As intensivists in our PICUs, we are faced with the above situations and questions daily. How would such questions be addressed at the time of the first edition of this textbook? We would have relied on a combination of our experience, discussions with colleagues, textbooks, or memory of a study in the medical literature. In this “classic” paradigm, few qualms were expressed about our reliance on unsystematic, anecdotal observations to draw conclusions. We believed that a thorough grounding in pathophysiology should usually enable us to determine the proper management of patients and that common sense was sufficient to adequately evaluate new therapies and diagnostic tests. Guidelines could be developed on the basis of the “expertise” of content knowledge and clinical experience. This approach was not considered “antiintellectual.” Indeed, the more experience one had, the more wisdom one acquired, and great respect has always been (and should always be) afforded to the wise among us. However,
the learning curve associated with gaining such wisdom was gradual and protracted.

Beginning formally in 1992, the paradigm shifted. Guyatt et al. coined the term evidence-based medicine (EBM) and formed the Evidence-Based Medicine Working Group (1). EBM “is the conscientious, explicit, and judicious use of current best evidence in making decisions about the care of individual patients” (2). EBM involves the integration of this evidence with clinical experience and each patient’s preferences and values. Instinct, experience, knowledge of disease mechanisms, and common sense are necessary but insufficient to properly evaluate and apply new therapies, diagnostic modalities, or prediction tools. Rules of evidence interpretation must be learned to practice EBM; the rules were developed and disseminated during more than a decade of publishing in the Journal of the American Medical Association (JAMA) in what has become the living handbook of EBM: The Users’ Guides to the Medical Literature (3). Now available in print (4,5) and on the Web (including an interactive textbook) (6), these guides outline core methods for the critical appraisal of evidence (Step 3 below).

Five steps are involved in the EBM approach to patient care:

EBM‘s roots extend into the 1980s, when the science of clinical epidemiology was codified by Sackett et al. (7) at McMaster University in Hamilton, Ontario. Their landmark text, Clinical Epidemiology: A Basic Science for Clinical Medicine, published in 1985, described the quantitative tools that would become the “acronym soup” of EBM: RR (relative risk), RRR (relative risk reduction), NNT (number needed to treat), etc. From just two citations in the National Library of Medicine’s PubMed (MEDLINE) in 1992 to 87,703 in 2013, EBM has grown to a worldwide phenomenon, to the extent that the basic paradigm is now rarely questioned. Although many now espouse its value, in assessing its impact, it is difficult to submit EBM to the same rigorous methodology that it requires of the questions that it is used to answer. Furthermore, EBM has several clear limitations.

Some critiques can be answered readily:

EBM engenders more troublesome questions. Despite a huge increase in the publication of well-designed and clinically meaningful research studies over the past several decades, many questions remain for which valid evidence simply does not exist. In our field of pediatric critical care in particular, it has been difficult to conduct the type of definitive, randomized, controlled trials that should form our evidence base. Two suggested solutions are: (a) This deficiency can often be addressed by careful consideration of trials in other populations, such as neonates or adults, and (b) this reality should, and indeed has, spurred our community to aggressively form networks and seek funding to conduct the multicentered trials necessary to address this void.

Another concern, given the often hectic nature of our practice, asks how one should find the time to create clinical questions, search for trials, properly and critically appraise them, and apply them judiciously to our patient care—in “real time?” The criticism has been leveled, therefore, that EBM is an “ivory tower” exercise that is unrealistic to expect busy practitioners to consistently undertake. This criticism is also not easily deflected because practicing EBM “by the book” does require additional time. Two answers to this concern are: (a) Many of our patients have similar conditions, so that once we learn the “correct” answers to our clinical questions, we need not reinvent the wheel with each subsequent patient (although we must remain attuned to possible changes from new research findings), and (b) “shortcuts” do exist, such as tapping into preappraised sources of evidence, so that all that needs to be critically considered is the applicability of the evidence to each individual patient (see “Secondary Evidence Sources”).

The first step in the EBM approach to obtain focused evidence involves creating a structured “clinical question,” which usually takes the “PICO” format: Population, Intervention, C

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