Prediction of fluid responsiveness in acute respiratory distress syndrome patients ventilated with low tidal volume and high positive end-expiratory pressure

OBJECTIVE: Dynamic preload indicators with pulse pressure variation and stroke volume variation are superior to static indicators for predicting fluid responsiveness in mechanically ventilated patients. However, they are influenced by tidal volume and the level of positive end-expiratory pressure. The present study was designed to evaluate the clinical applicability of pulse pressure variation and stroke volume variation in predicting fluid responsiveness on acute respiratory distress syndrome patients ventilated with protective strategy (low tidal volume and high positive end-expiratory pressure). DESIGN: Prospective, observational study. SETTING: A 20-bed medical intensive care unit of a tertiary medical center. PATIENTS: Twenty-two sedated and paralyzed early acute respiratory distress syndrome patients. INTERVENTIONS: After being enrolled, central venous pressure, pulmonary capillary wedge pressure, and cardiac output index were obtained from a pulmonary artery catheter (OptiQ SvO2/CCO catheter), and intrathoracic blood volume, global end-diastolic volume, stroke volume variation, and pulse pressure variation were recorded from a PiCCOplus monitor. The whole set of hemodynamic measurements was performed before and after volume expansion with 500 mL hydroxyethyl starch (10% pentastarch 200/0.5). MEASUREMENTS AND MAIN RESULTS: Cardiac output index, central venous pressure, pulmonary capillary wedge pressure, global end-diastolic volume, and intrathoracic blood volume significantly increased, and pulse pressure variation and stroke volume variation significantly decreased after volume expansion. Baseline pulse pressure variation significantly correlated with volume expansion-induced absolute changes (r ≤ .62), or percent changes in cardiac output index (r ≤ .75) after volume expansion. The area under the receiver operating characteristic curve was the highest for pulse pressure variation (area under the receiver operating characteristic curve ≤ 0.768) than other indicators. The threshold value for baseline pulse pressure variation greater than 11.8% predicted a significant positive response to volume expansion with a sensitivity of 68% and a specificity of 100%. CONCLUSIONS: Baseline pulse pressure variation accurately predicted the fluid responsiveness in early acute respiratory distress syndrome patients. Roughly, a baseline pulse pressure variation greater than the threshold value of 12% is associated with a significant increase in cardiac output index after the end of volume expansion.