225 The Use of Activated Clotting Time and Prothrombin Time to Predict the Heparin Dose in Paediatric Cardiac Patients on Venoarterial Extracorporeal Membrane Oxygenation Circuits

Abstract Aim Venoarterial extracorporeal membrane oxygenation (VA-ECMO) is a salvage intervention used to treat cardiorespiratory failure. Heparin is the main anticoagulation agent used to prevent clots within the lines and thus circuit failure, dosing is traditionally assessed using activated clotting time (ACT). We aimed to investigate the variables influencing circuit anticoagulation to predict therapeutic heparin dosing to reduce surgical re-exploration. Method A retrospective analysis of parameters (ACT, heparin, platelet and prothrombin time (PT)) used to identify bleeding at an early interval in paediatrics (N=10) patients on VA-ECMO at a single centre. The mean values of each variable for all samples taken during VA-ECMO for each patient when grouped by re-exploration due to bleeding or not. Results None of the patients experienced clots in the VA-ECMO circuit, suggesting an ACT between 146 - 165 was adequate for anticoagulation. There was a statistically significant difference between the mean ACT of each group, with those not requiring re-exploration having a mean 12.44 units higher than the re-exploration group (95% CI [6.17, 18.71] p<0.001) yet no statistically significant difference between platelet level between groups (p=0.098). PT and the off-set heparin dose were shown to have any predictive power of heparin dose using regression equations: Heparin dose=([Target ACT]-79-(5.2 ×[Prothrombin]))/0.4 Heparin dose=2.5 ×([Target ACT]-79-(5.2 ×[Prothrombin])). Conclusions The application of the formula has the potential to predict heparin dose in paediatric patients on ECMO which could help reduce the postoperative complication of returning to surgery due to rebleeding when extrapolated to a larger data set.