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

Warfarin for 3mo, 6 mo, 1 yr followed by aspirin Various strategies No aspirin or warfarin Lifelong Warfarin Lifelong aspirin Warfarin for 3mo, 6 mo, 1 yr followed by aspirin 3-6 mo aspirin