Differentiating “Volumetric Preload Monitoring” and Assessing “Fluid Responsiveness”

To the Editor: With great interest we read the concise review article by Grocott et al. (1). However, the authors did not differentiate between assessing “static” preload parameters considered to be indicative for cardiac filling volumes and assessing “fluid responsiveness,” the latter predicting the hemodynamic response to fluid loading (2). Measuring “static preload” allows quantifying a patient’s intravascular volume status and its changes over time. Numerous studies in different groups of patients demonstrated that volumetric parameters, such as the left ventricular end-diastolic area by transesophageal echocardiography (3) or the global end-diastolic volume by transcardiopulmonary thermodilution (4), are much more useful to answer that clinical question than measuring cardiac filling pressures. The more important question to answer in a hemodynamically instable patient is: will this patient benefit from fluid loading by an increase in cardiac output? Specifically, in patients with compromised cardiac function, this question has to be answered before fluid loading to prevent potentially deleterious fluid overload. This “prediction of fluid responsiveness” is the ratio behind the so-called “functional preload parameters,” such as the systolic pressure variation and stroke volume variation. First systolic pressure variation, and later stroke volume variation, as continuous “on-line parameters” have been shown to predict fluid responsiveness in a wide range of surgical and septic patients (5-10). Thus, those parameters seem to represent useful clinical tools for more rational perioperative fluid management in mechanically ventilated patients. Daniel A. Reuter, MD Alwin E. Goetz, MD, PhD Department of Anesthesiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany, [email protected]