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After the early phase of sepsis, excessive fluid administration may worsen pulmonary edema and prolong mechanical ventilation . Accurately predicting fluid responsiveness obviates unnecessary fluid loading, and helps to detect patients who may benefit from a volume expansion. Pulse pressure variation (DPP) is a reliable predictor of fluid responsiveness in mechanically ventilated patients only when tidal volume is at least 8 ml/kg . The aim of this study was to evaluate the predictive value of DPP for fluid responsiveness after a maneuver to change tidal volume to 8 ml/kg in patients ventilated with 6 ml/kg.
Prospective clinical study in 40 patients ventilated with 6 ml/kg after resuscitation phase of severe sepsis and septic shock. Fluid challenge was indicated by the attending physician (7 ml/kg of 6% hydroxyethyl starch 130/0.4). Complete hemodynamic measurements including DPP (DPP 6 ml/kg) were obtained at baseline. The tidal volume was then changed to 8 ml/kg and the DPP (DPP 8 ml/kg) was measured after 5 minutes. The ventilatory settings were returned to 6 ml/kg before fluid challenge. Patients whose cardiac output (CO) increased by ≥15% were considered to be fluid responders. Receiver operating characteristic (ROC) curve analysis was used to evaluate the predictive value of DPP.
In 19 patients (responders), CO increased by >15% after fluid infusion. Fluid responsiveness was better predicted with DPP 6 ml/kg (ROC curve area 0.92 ± 0.05) than with pulmonary artery occluded pressure (0.56 ± 0.09) and right atrial pressures (0.74 ± 0.08). Increasing tidal volume to 8 ml/kg did not improved prediction as the ROC curve area with DPP 8 ml/kg was 0.94 ± 0.03. The best cut-off values defined by the ROC curve analysis was 6.5% and 10.5% for DPP 6 ml/kg and DPP 8 ml/kg, respectively.
The maneuver to change tidal volume to 8 ml/kg in patients ventilated with protective ventilatory strategy to better predict fluid responsiveness is not useful. Fluid responsiveness can be correctly predicted in patients ventilated with tidal volume of 6 ml/kg.