Extracorporeal membrane oxygenation (ECMO) is an advanced medical technique that temporarily replaces the functions of the heart and lungs. By extracting and re-oxygenating blood outside the body, this sophisticated system provides an essential respite for these vital organs, promoting their recovery from severe pathologies.
Frequently used in cases of acute respiratory distress, severe heart failure or post-surgical complications, ECMO has established itself as a proven life-saving solution, particularly in critical situations such as ARDS or COVID-19. The benefits and limitations of this method are also the subject of ongoing research.
In intensive care units, it is a valuable aid, guiding teams in complex situations and increasing patients' chances of survival. ECMO, although technically demanding, remains an essential pillar of modern life support.
What is ECMO?
Definition and functioning
Extracorporeal membrane oxygenation (ECMO) is an extracorporeal circulation technique that provides simultaneous cardiac and respiratory support to patients whose heart and/or lungs cannot maintain sufficient gas exchange to sustain life. This procedure simulates the vital functions of the heart and lungs by removing deoxygenated blood, passing it through a special membrane that removes carbon dioxide and injects oxygen, before returning it to the bloodstream.
The process involves inserting cannulas into blood vessels to extract blood, which is then pumped through a membrane oxygenator. This oxygenator mimics the function of the pulmonary alveoli by removing carbon dioxide and adding oxygen. Once oxygenated, the blood is warmed and then re-injected into the body. To prevent coagulation in the extracorporeal circuit, systemic anticoagulation is necessary. In addition, antibiotic prophylaxis is frequently implemented to reduce the risk of infection.
The two main forms: VV-ECMO and VA-ECMO
ECMO comes in two main modes: veno-venous (VV-ECMO) and veno-arterial (VA-ECMO).
VV-ECMO is used specifically to provide respiratory support. In this context, blood is drawn from the venous system, oxygenated outside the body, and reintroduced into the venous system. This method is particularly suitable for patients with acute respiratory distress, such as in the case of acute respiratory distress syndrome (ARDS). Cannulas are generally inserted into large veins, such as the internal jugular vein and the femoral vein, and the oxygenated blood is redistributed to the right atrium to be pumped by the heart towards the lungs.
VA-ECMO, on the other hand, provides both cardiac and respiratory support. In this configuration, blood is drawn from the venous system, oxygenated, and directly reinjected into the arterial system. This method is used in patients suffering from severe heart failure or a combination of cardiac and respiratory failures. Cannulas for VA-ECMO are generally inserted into a large vein and artery, such as the femoral vein and carotid artery. Thanks to this technique, the system partially takes over the pumping function of the heart, allowing it to recover gradually.
When does ECMO become a treatment option?
ECMO eligibility criteria
ECMO is considered as a therapeutic option when patients suffer from severe respiratory or cardiac failure that may be potentially reversible. Although eligibility criteria may vary between institutions, certain universal criteria are commonly adopted.
In the context of acute respiratory distress, patients generally become eligible for ECMO if their PaO2/FiO2 ratio drops below 50 mmHg, despite mechanical ventilation with an FiO2 at 100% and a PEEP greater than or equal to 5 cm H2O. Similarly, refractory hypercapnia accompanied by a pH below 7.25, despite optimized maneuvers (alveolar recruitment and inhaled vasodilators), may also designate the patient as a potential candidate for ECMO.
With regard to cases of cardiac support, the indication for ECMO is particularly precise in situations of refractory cardiogenic shock, despite optimal medical treatment. Myocardial infarction, acute myocarditis, postpartum cardiomyopathy or decompensated heart failure may motivate this decision. In addition, some patients with septic shock, when the cause is identified and initial resuscitation is effective, may also benefit from ECMO.
Limitations and ethical considerations
Although ECMO can offer an opportunity for survival in critical circumstances, it is not without limitations and ethical questions. Frequently encountered exclusion criteria include factors such as extreme age (generally, patients under 12 or over 65), lung damage lasting more than 21 days, pulmonary capillary pressure exceeding 25 mmHg, severe burns, or terminal illnesses for which the short-term prognosis is fatal.
Decisions surrounding ECMO also require in-depth, collective ethical reflection, particularly when it comes to assessing the duration of treatment or deciding to terminate it. These decisions involve collaboration between doctors, patients and families, while respecting principles such as beneficence, non-maleficence and patient autonomy. Complex situations may arise, such as the use of ECMO as a " bridge to nowhere ", where the patient is neither eligible for transplantation nor expected to recover functionally, creating significant ethical issues.
Furthermore, limited medical resources and complications associated with ECMO are factors to consider. These complications include systemic infections, hemorrhagic or coagulopathic disorders, neurological damage, or limb ischemia caused by catheters. These risks highlight the need for transparent communication and shared decision-making to integrate the multiple complex dimensions of this type of treatment.
ECMO in the fight against critical cases
Use of ECMO in severe acute respiratory distress
Veno-venous ECMO (VV-ECMO) plays a decisive role in the management of severe acute respiratory distress, particularly during acute respiratory distress syndrome (ARDS). This pathology, marked by significant inflammation of the lungs, causes respiratory distress that is refractory to conventional treatments such as mechanical ventilation.
ECMO takes over pulmonary functions by enabling both oxygenation and the elimination of carbon dioxide from the body, thus providing valuable time to allow the lungs to regenerate.
Patients undergoing VV-ECMO benefit from so-called "ultra-protective" invasive ventilation, designed to limit pulmonary lesions often associated with mechanical ventilation. In accordance with the Extracorporeal Life Support Organization (ELSO) recommendations, initial settings include a positive end-expiratory pressure (PEEP) of 15 cmH2O, an inspiratory pressure of 25 cmH2O, and a respiratory rate of 5 cycles per minute.
These settings can be adjusted according to the patient's response and the need to optimize gas exchange during treatment.
ECMO in the context of COVID-19
During the COVID-19 pandemic, ECMO represented an essential option for patients with severe forms of ARDS. The disease often led to severe hypoxemia accompanied by respiratory acidosis unresponsive to conventional therapies, making ECMO vital for these critical cases.
Data collected during studies, such as those conducted by the Sorbonne Université team or the COVID-ICU registry, have illustrated the effectiveness of ECMO in improving survival rates in these patients. In addition, VV-ECMO was mostly used, although veno-arterial ECMO (VA-ECMO) also found application in certain specific situations.
Les critères d'accès à l'ECMO dans ce contexte incluaient une hypoxémie sévère (PaO2/FiO2 < 150) et/ou une acidose respiratoire (pH < 7,25 avec PaCO2 > 60 mmHg) résistantes aux stratégies conventionnelles de ventilation mécanique.
ECMO rescue in severe cardiogenic shock
Veno-arterial ECMO (VA-ECMO) proves to be an invaluable rescue technique for patients suffering from severe cardiogenic shock – a failure of the heart muscle preventing sufficient blood circulation to meet the body's physiological needs.
By temporarily taking over cardiac function and relieving the left ventricle, VA-ECMO allows for better patient management and is associated with optimized clinical outcomes.
It offers medical teams a critical period to intervene more definitively, whether through a heart transplant or other major surgical repairs. However, VA ECMO is not a treatment in itself, but rather acts as an essential bridge to more sustainable therapeutic options or partial to complete recovery.
Comparison of ECMO approaches with other techniques
Unlike many other life support techniques, ECMO (Extracorporeal Membrane Oxygenation) represents an advanced and sometimes decisive approach in the treatment of respiratory and cardiac failure. Although this strategy provides significant benefits, it is essential to examine its specific characteristics and comparisons with other therapeutic methods to fully understand its advantages and limitations.
Mechanical ventilation
Mechanical ventilation is frequently used to treat patients with acute respiratory distress. However, its prolonged use can lead to lung damage, particularly due to excessively high positive pressures or an inappropriate tidal volume.
ECMO, especially in its veno-venous form (VV-ECMO), offers an interesting alternative. It allows to reduce ventilation parameters and offers the lungs a real period of rest necessary for their recovery. This minimizes the potential damage induced by conventional mechanical ventilation.
Ventricular Assistance
The use of ventricular assist devices, such as left ventricular assist devices (LVADs), is primarily reserved for patients with chronic heart failure or awaiting transplantation. However, these devices do not address the respiratory needs of patients.
In comparison, veno-arterial ECMO (VA-ECMO) provides combined support for cardiac and respiratory functions. This characteristic makes it particularly useful in acute cardiorespiratory failure situations.
Portable Extracorporeal Membrane Gas Exchange
With the emergence of portable ECMO systems, such as the Cardiohelp®, increased flexibility is now possible. These lightweight devices allow patient transport while maintaining vital stability, particularly between different healthcare facilities.
Studies suggest that these portable devices can reduce transfusion requirements and improve certain clinical outcomes, offering a suitable solution in contexts where rapid intervention is essential. However, their use still requires an expert, experienced team.
Transplantation and Temporary Bypass
Finally, ECMO sometimes plays an indispensable role as a bridge to definitive solutions, such as heart or lung transplantation. It offers the patient a chance of temporary stabilization, allowing their vital functions to be maintained until a transplant is available.
This temporary bridging function combines the immediate benefits of ECMO with the long-term progress provided by transplants, thus creating a coherent and integrated therapeutic pathway.
Conclusion
ECMO truly stands out from other life support solutions. By combining respiratory and cardiac support while minimizing ventilator-induced lung injury, it is a valuable therapeutic option. However, its implementation requires high-level expertise as well as appropriate technical resources, highlighting the importance of a thorough assessment of each patient's context before a decision is made.
The future of ECMO and innovations
Current research and future developments
ECMO continues to evolve through major scientific and technological advances, aimed at improving clinical outcomes while expanding its fields of application. Current research focuses on several priority areas, including optimizing management protocols, improving the materials used, particularly for oxygenators, and reducing the complications commonly associated with ECMO.
One of the most promising areas concerns the development of more portable and easier-to-handle ECMO systems. These systems, by offering improved patient mobility, could revolutionize patient management by more easily integrating these devices into more dynamic and proximity care. For example, solutions such as Cardiohelp® are already used to support certain patients in critical condition, particularly while awaiting a transplant or functional recovery. Clinical validation of their effectiveness is underway and could pave the way for even wider use in different therapeutic contexts.
In parallel, research efforts are focused on better selection of eligible profiles for this device, and refinement of the criteria for triggering ECMO. These efforts aim to maximize effectiveness and limit risks, using more personalized and targeted approaches. The implementation of strategies adapted to the specific needs of each patient would indeed guarantee optimal results, while reducing adverse effects.
ECMO as a bridge to recovery or transplantation
ECMO now plays an essential role in the management of patients awaiting recovery or transplantation. Its role is to provide vital support while allowing patients to remain clinically stable and sometimes even active, an important aspect when it comes to, for example, multiple organ transplants or conditions that seriously compromise vital prognosis. In the context of multi-organ thoracic transplants, ECMO has demonstrated its value in increasing short-term survival rates, although long-term data still require further study.
In specific contexts, notably heart-lung, heart-kidney, or lung-kidney transplants, patients on ECMO show survival rates comparable to those of non-bridged patients after the critical 30-day post-transplantation mark. Once this initial phase has passed, clinical outcomes tend to align, confirming the strategic importance of ECMO in this specific setting.
In lung transplantation, ECMO offers an innovative approach often referred to as a "bridge to candidacy." This strategy allows patients to benefit from continuous physical activity and remain integrated into active therapeutic protocols, thereby improving their chances of success following the intervention. This approach is particularly relevant for patients suffering from acute exacerbations related to chronic lung diseases, opening up new perspectives for profiles that would once have been deemed ineligible for transplantation.
With regard to heart transplantation, ECMO also plays an important role, especially in complex post-operative situations, such as the occurrence of acute graft failure (EGF). In these specific cases, veno-arterial ECMO (VA-ECMO) provides both circulatory and respiratory support, giving the transplanted heart a valuable chance to recover. This intervention not only helps to reduce mortality related to EGF, but also helps to contain postoperative complications, significantly improving the overall prognosis of the patients concerned.
Conclusion
Extracorporeal membrane oxygenation (ECMO) is now positioned as an essential life support technique for patients in acute respiratory or cardiac distress. Thanks to its ability to simulate heart and lung functions, ECMO has proven its effectiveness in managing critical situations such as acute respiratory distress syndrome (ARDS), severe cardiogenic shock, and even major health crises such as the COVID-19 pandemic.
To optimize clinical outcomes, it is essential to ensure a thorough understanding of eligibility criteria, monitoring parameters, and ethical considerations related to this technique. These elements are the cornerstones for using ECMO accurately and safely.
Advances in medical research continue to refine treatment protocols, improve oxygenator materials, and perfect monitoring strategies. All of this underscores the importance of training and collaboration between medical teams. ECMO can thus play the role of a bridge to recovery or even transplantation, opening an invaluable path of hope for critically ill patients.
In summary, ECMO represents a powerful tool in the face of acute cardiorespiratory failure. It is essential to promote further research, standardize protocols, and strengthen the skills of medical personnel. This methodical approach will maximize the benefits of this technology. By integrating ECMO judiciously and in a planned manner into intensive care, we can aspire to improved survival rates and a better quality of life for critically ill patients.
FAQ
What are the main indicators for the use of ECMO in severe heart or respiratory failure?
The use of ECMO (Extracorporeal Membrane Oxygenation) in situations of severe heart or respiratory failure is based on several specific indicators:
- Acute respiratory failure: a P/F ratio (partial pressure of oxygen in the blood to fraction of inspired oxygen) less than 80 mmHg under FiO2 = 1 for at least 3 hours, or less than 50 mmHg under FiO2 = 1 despite optimization of ventilatory parameters.
- Insuffisance cardiaque : persistance de l’état de choc en dépit d’un traitement maximal, illustrée par des critères tels qu’une pression artérielle systolique < 100 mmHg, des doses élevées de dobutamine (> 10 μg/kg/min) ou d’adrénaline (> 0,5 μg/kg/min), ainsi que d’autres signes comme l’oligurie, une pression artérielle pulmonaire moyenne > 25 mmHg ou une défaillance multi-organique.
How does ECMO differ from conventional life support techniques, and what are its specific advantages?
Unlike conventional techniques, ECMO makes it possible to temporarily bypass the heart and lungs. This maintains blood circulation and blood gas balance (oxygen and carbon dioxide) without requiring direct treatment of cardiac or pulmonary pathologies. Its specific advantages include:
- The possibility of providing respite to organs by allowing them to recover after serious events such as severe acute respiratory illness, myocardial infarction, or major trauma.
- Its essential role in supporting patients who do not respond to traditional treatments in cases of severe heart or respiratory failure.
What are the potential risks and complications associated with ECMO, and how are they managed?
ECMO is not without risks. Several complications can occur, including:
- Bleeding, sometimes severe, especially in the cerebral area.
- Infections related to the use of catheters.
- Formation of blood clots or air bubbles in the tubing.
- Limb ischemia related to the position of the cannulas.
These complications are managed through the use of anticoagulants to prevent thrombosis, sterile measures to reduce infections, and reperfusion catheters to limit ischemia. Close monitoring, including echocardiograms and chest X-rays, allows for the rapid detection and treatment of other complications such as left ventricular distension or pulmonary edema.
When can ECMO be used as a "bridge" for patients awaiting heart or lung transplantation, and what are the criteria for its use?
ECMO can be valuable as a "bridge" for patients awaiting transplantation in critical contexts:
- Bridge to lung transplantation: It optimizes respiratory and hemodynamic functions, facilitating the wait for a graft and potentially replacing conventional extracorporeal circulation during transplantation. It is also used in cases of primary graft failure.
- Bridge to cardiac transplantation: ECMO, particularly in veno-arterial form (VA-ECMO), assists patients with severe heart failure by ensuring effective organ perfusion. It also allows the transplanted heart to "rest" after transplantation with primary graft dysfunction (PGD).
Criteria include significant hemodynamic instability, acute failure of cardiac or respiratory function, and inability to wean from cardiopulmonary bypass after cardiac surgery. Patients are assessed on a number of factors, including their functional status, length of time on the transplant list and need for mechanical ventilation.
