Extracorporeal Membrane Oxygenation Improves Survival in H1N1 Patients With Respiratory Failure

Pauline Anderson

October 12, 2009

October 12, 2009 — Despite the severity of illness and prolonged use of life support, the mortality rate among patients with severe hypoxemia receiving extracorporeal membrane oxygenation (ECMO) during the southern hemisphere winter outbreak of influenza A (H1N1) was only 21%, according to the results of a report published online October 12 in the Journal of the American Medical Association and scheduled for the November 4 print issue.

"Our findings have implications for health care planning and the clinical management of patients with 2009 influenza A (H1N1) during the 2009-2010 northern hemisphere winter," write the Australia and New Zealand Extracorporeal Membrane Oxygenation (ANZ ECMO) Influenza Investigators. "This information should facilitate health care planning and clinical management for these complex patients during the ongoing pandemic."

The goal of the observational study was to describe the incidence, clinical features, and other characteristics of patients with severe acute respiratory distress syndrome (ARDS) who were treated with ECMO during the H1N1 winter pandemic in Australia and New Zealand.

The investigators found that 68 patients with severe influenza-associated ARDS, including 53 with confirmed 2009 influenza A (H1N1), were treated with ECMO in 15 intensive care unit centers between June 1 and August 31, 2009. Affected patients were often young adults, many of whom were pregnant or postpartum.

Patients had a median age of 34.4 years, and 34 (50%) were men. Before ECMO, patients had severe respiratory failure despite advanced mechanical ventilatory support, with a median PaO2/fraction of inspired oxygen (FIO2) ratio of 56. The median duration of ECMO support was 10 days.

At the end of the study, 48 patients (71%; 95% confidence interval [CI], 60% – 82%) survived to intensive care unit discharge, of whom 32 survived to hospital discharge and 16 remained in the hospital. Fourteen patients (21%; 95% CI, 11% – 30%) died.

This mortality rate was lower than the 30% to 48% rate for use of ECMO for ARDS reported elsewhere. The authors said that the lower mortality rate could be, among other things, a result of the young age of the patients and improved ECMO technology.

With a similar ECMO use pattern, "rough estimates are that the United States and the European Union might expect to provide ECMO to approximately 800 and 1300 patients during the 2009-2010 winter, respectively," said the authors.

Among the limitations of the study were that the researchers were unable to report on the possible outcome of patients if ECMO had not been used and that final hospital outcomes were unavailable for some patients.

In an accompanying editorial, Douglas B. White, MD, MAS, and Derek G. Angus, MD, MPH, from the University of Pittsburgh School of Medicine, Pennsylvania, noted that the ability of the influenza virus to mutate "raises questions about whether the virus that will emerge this fall will produce similar rates and severity of clinical infection."

However, they said, this and 2 other reports on experiences with the H1N1 virus in Mexico and Canada that appear in the same issue of JAMA provide "important signals about what clinicians and hospitals may confront in the coming months."

The authors have disclosed no relevant financial relationships.

JAMA. Published online October 12, 2009.

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