Controversies in perioperative medicine.

Coexisting medical problems are common in surgical patients. Due to the lack of convincing studies, however, the optimal strategies for perioperative management of many medical problems remain unclear. Thus, practices are often based on inconclusive clinical studies or extrapolated from current understanding of pathophysiology. This article reviews guidelines and practices for endocarditis prophylaxis, perioperative anticoagulation in patients with mechanical heart valves, glucose control in diabetic patients undergoing surgery, and the use of beta-blockers to prevent postoperative cardiac complications. In addition, the strength of the evidence supporting these practices is evaluated.