Introduction: Hemodynamic stability based on normovolemia is mandatory for patients‘ outcome (1,2). A dynamic parameter like ΔPP is suitable to assess fluid responsiveness (3). A completelynoninvasive monitoring technology would be helpful. Pulse wave transit time (PWTT) is a real-timeflow-based hemodynamic parameter to be used at the bedside. The goal of the present study is to investigate how suitable PWTT is for predicting fluid responsiveness in the perioperative setting compared to ΔPP.
Methods: Following IRB-approval and written informed consent 40 patients scheduled for major urological surgery with an expected fluid turnover intraoperatively and a need for arterial blood pressure monitoring were enrolled. The respiratory variation of PWTT (ΔPWTT) after correction by Bazett’s formula with detection of PWTT’s beginning by the R-wave in ECG, and detection of PWTT’s end by detection of pulse oximetry at the ear lobe was monitored continuously (LifeScope® Modell J BSM-9101 Nihon Kohden Europe GmbH, Rosbach, Germany). The assessment of ΔPP was performed after cannulation of the non-dominant hand by reliable standard monitoring technology (4).
Stroke volume was monitored by Esophageal Doppler Monitoring (CardioQ-ODM®, Deltex Medical Ltd, Chichester, UK). In case of hypovolemia a fluid bolus of 7 ml/kg ideal body weight was administered at the discretion of the attending anesthesiologist. An increase in stroke volume of 10% was considered to reflect fluid responsiveness. A ROC model was used to compare ΔPWTT and ΔPP, a Wilcoxon test was used to discriminate fluid responders from non-responders.
Results: 42 fluid boluses were given in this clinical study. AUC was 0.7164 for ΔPWTT, and 0.6265 for ΔPP, respectively. The Wilcoxon test showed a p-value of 0.014 for for ΔPWTT, and 0.008 for for ΔPP, respectively.
Conclusion: ΔPWTT shows promise as a noninvasive parameter to predict fluid responsiveness. Further study is required.

05 / A comparison of assessing fluid responsiveness by Pulse Wave Transit Time (?PWTT) and ?PP