Extracorporeal Membrane Oxygenation Watershed

Abstract

A 55-year-old, previously healthy man was admitted to another hospital with deep-venous thrombosis in both legs and massive pulmonary embolism verified by chest computed tomography (CT). He presented with severe dyspnea and hypotension refractory to inotropes. Fibrinolytic therapy with recombinant tissue plasminogen activator was initiated, but the patient further deteriorated and required cardiopulmonary resuscitation for a period of 30 minutes. After return of spontaneous circulation, he remained in cardiogenic shock despite the use of inotropes and vasopressors, which is why our hospital was contacted.Our mobile extracorporeal membrane oxygenation (ECMO) team was dispatched and the patient received veno-arterial ECMO support with a 24 French venous cannula inserted via the right femoral vein and advanced into the right atrium and a 17 French arterial cannula inserted into the right femoral artery and advanced into the right iliacal artery. With an ECMO blood flow of 4.5 L/min, hemodynamics stabilized and the patient was transported to Hannover Medical School. Here, the patient was mechanically ventilated with an inspiratory oxygen fraction of 1.0 and the arterial PO 2 measured in blood obtained from the right radial artery was >400 mm Hg. The mean systemic blood pressure was 90 mm Hg, but the arterial pressure curves were almost nonpulsatile, and echocardiography showed little contractions of both the right and the left ventricle.Another CT scan performed approximately 14 hours after fibrinolysis showed persistent subtotal thromboembolic occlusion of the pulmonary vascular bed. In addition, there was an extensive filling defect in the ventral aspects of the ascending aorta (Figure 1). The left atrium, the left ventricle, and the aortic bulb were void of contrast material, whereas the aortic arch and the descending aorta were well contrasted (Figures 2 and 3).These images demonstrated the so-called ECMO watershed, where well-contrasted blood coming from the ECMO circuit met low-contrasted blood coming from the left ventricle. The patient with his subtotally occluded pulmonary vascular bed and near complete loss of cardiac contractility had almost complete blood supply from the ECMO and very little regular blood flow. The ECMO device took up most of the contrast media, whereas only a small amount passed the pulmonary vascular bed. Hence, the aorta was filled mostly retrograde. Most of the aorta, including all 3 supraaortic vessels, received well-contrasted and well-oxygenated blood from the ECMO whereas the aortic bulb with the coronary arteries received noncontrasted blood coming from the left ventricle (Figures 2 and 3).In patients receiving veno-arterial ECMO support, the term watershed describes the phenomenon that blood coming from the ECMO flows in the opposite direction than blood coming from the left ventricle.1,2 The level where these 2 blood streams meet (ie, the watershed) depends on the relative pressures and flows in both systems. The oxygen content of the blood coming from the left ventricle is un...

Flow Optimization, Management, and Prevention of LV Distention during VA-ECMO

“…Multiple studies have shown that coronary perfusion worsens, especially if the patient is cannulated peripherally. Because relative cerebral or coronary hypoxia occurs in many situations due to a "watershed" effect, it is imperative to check blood saturations at multiple sites to determine if perfusion is adequate everywhere to avoid to misdiagnose the "Harlequin syndrome" due to inadequate mixing of the two parallel circulations (ECMO and native heart) [23,54,55].…”

Triple Cannulation ECMO

“…As such, vasopressor dosing and volume supplementation have to be carefully adjusted during VA-ECMO. VA-ECMO has successfully been used in various conditions such as post-cardiotomy cardiogenic shock [26], shock caused by myocardial infarction [27], decompensated non-ischemic heart failure [28], fulminant myocarditis [29,30], or pulmonary embolism prior to embolectomy [31,32] in all of the aforementioned cases in a bridge-to-recovery strategy. As with VV-ECMO, VA-ECMO has successfully been used in awake patients avoiding mechanical ventilation [33].…”

“…One of the most important issues is the so-called watershed phenomenon, i.e., an artificial competition zone between antegrade blood flow from the heart and retrograde blood flow from the ECMO [6,31,44]. It is located at a region somewhere between the ascending aorta and the thoracic aorta at the diaphragm level in most cases, and varies over time [44] and between individual patients.…”

Feasibility and safety of watershed detection by contrast-enhanced ultrasound in patients receiving peripheral venoarterial extracorporeal membrane oxygenation: a prospective observational study

“…In bifemoral venoarterial extracorporeal membrane oxygenation (VA ECMO), the transition point at which the antegrade pulsatile output from the left ventricle and the retrograde non-pulsatile ECMO output collide is referred to as watershed [1]. Currently, no standard method is available to determine its location.…”

“…Currently, no standard method is available to determine its location. Occasionally, contrast-enhanced computed tomography (CT) or angiography has been used [1][2][3]. Both techniques, however, bear disadvantages including radiation exposure and use of iodinated contrast media.…”