Prevalence of heparin-dependent platelet antibodies in children after cardiopulmonary bypass.

OBJECTIVE: To determine the prevalence of heparin-dependent platelet antibodies (HDPA) in children requiring heparin for >5 days after cardiopulmonary bypass surgery. DESIGN: Prospective, observational study. SETTING: Tertiary care pediatric intensive care unit. PATIENTS: Thirty children were enrolled: 15 patients <30 days old and 15 patients between 30 days and 12 yrs of age. INTERVENTIONS: Detection of HDPA by heparin-platelet factor 4 enzyme-linked immunosorbent assay after 5-10 days of postoperative heparin exposure. Positive or equivocal results were confirmed with serotonin release assay. MEASUREMENTS AND MAIN RESULTS: There were no confirmed cases of HDPA in this study (95% confidence interval 0-11.6%). Despite the lack of HDPA, the study population was at high risk of thrombosis with symptomatic clot developing in six patients (20%). Clinical models developed in adults to determine the pretest risk of heparin-induced thrombocytopenia were not valid in this study population. CONCLUSIONS: The prevalence of HDPA in children after cardiopulmonary bypass surgery is low. After bypass surgery, critically ill children are at risk of developing thrombosis from multiple etiologies, and suspicion of heparin-induced thrombocytopenia needs to be confirmed with laboratory testing including a functional assay.