Appropriate Dose of Postoperative Intravenous Heparin Infusion in the Children undergoing Modified Blalock Taussig Shunt 4 mm and below in Size
Sanphasitvong V, MD1, Tocharoenchok T, MD1
Affiliation : 1 Division of Cardio-Thoracic Surgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
Background : Modified Blalock-Taussig shunt is the most common palliative systemic to pulmonary artery shunt performed in
cyanotic congenital heart disease. Shunt thrombosis occurred in 1 to 17% of the operation that led to mortality. One major risk
factor is a small shunt size under 4 mm. Systemic heparinization is a preventive measure for this subgroup with a cost of a bleeding
complication. However, there is no standard dose for heparin infusion. The objective of this study is to determine the appropriate
dose of heparin infusion to achieve APTT ratio of 1.5 to 2.
Materials and Methods : During 2007 to 2016, 220 patients who underwent off-pump modified Blalock-Taussig shunt of 4 mm and
below in size at Siriraj Hospital were studied. After exclusion of the patients with pre-operative coagulopathy (APTT >30.5 sec), out
of target APTT ratio and missing data, 60 patients were included. Demographic data, operative parameter, heparin infusion dosage,
postoperative complications such as shunt thrombosis and postoperative bleeding were analyzed.
Results : Appropriate heparin infusion dose to achieve an APTT ratio of 1.5 to 2.0 was 18.27+8.84 unit/kg/hour. In the patient
weight less than 2.5 kg, heparin infusion dose was 14.25+4.92 unit/kg/hour and never exceed 20 unit/kg/hour. Shunt thrombosis
and bleeding complication were occurred in 11.7% and 8.3% of patients, respectively, without correlation to heparin dosage and
time to achieve therapeutic APTT ratio.
Conclusion : To achieve an APTT ratio of 1.5 to 2, postoperative intravenous heparin infusion should be 18 unit/kg/hour. A smaller
dose should be considered in low birth weight patients.
Keywords : Modified Blalock-Taussig shunt, Postoperative intravenous heparin infusion, Shunt thrombosis
