Utilizatiion of ECMO in the Setting of Trauma

Extracorporeal Membrane Oxygenation (ECMO), also referred to as extracorporeal life support (ECLS), offers pulmonary and/or cardiac augmentation in the critical patient. While functioning in the V-V capacity, blood leaves the body, typically via a femoral catheter, and enters the ECMO circuit. This is where the blood is oxygenated via a membrane oxygenator. The blood then returns to the body to return to circulation, typically via an internal jugular catheter. While functioning in this capacity, the ECMO circuit is augmenting the function of the lungs while oxygenating the blood. Typical indications for this mode include ARDS and have also been used for traumatic tracheal or bronchial injury, including transections of the airways, until surgical correction may be performed. The other capacity in which ECMO may function is the V-A mode, or venous-arterial mode.  This mode provides cardiac augmentation by overcoming insufficient cardiac output via roller pumps. The setup for V-A mode ECMO may include venous cannulation of the femoral veins and arterial cannulation of either the femoral or subclavian arteries. Arterial cannulation is usually performed directly via cut down, however it may be obtained percutaneously via the femoral vessels.

The ECMO circuit is usually made up of sterile tubing, roller pumps, a gas exchange membrane oxygenator, a temperature controller, a polymethylpentene membrane to capture bubbles, and infusion ports. The catheters and tubing can be bonded with heparin, in an attempt to minimize systemic anticoagulation requirements. Commonly used catheters include 19-31 Fr venous cannula and 17-19 Fr arterial cannula.

The Extracorporeal Life Support Organization provides some guidelines regarding indications for cardiac and respiratory support. For respiratory support, severe acute respiratory distress syndrome remains the most common indication. ECLS is suggested with a PaO2:FiO2 ratio of less than 150, a mortality of 50%, and recommended with a P:F ratio less than 100 with a Murray Lung Injury score of 2-4, a mortality of 80%. Additionally severe air leak syndromes are an indication, such as traumatic tracheo-bronchial transection. Indications for V-A ECMO are less specific but in the patient subjected to traumatic injury it can be utilized when cardiac output remains insufficient despite adequate intravascular volume, or in the case of cardiac collapse as the result of controllable traumatic injury. In the latter setting, ECMO is considered an augmentation to CPR, sometimes called ECPR.  Major contraindications to ECMO/ECLS include acute CNS bleeding, advanced age, contraindication to anticoagulation, prolonged CPR, high ventilator requirements for greater than 7 days, and major pharmacologic immunosuppression.

Two recent studies retrospectively reviewed the utility of V-V and V-A ECMO in trauma. The first, performed by Derek M Guirand et. al. looked at the use of V-V ECMO compared to conventional ventilator management of ARDS in trauma patients at two level 1 trauma centers in Los Angeles and North Carolina. They identified 26 ECMO and 76 conventional ventilatory managed patients.  They were able to match 17 patients from each group into similar cohorts for comparison retrospectively. Matching characteristics included fluid balance, P:F ratio, Lung Injury Score, open abdomen, Renal replacement therapy, hemorrhagic complications, and pulmonary complications. Overall 15 ECLS and 42 conventional patients survived to discharge for a mortality of 42% vs. 45%. ECLS was shown to have an independent association with improved survival (AOR 0.193, CI 0.042 – 0.884, p= 0.034), along with chest abbreviated injury score (AOR 0.693, CI 0.496 – 0.967, p= 0.031) in the unmatched cohort. ECLS in the matched cohort of 17 patients had an AOR of 0.038 (CI 0.004 – 0.407, p=0.009).

A group from Taiwan recently published results retrospectively evaluating VA ECLS in trauma (Tseng YH et al. J of Trauma, Resuscitation and Emergency Medicine 2014). They reviewed 9 patients treated with V-A ECLS over a 9 year period. Eight of the nine patients mechanisms were blunt and the median injury severity score (ISS) was 34 with a median Chest Abbreviated injury score (AIS) of 4. Three of the nine patients survived to discharge. Each of these patients had lower ISS scores (10, 13, and 18) indicating less poly trauma. This review shows patient selection is critical and the primary injuries should be controllable for improved outcomes. Patient selection remains critical for V-A ECLS in trauma and not every cardiac arrest is a candidate.

In summary, ECMO or ECLS, remains an option in trauma patients for both cardiac (V-A) and respiratory (V-V) augmentation. It is an expensive resource requiring a multi-disciplinary approach with a number of trained health care providers.  Patient selection remains critical for successful outcomes and implementation.  However, in those select patients it can improve outcomes.

References:

1.       Guirand DM, Okoye OT, Schmidt BS, et al. Venovenous Extracorporeal Life Support Improves Survival in Adult Patients with Acute Hypoxemic Respiratory Failure: A Multicenter Retrospective Cohort Study.  J Trauma Acute Care Surg 2014, 76(5):1275-81.

2.       Tseng YH, Wu TI, Liu YC, et al. Venoarterial Extracorporeal Life Support in Post-Traumatic Shock and Cardiac Arrest: Lessons Learned. Journal of Trauma, Resuscitation, and Emergency Medicine 2014, 22(12): 1-6

3.       Arlt, M, Philipp A, Voelkel S, et al. Extracorporeal Membrane Oxygenation in Severe Trauma Patients with Bleeding Shock.  Resuscitation 2010, 81:804-9

from Dr. Ryan Knoper