title: Pitfalls in estimating the effect of interventions in the critically ill using observational study designs.
authors: A F
authors: AF
authors: Connors
mesh_terms: D015982:Bias; D002407:Catheterization, Swan-Ganz / Q000009:adverse effects*; D015986:Confounding Factors, Epidemiologic; D016638:Critical Illness; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D012107:Research Design; D012720:Severity of Illness Index