Originally published in MedPage Today
by Todd Neale, MedPage Today Staff Writer
Most patients who underwent extracorporeal membrane oxygenation (ECMO) for respiratory failure survived their struggle with pandemic H1N1 flu, according to a study by researchers from Australia and New Zealand.
Of the 68 patients treated with ECMO during the Southern Hemisphere’s winter, 54 were still alive as of Sept. 7, according to Andrew Davies, MBBS, of Monash University and Alfred Hospital in Melbourne, Australia, and colleagues.
The findings, reported online in the Journal of the American Medical Association, “should facilitate healthcare planning and clinical management for these complex patients during the ongoing pandemic,” the researchers said.
The study will be published in the Nov. 4 print issue.
After emerging in North America, the new H1N1 strain spread to the Southern Hemisphere, and patients infected with the virus stressed the capacity of intensive care units. (See ICUs Down Under Hit Hard by H1N1 Pandemic Flu)
Among the subset of patients who developed acute respiratory distress syndrome, those who had respiratory failure despite advanced mechanical ventilation were treated with ECMO.
Davies and his colleagues examined data from all 68 patients treated with ECMO in Australia and New Zealand at the 15 ICUs providing the service. Of those, 53 had laboratory-confirmed pandemic H1N1, while eight had confirmed infection with nonsubtyped influenza A. The other seven were regarded as having suspected infection with the pandemic strain.
The researchers estimated the incidence of ECMO use for confirmed and suspected H1N1 to be 2.6 per one million people (95% CI 2.0 to 3.2). This compares with a rate of just 0.15 per one million people the previous winter.
Assuming similar incidence of ECMO use for the current flu season in the Northern Hemisphere, the U.S. and Europe might expect to provide the treatment for 800 and 1,300 patients, respectively, they said.
They acknowledged, however, that these estimates could vary according to changes in the virus’s virulence and deployment of an effective vaccine. Preliminary results indicate that the pandemic vaccine being distributed is, in fact, effective.
The median age of the patients in the current study was 34.4, and half were male.
Three children younger than 15 received ECMO. None of the patients was older than 65.
The most common comorbidities were obesity in 50%, asthma in 28%, and diabetes in 15%.
Nearly one in 10 was pregnant.
More than a quarter (28%) were coinfected with a bacterium, most commonly Streptococcus pneumoniae in 10 and Staphylococcus aureus in four.
Before doctors initiated ECMO, about two-thirds (68%) of patients received vasoactive drugs and 24% received renal replacement therapy.
Almost all of the patients (94%) received oseltamivir (Tamiflu) for a median duration of eight days.
The median duration of ECMO was 10 days, and two patients were still receiving the treatment at the end of the study period.
Most patients (81%) received rescue therapies for acute respiratory distress syndrome, including recruitment maneuvers (67%), inhaled nitric oxide (32%), epoprostenol (22%), prone positioning (20%), and high-frequency oscillatory ventilation (5%).
Hemorrhagic complications were common, occurring in 54% of ECMO patients. The most common sources were ECMO cannulation sites (22%), the gastrointestinal tract (10%), and the respiratory tract (10%).
Infective complications occurred in 62% of patients, most commonly in the respiratory tract (44%) and bloodstream (21%).
As of Sept. 7, some 21% of patients who received ECMO had died. Of the survivors, 32 had been discharged from the hospital, 16 were still hospitalized but no longer in the ICU, and six remained in the ICU.
All three children treated with ECMO were still alive, although one was still in the ICU.
Among those who died, contributed causes were listed as intracranial hemorrhage in six, other hemorrhage in four, and intractable respiratory failure in four.
The authors acknowledged that the analysis was subject to the inherent limitations of a case series.
The study was also limited by the inability to report on the possible outcome if ECMO had not been used and on long-term outcomes.