Assessing cardiac preload or fluid responsiveness? It depends on the question we want to answer

Excerpt

Sir: We read the review by Bendjelid and Romand [1], describing the indices that have been proposed to predict fluid responsiveness in critically ill patients, with great interest. In this review, the authors emphasized the value of dynamic parameters, mainly the stroke volume variation, as compared to static indices of cardiac preload, in answering one of the most common clinical question concerning patients with shock: "Can we improve cardiac output and hence hemodynamics by giving fluid?" However, the authors suggest that the little value of cardiac preload indices in predicting fluid responsiveness is mainly due to technical limitations and that "ventricular volumes should theoretically reflect preload dependence (or fluid responsiveness) more accurately than other indices". Therefore, they leave the reader with the feeling that cardiac preload and fluid responsiveness are more or less synonymous. In our opinion, cardiac preload and fluid responsiveness are two quite different things, and hence any improvement in technology (including three dimensional echocardiography, as suggested by the authors) should not increase the value of static cardiac preload indices in predicting fluid responsiveness. …