Validation of pulse pressure variation and corrected flow time as predictors of fluid responsiveness in patients in the prone position

The aim of this prospective trial was to investigate the ability of pulse pressure variation (PPV) and corrected flow time (FTc) to predict fluid responsiveness in the prone position. Forty-four patients undergoing lumbar spine surgery in the prone position on a Wilson frame were prospectively studied. PPV and FTc were measured before and after a colloid bolus (6 ml kg−1) both in the supine and in the prone positions. Fluid responsiveness was defined as an increase in the stroke volume index of ≥10% as measured by oesophageal Doppler. In the supine position, 26 patients were responders and the areas under the curve (AUC) of the receiver-operator characteristic (ROC) curves of PPV and FTc were 0.935 [95% confidence interval (CI): 0.870–0.999, P