Quantification of Recirculation During Veno-Venous Extracorporeal Membrane Oxygenation: In Vitro Evaluation of a Thermodilution Technique

Abstract

Veno-venous extracorporeal membrane oxygenation (vv-ECMO) represents one of the most advanced respiratory support for patients suffering from severe acute respiratory distress syndrome. During vv-ECMO a certain amount of extracorporeal oxygenated blood can flow back from the reinfusion into the drainage cannula without delivering oxygen to the patient. Detection and quantification of this dynamic phenomenon, defined recirculation, are critical to optimize the ECMO efficiency. Our study aimed to measure the recirculation fraction (RF) using a thermodilution technique. We built an in vitro circuit to simulate patients undergoing vv-ECMO (ECMO flow: 1.5, 3, and 4.5 L/min) with different cardiac output, using a recirculation bridge to achieve several known RFs (from 0% to 50%). The RF, computed as the ratio of the area under temperature-time curves (AUC) of the drainage and reinfusion, was significantly related to the set RF (AUC ratio (%) = 0.979 × RF (%) + 0.277%, p < 0.0001), but it was not dependent on tested ECMO and cardiac output values. A Bland-Altman analysis showed an AUC ratio bias (precision) of −0.21% for the overall data. Test-retest reliability showed an intraclass correlation coefficient of 0.993. This study proved the technical feasibility and computation validity of the applied thermodilution technique in computing vv-ECMO RF.

Management of vascular access for extracorporeal life support: A cohort study

“…Furthermore, the fixing of ECMO tubing along the limbs aims to minimize any impact of patient movements on ECMO drainage and, consequently, on ECMO blood flow. 17 The overall “ cannula micro-motion ” in the enrolled patients was few millimeters, both for the drainage and reinfusion cannula. The distance between insertion site and the end of the wire-wound cannula (cm) of drainage cannulae was different for V-V and V-A ECMO, 18 (17–20) versus 6 (6–8) cm respectively.…”

“…The position of the cannulae within the vena cava is crucial, due to the possibility of blood recirculation, which greatly reduces the oxygenation performance of the V-V ECMO system. 14,17 The reinfusion cannulae used in our study were placed in 35 (75%) patients in the right femoral, 5 (25%) in the right internal jugular, and 5 in the femoral artery. Although the cannulae used for the three sites differ in length, the “ micro-motion ” was substantially similar and close to zero for all sites.…”

Modified Thermodilution for Simultaneous Cardiac Output and Recirculation Assessment in Veno-venous Extracorporeal Membrane Oxygenation: A Prospective Diagnostic Accuracy Study

“…Cipulli et al 6 recently proposed recirculation determination using the ratio of AUC In and AUC Out . 6 We had developed a method for cardiac output calculation on veno-arterial ECMO by calculating the passing injectate in the ECMO inlet and determining the injectate passing the pulmonary circulation. 10 We translate this method to VV-ECMO, in which recirculation can be calculated through the partition of injection volume, which is a direct function of recirculation.…”

“…[2][3][4][5] Recirculation is the fraction of decarboxylized and oxygenated blood, which drains directly from a return cannula back into the extracorporeal circuit. 6 It does not take part in the gas exchange of the body and limits the delivery of oxygen from the extracorporeal device. The recirculation fraction can in theory be measured by comparing the extracorporeal membrane oxygenation (ECMO) inlet oxygen content to the patient's mixed-venous oxygen content, which is not readily available.…”

“…Therefore, various indicator dilution techniques may be used. 6,7 Empirical studies show that adequate oxygenation requires an extracorporeal blood flow of roughly two thirds of the native cardiac output. 4 Thermodilution methods are the clinical gold standard for the determination of cardiac output, 8 but thermodilution is inaccurate in the setting of veno-venous or veno-arterial ECMO, since part of the cold indicator is drawn into the extracorporeal circuit.…”