Lung water and blood volume measurements in the critically ill

Cardiac filling pressures measured using a pulmonary artery catheter are routinely used to guide the hemodynamic management of critically ill patients. Unfortunately, there is considerable evidence that they perform poorly for this purpose, particularly as surrogates for cardiac preload, and there is increasing concern about possible harm associated with pulmonary artery catheter use. An alternative approach is to use intrathoracic blood volume and lung water measurements to guide fluid and vasoactive drug administration. Originally this required the use of double-indicator techniques, but these variables can now be obtained using thermodilution alone. This is a major advance, and deserves rigorous prospective assessment.