Risk Factor Analysis of Inadequate Heparin Response in Pediatric Cardiac Surgery

Abstract

Objectives: To identify risk factors associated with inadequate heparin response in pediatric congenital heart surgery requiring cardiopulmonary bypass and to develop age-specific predictive scoring systems. Design: Retrospective cohort study. Setting: Tertiary medical center. Participants: Pediatric patients (age <18 years) undergoing congenital heart surgery on cardiopulmonary bypass between December 2022 and May 2024. Interventions: None. Measurements and Main Results: Inadequate heparin response was defined as an activated clotting time of <400 seconds following our institutional standard weight-based heparin bolus dose (300 units/kg in neonates; 350 units/kg in non-neonatal patients). Separate risk scores were developed for neonates and non-neonates. Among 1,746 surgical procedures, inadequate heparin response was observed in 220 (12.6%). In the non-neonatal cohort, the incidence was 10.4% (n = 159) and was associated with surgical urgency, higher platelet count (≥380 K/µL), and higher absolute neutrophil count (≥4.6 K/µL). In the neonatal cohort, inadequate heparin response occurred in 61 (28.8%) of cases and was associated with lower hematocrit (<43%), lower absolute neutrophil count (<8.6 K/µL), and higher fibrinogen level (≥185 mg/dL). The non-neonatal risk score demonstrated fair discrimination (area under the curve 0.775), while the neonatal risk score demonstrated good discrimination (area under the curve 0.827). Conclusions: Inadequate heparin response is common in pediatric cardiac surgery. Factors associated with inadequate heparin response were identified in both neonatal and non-neonatal pediatric cohorts, enabling the development of age-specific risk scores based on routine laboratory values and thus facilitating early risk stratification and tailored anticoagulation strategies. These findings may be a surrogate of underlying coagulation pathology; further investigation is needed to delineate the fundamental pathophysiology.