Redefining critical illness

Both research and practice in critical care medicine have long been defined by syndromes. Though clinically recognizable entities, these are in fact loose amalgams of heterogeneous states, within which responses to therapy may vary. Mounting translational evidence suggests the current syndrome-based framework of critical illness should be reconsidered. Moreover, research done during the COVID-19 pandemic illustrates how the study of a more biologically homogeneous condition – respiratory failure due to SARS-CoV-2 infection – can increase the efficiency with which actionable results are generated. We discuss recent findings from basic science and clinical research in critical care, and explore how these might inform a new conceptual model of critical illness. De-emphasizing syndromes, we focus instead on the underlying biological changes that underpin critical illness states, and that may be amenable to treatment. We hypothesize that such an approach will accelerate translational critical care research, leading to a richer understanding of the pathobiology of critical illness, and of the proximate determinants of ICU outcomes. The specificity and granularity gained will support the design of more effective clinical trials, and inform a more precise, effective practice at the bedside.