Antithrombotic Therapy in Children: Thrombolytic Agents
In older children, aspirin rarely causes clinically important hemorrhage, except in the presence of an underlying hemostatic defect or in children also treated with anticoagulants or thrombolytic therapy so buying antibiotics online. The relatively low doses of aspirin used as antiplatelet therapy, as compared to the much higher doses used for anti-inflammatory therapy, seldom cause other side effects. For example, although aspirin is associated with Reye’s syndrome, this appears to be a dose-dependent effect of aspirin.
Treatment of Bleeding Due to Antiplatelet Agents: It is unusual for antiplatelet agents alone to cause serious bleeding. More frequently, antiplatelet agents are one of several other causes of bleeding, such as an underlying coagulopathy and antithrombotic agents. Transfusions of platelet concentrates and/or the use of products that enhance platelet adhesion (plasma products containing high concentrations of von Willebrand factor), or D-des amino arginine vasopressin may be helpful.
Mechanism of Action of Thrombolytic Agents: The actions of thrombolytic agents are mediated by converting endogenous plasminogen to plasmin. At birth, plasma concentrations of plasminogen are reduced to 50% of adult values (21 mg/100 mL). The decreased levels of plasminogen in newborns slows the generation of plasmin and reduces the thrombolytic effects of streptokinase (SK), urokinase (UK) and tissue plasminogen activator (tPA) in an in vitro fibrin clot system. A similar response occurs in children with acquired plasminogen deficiency. Supplementation of plasmas with plasminogen increases the thrombolytic effect of all three agents.
Contraindications: There are well-defined contraindications to thrombolytic therapy in adults. These include a history of stroke, intermittent cerebral ischemic attack, other neurologic disease and hypertension. It seems prudent to consider similar problems in children as relative contraindications to thrombolytic therapy.
Therapeutic Range and Monitoring of Thrombolytic Agents: There is no therapeutic range for thrombolytic agents. The correlation between hemostatic parameters and the efficacy/safety of thrombolytic therapy is too weak to have useful clinical predictive value. In patients with bleeding, however, the choice and doses of blood products used can be guided by appropriate hemostatic monitoring. The most useful single assay is the fibrinogen level, which usually can be obtained rapidly and helps to determine the need for cryoprecipitate and/or plasma replacement. A commonly used lower limit for fibrinogen level is 100 mg/dL. The APTT may not be helpful in the presence of low fibrinogen levels, concurrent heparin therapy, and presence of fibrin/fibrinogen degradation products. Measurement of fibrin/fibrinogen degradation products and/or D-dimers are helpful in determining whether a fibrinolytic effect is present.