Sources of Circuit Thrombosis in Pediatric Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) for cardiopulmonary support of critically ill patients is used frequently in the pediatric population. ECMO is burdened by complications, including thrombosis and hemorrhage. Here we demonstrate the focused location of clots, their histologic composition, and the relationship of in situ thrombus to local hemodynamics in ECMO circuits. Pediatric ECMO circuits from Children’s Healthcare of Atlanta, Emory University (Atlanta, GA) were obtained after removal from extracorporeal support over a 2.5 year period (n = 50). All clots and material deposited within the circuit were recorded. Location of clot was compared with local hemodynamics. Most clots were adherent to the junctions made by the tubing and connectors, as opposed to being randomly disturbed throughout the circuit tubing ( p << 0.05). Loose, nonadherent clots were also found at the entry side of oxygenators. The clots colocated directly with zones of low shear rate. Histology revealed a fibrinous composition, consistent with coagulation potentiated by low shear. Centrifugal pump circuits (n = 16) had more clots than roller pump (n = 34) circuits ( p << 0.05). In addition, all centrifugal pumps had clots that formed at the top of the pump shaft. The ECMO circuits from our single-center study demonstrate the concentrated location of fibrin clots at low shear zones created by tubing-connector junctions. Type of pump also influences the frequency of clot formation. Since the mechanism of the majority of ECMO circuit thrombosis is low shear and fibrin driven, optimization of hemodynamics and anticoagulation regimen may reduce clot formation and bleeding.