Did we learn evidence-based medicine in medical school? Some common medical mythology.
Medical myths occur for many different reasons. A common thread is that they all make some pathophysiologic sense. A good example is the concern about using oral cobalamin when treating pernicious anemia. The difficulty in absorbing vitamin B12 when intrinsic factor is not available does not make oral replacement impossible; the dose just needs to be higher. Pathophysiologic concerns have also been a key reason why physicians have avoided using beta-blockers in patients with diabetes. They fear that beta-blockers will block adrenergic symptoms, and patients will not know when they are hypoglycemic. In studies addressing this issue, there appears to be no real problem with increased severe episodes of hypoglycemia in patients on beta-blockers or increased hypoglycemic unawareness. Several studies commented on the unanticipated symptom of increased sweating associated with hypoglycemia in diabetic patients who are taking beta-blockers. Another important concept behind some medical myths is the overreliance on case reports or authoritative text. The concern about depression associated with beta-blocker use grew out of one widely referenced case report. Subsequent studies have not shown convincing evidence for a strong association with beta-blocker use and depression. The strong position taken against narcotic use in Cope's Early Diagnosis of the Acute Abdomen is probably the reason for the perpetuation of the myth of avoiding narcotics for pain relief in patients with undiagnosed acute abdominal conditions. The only two studies addressing this issue showed no problems with diagnosis caused by providing narcotic pain relief. Newer therapies usually undergo closer scrutiny before being accepted, often including placebo-controlled trials to show the efficacy of a medication. Such might not be the case with newer technologies. It is harder to evaluate the benefit of a new technology in the face of noncomparable previous technologies. Catheterization of the right side of the heart (Swan-Ganz catheter) was a technology that became widely used before any outcome studies became available. Multiple reports in the last decade have shown increased mortality and increased utilization of resources in patients who received catheterization of the right side of the heart. Most new drug therapies require randomized data to show effects before widespread use and acceptance occur. Older therapies that have been widely accepted for a long time might not have had controlled trial data behind recommendations for their use, and once practice patterns become widespread, it is hard to change. It is always good to ask the question, "Will this help my patient live better or longer?" when prescribing a therapy. These myths underscore the importance and utility of outcome-based research to help guide physicians in their practices.