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The role of anticoagulation in venous shunts. - a brief overview. The use of heparin. Activates antithrombin III Typical regime – loading dose of 75-100 units/kg followed by 28units/kg/hr < 1yr, 20 units/kg/hr >1 yr and 18 unit/kg/hr in older children
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The role of anticoagulation in venous shunts - a brief overview
The use of heparin • Activates antithrombin III • Typical regime – loading dose of 75-100 units/kg followed by 28units/kg/hr < 1yr, 20 units/kg/hr >1 yr and 18 unit/kg/hr in older children • Monitoring using APTT (other methods are heparin concentration, anti Factor Xa levels, ACT levels)
LMWH • Longer t ½ • Administered sub-cutaneously • Lower side effects – thrombocytopenia and osteoporosis • Enoxaparin 1.5mg/kg 12h (<2mo) and 1mg/kg 12h (> 2mo) • Reviparin 150units/kg 12h (< 2 mo) and 100 units/kg 12h (> 2 mo)
Warfarin etc • Inhibits Vit K dependent clotting factors • Oral loading dose 0.2mg/kg then adjusted using INR • Various ranges • 2-3 for prophylaxis against TE • 2.5-3.5 for valves • 3-4.5 for recurrent TE at lower range • 1.4-1.9 not tested in kids
Aspirin • Decreases Platelet aggregation Aspirin+cyclo-oxygenase = TXA2 • Effect lasts for 7-10 days • 3-5mg/kg/day
Dipyridamole • Inhibits phospho-diesterase cAMP • 2-5mg/kg/day • Adjunct therapy in patients with mechanical valves
Pentoxiphylline • Enhances RBC flexibility, blood viscosity, platelet aggregation, TNFα • 20mg/kg/day • Used in • PVD with marginal improvement in PBF • Kawasaki
Glenn and Fontan • Use of prosthetic material • Presence of fenestration and R-L shunting • Incidence of TE events 5-33% (retrospective, TTE) • One partially prospective study showed TEE to be superior to TTE and showed an incidence of thrombus formation in 33% of patients.
Coagulopathies in Fontan • Liver derangements • Protein C, antithrombin III, Protein S, Plasminogen, Factors II, VII, IX, X, XIII • Factor VIII, plasmin-antiplasmin complex, activated partial thromboplastin time, thrombin- antithrombin III complex, D-dimer, Gamma GT, SGOT/PT
Risk factors for development of thrombus • Low post op saturations • Large fenestration • Discordant sized bilateral SVC • Atrial dysrhythmia
Various strategies No aspirin or warfarin Lifelong Warfarin Lifelong aspirin Warfarin for 3mo, 6 mo, 1 yr followed by aspirin 3-6 mo aspirin