For patients with refractory acute respiratory distress syndrome (ARDS) caused by COVID-19 infections, extracorporeal membrane oxygenation (ECMO) may be the treatment of last resort.
But for reasons that aren’t clear, in the second wave of the COVID-19 pandemic at a major teaching hospital, the mortality rate of patients on ECMO for COVID-induced ARDS was significantly higher than it was during the first wave, despite changes in drug therapy and clinical management, reported Rohit Reddy, BS, a second-year medical student, and colleagues at Thomas Jefferson University Hospital in Philadelphia.
During the first wave, from April to September 2020, the survival rate of patients while on ECMO in their ICUs was 67%. In contrast, for patients treated during the second wave, from November 2020 to March 2021, the ECMO survival rate was 31% (P = .003).
The 30-day survival rates were also higher in the first wave compared with the second, at 54% versus 31%, but this difference was not statistically significant.
“More research is required to develop stricter inclusion/exclusion criteria and to improve pre-ECMO management in order to improve outcomes,” Mr. Reddy said in a
ARDS severity higher
ARDS is a major complication of COVID-19 infections, and there is evidence to suggest that COVID-associated ARDS is more severe than ARDS caused by other causes, the investigators noted.
“ECMO, which has been used as a rescue therapy in prior viral outbreaks, has been used to support certain patients with refractory ARDS due to COVID-19, but evidence for its efficacy is limited. Respiratory failure remained a highly concerning complication in the second wave of the COVID-19 pandemic, but it is unclear how the evolution of the disease and pharmacologic utility has affected the clinical utility of ECMO,” Mr. Reddy said.
To see whether changes in disease course or in treatment could explain changes in outcomes for patients with COVID-related ARDS, the investigators compared characteristics and outcomes for patients treated in the first versus second waves of the pandemic. Their study did not include data from patients infected with the Delta variant of the SARS-CoV-2 virus, which became the predominant viral strain later in 2021.
The study included data on 28 patients treated during the first wave, and 13 during the second. The sample included 28 men and 13 women with a mean age of 51 years.
All patients had venovenous ECMO, with cannulation in the femoral or internal jugular veins; some patients received ECMO via a single double-lumen cannula.
There were no significant differences between the two time periods in patient comorbidities prior to initiation of ECMO.
Patients in the second wave were significantly more likely to receive steroids (54% vs. 100%; P = .003) and remdesivir (39% vs. 85%; P = .007). Prone positioning before ECMO was also significantly more frequent in the second wave (11% vs. 85%; P < .001).
Patients in the second wave stayed on ECMO longer – median 20 days versus 14 days for first-wave patients – but as noted before, ECMO mortality rates were significantly higher during the second wave. During the first wave, 33% of patients died while on ECMO, compared with 69% in the second wave (P = .03). Respective 30-day mortality rates were 46% versus 69% (ns).
Rates of complications during ECMO were generally comparable between the groups, including acute renal failure (39% in the first wave vs 38% in the second), sepsis (32% vs. 23%), bacterial pneumonia (11% vs. 8%), and gastrointestinal bleeding (21% vs. 15%). However, significantly more patients in the second wave had cerebral vascular accidents (4% vs. 23%; P = .050).
Senior author Hitoshi Hirose, MD, PhD, professor of surgery at Thomas Jefferson University, said in an interview that the difference in outcomes was likely caused by changes in pre-ECMO therapy between the first and second waves.
“Our study showed the incidence of sepsis had a large impact on the patient outcomes,” he wrote. “We speculate that sepsis was attributed to use of immune modulation therapy. The prevention of the sepsis would be key to improve survival of ECMO for COVID 19.”
“It’s possible that the explanation for this is that patients in the second wave were sicker in a way that wasn’t adequately measured in the first wave,” CHEST 2021 program cochair Christopher Carroll, MD, FCCP, from Connecticut Children’s Medical Center in Hartford, said in an interview.
The differences may also have been attributable to changes in virulence, or to clinical decisions to put sicker patients on ECMO, he said.
Casey Cable, MD, MSc, a pulmonary disease and critical care specialist at Virginia Commonwealth Medical Center in Richmond, also speculated in an interview that second-wave patients may have been sicker.
“One interesting piece of this story is that we now know a lot more – we know about the use of steroids plus or minus remdesivir and proning, and patients received a large majority of those treatments but still got put on ECMO,” she said. “I wonder if there is a subset of really sick patients, and no matter what we treat with – steroids, proning – whatever we do they’re just not going to do well.”
Both Dr. Carroll and Dr. Cable emphasized the importance of ECMO as a rescue therapy for patients with severe, refractory ARDS associated with COVID-19 or other diseases.
Neither Dr. Carroll nor Dr. Cable were involved in the study.
No study funding was reported. Mr. Reddy, Dr. Hirose, Dr. Carroll, and Dr. Cable disclosed no relevant financial relationships.
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