Evaluation of corrected flow time in oesophageal Doppler as a predictor of fluid responsiveness

Background. Corrected flow time (FTc) by oesophageal Doppler is considered to be a 'static' preload index. We evaluated the ability of FTc to predict fluid responsiveness and compared this with the abilities of other preload indices, such as pulse pressure variation (PPV), central venous pressure (CVP), and left ventricular end-diastolic area index (LVEDAI). Methods. Twenty neurosurgical patients were studied. After induction of anaesthesia, FTc, PPV, LVEDAI, CVP, and stroke volume index (SVI) were measured before and 12 min after fluid loading with 6% hydroxyethyl starch solution (7 ml kg^-1). Responders and non-responders were defined as those patients with an SVI increase ≥10% or <10% after fluid loading, respectively. Pearson's correlation was used to assess correlations between changes in SVI and initial haemodynamic variables. Receiver operating characteristic (ROC) curves were constructed and compared to evaluate the overall performance of preload indices (FTc, PPV, LVEDAI, and CVP) in terms of predicting fluid responsiveness. Results. FTc and PPV before fluid loading differed between responders (n = 11) and non-responders (n = 9), and correlated with changes in SVI (r = -0.515 and r = 0.696, respectively), which was opposite to that observed for CVP or LVEDAI. Areas under ROC curves for FTc [0.944 (SD 0.058)] and PPV [0.909 (0.069)] were significantly greater than those for CVP [0.540 (0.133), P < 0.001] and LVEDAI [0.495 (0.133), P < 0.001]. The optimal threshold value given by ROC analysis was 357 ms for FTc. Conclusions. In this study, FTc predicted fluid responsiveness. However, FTc should be used in conjunction with other clinical information.