Alterations in Pre/Post Oxygenator Flows Due to Fibrin Deposition in the CardioHelp System-A Case Report

We present a 62-year-old patient with COVID-19 pneumonia on Veno-venous (VV) Extracorporeal Membrane Oxygenation (ECMO) with unique perturbations to pre and post oxygenator pressures due to fibrin deposition in despite being on a Heparin/Bivalirudin infusion and activated Partial Thromboplastin Time (aPTT) within therapeutic range of 60-80 seconds. On Day 8 of ECMO support, it was noticed that flows steadily decreased despite unchanged RPMs. Unlike typical blood flow to circuit pressure relationships, the circuit pressures did not correlate with the observed decreased flow. The Delta Pressure (ΔP) was not elevated. The patient's vitals were stable. On inspection post change-out, clots were noted in the oxygenator outlets. Oxygenator clots are usually associated with increased ΔP. In this scenario, clots in the oxygenator blocked 1 of the 4 outlets in the oxygenator causing the flow, pressures, and ΔP to drop consecutively. Due to reduced flow, the ΔP was not elevated despite extensive clots. The fibrin clot location in the CardioHelp ECMO circuit may lead to unexpected pressure and flow alterations. Sole reliance on ΔP as a marker for oxygenator clots may be misleading. Careful monitoring and timely diagnosis of coagulation status may lead to changes in anticoagulation goals and meaningfully impact patient outcomes.