Managing weighty issues on lean evidence: the challenges of bariatric medicine.

  • Arya M. Sharma
  • Published 2005 in
    CMAJ : Canadian Medical Association journal…

Abstract

© 2005 Canadian Medical Association or its licensors O currently affects more than 300 million people worldwide, and by the end of this decade as many as 20% of the adult population in North America may have a body mass index (BMI) greater than 40 kg/m. Thus, physicians and other health care workers will be delivering health care to a growing number of obese and morbidly obese patients. Over the last 50 years, demographic changes toward a growing elderly population, together with the recognition that a host of medical problems encountered in elderly people require special diagnostic and therapeutic approaches, led to the stillyoung discipline of geriatric medicine. Along similar lines, the term “bariatric medicine” (from the Greek baro, meaning weight) is increasingly being used to describe the field of medicine that deals with the multitude of medical problems encountered in morbidly obese patients. Diagnosing many common medical conditions, although straightforward in nonobese patients, can be fraught with difficulty in morbidly obese people because little is known about the sensitivity and specificity of diagnostic tests in this population. For example, in one study, almost two-thirds (24/39) of patients with a BMI greater than 40 kg/m who presented with severe symptoms and signs of chronic venous insufficiency had no detectable anatomic evidence of venous insufficiency with Doppler ultrasonography. In a comparison of angiography findings with precatheterization noninvasive functional test results (nuclear myocardial perfusion or stress echocardiography) in morbidly obese (n = 110) and nonobese (n = 4868) patients with suspected coronary artery disease, the prevalence of coronary artery disease was lower among the obese patients (45% v. 72%), which may indicate a higher prevalence of falsepositive noninvasive test results in that group. Newer radiological tests such as electron beam tomographic screening of coronary artery calcium require adjustments for BMI to decrease the number of false-positive results. However, obtaining imaging studies such as CT or MRI is often impossible for morbidly obese patients because of the size and weight limitations of the machines. Oversized equipment is unavailable in most hospitals. These limitations call for more research into diagnostic algorithms, tests and reference ranges for morbidly obese patients, to avoid misdiagnoses and to ensure optimal care. Of major concern is the lack of data on clinical aspects of morbid obesity and the medical and surgical management of comorbidities. Indeed, except for studies specifically focusing on weight loss, obese people are generally underrepresented in clinical trials. As a result, the majority of clinical practice guidelines, even for conditions commonly found in obese patients (e.g., hypertension, diabetes mellitus, asthma, ischemic heart disease, venous thrombosis and neuropsychiatric disorders) fail to make specific recommendations for patients with morbid obesity that go beyond a rather general appeal for weight loss. This issue is far from trivial, as obesity significantly affects the pathophysiology and pharmacodynamic response in a multitude of medical conditions. For example, in obese patients with essential hypertension (n = 10), β-blockers were found to effect a better diastolic response than calcium-channel blockers; however, such patients may be at increased risk of renal hyperfiltration and microalbuminuria and therefore may require reninangiotensin blockade. Another example is gastroesophageal reflux disease, where the pathophysiology in obese patients (increased intra-abdominal pressure, hiatal hernia, vagal abnormalities) may be distinctly different from that in nonobese patients. Responses to medications may be different, as metoclopramide may fail to decrease gastric volume or raise pH in obese patients. Similarly, although self-reported asthma is more frequent at higher BMI levels, obese individuals paradoxically are at lowest risk for significant airflow obstruction, and much of the respiratory symptoms may indeed be due to nocturnal aspiration of gastric reflux. Thus, asthma not only may be overdiagnosed in the obese population but, if present, may require a different approach to management. Few studies have examined the effects of excess weight on pharmacokinetics and pharmacodynamics, even of medications commonly used in obese patients. When available, studies are often limited to a few healthy obese volunteers or to patients with relatively uncomplicated health status. The pharmacokinetics of drugs in obese patients may be significantly influenced by differences in tissue distribution, hemodynamics, blood flow to adipose, splanchnic and other tissues, plasma composition, or liver and kidney function. This is of particular concern with drugs that have narrow therapeutic indices (e.g., cytostatic drugs) or minimal effective concentrations (e.g., antibacterial drugs, injectable contraceptives). Clearly, a systematic assessment of drug doses and clinical outcomes in obese patients is overdue. In addition, there are virtually no studies of the outcomes Managing weighty issues on lean evidence: the challenges of bariatric medicine OBESITY

Cite this paper

@article{Sharma2005ManagingWI, title={Managing weighty issues on lean evidence: the challenges of bariatric medicine.}, author={Arya M. Sharma}, journal={CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne}, year={2005}, volume={172 1}, pages={30-1} }