Limitations
The project has obvious limitations, including those which are typical
of any systematic review and meta-analyses. By pooling observational
studies, this review cannot overcome the limitations of its primary
studies included which were relatively of small numbers
( apart from one (21)) and, still none
were based on a randomised allocation. Indeed, the authors believe only
meta-analyses of homogeneous well-powered randomised trials should be
considered a solid scientific proof of the safety and efficacy of any
medical/surgical intervention which is difficult to achieve on the short
term period while we are still facing an unresolved pandemic and
literature guidance from the available data is needed to support
decision on a stretched medical resources setting in most countries The
secondary outcome data was missing in numerous studies and the focus by
the authors was mortality outcome and hence authors needed to be
contacted by emails to fill in missing information. However, systematic
reviews and meta-analyses of non-randomized studies (as in the current
case) can be meaningful and guide current practice, even if only by
emphasizing the limitations of the available clinical evidence (as in
the current ECMO use with the COVID 19 pandemic).
Furthermore, the exclusion of 14 reports because including less than 5
cases or being case reports is a call for more collaborative research
efforts. This type of collaboration is essential for the present
clinical challenges of the COVID 19 crisis. To complement this
collaboration, ASAIO has developed a database specific to ECMO use in
severe COVID-19 to aid in this effort. Merging and synergizing data
between databases such as those obtained by ASAIO, ESLO and
“SpecialtyCare” may provide insight about the relevant exposure,
demographics, comorbidities, and clinical and laboratory variables that
may predict outcome, aid selection of patients or even suggest futility
(against the evidence presented here).