Heparin Dose Response Curve for Heparin Dose Determination During Paediatric Cardiopulmonary Bypass for Cardiac Surgery: A Prospective Randomised Control Study

Cardiac surgery/ Open Heart Surgery (OHS) using cardiopulmonary bypass (CPB) exposes blood to a large artificial surface, which creates a pro-coagulant state leading to thrombin generation. Intravascular catheters and cannulae cause disruption in laminar blood flow, which predisposes to clot formation. Systemic anticoagulation to prevent thrombus formation is necessary during CPB. Unfractionated heparin has been the most used anticoagulant for more than 70 years since the development of cardiopulmonary bypass (CPB).Optimum dosing of heparin is necessary because excess dose of heparin during CPB had already been identified as a major factor in excessive postoperative bleeding. Other adverse effects of heparin administration include anaphylactic and allergic reactions, thrombocytopenia, osteoporosis, skin necrosis and hypoaldosteronism.

In children who undergo CPB, restoration of hemostasis following surgery with CPB is more difficult. Hemodilution, hypothermia, low flow, circulatory arrest and the age-related differences in the coagulation system, responses to heparin and protamine, hemostatic abnormalities, and polycythemia all contribute to the challenge.

To dose heparin, many of the protocols used in pediatrics have been extrapolated from adults without assessing the optimal heparin dose in pediatric patients of different ages and sizes.

Heparin dosing can be done by a weight-based (WB) or heparin dose ACT-curve response (HDR) method. The WB protocol calculates the dose based on the patient’s actual weight and uses an activated clotting time (ACT) test to ensure anticoagulation. The HDR method predicts the patient’s response to heparin by projecting a heparin dose–response (HDR) curve.

We have planned to conduct a prospective study of heparin dosing by heparin dose-ACT response curve (HDR method) and compare it with conventional weight-based (WB) method.

We hypothesise that heparin given by heparin dose-ACT response curve (HDR method) would provide accurate heparin dose before bypass indicated by attainment of target ACT in pediatric patients.