NM-331
Abnormal Heparin Response in Patients Undergoing Arterial Switch Operations
Fang Z, Quinonez Z, Vu E, Gottlieb E
Texas Children's Hospital, Houston, TX, USA
Introduction/Study Questions
Initiation of cardiopulmonary bypass (CPB) requires proper anticoagulation, generally achieved with heparin, the most accepted anticoagulant used in adult and pediatric cardiac surgery. Heparin binds to and increases the activity of antithrombin III (ATIII). Some patients mount an abnormal heparin response leading to suboptimal anticoagulation with standard doses used for CPB. The quoted incidence of heparin resistance in adults is up to 22%, with some evidence linking heparin resistance to death. Few studies have examined the incidence of abnormal heparin response in the pediatric population. And despite the fact that neonates possess decreased levels of ATIII, still less is known about neonatal heparin resistance. We thus aim to determine the incidence of abnormal heparin response in a neonatal population undergoing the arterial switch operation (ASO), and determine if abnormal heparin response is associated with post-bypass coagulopathy.
Methods
After approval from our institutional review board, we performed a retrospective analysis of all patients with D-TGA presenting for ASO at our institution from Jun. 2014 to Sep. 2017. We excluded patients requiring aortic arch reconstruction or palliative arterial switch. We gathered patient demographics, baseline coagulation profile, and heparin doses and blood product administration using EPIC electronic medical record. We defined abnormal heparin response as one requiring a second pre-bypass dose of heparin after the initial bolus of our standard dose of 400 IU/kg. We used R for all analysis, with Wilcoxon rank-sum test for continuous variables, and chi-squared test for nominal data.
Results
52 patients fit inclusion. 26.9% (14 of 52) of patients had an abnormal response to heparin. No differences in demographic characteristics were noted. Only starting hemoglobin was noted to differ between groups, 13.3g/dL [12.4 - 15.1g/dL] versus 14.6g/dL [13.6 - 16g/dL], p = 0.04), with those in the “Abnormal Response†group having a higher hemoglobin. There were no differences in baseline platelet count, prothrombin time, partial thromboplastin time, international normalized ratio and fibrinogen levels between the two groups. We did not find any difference in post-operative transfusion requirements between the two groups, including the use of factor VIIa.
Discussion
We found that at our institution the incidence of abnormal heparin response in neonates undergoing arterial switch operation is higher than the incidence quoted in literature for adults. The known ATIII deficiency and immature coagulation system in neonates would support our finding. Additionally, current routine testing of baseline coagulation profile may be inadequate at predicting the coagulation status of a neonate. Additional prospective studies, and studies examining larger cohorts could elucidate the true incidence of heparin resistance, and also alternative coagulation studies, such as ROTEM or TEG, could determine the baseline coagulation function of neonates undergoing cardiovascular surgery.
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