Perioperative hemodynamic monitoring. 
Hemodynamic monitoring is the cornerstone of perioperative anesthetic monitoring.  In the unconscious patient, hemodynamic monitoring not only provides information relating to cardiac output, volume status and ultimately tissue perfusion, but also indicates depth of anesthesia and adequacy of pain control.  In the 21st century the anesthesiologist has an array of devices to choose from.  No single device provides a complete assessment of hemodynamic status, and the use of all devices in every situation is neither practical nor appropriate.  This article aims to provide the reader with an overview of the devices currently available, and the information they provide, to assist anesthesiologists in the selection of the most appropriate devices for any given situation.