Chapter 5 Proving the Point

Evidence-Based Medicine in Pediatric Critical Care

R. Scott Watson, Mary E. Hartman, Derek C. Angus

“Not all clinicians need to appraise evidence from scratch, but all need some skills.”¹

What is evidence-based medicine (EBM)? How is it different from what we have always done? EBM is simply the integration of the best available evidence with individual clinical expertise and patient preferences.² The definition is not complicated, and one could easily make the incorrect assumption that its practice is, and always has been, ubiquitous. However, proven interventions are often misapplied, and striking variations in clinical practice (not attributable to patient differences) occur even when high-quality evidence is available.³^–⁸ Practicing EBM in critical care in general and pediatric critical care in particular poses unique challenges. Decisions that can have profound implications for a child and his or her family must be made quickly and, until recently, with little good external evidence. However, pediatric critical care and EBM both have matured to the point that EBM is an indispensable and realistic component of optimal practice.

Despite decades of international support and growth, the practice of EBM continues to be hindered by misconceptions. It is not “cookbook medicine” that suppresses the individual freedom of practitioners.⁹ (To the contrary, EBM relies on individual clinicians to accurately identify clinical situations to which external evidence can be applied.) It is not a cost-cutting tool. Treatments found to be effective may be more expensive than the previous standard of care. It is not unrealistic to think that physicians in the “real world” can practice it. Criticisms that EBM is too difficult and time consuming may have been valid in the past, but advances in literature search engines and the increasing availability of EBM resources make it accessible and applicable for busy clinicians.

This chapter provides an overview of the steps in practicing EBM, including a summary of common study types, information about many excellent EBM-related resources, and definitions of selected terms used in EBM (Appendix 5A, available online at http://www.expertconsult.com). EBM is here to stay, and the field of critical care is in the midst of a groundswell of outstanding clinical research that is improving the outcome of critically ill patients. Our goal is to demystify the process of EBM so that pediatric intensivists can keep up with these changes, understand EBM, and incorporate it as a fundamental element in their practice.

The Evidence-Based Medicine Process

The steps in the EBM process are straightforward: (1) define the problem, (2) search for relevant evidence, (3) evaluate the evidence, and (4) apply the evidence.

1. Define the problem

EBM starts with a well-built clinical question that is constructed to facilitate an efficient literature search (see http://www.cebm.net).¹⁰ The question needs to clearly state the patient population; the intervention(s), event(s), or exposure(s); and the outcome of interest. These steps were codified by Doig and Simpson¹⁰ in the simple mnemonic PICO: population, intervention, comparison, and outcome. Focusing the question is key because it enables identification of relevant search terms (described below).

2. Search for relevant evidence

Keeping up with the basic pediatric literature alone would require reading at least five articles per day, 365 days per year.¹¹ The objective of searching the literature is to find the answer to the clinical question as quickly and efficiently as possible amidst the 20,000 medical journals and more than 2 million articles published annually.¹² To hone in on relevant articles, a search strategy should take advantage of Medical Subject Headings (MeSH) and incorporate new and useful filters that have been developed. Taking advantage of specific combinations of MeSH terms has been found to increase the speed and effectiveness of searches.¹³

MeSH are descriptive terms assigned to each bibliographic reference in Medline by the National Library of Medicine. There are 25,186 terms organized into a hierarchical structure (http://www.nlm.nih.gov/mesh/meshhome.html). At the most general level are very broad headings such as “Diseases” or “Organisms.” More specific headings are found at more narrow levels of the 11-level hierarchy, such as “Sepsis” and “Neisseria meningitidis.” Thousands of cross-references also exist that assist in finding the most appropriate MeSH (e.g., “MODS, see Multiple Organ Failure”).

So that clinicians need not memorize complicated combinations of search terms, search engines have incorporated many of these terms into easy-to-use research methodology filters for clinicians. These filters are combinations of search terms that can increase searching efficiency. PubMed, for example, allows searchers to select filters for studies of etiology, diagnosis, therapy, and prognosis. Similar filters can be found in Ovid Technologies’ search engine, in addition to filters on clinical prediction guides, qualitative studies, costs, and economics. In both, the choices are presented under the “Clinical Queries” heading. Searchers can choose among highly sensitive searches to produce comprehensive retrievals (particularly useful for subjects in which little work has been done), highly specific searches to retrieve only the most rigorous studies and little nonrelevant material (for subjects in which much work has been published), or optimized searches to maximize the tradeoff between sensitivity and specificity.

In addition to Medline, multiple other specialized databases and Internet-based resources are available that can yield relevant results quickly. Table 5-1 lists a sample of these resources. One of the best known is the Cochrane Library, which contains a large collection of peer-reviewed systematic reviews on a wide variety of health care interventions.¹⁴ It is thoroughly indexed and easily searched. ACP (American College of Physicians) Journal Club and Evidence-Based Medicine are EBM-related journals that are linked for searching through Evidence-Based Medicine Reviews (EBMR) from Ovid Technologies. The British Medical Journal publishes Clinical Evidence, an annual compilation in book and CD-ROM format of the best available evidence on the effects of common medical interventions. In addition, the PedsCCM Evidence-Based Journal Club posts critical reviews of studies related to pediatric critical care.

3. Evaluate the evidence

Table 5–1 Partial List of EBM Resources on the Internet

Resource	Web Site
EBM WEB SITES
Centre for EBM, Oxford	www.cebm.net
Centre for Evidence-Based Child Health	http://www.ich.ucl.ac.uk/ich/academicunits/Centre_for_evidence_based_child_health/Homepage
EBM Toolkit, University of Alberta	http://www.ebm.med.ualberta.ca/
User’s Guide to Evidence-Based Practice, Centre for Health Evidence	http://www.cche.net/usersguides/main.asp
University of Washington EBM Internet resources	http://healthlinks.washington.edu/ebp
Netting the Evidence: Database of EBM Web sites	http://www.sheffield.ac.uk/~scharr/ir/netting/
Health Information Research Unit, McMaster University	http://hiru.mcmaster.ca
MEDLINE SEARCHES
PubMed	www.pubmed.org
SYSTEMATIC REVIEWS
Cochrane Collaboration	http://www.cochrane.org/
AHRQ Evidence-Based Practice	http://www.ahrq.gov/clinic/epcix.htm
National Guideline Clearinghouse (AHRQ)	http://www.guidelines.gov/
Clinical Evidence (from the British Medical Journal)	http://www.clinicalevidence.com/ceweb/conditions/index.jsp
Best Evidence Topics	http://www.bestbets.org
Centre for Reviews and Dissemination, University of York	http://www.york.ac.uk/inst/crd
CRITICAL CARE JOURNAL CLUBS
Critical Care Journal Club, Critical Care Forum	http://ccforum.com/articles/browse.asp?sort=Journal%20club%20critique
PedsCCM Evidence-Based Journal Club	http://pedsccm.org/EBJournal_Club_intro.php
American Thoracic Society, Evidence-Based Critical Care	http://www.thoracic.org/sections/clinical-information/critical-care/evidence-based-critical-care/index.html
ONLINE EBM JOURNALS
ACP Journal Club	http://www.acpjc.org/
Bandolier	http://www.medicine.ox.ac.uk/bandolier/
Evidence-Based Medicine	http://ebm.bmjjournals.com/
JOURNALS
Pediatric Critical Care Medicine	http://www.pccmjournal.com
Critical Care Medicine	http://www.ccmjournal.com
Critical Care Forum	http://ccforum.com/
Pediatrics	http://pediatrics.aappublications.org/
Journal of Pediatrics	http://www.jpeds.com/
Archives of Pediatrics and Adolescent Medicine	http://archpedi.ama-assn.org/
JAMA	http://www.jama.com
New England Journal of Medicine	http://www.nejm.com
British Medical Journal	http://www.bmj.com
The Lancet	http://www.thelancet.com