Extracorporeal membrane oxygenation (ECMO) is a potentially life-saving temporizing strategy for patients, which has seen an ever-increasing utilization rate1,2. ECMO has two different configurations: veno-venous (V-V) and veno-arterial (V-A). Over the past several decades, V-A ECMO has emerged as a fundamental tool in the care of patients with severe cardiogenic shock and cardiopulmonary failure3,4,5,6. The two cannulation strategies for V-A ECMO are central and peripheral7. Central V-A ECMO usually requires sternotomy for direct cannulation of the right atrium for venous drainage and proximal aorta for antegrade arterial return. On the other hand, peripheral V-A ECMO has arterial return via the femoral artery via a retrograde mechanism. This retrograde flow can cause the following issues: differential oxygenation of the upper and lower body, worsening biventricular function, and LV distension, particularly if there is no strategy in place to unload the LV8. These complications of peripheral V-A ECMO, in addition to the inherent risks with ECMO, necessitate frequent, vigilant monitoring9,10,11. Due to the inherent instability of these patients, it is not practical to frequently transfer them out of the intensive care unit (ICU) for diagnostic testing and evaluation of their mechanical circulatory support and evolving cardiopulmonary status3,6. Therefore, bedside diagnostic tools are essential in their daily care. One such tool is point-of-care ultrasound (POCUS)12,13,14,15 of the heart, which can be used to assess all of the following non-invasively: left ventricular (LV) performance (size, systolic function, stroke volume, aortic valve opening)3,13,14,16,17,18,19, right ventricular (RV) performance (size, systolic function)20,21, and presence versus absence of intra-cardiac thrombus10,11. Furthermore, POCUS can be used to assess readiness for V-A ECMO weaning and eventual decannulation22,23,24,25,26,27,28.
Diagnostic ultrasound generally falls into two categories: point-of-care and consultative29,30 Consultative ultrasound is an exam requested by a patient's primary treating provider but performed by a separate specialist team29,30, whereas point-of-care ultrasound is performed and interpreted by a patient's primary treating provider29,30,31. Although ultrasound assessment of the heart on V-A ECMO has traditionally been performed through consultative services, such services are not always immediately available around the clock to meet an ECMO unit's high-volume and unpredictable sonographic needs. Thus, it behooves ECMO intensivists to be able to perform serial cardiac point-of-care ultrasound (POCUS) exams on their own patients for more efficient and timely patient care.
The utilization of POCUS in the V-A ECMO setting, however, remains heterogeneous due to the variability in training among providers. This study aims to address this gap in training by describing the POCUS image acquisition in peripheral V-A ECMO, particularly in the absence of LV venting, including details on patient positioning, transducer selection, probe placement, acquisition sequence, and image optimization. Other ECMO scenarios, such as LV venting in place, will be covered separately in other manuscripts in this special collection on diagnostic POCUS image acquisition.