Tidal volume challenge to predict fluid responsiveness in the operating room: A prospective trial on neurosurgical patients undergoing protective ventilation BACKGROUND Pulse pressure variation (PPV) and stroke volume variation (SVV) do not predict fluid responsiveness when using a protective ventilation strategy: the use of functional haemodynamic tests can be useful to overcome this limitation. OBJECTIVES We tested the use of a tidal volume challenge (VTC), during 6 ml kg−1 [predicted body weight (PBW)] ventilation, and the end-expiratory occlusion test (EEOT) for prediction of fluid responsiveness. DESIGN An interventional prospective study. SETTING Supine elective neurosurgical patients. INTERVENTIONS The study protocol was, first, the initial EEOT test was performed during baseline 6 ml kg−1 PBW ventilation; second, VTC was performed by increasing the VT up to 8 ml kg−1 PBW and PPV and SVV changes were recorded after 1 min; third, a second EEOT was performed during 8 ml kg−1 PBW ventilation; and VT was reduced back to 6 ml kg−1 PBW and a third EEOT was performed. Finally, a 250 ml fluid challenge was administered over 10 min to identify fluid responders (increase in stroke volume index ≥10%). RESULTS In the 40 patients analysed, PPV and SVV values at baseline and EEOT performed at 6 ml kg−1 PBW did not predict fluid responsiveness. A 13.3% increase in PPV after VTC predicted fluid responsiveness with a sensitivity of 94.7% and a specificity of 76.1%, while a 12.1% increase in SVV after VTC predicted fluid responsiveness with a sensitivity of 78.9% and a specificity of 95.2%. After EEOT performed at 8 ml kg−1 PBW, a 3.6% increase in cardiac index predicted fluid responsiveness with a sensitivity of 89.4% and a specificity of 85.7%, while a 4.7% increase in stroke volume index (SVI) with a sensitivity of 89.4% and a specificity of 85.7%. CONCLUSION The changes in PPV and SVV obtained after VTC are reliable and comparable to the changes in CI and SVI obtained after EEOT performed at 8 ml kg−1 PBW in predicting fluid responsiveness in neurosurgical patients. TRIAL REGISTRATION ACTRN12618000351213. Correspondence to Antonio Messina, MD, PhD, Department of Anaesthesia and Intensive Care Medicine, IRCCS Humanitas, Humanitas University, Via Alessandro Manzoni, 56, Rozzano – Milan 20089, Italy. Tel: +39(0)2 8224 8282; e-mail: mess81rc@gmail.com Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Website (www.ejanaesthesiology.com). © 2019 European Society of Anaesthesiology