Inferior vena cava diameter correlates with invasive hemodynamic measures in mechanically ventilated intensive care unit patients with sepsis

Early optimization of fluid status is of central importance in the treatment of critically ill patients. This study aims to investigate whether inferior vena cava (IVC) diameters correlate with invasively assessed hemodynamic parameters and whether this approach may thus contribute to an early, non-invasive evaluation of fluid status. Thirty mechanically ventilated patients with severe sepsis or septic shock (age 60 +/- 15 years; APACHE-II score 31 +/- 8; 18 male) were included. IVC diameters were measured throughout the respiratory cycle using transabdominal ultrasonography. Consecutively, volume-based hemodynamic parameters were determined using the single-pass thermal transpulmonary dilution technique. This was a prospective study in a tertiary care academic center with a 24-bed medical intensive care unit (ICU) and a 14-bed anesthesiological ICU. We found a statistically significant correlation of both inspiratory and expiratory IVC diameter with central venous pressure (p = 0.004 and p = 0.001, respectively), extravascular lung water index (p = 0.001, p < 0.001, respectively), intrathoracic blood volume index (p = 0.026, p = 0.05, respectively), the intrathoracic thermal volume (both p < 0.001), and the PaO(2)/FiO(2) oxygenation index (p = 0.007 and p = 0.008, respectively). In this study, IVC diameters were found to correlate with central venous pressure, extravascular lung water index, intrathoracic blood volume index, the intrathoracic thermal volume, and the PaO(2)/FiO(2) oxygenation index. Therefore, sonographic determination of IVC diameter seems useful in the early assessment of fluid status in mechanically ventilated septic patients. At this point in time, however, IVC sonography should be used only in addition to other measures for the assessment of volume status in mechanically ventilated septic patients.