• Katherine Irby, Christopher Swearingen, Jonathan Byrnes, Joshua Bryant, Parthak Prodhan, and Richard Fiser.
• 1Division of Pediatric Critical Care, Department of Pediatrics, University of Arkansas for Medical Sciences College of Medicine, Little Rock, AR. 2Division of Biostatistics, Department of Pediatrics, University of Arkansas for Medical Sciences College of Medicine, Little Rock, AR. 3Division of Cardiology, Department of Pediatrics, University of Arkansas for Medical Sciences College of Medicine, Little Rock, AR. 4Arkansas Children's Hospital, Little Rock, AR.
• Pediatr Crit Care Me. 2014 May 1; 15 (4): e175-82.

ObjectiveInvestigate whether anti-Factor Xa levels are associated with the need for change of circuit/membrane oxygenator secondary to thrombus formation in pediatric patients.Design And SettingsRetrospective single institution study.PatientsRetrospective record review of 62 pediatric patients supported with extracorporeal membrane oxygenation from 2009 to 2011.InterventionsData on standard demographic characteristics, indications for extracorporeal membrane oxygenation, duration of extracorporeal membrane oxygenation, activated clotting time measurements, anti-Factor Xa measurements, and heparin infusion rate were collected. Generalized linear models were used to associate anti-Factor Xa concentrations and need for change of either entire circuit/membrane oxygenator secondary to thrombus formation.Measurements And Main ResultsSixty-two patients met study inclusion criteria. No-circuit change was required in 45 of 62 patients. Of 62 patients, 17 required change of circuit/membrane oxygenator due to thrombus formation. Multivariate analysis of daily anti-Factor Xa measurements throughout duration of extracorporeal membrane oxygenation support estimated a mean anti-Factor Xa concentration of 0.20 IU/mL (95% CI, 0.16, 0.24) in no-complete-circuit group that was significantly higher than the estimated concentration of 0.13 IU/mL (95% CI, 0.12, 0.14) in complete-circuit group (p = 0.001). A 0.01 IU/mL decrease in anti-Factor Xa increased odds of need for circuit/membrane oxygenator change by 5% (odds ratio = 1.105; 95% CI, 1.00, 1.10; p = 0.044). Based on the observed anti-Factor Xa concentrations, complete-circuit group had 41% increased odds for requiring circuit/membrane oxygenator change compared with no-complete-circuit group (odds ratio = 1.41; 95% CI, 1.01, 1.96; p = 0.044). Mean daily activated clotting time measurement (p = 0.192) was not different between groups, but mean daily heparin infusion rate (p < 0.001) was significantly different between the two groups.ConclusionsHigher anti-Factor Xa concentrations were associated with freedom from circuit/membrane oxygenator change due to thrombus formation in pediatric patients during extracorporeal membrane oxygenation support. Activated clotting time measurements did not differ significantly between groups with or without circuit/membrane oxygenator change. This is the first study to link anti-Factor Xa concentrations with a clinically relevant measure of thrombosis in pediatric patients during extracorporeal membrane oxygenation support. Further prospective study is warranted.

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