How to Care for an ECMO Patient- Bedside Nurse Perspective Tukacs 1Cardio-Thoracic
Introduction ECMO delivered in intensive care evolved from cardiopulmonary bypass used intraoperatively. The team caring for the ECMO patient expanded to involve disciplines other than the operating room team, including critical care nurses. High clinical nursing competency in ECMO is essential for timely recognition of crucial changes within the ever-changing hemodynamic state during ECMO. These changes include differential hypoxemia, lower extremity ischemia, recovering heart syndrome, and hyperperfusion syndrome. Delay in recognition can lead to further worsening in condition. The aim of this review is to discuss four pivotal hemodynamic changes during ECMO and their timely identification through clinical nursing perspective.
1 M.
Intensive Care Unit, Columbia University Irving Medical Center- New York Presbyterian, New York, New York
Lower Extremity Ischemia
Recovering Heart Syndrome
Exclusive to femoral VA ECMO, lower extremity ischemia (LEI) is one of the main complications related to this ECMO configuration. In femoral VA ECMO, the blood is drained from a femoral vein and is reinfused into a femoral artery providing retrograde blood flow.
In femoral VA ECMO, recovering heart syndrome (RHS) is described as improving cardiac function, decreased ECMO flow and unchanged pump speed. Increase in blood volume ejected by the left ventricle augments blood pressure and a decrease in blood volume diverted into the ECMO circuit reduces ECMO flow (Figure 4.).
The anatomy of the femoral artery, as well as the the ECMO cannula in situ in the arterial lumen, may impede ipsilateral circulation and lead to LEI (Figure 2). If LEI develops, timely insertion of an antegrade distal perfusion cannula (DPC) is needed to reestablish adequate distal perfusion (Figure 3A.). Blood flow in DPC is generally relatively low (0.2- 0.5 L/min), and any decrease in ECMO flow can provoke thrombus or fibrin formation in DPC and redispose to LEI (Figure 3B).
Hyperperfusion Syndrome Hyperperfusion syndrome (HS) develops in VA ECMO with reinfusion cannula in the axillary or innominate artery, affecting the ipsilateral upper extremity (IUE). The angle of the surgical graft created to connect the reinfusion ECMO cannula to the artery determines perfusion to the IUE. If it allows oversupply of blood to the IUE, HS manifests with blood pressure high in cannulated UE, and normal in contralateral UE (Figure 5.).
Discussion Differential Hypoxemia Differential hypoxemia (DH) occurs in femoral VA ECMO with concomitant respiratory failure, preserved left ventricular function (ejection fraction >20%) and ECMO flow that provides partial cardiac support. Hypoxemic blood is delivered to the brain and coronary arteries (Figure 1B). Medical treatment of the underlying cause is necessary, along with ECMO reconfiguration into veno-arterial-venous (VAV) ECMO to provide oxygenation to the entire body (Figure 1C).
Figure 2. Correlation between distal perfusion, size of ECMO cannula and size of femoral artery.
Figure 4. RHS in femoral VA ECMO. As cardiac function increases, ECMO flow decreases without changing pump speed.
To best assess for RHS, other variables (e.g. intravascular volume, sedation, pump speed, vasopressor and inotropic therapy) need to be unchanged (Graph 1.). RHS is treated by lowering pump speed- weaning ECMO.
Figure 5. HS in femoral VA ECMO with right axillary arterial cannulation. Hypertension in right UE is demonstrated via right radial arterial line and normotension in left UE via left non-invasive blood pressure monitoring.
Reconfiguring ECMO or banding of the cannulated artery distal to the graft is necessary. If not treated, HS can lead to compartment syndrome, rhabdomyolysis and acute kidney injury. Nursing skills are fundamental in timely recognition of HS (Table 4.).
Figure 3. DPC in femoral VA ECMO. Standard direction of blood flow, marked with orange arrows (A), thrombi evacuated from DPC (B).
Figure 1. DH in femoral VA ECMO by Choi et al. Evolution of DH: No DH (A), DH present (B) and resolution of DH with VAV ECMO.
If not treated, LEI can lead to compartment syndrome, rhabdomyolysis, and amputation of the lower extremity (LE), as well as acute renal failure. Technological advances coupled with, at minimum, hourly clinical assessments of the patient and the ECMO circuit are imperative nursing interventions (Table 2.).
Untreated, DH can cause systemic hypoxemia and lead to brain and myocardial hypoxia. Clinical nurses’ understanding of dual circulation in femoral VA ECMO, following the trend in hypoxemia, hypercarbia and respiratory acidosis, along with increase in ECMO flow for worsening cardiac function are essential (Table 1.).
Graph 1. RHS in femoral VA ECMO. Example case, parameters with values: mean arterial pressure (MAP), ECMO flow L/min, pump speed RPM, fentanyl mcg/hr, urine output (UO) ml/hr, norepinephrine (NE) mcg/min.
Untreated, RHS can lead to increased cardiac workload and oxygen demand; redundant increase in pump speed, systemic vascular resistance, and medical therapy. Monitoring of vital signs, intravascular fluid management, titration of IV medications and ECMO flow help nurses recognize RHS and advocate for timely weaning from ECMO (Table 3.).
Table 4. Nursing interventions in HS in VA ECMO with axillary reinfusion. Legend: Bilateral upper extremity (BUE).
Conclusion The skill to timely identify changes in the hemodynamic state of the ECMO patient adds to nursing expertise and enhances clinical nursing standards in ECMO. Increased nursing knowledge leads to improved efficiency of the entire ECMO team to prevent complications and improve outcomes.
References 1.
www.elso.org
2.
MaBarbaro RP, Odetola FO, Kidwell KM, et al. Association of Hospital-Level Volume of Extracorporeal Membrane Oxygenation Cases and Mortality. Analysis of the Extracorporeal Life Support Organization Registry. American Journal of Respiratory and Critical Care Medicine. 2015;191(8):894-901. doi:10.1164/rccm.201409-1634OC.
3.
Karamlou T, Vafaeezadeh M, Parrish AM, Cohen GA, Welke KF, Permut L, et al. Increased extracorporeal membrane oxygenation center case volume is associated with improved extracorporeal membrane oxygenation survival among pediatric patients. J Thorac Cardiovasc Surg. 2013;145:470–475. doi: 10.1016/j.jtcvs.2012.11.037
Table 2. Nursing interventions relevant to LEI in femoral VA ECMO. Table 1. Nursing interventions in DH in femoral VA ECMO.
Table 3. Nursing interventions in RHS in femoral VA ECMO.
www.postersession.com
Contact Monika Tukacs, BSN, RN, CCRN
[email protected] www.linkedin.com/in/monika-tukacs-575a0124
