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| Evidence Based Medicine: Introduction | |
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Introduction The goal of this book is to provide an introductory framework for evidence-based medicine. In this introduction, we first address the importance of evidence-based medicine and provide its definition. Next, we discuss the individual components of evidence-based medicine that serve as the basis for the structure of the book. Importance of Evidence-Based Medicine Consider these two scenarios:
Your patient has just had a Q-wave myocardial infarction that resulted in moderate congestive heart failure. You are considering administering a beta-blocker in the patient, but a professor in the Division of Cardiology advises against this, stating that instituting such medication will further decrease cardiac function. What should you do?
You are a fresh-out-of-residency surgeon caring for a patient with 70% occlusion of the left carotid artery. The patient has had no neurologic symptoms and was referred to you after his primary care physician noted a left carotid artery bruit. You are being asked to consider the patient for carotid endarterectomy. You discuss the case with a former attending physician, who states that the intervention makes good sense and is supported by recent medical literature. The attending physician also states, "This is now what we always do." What should you do? Evidence-based medicine is a movement that has developed to help us make such decisions with our patients systematically. This movement is represented by a recent profusion of literature and course work in evidence-based medicine and, as described below, has been characterized as a paradigm shift.1 The traditional medical paradigm comprises four assumptions:
The new evidence-based medicine paradigm comprises a different set of assumptions:
If we use the traditional paradigm to make decisions in the first scenario, we would avoid the use of a beta-blocker in a patient who has just had a myocardial infarction that resulted in moderate congestive heart failure. According to pathophysiologic principles, a negative inotropic agent could decrease cardiac pump function and therefore should not be used in a patient with moderate congestive heart failure. Furthermore, the stature and experience of the consultant contributes considerable weight to our decision. In the new evidence-based medicine paradigm, decisions are based primarily on certain rules of evidence that are applied to systematic studies. In this paradigm, we are more likely to recommend a beta-blocker on the basis of results of the Beta-Blocker Heart Attack Trial,2,3 which showed a mortality benefit of beta-blockers after Q-wave myocardial infarction. With the application of a simple calculation, we note that the number of patients who were treated to prevent a single death was smaller in the group who had their infarct complicated by congestive heart failure than it was in the asymptomatic subset. In other words, the mortality benefit of the medication after myocardial infarction is expected to be greater in patients with congestive heart failure than in those who are asymptomatic. If we were following the traditional paradigm in the second scenario, we would undoubtedly recommend the surgical intervention. Our recommendation would be strongly influenced by the counsel of an experienced surgeon, as well as the biological plausibility that if our patient has narrowing in the internal carotid artery, removal of this narrowing should decrease subsequent risk of cerebrovascular events. While the new evidence-based medicine paradigm does not always provide a definitive answer, it does provide an explicit framework that helps us evaluate the validity of the relevant literature4 and, with application of certain key concepts and calculations, better estimate the net benefit of this intervention for our patient. In Chapter 9, we demonstrate how to assess the validity of the information relevant to this scenario and how to determine its net benefit for the patient. With this framework, we are able to counsel our patients more effectively. Although evidence-based medicine has been beneficial in providing a new systematic approach to medical decision-making, its characterization as a paradigm shift has met with some resistance. This resistance may be due to the presumption that before the development of evidence-based medicine, medical decisions were not made on the basis of any evidence at all. A letter recently published in The Lancet 5 states that the new evidence-based medicine paradigm presumes "the practice of medicine was previously based on a direct communication with God or by tossing a coin." An alternative and possibly more palatable way of characterizing evidence-based medicine is not as a paradigm shift but rather as an evolution of the tools used to practice scientific medicine. The paradigm shift to practice scientific medicine probably dates to 1910, when Abraham Flexner reported on the quality of education at approximately 130 U.S. medical schools.6 Medicine was no longer practiced and taught as a trade. Its new foundation rested on biomedical science, which at that time served as the best available evidence on which medical decisions were made. Medical decision-making tools of the time thus relied on a thorough knowledge of pathophysiology and clinical judgment. As an evolution of these tools, evidence-based medicine by no means substitutes for clinical judgment or pathophysiology, but rather incorporates them within a more explicit and rigorous framework. Our assumption is that evidence-based medicine will lead to an improvement in patient outcomes and teaching and result in more cost-effective medical care by providing an explicit framework to make medical decisions in following rules of evidence applied to systematically obtained information. With further development, evidence-based medicine itself will need to be systematically evaluated to provide supporting evidence for its role in medical practice. So, then, what is this term, evidence-based medicine?
For the DEFINITION return to the chart and click on the box "Evidence-Based Medicine." You will see how the definition gives rise to three fundamental COMPONENTS of EBM. For a brief description of each of these components, click on their respective boxes. The components of EBM divide the book into three sections. For an outline of each chapter, click on its respective box. The box for Chapter 6, Searching the INTERNET, provides a search strategy and Web links to EBM resource sites.
REFERENCES
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