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A5112 - Influence of Blood Flow and Recirculation Volume on Thermodilution-Based Measurements of Cardiac Output During Extracorporeal Membrane Oxygenation in Pigs
Author Block: M. Russ1, E. Steiner2, R. C. E. Francis3, W. Boemke1, T. Busch4, E. R. Swenson5, P. A. Pickerodt6; 1Department of Anesthesiology and Operative Intensive Care Medicine, Campus Virchow and Campus Mitte, Charité - Universitätsmedizin Berlin, Berlin, Germany, 2Anesthesiology and Operative Intensive Care Medicine, Campus Virchow and Campus Mitte, Charité-Universitätsmedizin Berlin, Berlin, Germany, 3Anesthesiology and Operative Intensive Care Medicine, Campus Virchow and Campus Mitte, Charité - Universitätsmedizin Berlin, Berlin, Germany, 4Department of Anesthesiology and Intensive Care Medicine, University of Leipzig Medical Faculty, Leipzig, Germany, 5Division of Pulmonary, Critical Care and Sleep Medicine, VA Puget Sound Health Care System, University of Washington, Seattle, WA, United States, 6Department of Anesthesiology and Operative Intensive Care Medicine, Campus Virchow and Campus Mitte, Charité – Universitätsmedizin Berlin, Berlin, Germany.
Rationale
Veno-venous extracorporeal membrane oxygenation (vvECMO) is used to treat life-threatening hypoxemia in patients with acute respiratory distress syndrome (ARDS). The contribution of ECMO to systemic oxygen delivery is determined by the ratio of ECMO blood flow to cardiac output (CO). Classic thermodilution-based measurements of CO may be influenced by blood recirculation through the extracorporeal circuit. We investigated the effects of increasing ECMO blood flows on thermodilution-based measurements of CO in a porcine model of acute lung injury treated with vvECMO.
Methods
Anesthetized pigs (n = 6; mean body weight = 77 kg) were cannulated for vv-ECMO with bifemoral drainage cannulae and one jugular return cannula. CO was measured with an ultrasound vascular flow probe placed around the ascending aorta. ECMO blood flow was set in a randomized order at 25, 50, 75, 100, 125% of CO. Cardiac output was measured at each ECMO blood flow setting with the thermodilution technique using a pulmonary artery catheter (PAC) in conjunction with measurements of blood recirculation volume. All experiments were conducted in healthy animals and repeated after induction of ALI with repeated whole lung saline lavages. Data were analyzed using Bland-Altman plots.
Results
PAC measurements overestimated CO at all ECMO blood flow settings (mean difference = 2 l/min) both in healthy and lung injured pigs. The difference between CO as measured by the PAC and blood flow measured at the ascending aorta increased when the results were analyzed for low ECMO blood flows (mean difference between measurements: 1.3 l/min) vs. high ECMO blood flows (mean difference 3 l/min). The overestimation of CO by thermodilution was highest when high ECMO blood flow resulted in relevant recirculation of ECMO blood flow.
Conclusion
Thermodilution-based measurements overestimate cardiac output during veno-venous ECMO therapy in healthy and lung-injured pigs. Overestimation of CO by thermodilution depends on the proportion of ECMO blood flow to cardiac output.