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Extracorporeal CO2 removal in severe chronic obstructive pulmonary disease exacerbations: a work in progress.

To the Editor: In a recent issue of Critical Care Medicine, we read with great interest the article by Del Sorbo et al (1) on the use of extracorporeal carbon dioxide removal (ECCO 2 R) in patients with chronic obstructive pulmonary disease (COPD) exacerbations and acute respiratory acidosis at high risk of noninvasive ventilation (NIV) failure. Although endotracheal intubation and invasive mechanical ventilation (IMV) remain the standard treatment for acute respiratory acidosis after NIV failure, IMV may have several deleterious consequences, including dynamic hyperinflation, elevated intrinsic positive end-expiratory pressure, impaired delivery of aerosolized medications, ventilator-associated pneumonia, and relative immobility with deconditioning, all of which may significantly affect morbidity and mortality (2, 3). In this context, ECCO 2 R represents an attractive approach to correct acute respiratory acidosis, potentially decreasing the need for endotracheal intubation and IMV. Nevertheless, ECCO 2 R should still be considered an experimental therapy and its clinical use is not without risks. The earlier use of arteriovenous ECCO 2 R systems (4, 5) was associated with the complications of arterial cannulation, such as arterial pseudoaneurysm, lower limb ischemia, and compartment syndrome, as well as inherent difficulties in controlling blood flow rate (4, 5). The development of pump-assisted venovenous ECCO 2 R systems all but eliminates these issues. However, significant concerns remain for complications related to venous cannulation and the use of systemic anticoagulation. In a recent study using venovenous ECCO 2 R, significant bleeding events requiring blood transfusion occurred in three of 20 patients, and one patient died due to a retroperitoneal bleed following femoral vein catheterization (6). Accordingly, in the study by Del Sorbo et al (1), bleeding episodes were observed in three of 25 patients and one patient experienced vessel perforation after femoral vein cannulation (1). Of note, suboptimal functioning of the ECCO 2 R system was also an issue in this study, with 36% of patients experiencing a mechanical adverse event using the venovenous hemofiltration device chosen for the study (1). In the study by Del Sorbo et al (1), the endotracheal intubation rate in the group of patients at high risk of NIV failure 4. Gaieski DF, Mikkelsen ME, Band RA, et al: Impact of time to antibiotics on survival in patients with severe sepsis or septic shock in whom early goal-directed therapy was initiated in the emergency department. Crit Care Med 2010; 38:1045–1053 5. Puskarich MA, Trzeciak S, Shapiro NI, et al; Emergency Medicine Shock Research Network (EMSHOCKNET): Association between timing of antibiotic administration and mortality from septic shock in patients treated with a quantitative resuscitation protocol. Crit Care Med 2011; 39:2066–2071 Antibiotic Initiation in Severe Sepsis: Does Sequence Impact Outcome?