ECMO for severe ARDS (Review, NEJM)
Daniel Brodie and Matthew Bacchetta offer a nice review of extracorporeal membrane oxygenation (ECMO) for acute respiratory distress syndrome (ARDS) in adults, based on their experience at Columbia University in New York City.
This general overview describes ECMO techniques and re-visits the CESAR trial results -- the only major randomized controlled trial on ECMO in ARDS -- acknowledging its limitations in concluding on benefits of ECMO (at least 30% of the patients in the control arm in CESAR did not get standard-of-care low-tidal-volume mechanical ventilation).
They argue that adverse events resulting from ECMO are low, citing their experience. They also note that there was only one adverse event related to ECMO reported in CESAR (a death after vessel perforation during cannulation). However, the ECMO centers in the U.K. reported significantly more adverse events (mainly serious bleeding due to the required anticoagulation) when describing their results treating ARDS during the H1N1 epidemic. (Out of 80 patients, 8 patients had intracranial hemorrhage; 1 a fatal pulmonary hemorrhage; 4 had hemothorax, and 2 had retroperitoneal bleeds.)
ECMO for ARDS is still in bragging-rights, leading-edge, early-adopter territory, as the authors' "Areas of Uncertainty" section confirms:
The role and proper use of ECMO for patients with ARDS have not been definitively established. The continued evolution of ECMO technology also limits the conclusions that may be drawn from recent studies. The role of extracorporeal carbon dioxide removal in ARDS, although potentially promising, remains to be defined.
Although the CESAR trial provides some guidance for the use of ECMO, it is not clear which patients with ARDS are the best candidates for this treatment. The most favorable timing for the initiation of ECMO has not been established, and it is not clear whether patients who have required more than 7 days of high-pressure or high-FIO2 ventilation should be excluded from receiving ECMO. Various strategies to achieve lung rest and their effects on the inflammatory process have not been compared, nor have any such strategies been shown to be superior to standard-of-care lung-protective ventilation during ECMO.
(That's a fairly large Area, I daresay.) Continuing advances in ECMO technology and accumulating experience and comfort with its use by physicians, nurses, and institutions may someday lead to an expanded role for ECMO beyond a salvage therapy at tertiary centers. Less sanguine academics have called ECMO for ARDS "unproven, expensive, and dangerous" and argue it should be relegated to the dustbin of bad ideas. For now,"ECMO should be performed at centers with high case volumes, established protocols, and clinicians who are experienced in its use," argue Drs. Brodie and Bacchetta.
Brodie D, Bacchetta M. Extracorporeal Membrane Oxygenation for ARDS in Adults. N Engl J Med 2011;365:1905-1914.