To the Editor:—I read the study by Fellahi JL et al. titled “Perioperative use of dobutamine in cardiac surgery and adverse cardiac outcome” with great interest. This study showed that the use of dobutamine was associated with adverse outcomes in adult cardiac surgery, and the authors concluded that these results suggest that dobutamine should only be administered when the benefit is judged to ...

T he randomized clinical trial is a well established and frequently used study design and is generally accepted as the gold standard (1). Nevertheless, many questions can only be answered with epidemiological observational studies, such as the influence of cigarette consumption on the development of lung cancer (2), the effects of sport, nutrition and overweight on cardiovascular diseases (3), ...

Practical and ethical constraints mean that many clinical and/or epidemiological questions cannot be answered through the implementation of a randomized controlled trial. Under these circumstances, observational studies are often required to assess relationships between certain exposures and disease outcomes. Unfortunately, observational studies are notoriously vulnerable to the effect of diffe...