Hemodynamic Assessment and Monitoring in the Intensive Care Unit: an Overview

The goal of hemodynamic monitoring in intensive care is to assess the adequacy of perfusion, specifically with regard to maintaining sufficient perfusion pressures and oxygen delivery. Precise volume management of peri-operative and critical care patients is crucial as under or over resuscitation is associated with adverse outcomes. Hemodynamic monitoring allows care to be individualized based on specific patient response to therapy and can provide early warning of impending perfusion deficits or instability. Physiologic monitoring aids determination of appropriate therapy. Methods for obtaining accurate and continuous measurements in the critically ill patient have evolved from surgical and anesthetic techniques dating back more than a century. These techniques transitioned from the operating room to early intensive care units as necessitated by the polio epidemics of the 1950s. The advantages of cohorting critically ill patients led to specialized intensive care and later cardiac care units. Telemetry developed to monitor astronauts and miniaturization of electronics made possible by substituting transistors for vacuum tubes helped create the first generation of intensive care monitors in the 1960s. Transcutaneous oxygen sensors, end-tidal measurement of carbon dioxide, and pulse oximetry took monitoring to a new level by the 1980s. Monitors became more sophisticated and capable of calculating derived variables such as oxygen delivery and consumption as computer processing became routine. These data sets were useful to clinicians using fluids and vasoactive agents primarily to manipulate oxygen delivery in hemodynamically unstable patients. Recently, simply monitoring vascular pressures has given way to dynamic monitoring where physiologic changes with respiration can be used to derive additional parameters such as pulse pressure variation (PPV) and stroke volume variation (SVV). Today’s clinician has a wealth of information available at the bedside. This review will focus on hemodynamic assessment and monitoring, and characterize types of monitors as non-invasive, minimally invasive or invasive.