title: Antithrombin activity and heparin response in neonates and infants undergoing congenital cardiac surgery: a retrospective cohort study.
abstract: OBJECTIVE
  The immature coagulation system during infancy has age-related physiological differences in proteins that contribute to significant variation in heparin responsiveness through alterations in heparin-enhanced thrombin inhibition. The primary aim of this study was to evaluate the relationship between preoperative antithrombin (AT) activity and heparin responsiveness in neonates and infants undergoing congenital cardiac surgery.
  
  
  METHODS
  In this retrospective cohort study, neonates (aged 0-28 days) and infants (aged 29-365 days) undergoing congenital cardiac surgery in the 12-month period from October 2013 to 2014 were studied. The two age groups were compared for the primary endpoint of heparin response measured by the heparin sensitivity index (HSI), with heparin loading doses and heparin resistance being secondary endpoints. Multivariable linear regression analyses were used to explore the relationship between AT activity and heparin response measured by HSI.
  
  
  RESULTS
  There were 122 infants and 19 neonates included in the study. After adjusting for low-molecular-weight heparin, unfractionated heparin, and platelet count, there was a significant relationship between AT activity and HSI (r = 0.44; P = 0.009). The median [interquartile range] HSI did not differ between neonates and infants (0.76 [0.69- 0.98] vs 0.89 [0.70-1.10] sec·unit(-1)·kg(-1), respectively; median difference, 0.08; 95% confidence interval [CI], -0.01 to 0.17; P = 0.182), despite the mean (standard deviation) AT activity differing between age groups [60 (16)% vs 84 (18)%, respectively; mean difference, 24; 95% CI, 15 to 32; P < 0.001].
  
  
  CONCLUSIONS
  There was a moderate relationship between AT activity and heparin response measured by HSI. Comparing neonates and infants, there was similar heparin responsiveness measured by HSI despite differing AT activity levels. These findings should help guide the perioperative administration of exogenous AT to neonates and infants and suggest that, outside the neonatal period, preoperative AT activity may be used to identify children at risk of decreased heparin responsiveness.
authors.affiliation: The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Vannessa M
authors.initials: VM
authors.lastname: Chin
authors.affiliation: The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Marie-Laure Laskine
authors.initials: ML
authors.lastname: Holland
authors.affiliation: The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Marlee M
authors.initials: MM
authors.lastname: Parker
authors.affiliation: The Hospital for Sick Children, Toronto, ON, Canada.
authors.forename: Helen M
authors.initials: HM
authors.lastname: Holtby
authors.affiliation: The Hospital for Sick Children, Toronto, ON, Canada. james.oleary@sickkids.ca.|Division of Cardiac Anesthesia, The Hospital for Sick Children, Rm 2212J, 555 University Avenue, Toronto, ON, M5G 1X8, Canada. james.oleary@sickkids.ca.
authors.forename: James D
authors.identifier: http://orcid.org/0000-0001-9801-5312
authors.initials: JD
authors.lastname: O'Leary
mesh_terms: D000991:Antithrombins / Q000494:pharmacology*; D006348:Cardiac Surgical Procedures; D015331:Cohort Studies; D005260:Female; D006330:Heart Defects, Congenital / Q000601:surgery*; D006493:Heparin / Q000494:pharmacology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016014:Linear Models; D008297:Male; D012189:Retrospective Studies
chemical_list: D000991:Antithrombins; D006493:Heparin