Noninvasive techniques for measurements of cardiac output

Measuring stroke volume or cardiac output is of paramount importance for the management of critically ill patients in the intensive care unit, or 'high risk' surgical patients in the operating room. The new noninvasive techniques are gaining acceptance among intensivists and anesthesiologists who have been trained almost exclusively in the pulmonary artery catheter and the thermodilution technique.

The present review focuses on the recent publications related to esophageal Doppler, Fick principle applied to carbon dioxide associated with partial rebreathing, and pulse contour analysis. Recent validation studies have confirmed the previous findings: all three methods provide reliable estimations of cardiac output and its variations. There is not a single method standing out and ruling out the others. Many investigators are now using one of the 'noninvasive' monitors to measure cardiac output in clinical or experimental studies.

By making cardiac output easily measurable in various settings, these techniques should all contribute to improve hemodynamic management in critically ill or high-risk surgical patients.