LAUSR

The impact of anesthetic management on short and longterm postoperative outcomes is a subject of current research in anesthesiology [1]. There is increasing evidence that certain aspects of anesthetic management—including perioperative goal-directed blood flow and fluid optimization [2, 3] and monitoring of the depth of anesthesia [4, 5]—can have a beneficial impact on postoperative complication rates. Lima et al. [6] need to be commended for their study investigating the effects of implementing a multimodal “hemodynamic and depth of anesthesia treatment protocol” on patient outcome after major open abdominal cancer surgery [6]. The authors demonstrated that in patients treated after the implementation of the treatment protocol (which included mean arterial pressure, stroke volume variation, cardiac index, central venous oxygen saturation, and bispectral index as targets) the incidence of postoperative delirium was significantly lower and the median hospital length of stay was significantly shorter compared to patients having the same kind of surgery prior to protocol implementation [6]. The study adds another piece to the puzzle of how perioperative anesthetic management can improve postoperative patient outcome. The study also prompts a discussion about different types of studies in anesthesiological research and triggers the question: What is the best study design to investigate a potentially beneficial impact of perioperative goaldirected therapy on patient outcome? There is no definite answer to this question because one perfect study design does not exist and the optimal study design depends on the specific research question being asked. Perioperative care is characterized by multidisciplinary teamwork, and postoperative outcomes have various pathophysiologic mechanisms and complex multifactorial etiologies. Therefore, expecting that it is simple to design a study that provides generalizable evidence that a single specific intervention can change a single specific postoperative outcome is unrealistic. Rather, it takes multiple steps and differently designed studies to progress from hypothesizing that a certain intervention may have a beneficial impact on patient outcome to eventually demonstrating that it works in daily clinical practice. As a first step, animal studies and small observational “proof of concept” studies in humans may be necessary to show that a certain intervention can have an effect on certain physiologic and biologic variables or outcomes. Further explanatory studies may then be performed to describe the details of the therapeutic intervention (dosing, timing, etc.). Feasibility studies might also be necessary to demonstrate that the therapeutic intervention and measurement systems needed to guide the intervention can be safely and precisely used in a clinical setting. Finally, the therapeutic intervention might be tested in a randomized controlled trial (Fig. 1). Smaller exploratory monocentric randomized controlled trials (with complex treatment algorithms, strict inclusion and exclusion criteria, and optimal conditions for the study intervention to work) enable the efficacy of an intervention to be tested to answer the question “Can this intervention work?” [7]. Large pragmatic multicenter randomized controlled * Bernd Saugel [email protected]; [email protected]