ACT variation after a weight-based heparin bolus before CPB is not predictable in infant

BackgroundIn pediatric cardiac surgery, anticoagulation protocols are derived from adult protocols. Age, Antithrombin III level, and capacity to generate thrombin are factors that affect unfractionated heparin (UFH) action in children. A starting UFH dose of 400 UI/kg is recommended to get an Activated Clotting Time (ACT) target over 400seconds. In our daily practice, we noticed a wide range of ACT increase (ΔACT) after this standardized weight based bolus of UFH.ObjectiveTo define factors affecting UFH effectiveness based on ΔACT before CPB initialization in pediatric cardiac surgery.MethodsA retrospective chart review of patient undergoing cardiac surgery requiring CPB in a single university hospital was performed. Patients receiving preoperative anticoagulation therapy or platelet aggregation inhibitors were excluded. We searched predictive factors for ΔACT. We defined 2 groups: hyperrespondents (HR; ΔACT>500) and normorespondents (NR; ΔACT<500).ResultsSeventy-nine charts were reviewed. Median [25–75] age and weight were respectively 13.8 [5–72] months and 8.7 kg [5.5–18.8]. UFH pre CPB bolus was 384 [358–410] to increase pre operative ACT from 124 [115–137] to 536 s[463–582]. HR are younger (4.9 [3.7–13] vs 24.6 [5.7–76] months, P<0.05) and have smaller weight (6,1 [4.6–7.8] vs 10 kg[5,8–19.5], P<0,05) than NR. ΔACT is correlated to UFH dose for patients>5 months (r=0.59 P=0.00001) and>5kg (r=0.54 P=0.00001) for with a predictive ΔACT of 386 s [325–443]. There is no correlation between ΔACT and UFH dose for patients<5 months and<5kg.ConclusionA dose UFH of 400 UI/kg before starting CPB in pediatrics is overestimated, especially for children<5 months and<5kg. Accurate dose for ACT target>400 s in this specific population should be calculated using other method that still needs to be developed to avoid complications associated to excessive dose of UFH