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An Insight Into a Potential Antithrombin-Independent Mechanism of Inadequate Heparin Response in Neonates and Infants
Sirintip Swangwong1, Kelsey Sullivan2, Erik Malm2
1Department of Anesthesiology, Critical Care and Pain Medicine, Boston Children's Hospital, Boston, MA; Department of Anaesthesia, Harvard Medical School, Boston, MA; Department of Anesthesiology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.
Journal of Cardiothoracic and Vascular Anesthesia
|July 1, 2026
Summary
Inadequate heparin response in infants undergoing cardiac surgery may be linked to lower levels of alpha2-macroglobulin and protein S, not just antithrombin. This finding impacts pediatric anticoagulant therapy.
Area of Science:
- Pediatric Cardiology
- Hematology
- Coagulation Science
Background:
- Inadequate heparin response is common in neonates and infants, particularly those undergoing cardiac surgery.
- Low antithrombin levels are traditionally cited as the cause, but this is not always the case.
- Limited data exists on comprehensive coagulation factor profiles in this population.
Purpose of the Study:
- To investigate the coagulation factor profiles associated with inadequate heparin response in neonates and infants undergoing cardiac surgery.
- To identify potential alternative causes beyond antithrombin levels for heparin resistance.
Main Methods:
- Prospective, single-center study conducted at a tertiary academic hospital in the United States.
- Included 30 neonates and infants undergoing cardiac surgery with cardiopulmonary bypass.
- Coagulation factor levels were analyzed and compared between patients with adequate and inadequate heparin response.
Main Results:
- Antithrombin levels were similar between groups with adequate and inadequate heparin response.
- Significantly lower levels of alpha2-macroglobulin (a thrombin inhibitor) and protein S were observed in the inadequate heparin response group.
- These findings suggest a potential role for these factors in heparin resistance.
Conclusions:
- Lower levels of alpha2-macroglobulin and protein S may contribute to inadequate heparin response in pediatric cardiac surgery patients.
- These factors should be considered alongside antithrombin when evaluating heparin efficacy in this vulnerable population.
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