Central venous pressure: A useful but not so simple measurement.

OBJECTIVE: To review the clinical use of central venous pressure measurements.

DATA SOURCES: The Medline database, biographies of selected articles, and the author's personal database.

DATA SYNTHESIS: Four basic principles must be considered. Pressure measurements with fluid-filled systems are made relative to an arbitrary reference point. The pressure that is important for preload of the heart is the transmural pressure, whereas the pressure relative to atmosphere still affects other vascular beds outside the thorax. The central venous pressure is dependent upon the interaction of cardiac function and return function. There is a plateau to the cardiac function curve, and once it is reached, further volume loading will not increase cardiac output.

CONCLUSIONS: If careful attention is paid to proper measurement techniques, central venous pressure can be very useful clinically. However, the physiologic or pathophysiological significance of the central venous pressure should be considered only with a corresponding measurement of cardiac output or at least a surrogate measure of cardiac output.