Version May 2024
INTRODUCTION — Extracorporeal membrane oxygenation (ECMO) is an advanced form of life support used mostly in patients with severe respiratory or cardiac failure when standard therapy fails. While in the past ECMO was associated with poor outcomes and high complication rates, technical advances coupled with accumulating data that describe successful outcomes [1-4] have resulted in a resurgence of ECMO use.
This topic will provide an overview of ECMO, including terminology and physiology and the selection of an appropriate ECMO configuration for patients with respiratory and/or cardiac failure. Other ECMO-relevant topics are found elsewhere:
●(See "Extracorporeal life support in adults: Extracorporeal carbon dioxide removal (ECCO2R)".)
●(See "COVID-19: Extracorporeal membrane oxygenation (ECMO)".)
TERMINOLOGY
Extracorporeal life support (ECLS) — Extracorporeal life support (ECLS) encompasses a set of extracorporeal modalities that can provide oxygenation, carbon dioxide (CO2) removal, and/or circulatory support, excluding cardiopulmonary bypass for cardiothoracic or vascular surgery (table 1) [5].
Extracorporeal membrane oxygenation (ECMO) — Extracorporeal membrane oxygenation (ECMO) is a form of ECLS used for temporary support of patients with respiratory failure (for gas exchange) and/or cardiac failure (for cardiac support).
Venovenous ECMO (almost exclusively for respiratory failure) or venoarterial ECMO (for circulatory failure) are the two most common forms of ECMO used in the intensive care unit, although more complex configurations are sometimes needed.
Further details regarding configurations and indications for such configurations are discussed separately.
●(See 'Drainage-reinfusion configurations' below.)
Extracorporeal carbon dioxide removal (ECCO2R) — Extracorporeal CO2 removal (ECCO2R) is another form of ECLS, used for the sole purpose of CO2 removal. It is not intended to impact the patient's oxygenation and typically provides only modest oxygenation at best. It provides no cardiac support. It is a common configuration used in patients with pure hypercapnic respiratory failure or patients with less severe forms of the acute respiratory distress syndrome who might benefit from increased lung-protective ventilatory strategies.
Configurations for ECCO2R are discussed separately.
●(See 'Drainage-reinfusion configurations' below.)
ECMO AND ECCO2R CIRCUITS — An extracorporeal membrane oxygenation (ECMO) circuit pumps blood through an "artificial" or "membrane" lung, which performs the function of gas exchange (ie, oxygenation and carbon dioxide [CO2] removal). It can also be configured to provide circulatory support.
Components — In general, we prefer a simplified circuit consisting only of drainage and reinfusion cannulae, a pump, membrane lung, heat exchanger, oxygen source, blender, and connection tubing (figure 1 and figure 2 and figure 3).
Occasionally, additional tubing (eg, Y-connectors) or additional cannulae (for enhanced drainage or reinfusion of blood) is required (eg, venoarteriovenous [V-AV] configuration (figure 4)).
The rationale for simple circuitry is to minimize turbulent blood flow that can promote thrombus formation and hemolysis and avoid sites of potential air entrainment, blood loss, or contamination.
Drainage-reinfusion configurations — ECMO/extracorporeal CO2 removal (ECCO2R) circuits remove blood from a large, often central blood vessel or cardiac chamber (drainage cannula). That blood is pumped through a semipermeable membrane ("membrane lung"). The membrane lung directly oxygenates and removes CO2, and blood is returned to a large blood vessel or cardiac chamber (reinfusion cannula). Reinfused blood mixes with the native circulation to perfuse end-organs.
Configuration terminology describes the drainage and perfusion cannulae. Several configurations are available and comprehensive descriptions of them all is beyond the scope of this topic review. By convention, V denotes venous access, A denotes arterial access and the hyphen denotes where the membrane lung is in the circuit [5]. Common configurations include the following:
●Venovenous (V-V) ECMO/ECCO2R configurations – The primary function of V-V ECMO is oxygenation and/or CO2 removal. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)".)
In V-V circuits, blood is drained from a vein or venous chamber (eg, central vein or right atrium), pumped through the membrane lung, and reinfused back into a vein (sometimes the same vein/chamber as drainage component or a different vein or chamber). V-V ECMO relies on native cardiac function to circulate the reinfused blood. Examples are shown in the figures (figure 1 and figure 2).
In V-V ECMO, the circuit can be implemented through the following:
•Two anatomically separate sites using two separate cannulae (two-site configuration (figure 1))
•A single site using a cannula that has two lumens (ie, dual-lumen single-site configuration (figure 2))
In two-site configurations, when the drainage and reinfusion cannulae are too close together, reinfused, oxygenated blood may be drawn into the drainage cannula and therefore back into the circuit without entering the systemic circulation ("recirculation"). This phenomenon is typically less common with dual-lumen single-site configurations. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Troubleshooting circuit dysfunction'.)
For V-V ECCO2R, the circuit and configuration are similar to that described for V-V ECMO. However, compared with V-V ECMO, lower blood flow rates and smaller cannulae are typically used because CO2 removal is more efficient than oxygenation. ECCO2R, when performed at low blood flow rates, generally provides little in the way of meaningful oxygenation. (See "Extracorporeal life support in adults: Extracorporeal carbon dioxide removal (ECCO2R)".)
●Venoarterial (V-A) ECMO configurations – The primary function of V-A configurations is cardiac support while also providing gas exchange (when needed). (See "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)".)
In V-A circuits, blood is drained from a central vein, pumped through the membrane lung, and reinfused into an artery (most commonly the femoral artery), thereby providing both gas exchange and circulatory support. An example is shown in the figure (figure 3).
●Hybrid ECMO configurations – Some circuits have two reinfusion cannulae (one into a vein and one into an artery), effectively providing both venovenous and venoarterial support, referred to as a hybrid configuration. In general, the terminology is specific for what the patient started with and what was added. For example, patients receiving V-V ECMO may have an arterial reinfusion cannula placed when additional cardiac support is needed (venovenoarterial [V-VA]); patients on V-A ECMO may need a venous reinfusion cannula placed when additional respiratory support is needed (venoarteriovenous [V-AV]). In most situations, a second reinfusion cannula is added to an existing circuit, although some patients may require a hybrid configuration from the outset in the setting of concomitant severe respiratory and cardiac failure. An example is shown in the graphic (figure 4). (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Managing concomitant cardiac failure' and "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)", section on 'Concomitant respiratory failure'.)
While a hybrid configuration is defined by additional reinfusion cannulae, it does not refer to the addition of a second drainage cannula. For example, in circumstances where blood flow is limited by excess negative drainage pressure, a second drainage cannula may be appropriate (eg, venovenovenous [VV-V] or venovenoarteriovenous [VV-AV]).
Less common configurations include the following:
●Pumpless arteriovenous (A-V) ECLS configurations – The primary functions of A-V configurations include ECCO2R (eg, femoral artery-to-femoral-vein configuration) and "off-loading" of the right ventricle (pulmonary artery-to-left atrium configuration) [6].
Pumpless A-V ECLS is a far less common, low-flow arteriovenous cannulation strategy, relying on native cardiac output rather than an external pump to generate extracorporeal blood flow, which will be more limited in flow when compared with extracorporeal blood flow generated by a centrifugal pump [7]. Drainage and reinfusion cannulae are most commonly located in the femoral artery and femoral vein, respectively, with the membrane lung in between, which provides A-V ECCO2R. In select patients with pulmonary hypertension awaiting lung transplantation, a comparable pumpless arteriovenous configuration may be applied, wherein blood is pumped by the right ventricle from the pulmonary artery, through the membrane lung, and returned to the pulmonary vein or left atrium, thereby offloading the right ventricle and providing an oxygenated right-to-left shunt.
●Venous-to-pulmonary artery (V-PA) ECMO configurations – An alternative configuration for V-V ECMO is a V-PA configuration. It may also serve as an alternative to V-A ECMO for isolated acute right ventricular failure.
This configuration drains blood from the right atrium, pumps it through the membrane lung, and returns it to the pulmonary artery either through the second lumen of a dual-lumen cannula or using a two-site set up. An example is shown in the graphic (image 1 and figure 5). Challenges with placement and maintenance of proper positioning, along with cost, may make this approach less desirable than the traditional two-site V-V ECMO for the majority of patients.
DETERMINANTS OF GAS EXCHANGE — The table lists the major determinants of oxygenation and carbon dioxide (CO2) removal (table 2).
Oxygenation
ECMO blood flow rate — The degree of oxygenation derived from the circuit is largely determined by the extracorporeal membrane oxygenation (ECMO) blood flow rate (ie, the rate at which blood enters the membrane), which is most often manually set (typically 3 to 7 L/minute) [8]. Most of the time, blood exiting the membrane lung is 100 percent saturated with oxygen, provided the membrane is functioning properly.
ECMO blood flow rate relative to native cardiac output (V-V ECMO) — In venovenous (V-V) ECMO, systemic oxygenation is largely determined by the contribution of V-V ECMO-derived oxygenated blood relative to the overall circulating blood volume (ie, the proportion of blood flowing through the ECMO circuit relative to native cardiac output), along with the contribution from native lung function.
●When the ECMO blood flow rate is high (eg, 4 L/minute) relative to the native cardiac output (eg, 5 L/minute; 80 percent of cardiac output going through the membrane lung), then most of the systemic oxygenation is derived from the ECMO circuit.
●When the ECMO blood flow rate is low (eg, 2 L/minute) relative to the native cardiac output (eg, 5 L/minute; 40 percent of cardiac output going through the membrane lung), then the contribution of ECMO-derived oxygenation is lower.
●When the ECMO blood flow rate is steady (eg, 4 L/minute) but native cardiac output changes (eg, increase from 5 to 10 L/minute in the setting of vasodilatory shock), then the contribution of ECMO-derived oxygenation will decrease (from 80 to 40 percent of cardiac output going through the membrane lung), resulting in decreased systemic oxygenation.
A clinical study of V-V ECMO patients demonstrated that a ratio of ECMO blood flow to cardiac output >60 percent consistently resulted in systemic arterial oxygen saturation >90 percent [8].
Dual circulation (V-A ECMO) — In venoarterial (V-A) ECMO, a phenomenon known as dual circulation may also affect regional differences in oxygen delivery [1].
●During femoral V-A ECMO, when left ventricular (LV) output is minimal or absent, the reinfused extracorporeal blood flows retrograde up the aorta and across the aortic arch, perfusing the entire body including the cerebral and coronary vascular beds. However, in the presence of native LV ejection, a mixing point will develop between the reinfused blood from the ECMO circuit and that from the native cardiac output. The mixing point is dynamic depending upon the relative strengths of the native and extracorporeal pumps, a phenomenon known as competitive flow. If the mixing point occurs in the descending aorta, then upper body oxygenation will be supplied by native cardiac output while the lower body is supplied by the ECMO circuit, effectively establishing dual circulations. If the native cardiac output ejects poorly oxygenated blood (eg, in the setting of concomitant cardiogenic pulmonary edema or underlying lung injury), then the upper body and, most importantly, the coronary and cerebral circulations, may be inadequately oxygenated while the lower body is well-oxygenated, referred to as differential oxygenation. Differential CO2 tension may likewise occur as a consequence of dual circulation.
●Axillary, subclavian, and innominate artery reinfusion circuits may have relatively less differential oxygenation due to the reinfused blood being delivered close to the aortic arch. In antegrade proximal aortic reinfusion, there is minimal if any differential oxygenation due to anterograde flow from the aortic root, and in left atrial reinfusion, there is no differential oxygenation.
Complications that can develop from dual circulation and competitive flow are discussed separately. (See "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)", section on 'V-A ECMO-specific complications'.)
Others — Other determinants of oxygenation include the following:
●Diffusion properties of the membrane lung (eg, properties intrinsic to the material itself or the presence of thrombus).
●Membrane surface area and design.
●The degree of recirculation (ie, blood recirculating back to the reinfusion port; applies to V-V ECMO only). (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Troubleshooting circuit dysfunction'.)
●Native lung gas exchange.
Carbon dioxide removal — The degree of CO2 removal by the circuit is largely determined by the sweep gas flow rate at high blood flow rates and by both sweep gas and blood flow rates at lower blood flow rates. Sweep gas is a controlled blend of oxygen and air that passes through the membrane lung; the fraction of oxygen that is delivered to the membrane lung is referred to as the fraction of delivered oxygen (FDO2). The FDO2 should be distinguished from the fraction of oxygen inspired into the lungs (ie, oxygen delivered via mechanical ventilation to the native lung). FDO2 is typically set at 100 percent unless a patient is undergoing weaning from ECMO or is hyperoxemic.
Membrane lung surface area and the partial pressure of CO2 entering the membrane are also major determinants of CO2 removal.
Other determinants include diffusion properties of the membrane lung and native gas exchange.
CO2 removal is more efficient than oxygenation owing to diffusion properties of CO2 and the ability to maintain a large gradient across the membrane through increases in the sweep gas flow rate. Thus, extracorporeal CO2 removal (ECCO2R) may be used in most circumstances at lower blood flow rates and through smaller cannulae than what is usually required for oxygenation during V-V or V-A ECMO, although blood flow rate itself does not define ECCO2R. (See "Extracorporeal life support in adults: Extracorporeal carbon dioxide removal (ECCO2R)".)
INITIAL PATIENT SELECTION FOR SPECIFIC ECLS MODE — The approach outlined in the sections below is considered a high-level, broad, overview of ECLS mode selection.
●Selecting an appropriate mode of ECLS is largely dependent upon the organ failure that needs supporting and the pattern of gas exchange that needs to be corrected. (See 'Type of support needed' below.)
●Once selected, individual patient-related factors influence the decision to proceed with ECLS (eg, comorbidities, underlying lung or cardiac disease) and the technical factors surrounding implementation. (See 'Patient-specific factors' below.)
●The process is a team-directed approach. (See 'Staffing (ECMO teams)' below.)
Guidelines that describe the indications and practice of ECLS are published by the Extracorporeal Life Support Organization (ELSO) [9,10].
In general, supportive data for the practice of extracorporeal membrane oxygenation (ECMO) are lacking and mostly derived from observational case series with the exception of acute hypoxemic respiratory failure due to the acute respiratory distress syndrome (ARDS). (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Clinical applications' and "Extracorporeal life support in adults: Extracorporeal carbon dioxide removal (ECCO2R)", section on 'Clinical applications' and "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)", section on 'Clinical applications'.)
Type of support needed
Patients who need respiratory support and oxygenation (V-V ECMO) — We evaluate patients who primarily have hypoxemic or hypercapnic respiratory failure as potential candidates for venovenous (V-V) ECMO. The goals of V-V ECMO under these circumstances are to support oxygenation and manage carbon dioxide (CO2) removal to facilitate lung-protective ventilation. Further details regarding the implementation of V-V ECMO are provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)".)
Patients who need cardiac/circulatory support (V-A ECMO) — We evaluate patients who primarily have cardiac/circulatory failure as potential candidates for venoarterial (V-A) ECMO; this includes patients with left-sided heart failure and/or right-sided heart failure (eg, from right ventricular infarction, massive pulmonary embolism, or pulmonary hypertension), patients with refractory shock due to other conditions, including trauma, anaphylaxis, drowning, organ donation, poisoning (table 3), and hypothermia, and patients who need support during cardiopulmonary resuscitation. The goal of V-A ECMO under those circumstances is circulatory support, but patients may also derive benefit from extracorporeal oxygenation and CO2 removal if needed. Further details regarding the implementation of V-A ECMO are provided separately. (See "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)".)
Patients with pure hypercapnic respiratory failure who only need carbon dioxide removal (V-V ECCO2R) — We evaluate patients who have predominantly hypercapnic respiratory failure as potential candidates for V-V extracorporeal CO2 removal (ECCO2R). The goal of V-V ECCO2R under those circumstances is CO2 removal. Oxygenation support is minimal. Further details regarding the implementation of ECCO2R are provided separately. (See "Extracorporeal life support in adults: Extracorporeal carbon dioxide removal (ECCO2R)".)
Patient-specific factors
ECLS as a bridge to an endpoint — During the evaluation for ECLS, we assess patients for their suitability for advanced life support therapies in general. One of the most important aspects of the decision to proceed with ECLS is whether it will provide any of the following:
●A bridge to recovery (ie, is the disease potentially reversible?).
●A bridge to receiving an additional life-saving intervention, such as lung or heart transplant, a ventricular assist device, total artificial heart, thoracic or airway surgical procedure, coronary artery stenting, or bypass grafting.
●A bridge to decision (eg, organ transplant).
In general, most experts would not consider ECLS as appropriate for patients in whom such endpoints are not achievable (ie, ECLS as a "bridge-to-nowhere").
This can be a difficult assessment in an acute setting when the details required for such a prediction may be unknown or missing and the process may be fraught with ethical dilemmas. When recovery or device/transplant candidacy is uncertain, we use the term "bridge to decision." This is most commonly encountered for ECLS in cardiac failure; in such cases, recovery, transplantation, and destination device therapy are all potential options, but candidacy for a given endpoint is often uncertain until there is clarity on the likelihood of both cardiac and extra-cardiac organ recovery.
However, the use of ECLS as "bridge to decision" may create a greater opportunity for a "bridge-to-nowhere," especially in the setting of end-stage lung disease where determination that the patient is not a candidate for transplantation leaves few other options. In that context, we only use ECLS as a bridge to lung transplantation for patients who have already been deemed appropriate candidates for transplantation [11,12]. In exceptional circumstances, ECLS may be considered in patients not previously evaluated for transplantation if patient characteristics suggest both feasibility of transplant evaluation and a high likelihood of candidacy for transplantation once receiving ECMO [13]. The International Society of Heart and Lung Transplantation highlights younger age, absence of multiorgan dysfunction, and good rehabilitation potential as patient characteristics for which ECLS is suitable for bridging to lung transplantation [14]. Recommendations against ECMO for bridge to transplant include septic shock, multiorgan dysfunction, severe arterial occlusive disease, heparin-induced thrombocytopenia, prior prolonged mechanical ventilation, advanced age, and obesity. (See "Lung transplantation: General guidelines for recipient selection".)
Ethical dilemmas exist when making the decision to proceed with ECLS; such discussions are beyond the scope of this review. [15-18].
Technical factors of implementation — Once it is decided that ECLS is appropriate, we then assess patients for their suitability for the selected mode (eg, V-V ECMO, V-A ECMO, venoarteriovenous ECMO). This assessment is provided separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Initial clinical assessment' and "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)", section on 'Initial clinical assessment'.)
Staffing (ECMO teams) — ECLS should only be administered in institutions that have a trained team qualified to perform ECLS care. We obtain input from an interprofessional team of healthcare providers as well as the patient or family members or surrogate decision-makers to make an informed decision to proceed or not proceed with ECLS.
Teams include the following:
●A primary team responsible for the overall care of the patient in the intensive care unit – This typically consists of attendings (eg, intensivist, surgeon, cardiologist), fellows, residents, advanced practice providers, registered nurses, respiratory therapists, physical and occupational therapists, speech and language therapists, nutritionists, social workers, pastoral care, and psychologists.
●Individuals performing cannulation – This varies by institution and may include cardiothoracic or vascular surgeons, interventional cardiologists, anesthesiologists, intensivists, or emergency medicine physicians.
●Individuals responsible for circuit monitoring, management, and troubleshooting – These are often referred to as "ECLS/ECMO specialists," vary by institution, and may include perfusionists, nurses, respiratory therapists, physicians, or other clinicians.
●Other specialists – Beyond cannulation and circuit management, a broad range of disciplines is often involved in the care of this critically ill population (eg, infectious diseases, hematology, and neurology consultants).
We encourage the development of referral networks in which hospitals with less ECLS/ECMO experience and limited resources develop relationships with high-volume ECMO centers capable of providing all such therapies. This opinion is based upon the positive correlation between ECLS/ECMO center case volume and outcomes [19], the high resource intensity of ECLS, and the frequent need for other concomitant advanced therapies in this patient population (eg, prone positioning, lung or heart transplantation, cardiac catheterization, or other forms of temporary and durable mechanical circulatory support). [20,21]. These relationships should have mutually agreed-upon indications and contraindications for ECMO and may involve cannulation by either the originating or the receiving center. The latter arrangement also requires the ability to safely perform interfacility transport with ECMO support [22-25].
Interdisciplinary and interprofessional collaboration, with clearly defined roles and responsibilities, is vital to a successful ECLS program [20,21]. An education curriculum with initial and ongoing ECMO role-specific training, including simulation training, should be provided to all members of the program.
COMPLICATIONS — The complications of ECLS (extracorporeal membrane oxygenation [ECMO], extracorporeal carbon dioxide removal) are listed in the table (table 4). Common complications, regardless of venovenous or venoarterial configuration, include the following [26,27]:
●Hemorrhage (cannula-related, surgical site, other sites, such as gastrointestinal or retroperitoneal)
●Thrombosis (circuit-related, cannulae-related, arterial or venous thromboembolism)
●Infection (eg, surgical site, systemic)
●Hemolysis
●Thrombocytopenia, including heparin-induced thrombocytopenia
●Cardiac or vascular perforation during cannulation
These and other complications specific to ECMO configuration or mode are discussed separately. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Complications' and "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)", section on 'V-A ECMO-specific complications'.)
PROGNOSIS AND LONG-TERM OUTCOMES
Prognosis and prognostic scores — Survival in patients who receive ECLS can be expected to vary by indication for extracorporeal membrane oxygenation (ECMO) or extracorporeal carbon dioxide removal (ECCO2R), complications that occur, and patient-related factors (eg, underlying comorbidities) [3,4,28-35]. For example, patients who receive venoarterial (V-A) ECMO for cardiac arrest (referred to as extracorporeal cardiopulmonary resuscitation) might be expected to have a worse outcome than those who receive V-A ECMO for sepsis-related cardiogenic shock. Retrospective data suggest that repeat ECMO after failing decannulation and hematopoietic stem cell transplantation are associated with poor outcomes [36,37].
Several scoring systems have been derived to help prognosticate survival of patients being considered for ECLS for both respiratory and cardiac failure [31,38-42]. These prognostic scores all have limitations in their clinical applications and are used variably in clinical practice.
Specific outcomes are discussed separately under the relevant indications.
Sequalae — Among those who recover from ECMO support, many experience physical, psychological, and neurocognitive dysfunction, similar to that experienced by survivors of critical illness (also known as "post-intensive care unit syndrome" [PICS]) and survivors of the acute respiratory distress syndrome. Details regarding PICS are provided separately. (See "Acute respiratory distress syndrome: Prognosis and outcomes in adults", section on 'Morbidity among survivors' and "Post-intensive care syndrome (PICS) in adults: Clinical features and diagnostic evaluation".)
Data to support components of PICS in survivors of ECLS include the following [43-47].
●In a large retrospective Canadian study of 642 survivors of ECMO, the incidence of new mental health conditions was 22 per 100 person-years compared with 14.5 per 100 person-years in 3820 matched intensive care unit survivors who did not receive ECMO [47]. These conditions mostly included mood disorders, anxiety, and posttraumatic stress disorder.
●In an Australian cohort of 442 ECMO survivors, death or moderate-to-severe disability at six months was reported in two thirds of survivors and only one third were alive without moderate disability [48].
●Data comparing outcomes with those who have undergone mechanical ventilation only are conflicting. A meta-analysis of ECMO survivors (for ARDS) suggested worse health-related quality of life but less psychological morbidity compared with ARDS patients supported with conventional mechanical ventilation alone [43]. One small retrospective case series of patients who received venovenous ECMO for acute respiratory failure reported no differences in cognitive or sleep outcomes at 6 and 12 months compared with patients who were managed with mechanical ventilation alone [44].
FUTURE RESEARCH AND RESOURCES — Future trials will help to identify patients most likely to benefit from ECLS, including extracorporeal membrane oxygenation (ECMO) facilitated cardiopulmonary resuscitation (NCT03813134) [49].
National and international ECMO organizations help facilitate collaboration across centers in the performance of trials.
●The Extracorporeal Life Support Organization (ELSO) maintains the largest registry of ECMO patients, which has proven to be a valuable tool both for research and quality benchmarking [50].
●The International ECMO Network (ECMONet) is a research consortium that includes ECMO-specific expertise dedicated to conducting and supporting high-quality, high-impact research in the field [51].
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Extracorporeal membrane oxygenation (ECMO) (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Terminology – Extracorporeal life support (ECLS) encompasses a set of extracorporeal modalities that can provide oxygenation, carbon dioxide (CO2) removal, and/or circulatory support (table 1). (See 'Terminology' above.)
•Venovenous (V-V) extracorporeal membrane oxygenation (ECMO) and venoarterial (V-A) ECMO are the two most common forms of ECMO used in the intensive care unit. V-V ECMO is used for the temporary support of patients with respiratory failure (for gas exchange), and V-A ECMO is used to support patients with cardiac failure (for circulatory support).
•Extracorporeal CO2 removal (ECCO2R) is another uncommon form of ECLS, used for the sole purpose of CO2 removal.
●Circuits and configurations – An ECMO circuit pumps blood through an "artificial" or "membrane" lung that performs the functions of gas exchange (ie, oxygenation and CO2 removal) and/or circulatory support (table 2). (See 'ECMO and ECCO2R circuits' above.)
•Circuits typically consist of drainage and reinfusion cannulae, a pump, membrane lung, heat exchanger, oxygen source, blender, and connection tubing (figure 1 and figure 2 and figure 3).
•Occasionally, additional tubing (eg, Y-connectors) or additional cannulae (for enhanced drainage or reinfusion of blood) is required (eg, venoarteriovenous [V-AV] configuration (figure 4)).
●Initial ECLS mode selection – Selecting an appropriate mode of ECLS is largely dependent upon the organ failure that needs supporting and the pattern of gas exchange that needs to be corrected. (See 'Type of support needed' above.)
•Primary respiratory failure
-Patients who primarily have hypoxemic or hypercapnic respiratory failure are potential candidates for V-V ECMO. (See 'Patients who need respiratory support and oxygenation (V-V ECMO)' above and "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)".)
-Patients who have predominantly hypercapnic respiratory failure and do not need oxygenation support are potential candidates for V-V ECCO2R. (See 'Patients with pure hypercapnic respiratory failure who only need carbon dioxide removal (V-V ECCO2R)' above and "Extracorporeal life support in adults: Extracorporeal carbon dioxide removal (ECCO2R)".)
•Patients who primarily have cardiac failure, including right-sided heart failure (eg, from right ventricular infarction, massive pulmonary embolism or pulmonary hypertension), are potential candidates for V-A ECMO. (See 'Patients who need cardiac/circulatory support (V-A ECMO)' above and "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)".)
●Multidisciplinary approach – Individual patient-related factors influence the decision to proceed with ECLS (eg, comorbidities, underlying lung or cardiac disease, technical factors). The process is a team-directed approach ensuring a bridge to recovery, intervention, or a decision. (See 'Patient-specific factors' above and 'Staffing (ECMO teams)' above.)
●Complications – Complications are listed in the table (table 4), among which hemorrhage, thrombosis, hemolysis, thrombocytopenia, and infection are the most common. (See "Extracorporeal life support in adults: Management of venovenous extracorporeal membrane oxygenation (V-V ECMO)", section on 'Complications' and "Extracorporeal life support in adults: Management of venoarterial extracorporeal membrane oxygenation (V-A ECMO)", section on 'V-A ECMO-specific complications'.)
●Prognosis – Survival in patients who receive ECLS can be expected to vary by indication, complications that occur, and patient-related factors (eg, underlying comorbidities).
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