Methodology in systematic reviews of goal-directed therapy: improving but not perfect

There has been a recent tsunami of articles on goal-directed (fluid) therapy, haemodynamic optimization and validation of cardiovascular monitoring devices. This has been followed by a wave of systematic reviews, in particular over the last five years, trying to summarize and derive conclusions and recommendations from many of these studies.^1–19 Terminology for systematic reviews and meta-analyses is frequently used incorrectly. A systematic review refers to a rigorous scientific process of reviewing relevant literature whereas meta-analysis refers to a statistical method of pooling data from multiple studies to derive a summary effect estimate. Any well-conducted scientific process needs to comply with quality standards. Likewise, systematic reviews need to meet quality criteria before qualifying for the highest level of evidence (http://ift.tt/17HmMli, accessed May 29, 2017), including a sufficiently detailed published protocol, full search strategy in multiple databases, outcome selection following GRADE²⁰ (http://ift.tt/YgVdNI, accessed May 29, 2017), assessment of risks of bias, assessment of risks of random errors, and reporting results following PRISMA²¹ and GRADEpro. Producing pooled estimates is always tempting whereas frequently not pooling data because of large heterogeneity might be much wiser. Eventually, only a few systematic reviews qualify for Level 1A evidence.

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