Assessing fluid responsiveness by stroke volume variation in mechanically ventilated patients with severe sepsis

Background and objective: Our hypothesis was that stroke volume variation during mechanical ventilation of the lungs would allow accurate prediction and monitoring of changes in cardiac index in response to fluid loading in patients with severe sepsis. Methods: This was a prospective clinical study in a university hospital. Ten mechanically ventilated patients with severe sepsis or septic shock were given fluid loading with 5 00 mL 10% hydroxyethylstarch 200/0.5 over 30 min. Before and after fluid loading pulmonary arterial occlusion pressure and central venous pressure were measured. Intrathoracic blood volume index, stroke volume variation and cardiac index were measured by the transpulmonary thermodilution technique. After verifying normal distribution of the data (skewness <1.0) the paired t-test was used for statistical analysis. Results: After fluid loading stroke volume variation decreased significantly, whereas central venous pressure, pulmonary arterial occlusion pressure, intrathoracic blood volume index and cardiac index increased significantly. Changes of cardiac index in response to fluid loading were correlated to baseline values of stroke volume variation (r = 0.64, P = 0.02) and intrathoracic blood volume index (r = -0.73, P = 0.009). Changes in cardiac index were significantly correlated to percentage changes in stroke volume variation (r = -0.65, P < 0.001) and changes in intrathoracic blood volume index (r = 0.52, P = 0.002), whereas changes in cardiac index revealed no significant correlation to changes in central venous pressure (r = 0.28, P = 0.07) and changes in pulmonary arterial occlusion pressure (r = 0.29, P = 0.06). Conclusions: Measuring stroke volume variation may be a useful way of guiding fluid therapy in ventilated patients with severe sepsis because it allows estimation of preload and prediction of cardiac index changes in response to fluid loading.