Invasive and Non-invasive Monitoring Of Cardiac Output

Abstract

Derangements in the circulation are a common feature of sepsis, trauma, major surgery and other critical illnesses. Detailed evaluation of the circulation is therefore an essential aspect of the clinical management of such patients. Accurate assessment of the hemodynamic status is desirable in the treatment of critically ill patients with hemodynamic instability or in perioperative patients at increased risk for cardiac complications. Measurement of CO is 1 cornerstone of this hemodynamic assessment. Determination of cardiac output and systemic oxygen delivery can be helpful in patients with perfusion status that is poorly defined by other methods or that do not respond to therapy. The use of cardiac output monitoring technology is an increasingly important aspect of evaluating patients in the operating theatre and critical care unit. There are now a number of different technologies available for this purpose which use a diverse range of physiological principles. A detailed understanding of the physiological principles applied by such technology is essential for safe and effective use in clinical practice. An ideal CO monitor should be minimally or non-invasive, continuous, cost effective, reproducible, reliable during various physiological states and have fast response time.

Until recently, the only tool available to anesthesiologists to monitor CO was the pulmonary artery catheter with the use of balloon flotation catheters is an easy and rapid technique for bedside hemodynamic monitoring. The widely used PAC is very versatile, providing both measurement of CO by thermodilution and dye dilution as well as PA pressures and mixed venous Svo2. However, its abuse has been associated with complications that can be avoided if it is used by experienced operators. Despite controversies and complications pulmonary artery catheter (PAC) continuous and intermittent bolus techniques of CO measurement continue to be the gold standard.