Elsevier

Journal of Critical Care

Volume 41, October 2017, Pages 64-71
Journal of Critical Care

Pulmonary
Extracorporeal membrane oxygenation (ECMO) as a treatment strategy for severe acute respiratory distress syndrome (ARDS) in the low tidal volume era: A systematic review,☆☆,,★★

https://doi.org/10.1016/j.jcrc.2017.04.041Get rights and content

Highlights

  • Identified 27 studies of ECMO for ARDS patients receiving lung protective ventilation

  • Five have appropriate control groups to allow for comparison.

  • High degree of variability between studies

  • Two studies show a statistically significant difference, both favouring ECMO.

  • Confidence in a difference in outcomes with the addition of ECMO is weak.

Abstract

Objective

To evaluate the hospital survival in patients with severe ARDS managed with ECMO and low tidal volume ventilation as compared to patients managed with low tidal volume ventilation alone.

Methods

Electronic databases were searched for studies of at least 10 adult patients with severe ARDS comparing the use of ECMO with low tidal volume ventilation to mechanical ventilation with a low tidal volume alone. Only studies reporting hospital or ICU survival were included. All identified studies were assessed independently by two reviewers.

Results

Of 1782 citations, 27 studies (n = 1674) met inclusion criteria. Hospital survival for ECMO patients ranged from 33.3 to 86%, while survival with conventional therapy ranged from 36.3 to 71.2%. Five studies were identified with appropriate control groups allowing comparison, but due to the high degree of variability between studies (I2 = 63%), their results could not be pooled. Two of these studies demonstrated a significant difference, both favouring ECMO over conventional therapy.

Conclusion

Given the lack of studies with appropriate control groups, our confidence in a difference in outcome between the two therapies remains weak. Future studies on the use of ECMO for severe ARDS are needed to clarify the role of ECMO in this disease.

Introduction

Despite recent advances in the management of acute respiratory distress syndrome (ARDS), including low tidal volume ventilation [1], neuromuscular blockade [2], and prone positioning [3], severe ARDS is still associated with a 46–52% mortality [4], [5].

In light of the favourable results of extracorporeal membrane oxygenation (ECMO) during the most recent H1N1 pandemic, and the randomized control trial by the CESAR collaboration, ECMO's appeal as a potential therapy for patients with severe ARDS has increased [6], [7], [8], [9]. The positive findings from the H1N1 pandemic and CESAR trial contradict those of two previous randomized controlled trials [10], [11], purportedly due to improved ECMO technology and better patient selection [6].

Although previous systematic reviews have examined the benefit of ECMO in ARDS, they included studies in which patients received mechanical ventilation with tidal volumes of up to 10–12 cm3/kg, as well as studies with patients that did not meet the current criteria for severe ARDS [12], [13]. Inclusion of such patients may bias the results of these reviews. Although the direction of the bias remains unclear, it is our hypothesis that the inclusion of studies in which patients received high tidal volumes has led to an overestimate of the benefit of ECMO. As such, to better reflect the impact of ECMO use in current clinical practice, we performed a systematic review of observational studies and randomized controlled trials comparing patients with severe ARDS managed with ECMO and low tidal volume mechanical ventilation to those managed with low tidal volume mechanical ventilation only. We excluded all trials that did not use a low tidal volume ventilation strategy prior to the initiation of ECMO and for patients in the control group. Furthermore, given that much of the resurgence in the use of ECMO technology has been related to its use during the H1N1 epidemic, we performed a subgroup analysis on articles that include only patients with a primary diagnosis of H1N1.

Section snippets

Data sources and searches

Trials and conference abstracts were identified using an electronic search of MEDLINE, PubMed, Cochrane Central Register of Controlled Trials, and EMBASE, including publications in all languages. Reference lists of relevant articles as well as works cited were hand searched by two independent authors (BT, MK). Our search combined Medical Subject Headings and keywords for ECMO and ARDS to identify relevant articles (Fig. S1). Randomized control trials and observational studies with > 10 subjects

Study selection

The search strategy retrieved 1782 citations comprising 1725 unique abstracts. After review, 1602 abstracts were excluded for failure to meet eligibility criteria. Of the 123 identified for full text review 26 met inclusion criteria (Fig. 1). These studies included one randomized control trial [6], 4 matched cohort studies [7], [8], [9], [18], 2 non-matched cohort studies [19], [20], 2 prospective cohort studies without a control group [31], [33], 9 retrospective cohort studies without a

Discussion

As the first systematic review to focus on ECMO patients treated with low tidal volume ventilation, this paper better reflects the use of ECMO in the current clinical environment. The finding of a wide range of survival to hospital discharge is a testament to the current high clinical variability regarding the initiation of ECMO, and undoubtedly reflects local differences in patient selection, implementation strategies, ECMO setup, patient management, and provider comfort.

Interestingly, these

Conclusion

Current data demonstrates that patients with severe ARDS treated with ECMO and low tidal volume ventilation have a survival to hospital discharge ranging from 33.3 to 86%, compared to 36.3–71.2% among patients treated with low tidal volume mechanical ventilation alone. Five studies were identified with appropriate control groups allowing comparison between these therapies and two demonstrated a significant difference in survival to hospital discharge, both favouring ECMO over conventional

Acknowledgements

Lee Bowman – translation services.

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    Work performed at London Health Sciences Centre, London Ontario Canada.

    ☆☆

    No reprints required.

    No financial support was provided for this project.

    ★★

    No conflicts of interest.

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