Category: Antithrombotic Therapy

Antithrombotic Therapy in Peripheral Arterial Occlusive Disease: Recommendations7.    Antithrombotic therapy should not be used to maintain patency of vascular reconstructions involving high-flow, low-resistance arteries greater than 6 mm indiameter. This is a grade Cl recommendation. However, for the same rationale provided in recommendation 3, life-long aspirin therapy should be considered in these patients to reduce long-term cardiovascular morbidity and mortality.
8.    Aspirin, 81 to 325 mg^d (with or witiiout dipyridamole, 75 mg three times daily) may be useful in patients having prosthetic, femoral-popliteal bypass operations, and antiplatelet therapy should be begun preopera-tively. This is a grade B1 recommendation. In addition, life-long aspirin should be continued for the same rationale provided in recommendation 3. …Read the rest of this article

Two randomized clinical trials have evaluated low-dose and high-dose aspirin for antiplatelet therapy administered in conjunction with peripheral PTA.’ Both studies showed equivalent 1- and 2-year patency rates with either a low dose (50 mg/d or 100 mg/d) or high dose (900 mg/d or 1,000 mg/d) of aspirin. GI side effects were greater in the high-dose groups. In another study, 100 patients with claudication treated with 100 mg aspirin daily were followed for 18 months after elective PTA, during which time platelet function was monitored by aggregometry. Only 40% of male patients demonstrated normal platelet inhibition on in vitro aggregation testing, and none of these 40% sustained occlusion of the angioplasty site. On the other hand, all eight occlusions that occurred by 18 months were in male patients who had inadequate platelet inhibition. These results suggest that some patients might require higher aspirin doses or alternative antiplatelet agents such as ticlopidine in order to achieve adequate platelet inhibition. …Read the rest of this article

Antithrombotic Therapy in Peripheral Arterial Occlusive Disease: Peripheral angioplastyThe combined use of aspirin and ticlopidine after coronary angioplasty and stenting appears to result in synergistic platelet inhibition compared to monotherapy with either agent; however, differences in clinical outcome were not shown in a trial that evaluated changes in platelet activation In a randomized clinical trial comparing ticlopidine and aspirin to aspirin alone in 226 patients undergoing PTCA with stenting, the rates of stent thrombosis and composite major clinical adverse events were higher in the group treated with aspirin alone (2.9% and 3.9%, respectively) than with combination therapy (0.8% and 0.8%, respectively), but these differences failed to achieve statistical significance Other investigators have shown a reduction in stent thrombosis using a combination of ticlopidine and aspirin compared with aspirin alone; however, the study was not randomized and few patients were in the aspirin-only group. flovent inhaler
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The mechanism of transluminal dilation of stenotic arteries involves overstretching of the arterial wall leading to longitudinal splits and fractures of the plaque and intima, with splits often extending into the media. Platelet-rich thrombi rapidly accumulate on areas of intimal disruption, and studies with indium-Ill-labeled platelets demonstrate marked uptake of labeled platelets at angioplasty sites. In experimental animals, platelet accumulation occurs at sites of angioplasty after 30 min, persists for hours, and is most excessive when there is increased histologic evidence of dissection. Theoretically, effective antithrombotic therapy could be expected to decrease thromboembolic complications associated with angioplasty and might reduce the incidence of recurrent stenoses. Scintigraphic studies with indium-ill-labeled platelets demonstrate that aspirin treatment prior to angioplasty in humans reduces platelet deposition at angioplasty sites. ventolin inhaler
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Antithrombotic Therapy in Peripheral Arterial Occlusive Disease: Protective effects of aspirinBased on these considerations, perioperative aspirin therapy, 80 to 650 mg twice daily, can be recommended in patients undergoing carotid endarterectomy. Therapy should be started at the time of clinical presentation and continued through the perioperative period. Bleeding complications, particularly wound hematomas, occur in 1.4 to 3.0% of patients undergoing carotid endarterectomy and are associated with incomplete reversal with protamine of intraoperative heparin, hypertension, and perioperative antiplatelet therapy. If intraoperative heparin is not fully reversed or continuous heparin anticoagulation is administered postoperatively, perioperative aspirin therapy would potentially increase the incidence of hematomas and other bleeding complications. …Read the rest of this article

In patients undergoing carotid endarterectomy, aspirin therapy may be an important adjunct. The goal of antithrombotic therapy in this setting is to prevent immediate, perioperative, and long-term neurologic complications stemming from thrombus formation at the endarterectomy site. Scintigraphic studies with indium-ill-labeled platelets document marked deposition of platelets at the endarterectomy site immediately after operation. The intensity of platelet accumulation decreases over time, possibly because of re-endothelialization of the endarterectomy site. In one study (level II), treatment of patients undergoing carotid endarterectomy with aspirin plus dipyridamole significandy decreased indium-111 platelet deposition and appeared to decrease the incidence of perioperative stroke. A much larger study assessing the benefit of aspirin therapy for longer periods after carotid endarterectomy has been reported (level I). …Read the rest of this article

Antithrombotic Therapy in Peripheral Arterial Occlusive Disease: Vascular surgeonsAmounts of heparin to achieve conventional systemic anticoagulation may not be adequate to prevent local clotting at the site of vascular reconstruction. This consideration, coupled with the highly variable response to heparin among patients undergoing vascular reconstruction, argues for relatively high-dose heparin therapy. Based on these considerations, a rational heparin regimen is to administer 100 to 150 U/kg IV prior to application of cross clamps and to supplement this every 45 to 50 min with 50 U/kg until cross clamps are removed and circulation is reestablished. The timing of the supplemental doses is based on the half-life of heparin (50 to 80 min). Alternatively, some surgeons routinely obtain baseline activated clotting times in the operating room and adjust heparin dosage to maintain a twofold prolongation of the activated clotting time. …Read the rest of this article