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.

Nitric oxide added to the sweep gas of the oxygenator during cardiopulmonary bypass in infants: A pilot randomized controlled trial

Our objective was to assess the effect of nitric oxide added to the sweep gas of the oxygenator during cardiopulmonary bypass (CPB) in infants on platelet count, platelet function, clinical outcomes, and safety. A randomized, double-blinded, placebo-controlled clinical trial in infants less than a year of age undergoing cardiac surgery requiring CPB was undertaken. Nitric oxide at a dose of 20 ppm was added to the sweep gas in the treatment group. Blood was collected at baseline and prior to separation from CPB to measure platelet count and function as determined by responsiveness to specific agonists. Clinical outcomes were observed through hospital discharge. Methemoglobin levels were measured preoperatively, at the conclusion of CPB, and upon admission to the ICU. Forty patients consented and were randomized in the trial. Eighteen patients were randomized to the treatment group and 22 were included in the placebo group. The groups were similar in terms of age, weight, gender, and surgical complexity. No significant differences were found in measures of platelet count, platelet response to agonist, or clinical outcomes. Patients in the treatment group had higher methemoglobin levels after receiving nitric oxide, but no levels approached toxicity (maximum 2.4%). Nitric oxide added to the sweep gas of the oxygenator during CPB in infants did not have an appreciable effect on the preservation of platelet count, platelet responsiveness to agonist, or clinical outcomes. Methemoglobin levels were increased after receiving nitric oxide but were far below a toxic level of 15%.