Extracorporeal Membrane Oxygenation Is First-Line Therapy for Acute Respiratory Distress Syndrome

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Excerpt

Extracorporeal membrane oxygenation (ECMO) for the acute respiratory distress syndrome (ARDS) has evolved considerably since its debut in the early 1970s. What was once a conceptually elegant but practically cumbersome endeavor is now an efficient, compact intervention that can be readily deployed at the bedside (1). The physiologic rationale for modern ECMO in patients with the most severe forms of ARDS is two-fold: First, to provide gas exchange where invasive mechanical ventilation appears insufficient to provide this support or where doing so comes at the expense of unacceptably high plateau airway pressures and a consequent risk of ventilator-associated lung injury (VALI) (2). Second, ECMO may be used to facilitate lung-protective ventilation strategies beyond the current standard of care for minimizing tidal volumes, airway pressures, and respiratory rates with the goal of further minimizing VALI (3–5).
Despite recent technological advances, ECMO is often reserved as the last option in an ARDS management pathway, considered only after having exhausted all other therapies. This limited role in many centers, at the present time, is due in large part to a growing but, as yet, inconclusive body of evidence supporting the use of ECMO in patients with ARDS (6). Knowing the capabilities of this intervention but faced with a paucity of data from randomized controlled clinical trials, we are challenged to answer a very loaded question: Should ECMO be first-line therapy for ARDS? The short answer is no. Yet, in routine clinical practice, the answer may be less clear, at least under certain very specific circumstances.
Although there is an evolving role for extracorporeal support in optimizing outcomes in ARDS, we do not advocate that ECMO should supplant an initial management strategy involving standard of care low-volume, low-pressure ventilation, which has been proven to reduce mortality in ARDS (7, 8). In fact, existing data from randomized controlled trials have led to the development and adoption of algorithms for the management of patients with ARDS (Fig. 1).
Although such algorithms vary by center and region, a low-volume, low-pressure ventilation strategy is a key component in all of them. In addition, they typically, although not universally, include some combination of a restrictive fluid strategy, the use of neuromuscular blocking agents, prone positioning, and a strategy of high positive end-expiratory pressure (PEEP), among others (9–12). Ideally, every patient with ARDS would be managed with such an approach. However, implementation of this strategy first requires prompt and accurate identification of the syndrome. A recent international, prospective cohort study evaluating the prevalence and outcome of ARDS demonstrated that—outside of study conditions—ARDS appears to be underrecognized and suboptimally managed, with high rates of nonadherence to the current standard of care and limited application of evidence-based, advanced interventions, including prone positioning (13). When ARDS is not recognized early and lung-protective ventilation is either delayed or not applied, mortality increases significantly (14). Still other patients may be perceived by clinicians as being too tenuous in their gas exchange to tolerate low-volume, low-pressure ventilation or too hemodynamically unstable to tolerate higher levels of PEEP or prone positioning.
This lack of recognition and inexperience with managing patients with the most severe forms of ARDS has given rise to a potentially important role for ECMO—facilitating the safe transport of patients with refractory ARDS to centers more experienced in managing such patients.

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