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Swine flu deaths cut by blood oxygenation

ECMO system reduced very ill patients’ risk of dying from 2009 H1N1 flu

Louise Prime

Wednesday, 05 October 2011

Patients with severe 2009 H1N1 influenza were more likely to survive if they were treated with extracorporeal membrane oxygenation, shows UK research presented today at the European Society of Intensive Care Medicine meeting in Berlin.

The study, also published early online in this week’s JAMA, compared in-hospital death rates in patients with acute respiratory distress syndrome (ARDS) who were treated with the blood oxygenation system, with death rates in similarly ill patients not treated with ECMO.

Researchers from Leicester wanted to investigate further the value of ECMO, because it is twice as costly as usual care; and, in earlier research that had suggested it could improve outcomes in people with ARDS, confounding factors could not be excluded.

They compared mortality among 80 critically ill patients with H1N1 who had been referred, accepted and transferred to one of the UK’s four adult ECMO centres in the 2009-10 pandemic, with mortality among a similar number of carefully matched patients with suspected or confirmed swine flu (using data from the longitudinal Swine Flu Triage study) who were not referred for ECMO. Only 69 of the 80 transferred patients actually received ECMO.

More than a quarter (27.5%) of all patients transferred to an ECMO centre died in hospital; mortality was roughly doubled in non-referred patients (46.7-52.5%, depending on how matching was done).

Even when early deaths – within 48 hours – were excluded from the analysis, ECMO was still beneficial.

The writer of an accompanying editorial agreed with the study’s authors that the results should lay to rest concerns raised in the 1970s about the safety of using ECMO in people with ARDS.

He said: “While underlying risk factors may be different, severe respiratory failure from H1N1 infection presents a clinical challenge similar to that involving ARDS from other causes. Despite several decades of investigation into potential treatment strategies, use of low tidal volumes remains the only proven therapy to decrease mortality in ARDS.

“In light of the large observed differences in mortality with and without ECMO, large consortia of triallists may be enticed to consider ECMO as a potential target for a randomized controlled trial early in the course of severe ARDS from all causes.”

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