BEST evidence in critical care medicine. Extracorporeal membrane oxygenation (ECMO) in severe adult respiratory distress syndrome

Histopathologic Findings in Lungs of Patients Treated With Extracorporeal Membrane Oxygenation

BACKGROUND

The outcome of extracorporeal membrane oxygenation (ECMO) might be influenced by its complications. Only limited information is available regarding the pathologic consequences of ECMO, especially in the era of modern ECMO technology.

METHODS

We studied the histopathologic findings in autopsy lungs of patients treated with ECMO compared with those without ECMO. Autopsy files were queried for cases with ECMO. An age- and sex-matched control group comprised of patients who died in the ICU without acute respiratory distress syndrome, pneumonia, or ECMO was compared with patients with ECMO for cardiac reason. Histopathology and medical records were reviewed.

RESULTS

Seventy-six patients treated with ECMO (38 men; median age, 40 years) and 47 control patients (23 men; median age, 45 years) were included. Common histologic pulmonary findings in the ECMO group were pulmonary hemorrhage (63.2%), acute lung injury (60.5%), thromboembolic disease (47.4%), calcifications (28.9%), vascular changes (21.1%), and hemorrhagic infarct (21.1%). Pulmonary hemorrhage was associated with longer ECMO duration (median, 7.0 vs 3.5 months; P = .014), acute lung injury with venovenous ECMO (91.7% vs 54.7%; P = .039) and longer ECMO (6.0 vs 4.0 months; P = .044), and pulmonary calcifications with infants (50.0% vs 22.4%; P = .024). Patients with ECMO for cardiac reasons (n = 60) more frequently showed pulmonary hemorrhage (P < .001), diffuse alveolar damage (P = .044), thromboembolic disease (P = .004), hemorrhagic infarct (P = .002), pulmonary calcifications (P = .002), and vascular changes (P = .001) than patients in the non-ECMO group.

CONCLUSIONS

Some findings are suspected to be associated with the patient's underlying disease, whereas others might be related to ECMO. Our results provide a better understanding of ECMO-related lung disease and might help to prevent it.

Veno-venous ECMO: a synopsis of nine key potential challenges, considerations, and controversies

Background

Following the 2009 H1N1 Influenza pandemic, extracorporeal membrane oxygenation (ECMO) emerged as a viable alternative in selected, severe cases of ARDS. Acute Respiratory Distress Syndrome (ARDS) is a major public health problem. Average medical costs for ARDS survivors on an annual basis are multiple times those dedicated to a healthy individual. Advances in medical and ventilatory management of severe lung injury and ARDS have improved outcomes in some patients, but these advances fail to consistently “rescue” a significant proportion of those affected.

Discussion

Here we present a synopsis of the challenges, considerations, and potential controversies regarding veno-venous ECMO that will be of benefit to anesthesiologists, surgeons, and intensivists, especially those newly confronted with care of the ECMO patient. We outline a number of points related to ECMO, particularly regarding cannulation, pump/oxygenator design, anticoagulation, and intravascular fluid management of patients. We then address these challenges/considerations/controversies in the context of their potential future implications on clinical approaches to ECMO patients, focusing on the development and advancement of standardized ECMO clinical practices.

Summary

Since the 2009 H1N1 pandemic ECMO has gained a wider acceptance. There are challenges that still must be overcome. Further investigations of the benefits and effects of ECMO need to be undertaken in order to facilitate the implementation of this technology on a larger scale.

Extracorporeal membrane oxygenation for severe respiratory failure in adult patients: a systematic review and meta-analysis of current evidence

BACKGROUND

Extracorporeal membrane oxygenation (ECMO) for acute respiratory failure is still a matter of debate.

METHODS

We performed a structured search on Pubmed, EMBASE, Lilacs, and the Cochrane Library for randomized controlled trials and observational case-control studies with severity-paired patients, evaluating the use of ECMO on severe acute respiratory failure in adult patients. A random-effect model using DerSimonian and Laird method for variance estimator was performed to evaluate the effect of ECMO use on hospital mortality. Heterogeneity between studies was assessed with Cochran's Q statistic and Higgin's I(2).

RESULTS

Three studies were included on the metanalysis, comprising 353 patients in the main analysis, in which 179 patients were ECMO supported. One study was a randomized controlled trial and two were observational studies with a propensity score matching. The most common reason for acute respiratory failure was influenza H1N1 pneumonia (45%) and pneumonia (33%). ECMO was not associated with a reduction in hospital mortality (OR = 0.71; CI 95% = 0.34 - 1.47; P = 0.358). If alternative severity-pairing method presented by the two observational studies was included, a total of 478 cases were included, in which 228 received ECMO support. In the former analysis, ECMO had a benefit on hospital mortality (OR = 0.52; CI 95% = 0.35 - 0.76; P < 0.001).

CONCLUSION

Extracorporeal membrane oxygenation benefit on hospital mortality is unclear. Results were sensitive to statistical analysis, and no definitive conclusion can be drawn from the available data. More studies are needed before the widespread use of ECMO can be recommended.

Clinical review: Extracorporeal membrane oxygenation

The H1N1 flu pandemic led to a wider use of extracorporeal membrane oxygenation (ECMO), proving its power in hypoxemic emergencies. The results obtained during this pandemic, more than any randomized trial, led to the worldwide acceptance of the use of membrane lungs. Moreover, as centers that applied this technique as rescue therapy for refractory hypoxemia recognized its strength and limited technical challenges, the indications for ECMO have recently been extended. Indications for veno-venous ECMO currently include respiratory support as a bridge to lung transplantation, correction of lung hyperinflation during chronic obstructive pulmonary disease exacerbation and respiratory support in patients with the acute respiratory distress syndrome, possibly also without mechanical ventilation. The current enthusiasm for ECMO in its various aspects should not, however, obscure the consideration of the potential complications associated with this life-saving technique, primarily brain hemorrhage