Extracorporeal Gas Exchange for Acute Respiratory Distress Syndrome: Open Questions, Controversies and Future Directions

Abstract

Veno-venous extracorporeal membrane oxygenation (V-V ECMO) in acute respiratory distress syndrome (ARDS) improves gas exchange and allows lung rest, thus minimizing ventilation-induced lung injury. In the last forty years, a major technological and clinical improvement allowed to dramatically improve the outcome of patients treated with V-V ECMO. However, many aspects of the care of patients on V-V ECMO remain debated. In this review, we will focus on main issues and controversies on caring of ARDS patients on V-V ECMO support. Particularly, the indications to V-V ECMO and the feasibility of a less invasive extracorporeal carbon dioxide removal will be discussed. Moreover, the controversies on management of mechanical ventilation, prone position and sedation will be explored. In conclusion, we will discuss evidences on transfusions and management of anticoagulation, also focusing on patients who undergo simultaneous treatment with ECMO and renal replacement therapy. This review aims to discuss all these clinical aspects with an eye on future directions and perspectives.

Cumulative Fluid Balance during Extracorporeal Membrane Oxygenation and Mortality in Patients with Acute Respiratory Distress Syndrome

“…The number of ventilator-free days at day 28 and day 60 was significantly lower in higher CFB quartiles, indicating that early fluid status during ECMO may also affect the weaning of severe ARDS patients from mechanical ventilators. Finally, mechanical ventilator settings were associated with mortality in ARDS patients undergoing ECMO [ 2 , 3 , 4 ], and VA ECMO patients received higher airway pressures and higher tidal volume during ECMO than VV ECMO patients, which may be associated with significantly higher hospital mortality in VA ECMO patients.…”

“…Extracorporeal membrane oxygenation (ECMO) is considered a rescue therapy for life-threatening hypoxemia in patients with severe acute respiratory distress syndrome (ARDS) [ 1 , 2 , 3 , 4 ]. Oxygen delivery during ECMO depends on the flow of blood through the circuit, which is limited primarily by the size of the drainage cannula, the diffusion properties of the membrane oxygenator and the concentration of hemoglobin.…”

“…Oxygen delivery during ECMO depends on the flow of blood through the circuit, which is limited primarily by the size of the drainage cannula, the diffusion properties of the membrane oxygenator and the concentration of hemoglobin. Increasing hemoglobin concentrations via red blood cell transfusion is commonly used to maintain adequate oxygen delivery during ECMO [ 1 , 2 , 3 , 4 , 5 , 6 ]. During the initial phase of ECMO, high-volume fluid resuscitation and blood transfusions are often required to ensure sufficient blood flow and to correct anemia or coagulopathy [ 1 , 6 , 7 ].…”

Comparisons of Outcomes between Patients with Direct and Indirect Acute Respiratory Distress Syndrome Receiving Extracorporeal Membrane Oxygenation

“…ECMO facilitates ultra-protective ventilation to allow lower energy loads (i.e., mechanical power) and airway pressures, thereby mitigating ventilator-induced lung injury (VILI) and improving gas exchange [ 12 , 14 , 16 ]. It has been reported that there are survival benefits to severe ARDS patients receiving higher airway pressures to receive ECMO treatment [ 20 ].…”

“…Previous studies have reported that patients with direct or indirect ARDS differ in terms of pathophysiology, biochemistry, radiography, respiratory mechanics, and responses to ventilatory and clinical management strategies, all of which contribute to diverse clinical outcomes and mortality [ 2 , 3 , 4 , 5 , 6 , 10 , 11 ]. Extracorporeal membrane oxygenation (ECMO) is considered to be a rescue therapy for refractory hypoxemia in cases of severe ARDS [ 12 , 13 , 14 ]. Differences in the etiology of ARDS (i.e., direct or indirect lung injury) may also be responsible for the observed diversity of clinical characteristics and clinical outcomes.…”