Discussion
The primary finding of this study is that among the 20 COVID-positive
patients that we treated with ECMO, the survival rate to hospital
discharge was 55%. Also, our results suggest that proper patient
selection and control of bacterial infections prior to and/or during
ECMO placement may be key to improving survival, as culture-positive
septic shock and culture-negative SIRS were the main causes of death and
were only observed in patients who failed to survive to hospital
discharge.
The treatment of ARDS with ECMO remains disputed, even though its use in
treating ARDS has increased in the past decade.(11,12) While the exact
mortality rate of treating ARDS with ECMO varies by research study, it
is generally accepted to range between 34-39%.(11,13,14) Thus, it is
generally recognized that ECMO should be primarily used for refractory
cases of ARDS, in which a patient remains severely hypoxic despite
aggressive treatment.(12)
Interestingly, our study and others on COVID-19 have found that the
mortality rates of treating ARDS due to COVID-19 with ECMO are similar
to the previously reported mortality rates of treating non-COVID ARDS.
Recently, there have been a few articles published that specifically
investigated the use of ECMO in treating ARDS due to COVID-19. The
largest of these studies was conducted by Barbaro et al., who drew from
an Extracorporeal Life Support Organization (ELSO) registry to analyze
the outcomes of 1035 COVID-positive patients who were treated with
ECMO.(15) The researchers found that among these patients, the 90-day
post-ECMO mortality rate was 37.4%. The study included data from 213
different hospitals and included patients treated from January
16th to May 1st of 2020. Another
study that more closely resembles our own is from Schmidt et al, who
documented the outcomes of 83 COVID-positive patients who were treated
at their hospital.(16) They discovered that the 60-day mortality of
these patients was 31%. Compared to these studies, our patients had a
slightly higher mortality rate of 45%; however, it should be noted that
our sample size was significantly smaller than either of these two
articles.
Based on this current research on the use of ECMO in ARDS due to
COVID-19, the mortality rate appears to be anywhere between 31-45%.
This mortality rate is similar to the 34-39% mortality rate in treating
non-COVID ARDS with ECMO in select patients. Therefore, it is possible
that ECMO is just as effective at treating ARDS due to COVID-19 as it is
at treating ARDS due to non-COVID-19 etiologies if appropriate patient
selection was applied. For example, none of the patients in our study
had cardiac dysfunction. This is because our selection committee
considered COVID-19 patients with cardiac dysfunction and ARDS to have
multiorgan failure, which was a contraindication for ECMO placement.
While there needs to be far more research done on this topic to
definitively state that ECMO is effective in treating COVID-19, it is
possible that it is an effective treatment option for refractory cases
of ARDS due to COVID-19.
Sepsis and SIRS were the causes of death in all but one patient in our
study, suggesting that bacterial infections during ECMO placement may be
a significant factor in mortality rates. While immunomodulation therapy
has been shown to decrease the mortality rate of COVID-19,(20,21) it has
also been associated with an increased infection rate. For example, one
study demonstrated that 13% of patients treated with tocilizumab were
diagnosed with new infections, compared to only 4% of patients treated
solely with the standard of care.(21) There should be particular
attention to preventing, monitoring for, and responding early to
bacterial infections in COVID-19 patients placed on ECMO.
During the first wave of COVID-19 in Pennsylvania, the highest number of
daily COVID-19 cases occurred on April 8th with 2,059
cases. By the end of our study period on June 11th,
the daily number of cases fell to 680, which was one of the lowest
number of daily cases in Pennsylvania since the beginning of the
pandemic. Our study beings on April 1st and ends on
June 11th, which fairly accurately represents the
beginning and end of the first wave of COVID-19 in Pennsylvania.
Beginning in late October, Pennsylvania entered a second wave, with
daily cases greatly exceeding those of the first wave. Future studies of
the second wave of COVID-19 will differ from this study, for multiple
reasons, including changes in pre-ECMO immunomodulation treatment.
During the second wave, interleukin inhibitors are no longer recommended
and steroids are more widely used.
Our study is limited by its small sample size and being based in one
hospital center. It is also possible that there was selection bias in
this study, even though ECMO placement was determined by a
multidisciplinary team of physicians.
Despite its limitations, this study provides extensive data on 20
patients with ARDS due to COVID-19 who were treated with ECMO. While we
cannot extrapolate from a sample size of 20 patients, we hope our
evidence can complement other studies and contribute to meaningful
meta-analyses and statistical analyses. Cases of ARDS due to COVID-19
will continue in the coming months and years, and we hope that our
analysis contributes to the growing research on how to treat this deadly
disease.