Using ECMO to treats ARDS
The current standards of care for adults with the Acute Respiratory Distress Syndrome (ARDS) encompass a variety of processes that are best delivered with an integrated and protocolized approach. The strength of evidence supporting the various components of such a standardized approach varies, but most aspects of today’s modern approach to ARDS are based upon solid evidence. The major components of therapy are related to modes of mechanical ventilation, pharmacological adjuvants, and ancillary maneuvers. It has long been our approach at Emanuel to provide a rapid and lung-protective escalation of intervention focused on providing the least harmful but adequate oxygen delivery1.
Towards this end, we recognize the relative roles of ARDSnet pressure control ventilation, airway pressure release ventilation (APRV) and high frequency oscillatory ventilation (HFOV) and the data that supports their selected uses. In our center, we also utilize the volume diffusive respirator (VDR, Percussionairre Corporation, Sand Point Idaho), a pressure-controlled tidal ventilator with a superimposed hi frequency, low volume percussive component.
We utilize advanced imaging and interventions to include recruitment maneuvers and prone positioning when anatomically appropriate. We use endpoint directed therapies and trend a combination of cerebral and tissue infra-red spectroscopy, mixed venous oxygen saturations and serum markers of an adequate DO2:VO2 relationship. We strive for adequate resuscitation, total body and intravascular euvolemia, and aggressive immunological surveillance and nutritional support. We selectively employ inhaled nitric oxide and prostacyclins when indicated.
If, despite and after the above measures, a patient cannot adequately deliver oxygen on “safe” ventilator settings, we treat them with extra-corporeal membrane oxygenation (ECMO). ECMO, as a therapy for ARDS in adults has been controversial for many years but current research indicates that ECMO is a standard of care in the modern treatment regimen for adults with severe ARDS. We utilize ECMO when indicated as a routine aspect of our protocolized approach to ARDS when other means of oxygenation and/or ventilation are insufficient or less safe. We also use ECMO to support circulation as appropriate for profound shock, cardiac “stun”, hypothermia or in the extremes of resuscitation. We consider most contraindications to be “relative” and, with few exceptions” consider each case individually
The early reports of Zapol and Morris, in 1979 and 1992 respectively, showed no benefit to ECMO for adult ARDS, but these studies utilized protocols and equipment that are obsolete. More recent reports from the UK have demonstrated that outcomes are significantly improved with both adult ARDS2 and H1N1 pneumonia3 if patients are cared for in an ECMO center. This reflects both the benefit of modern ECMO as well as the benefit of an evidence based, protocolized approach to pulmonary failure.
The new Berlin Classification of ARDS4 reports that the survival rate for “severe” ARDS, (i.e.: a PaO2:FiO2 ratio < 100) to be 45%. The international registry of the Extracorporeal Life Support Organization (ELSO)5 reports a survival rate of 60% for patients who were placed on ECMO with a mean PF ratio of 73.0 ± 1.8. At Emanuel, over the past three years, for adult patients with a mean PF ratio of 55.0 ± 3.1 (n = 41), our survival rate has been 65%. In addition, by our protocolized approach to these patients including the dynamic application of the VDR, we have demonstrated a significantly shortened time on ECMO for both adults with ARDS6 as well as those with H1N1 pneumonia7 in comparison to the ELSO registry.
ECMO is not, nor should it be, available in every ICU that treats patients with ARDS. It is a regional resource. We are the most experienced ECMO center in the Pacific Northwest and offer these therapies to patients of all ages; neonatal, pediatric and adult. We also provide the only formal, experienced and immediately available ECMO transport program in our region. Over the past three years we have retrieved patients in extremis from more than 15 medical centers, cannulated them in the referring hospital’s ICU and transported them to Portland without a single death. Over 90% of our patients are referred to Emanuel, and more than 70% have required transport on ECMO. Our mobile ECMO transport team consists of two attending surgeons, a perfusionist, a respiratory therapist, an OR nurse and a trauma resuscitation/ICU nurse. Generally, we can mobilize within 90 minutes of a referral call, any time, any day.
We know that ECMO is more effective if utilized early. It is a misconception to consider ECMO as a salvage, or “rescue” therapy. The consequences of profound, refractory hypoxemia and ventilator induced lung injury are very severe and widespread. Please consider a referral to our center as soon as it is apparent that advanced approaches are failing, preferably over the course of hours, not days. Our criteria for ECMO include those who have a PF ratio < 100 on a high FiO2 despite the timely application of advanced ventilation regimens (hi PEEP ARDSnet CMV, APRV, and/or HFOV), positional therapy, inhalation agents (iNO and/or prostacyclin) and recruitment maneuvers. It is our experience that true, non-cardiogenic, ARDS is readily apparent and outcomes are better if patients are referred for ECMO before they have been on the ventilator for more than 5 days.
We have been a regional referral center for a variety of conditions for a many years and we took our first referrals for ECMO over 25 years ago. We are committed to serving our community together with all of the facilities in our region. Our ECMO service is staffed with surgeons, intensivists, pulmonologists and a full spectrum of allied specialists, therapists, nurses and perfusionists. We are improving the outreach and follow-up, education, quality improvement and transport aspects of our program and invite you to join us in what we feel should be a shared and regional approach to severe, refractory, hypoxemic ARDS.
1. Michaels AJ, Wanek SM, Dreifuss BA, et al: A protocolized approach to pulmonary failure and the role of intermittent prone positioning. J Trauma. 2002 Jun;52(6):1037-47; discussion 1047.
2. Peek GJ, Mugford M, Tiruvoipati R, et al; CESAR Trial Collaboration. Efficacy and economic assessment of Conventional Ventilatory Support Versus Extracorporeal Membrane Oxygenation for Severe Adult Respiratory Failure (CESAR): a multicentre randomized controlled trial. Lancet. 2009;374(9698):1351-1363.
3. Noah MA, Peek GJ, Finney SJ, et al: Referral to an extracorporeal membrane oxygenation center and mortality among patients with severe 2009 influenza A(H1N1). JAMA. 2011 Oct 19;306(15):1659-68. Epub 2011 Oct 5.
4. The ARDS Definition Task Force: Acute Respiratory Distress Syndrome
The Berlin Definition, JAMA. 2012;307(23):2526-2533
5. Extracorporeal Life Support Organization’s (ELSO) International Registry for Adults Respiratory Failure treated with ECMO. http://www.elsonet.org/index.php/registry/statistics/limited.html
6. Michaels AJ, Hill JG, Long WB, et al.: The Protocolized Use of Percussive Ventilation Reduces the Cost and Risk of ECMO for Refractory Hypoxemic ARDS in Adults. the 84th annual meeting of the Pacific Coast Surgical Association, Kauai HI, 2013, Archives of Surgery 2013 (in review)
7. Michaels, AJ, Hill JG, Long WB, et al.: Reducing the Time on ECMO with the Use of the Volume Diffusive Respirator (VDR) for Adults with H1N1 Pneumonia, annual meeting of the North Pacific Surgical Association, Spokane WA, 2012, Am J Surg, May 2013 (in press)