Extracorporeal Membrane Oxygenation May Improve Outcomes in Severe Acute Respiratory Failure

Laurie Barclay, MD

September 24, 2009

September 24, 2009 — Extracorporeal membrane oxygenation (ECMO) vs conventional ventilator management may improve the odds of survival without disability for patients with severe acute respiratory failure, according to the results of a UK-based, multicenter trial reported in the September 16 Online First issue of The Lancet.

"Swine flu causes a viral pneumonia which can result in severe respiratory failure in young adults," lead author Giles Peek, MD, from Glenfield Hospital, University Hospitals of Leicester National Health Service Trust, Leicester, United Kingdom, said in a news release. "We have already used ECMO during the first wave of the pandemic with good effect and we are expecting ECMO to prove an invaluable weapon in the fight against the winter resurgence of the infection, as has already been seen during the Australasian winter."

The goal of this study was to evaluate the safety, clinical efficacy, and cost-effectiveness of ECMO vs conventional ventilatory support. With use of an independent central randomization service, 180 adults with acute respiratory failure were assigned in a 1:1 ratio to receive continued conventional management or referral to consideration for treatment by ECMO.

Inclusion criteria were ages 18 to 65 years and severe but potentially reversible respiratory failure (Murray score > 3.0 or pH < 7.20). Patients were excluded if they were receiving high-pressure (> 30 cm H2O of peak inspiratory pressure) or high FiO2 (> 0.8) ventilation for more than 7 days or had intracranial bleeding, any other contraindication to limited treatment with heparin, or any contraindication to continuing active treatment.

The main endpoint of the study was death or severe disability at 6 months after randomization or before discharge from the hospital, and primary analysis was by intent-to-treat. Other outcomes included data concerning resource use and economic outcomes (quality-adjusted life-years). Blinding was incomplete, with only those investigators who conducted the 6-month follow-up masked to treatment assignment.

The investigators also studied the key cost-generating events, performed analyses of cost-utility at 6 months after randomization, and modeled lifetime cost-utility.

Of 766 patients who were screened, 180 were randomly assigned to consideration for treatment by ECMO (n = 90) or to receive conventional management (n = 90), and 68 patients (75%) actually received ECMO. Of patients assigned to consideration for treatment by ECMO, 63% (57/90) survived to 6 months without disability vs 47% (41/87) of those assigned to conventional management (relative risk, 0.69; 95% confidence interval [CI], 0·05 - 0·97; P = .03).

Referral to consideration for treatment by ECMO treatment was associated with a gain at 6-month follow-up of 0.03 quality-adjusted life-years. According to results from a lifetime model, the predicted cost per quality-adjusted life-year of ECMO was £19,252 (95% CI, 7622 - 59,200) at a discount rate of 3.5%.

"We recommend transferring of adult patients with severe but potentially reversible respiratory failure, whose Murray score exceeds 3.0 or who have a pH of less than 7.20 on optimum conventional management, to a centre with an ECMO-based management protocol to significantly improve survival without severe disability," the study authors write. "This strategy is also likely to be cost effective in settings with similar services to those in the UK."

Limitations of this study include absence of a standardized treatment protocol in the conventional management group.

"The cost-effectiveness of ECMO would be improved if costs of both transport and provision of the technique could be reduced," the study authors conclude. "We are confident that ECMO is a clinically effective treatment for acute respiratory distress syndrome, which also promises to be cost effective in comparison with other techniques competing for health resources."

In an accompanying comment, Joseph B. Zwischenberger, MD, from the University of Kentucky College of Medicine in Lexington, and James E. Lynch, BS, RRT, from University of Texas Medical Branch in Galveston, congratulate the Conventional ventilation or ECMO for Severe Adult Respiratory failure (CESAR) group on completing such a large, complex trial.

"The debate that will surround this study reflects the difficulty of this type of research in the critically ill patient," they write. "This study will likely provide ammunition for both those in favour and those against the use of ECMO in the adult population."

The UK National Health Service Health Technology Assessment, English National Specialist Commissioning Advisory Group, Scottish Department of Health, and Welsh Department of Health supported this study. Three of the study authors are clinicians who provide EMCO services. Two authors study have received travel grants from Chalice Medical. The editorialists have disclosed no relevant financial relationships.

Lancet. Published online September 16, 2009.

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