Extracorporeal membrane oxygenation(ECMO), also known as extracorporeal life support (ECLS), is a technique used in medicine to partially take up the task of respiratory and/or cardiac function of the patient when his/her heart and lung is having problems sustaining life. Cannulas are put into the human body to extract and infuse blood. After the extraction, the blood passes through the ECMO circuit, undergoes oxygenation and the removal of CO2 and then returns to the body. The ECMO circuit is lined with multiple monitors that ensures the pressure and other conditions of the blood. Specialists are trained to closely monitor the ECMO machine during the treatment. There are several types of ECMO machines, the two most common of which are veno-arterial (VA) ECMO and veno-venous (VV) ECMO. While VV ECMO only provides respiratory support, VA ECMO supports both the heart and the lung by additionally assisting in pumping blood.

ECMO is used as respiratory support for severe acute respiratory distress syndrome (ARDS), which can be caused by severe pneumonia and trauma. It is also used as a bridging mechanism to transplant. ECMO is used as cardiac support for disorders such as congestive heart failure (CHF), cardiogenic shock, etc.

In terms of outcome, ECMO has shown positive survival rate for acute respiratory distress syndrome (ARDS) [1][2].A registry maintained by ELSO of nearly 51,000 people that have received ECMO has reported outcomes with 75% survival for neonatal respiratory failure, 56% survival for pediatric respiratory failure, and 55% survival for adult respiratory failure[3][4].

ECMO has its unique benefits comparing to other similar techniques. What differentiates it from cardiopulmonary bypass (CPB) and mechanical ventilating is that it can potentially limit sedation and allow for spontaneous breathing and communication, accommodate early mobilization or physical therapy, avoid the complications of mechanical ventilation damage such as lung injury and minimize the risk of ventilator dependence.

However, ECMO, like any other medical treatment, has its own complications. The most common one is bleeding, which is most likely caused by the anticoagulant heparin that thins the blood to prevent clotting. Up to 4% of the patients on VV-ECMO develop intracranial bleeding.[5] Another study found that among 878 VA-ECMO treated patients, 2.8% developed intracranial bleeding.[6] Another complication is the potential failure or rupture of the ECMO circuit. Additionally, small blood clots or air bubbles can develop in the blood stream[7].

Some contraindications of ECMO that suggests against using such treatment include the following. First of all, ECMO is generally not considered when there is inability to anticoagulate patients. But noticeably, medical professionals have found that in some cases, they can provide ECMO support with limited or no coagulation for longer and extended periods of time. Secondly, it is hard to support patients with irreversible disease processes or patients who are not a candidate for transplant or device using ECMO. Thirdly, most literature suggests that it is more challenging to support the patient using ECMO if a patient has been on high pressure and high FiO2 mechanical ventilator for more than seven days[8][9]. In addition, multiple organ dysfunction and significant neurologic injury can also affect the consideration of using ECMO support.

Research is underway to improve ECMO techniques. Directions of further investigation include but are not limited to anticoagulation, threshold for monitoring, reducing infection risk, extubation and optimizing rehabilitaition.

[1] Peek, GJ; Moore, HM; Moore, N; Sosnowski, AW; Firmin, RK (1997). "Extracorporeal membrane oxygenation for adult respiratory failure". Chest. 112 (3): 759–64. doi:10.1378/chest.112.3.759

[2] Lewandowski, K.; Rossaint, R.; Pappert, D.; Gerlach, H.; Slama, K.-J.; Weidemann, H.; Frey, D. J. M.; Hoffmann, O.; Keske, U. (1997). "High survival rate in 122 ARDS patients managed according to a clinical algorithm including extracorporeal membrane oxygenation". Intensive Care Medicine. 23 (8): 819–35. doi:10.1007/s001340050418

[3] Hemmila, Mark R.; Rowe, Stephen A.; Boules, Tamer N.; Miskulin, Judiann; McGillicuddy, John W.; Schuerer, Douglas J.; Haft, Jonathan W.; Swaniker, Fresca; Arbabi, Saman (2004). "Extracorporeal Life Support for Severe Acute Respiratory Distress Syndrome in Adults" . Annals of Surgery. 240 (4): 595–605, discussion 605–7. doi:10.1097/01.sla.0000141159.90676.2d

[4] Brogan, Thomas V.; Thiagarajan, Ravi R.; Rycus, Peter T.; Bartlett, Robert H.; Bratton, Susan L. (2009). "Extracorporeal membrane oxygenation in adults with severe respiratory failure: A multi-center database". Intensive Care Medicine. 35 (12): 2105–14. doi:10.1007/s00134-009-1661-7

[5] Fan, E., Gattinoni, L., Combes, A., Schmidt, M., Peek, G., & Brodie, D. et al. (2016). Venovenous extracorporeal membrane oxygenation for acute respiratory failure. Intensive Care Medicine, 42(5), 712-724. doi: 10.1007/s00134-016-4314-7

[6] Le Guennec, L., Cholet, C., Huang, F. et al. Ischemic and hemorrhagic brain injury during venoarterial-extracorporeal membrane oxygenation. Ann. Intensive Care 8, 129 (2018). https://doi.org/10.1186/s13613-018-0475-6

[7] Extracorporeal Life Support Organization - ECMO and ECLS > Resources > RisksandComplications. (2020). Retrieved 1 March 2020, from https://www.elso.org/Resources/RisksandComplications.aspx

[8] Tripathi, R. (2017). Moving From Pre-ECMO Ventilation to Post-ECMO Ventilation and Mortality. ASAIO Journal, 63(5), 523. doi: 10.1097/mat.0000000000000643

[9] Hemmila, M., Rowe, S., Boules, T., Miskulin, J., McGillicuddy, J., & Schuerer, D. et al. (2004). Extracorporeal Life Support for Severe Acute Respiratory Distress Syndrome in Adults. Transactions Of The ... Meeting Of The American Surgical Association, CXXII(&NA;), 193-205. doi: 10.1097/01.sla.0000141159.90676.2d

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