton thread with the thrombus, the net thread weight will be subtracted to determine the corrected thrombus weight. 

Embolism associated with long flights is generally due to thrombus formation in deep leg veins (deep-vein thrombosis, or DVT). The thrombus may move to the pulmonary circulation, where effects on lung function depend on the extent of the blockage produced. A massive embolus may occlude the main pulmonary artery, resulting in hypotension, shock and possibly death multiple small emboli cause little problem and are lysed by the fibrinolytic system. Sometimes surgical removal of the embolus is necessary, but in Pats/s case clot lysis was successful and she made an uneventful recovery. 

Q9 Fibrinolytic drugs, such as streptokinase, are given intravenously to lyse clots in the pulmonary circulation and coronary circulation. Occasionally, the thrombotic mass must be removed surgically. Streptokinase activates plasminogen to form plasmin, which degrades the fibrin in the thrombus. Heparin may be given intravenously to prevent further coagulation. 

It is doubtful whether this differs in its origins or sequelae from atrial fibrillation. The ventricular rate is usually faster (typically, half an atrial rate of 300, where 2 1 block is present), which is too fast to leave without treatment. Since, similarly, the patient is unlikely to have been in this rhythm for a prolonged period, there is less likelihood that atrial thrombus has accumulated. Conversion without prior anticoagulation may occasionally be considered safe but anticoagulation is usually also needed. Patients should not be left in chronic atrial flutter, and DC conversion will usually restore either sinus rhythm or result in atrial fibrillation. The latter is treated as above. Patients who fail to convert, or who revert to atrial flutter should be referred for consideration of radiofrequency ablation that is highly effective and may remove the cause of the atrial flutter > 80% of cases. 

Infective endocarditis is a serious complication of centrally placed venous access devices. The successful treatment in situ of a large thrombus associated with the tip of the catheter has been described (29). The antibiotic regimen was gentamicin and vancomycin, both delivered via the venous access device vancomycin was allowed to remain in situ between each 8-hourly dosing. This regimen successfully eradicated the thrombus within 3 weeks, without removal of the hue. 

Ultrasonography of a catheterized vein can help to identify thrombus formation. It is prudent to continue to check the vein for 2-3 days after catheter removal because thrombophlebitis may develop or become apparent in this period. 

Drugs to Remove a Pathogenic Thrombus or Embolus "Clot Busters"... 

Anticoagulants and thrombolytics, particularly warfarin, can systemically embolize cholesterol particles from aortic atherosclerotic plaques to small arteries and arterioles, including renal arterioles. These agents remove or prevent thrombus formation over ulcerative plaques, causing emboh. Cholesterol emboli induce an inflammatory obliterative vascular response, causing renal ischemia. Purple discoloration of the toes and mottled skin over the legs are important clinical clues. 

Feng et al. [139] studied the activity of TM reconstituted into the PEM/HBM assembly described in Sect. 2.1. TM is a type ITMP that is a receptor for thrombin and mediates protein C activity in anticoagulant and antiinflammatory pathways. TM functionalization represents a promising strategy to control thrombus formation on the surface of a biomaterial that comes into direct contact with blood, such as the inner surface of an arterial graft. TM was incorporated into vesicles of mono-acrylatePC (Fig. 1) that were then fused onto an amphiphilic terpolymer/PEM/glass coverslip (see Fig. 2). The eosin Y/triethanolamine method [56] was used to polymerize the lipids, after which the supported assembly could be removed from solution for characterization purposes. 

There are now two therapeutic avenues possible. One is to inhibit the clot or thrombus from forming (i.e., antithrombotic therapy). Drugs capable of doing this will be now considered. The second approach, which becomes necessary if the first and preferable method is not undertaken (or was unsuccessful), is to lyse the clots once formed with thrombolytic agents. In the case of coronary occlusions surgical intervention (bypass) or angioplasty ( balloon ) may physically intervene to remove the thrombus. 

Thrombus formed on central rod is removed and the composition measured. In experiments to evaluate the effect of shear, the rod was made of polypropylene. In other experiments, segments of rod surface were coated with different materials or vein segments placed on the rod (7). 

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