VOLUME 29, Issue 1

ECMO involves draining venous blood, passing it through a membrane oxygenator for carbon dioxide removal and oxygenation, and pumping it back into the central venous (venovenous or VV ECMO) or arterial (venoarterial or VA ECMO) system. When delivered back into the arterial system, it serves as an additional source of cardiac output to supplement that of the native cardiopulmonary system. There are two common peripheral cannulation configurations that are used for ECMO. Femoral cannulation via the femoral vein and femoral artery for VA ECMO, and the right internal jugular vein utilizing a dual-lumen cannula for VV ECMO. Traditionally, the institution of ECMO was performed primarily by cardiothoracic surgeons in the operating room. However, with the advancement of percutaneous techniques performed at the bedside or in a catheterization suite with fluoroscopy guidance, the number of providers comfortable instituting ECMO has expanded ^[1].

Acute respiratory distress syndrome (ARDS) is the most researched indication for VV ECMO. There have been conflicting results regarding the mortality benefit of ECMO in ARDS. The 2009 H1N1 influenza epidemic led to a worldwide spike in cases of severe ARDS. By facilitating gas exchange, ECMO allows for lung protective ventilation strategies, which is believed to reduce mortality in ARDS. Studies from the 2009 H1N1 epidemic reported possible benefits of ECMO in reducing mortality, particularly in younger patients ^[2]. VV ECMO is also widely used as a bridge to lung transplantation and to manage primary graft dysfunction after lung transplantation. By using dual lumen cannulas in the neck, femoral cannulation is avoided, enabling the patient to ambulate while on VV ECMO support.

Another emerging application of VV ECMO is extracorporeal carbon dioxide removal (ECCO2R) for hypercapnic respiratory failure such as COPD and asthma exacerbation. Smaller cannulas can be used with lower flows since the membrane exchanger more efficiently removes carbon dioxide. By correcting respiratory acidosis, mechanical ventilation can be prevented ^[3]. VA ECMO can be utilized for various forms of cardiac or cardiorespiratory failure, including post-cardiotomy cardiogenic shock, shock from acute myocardial infarction, shock from intractable ventricular arrhythmias, and less common causes such as fulminant myocarditis or sepsis associated cardiomyopathy ^[3]. Due to the ability to augment and support the right ventricle, VA ECMO is also helpful in cases of decompensated pulmonary hypertension and right ventricular failure due to pulmonary embolism.

Additionally, VA ECMO utilization is increasing in patients who experience in hospital cardiac arrest. Decreased mortality and improved neurological outcomes with extracorporeal cardiopulmonary resuscitation (ECPR) versus traditional cardiopulmonary resuscitation (CPR) have been reported.

VA ECMO is often combined with percutaneous coronary intervention for cardiac arrest related to acute coronary syndrome. The updated 2015 American Heart Association Guidelines for Advanced Cardiac Life Support now recommend considering ECPR for cardiac arrest patients with potentially reversible causes not responding to conventional CPR ^[3]. The expanding indications for ECMO need to be balanced against its associated costs and the potential for complications. ECMO is a resource intensive modality requiring special equipment and trained technicians and medical staff. Severe complications such as hemorrhage, limb ischemia, embolism and compartment syndrome may be encountered with ECMO. Additionally, hemolysis, thrombocytopenia, acquired von Willebrand syndrome, disseminated intravascular coagulopathy, and infection are other complications reported in patients on ECMO ^[3]. In conclusion, ECMO utilization is increasing in the state of Texas and worldwide. Percutaneous placement of the ECMO cannulas has brought this level of support into the community. As influenza and other respiratory illnesses continue to affect our region, the need for this life support technique is increasing.

Additionally, the body of evidence supporting the use of ECMO in a variety of other life threatening conditions is growing. Familiarity with the indications for the different ECMO strategies is paramount as anesthesiologists are often involved with the institution and support of patients on ECMO. (For more information, please also visit www.elso.org).

References:

1. Chauhan S, Subin S. Extracorporeal membrane oxygenation, an anesthesiologist’s perspective: physiology and principles. Part 1. Ann Card Anaesth. 2011;14(3):218–29.
2. Shekar K, Mullany DV, Thomson B, Ziegenfuss M, Platts DG, Fraser JF. Extracorporeal life support devices and strategies for management of acute cardiorespiratory failure in adult patients: a comprehensive review. Critical Care. 2014;18(3):219.
3. Abrams D, Combes A, Brodie D. Extracorporeal membrane oxygenation in cardiopulmonary disease in adults. J Am Coll Cardiol. 2014;63(25 Pt A):2769–78.