[Measurement of cardiac output]

Diagnosis and therapy of hemodynamic instability are of the utmost importance in the treatment of critically ill patients during surgery and in intensive care. For both diagnosis and therapy, adequate and preferably continuous hemodynamic monitoring is essential. Besides the assessment of cardiac preload and blood pressure, cardiac output represents an important clinical marker of cardiac performance and global perfusion. Since its clinical introduction by Swan and Ganz in 1970, the standard technique for measuring cardiac output has been the pulmonary arterial thermodilution technique using a pulmonary artery catheter. The ongoing discussion on the risk-benefit ratio of such a pulmonary artery catheter has led to the introduction of several less invasive methods for determining cardiac output. The aim of this review is to provide background information on these alternative methods and to discuss the individual advantages and disadvantages of each method in the context of their clinical applicability.