BackgroundPredicting fluid responsiveness may help to avoid unnecessary fluid administration during acute respiratory distress syndrome (ARDS). The aim of this study was to evaluate the diagnostic performance of the following methods to predict fluid responsiveness in ARDS patients under protective ventilation in the prone position: cardiac index variation during a Trendelenburg maneuver, cardiac index variation during an end-expiratory occlusion test, and both pulse pressure variation and change in pulse pressure variation from baseline during a tidal volume challenge by increasing tidal volume (VT) to 8 ml.kg-1.MethodsThis study is a prospective single-center study, performed in a medical intensive care unit, on ARDS patients with acute circulatory failure in the prone position. Patients were studied at baseline, during a 1-min shift to the Trendelenburg position, during a 15-s end-expiratory occlusion, during a 1-min increase in VT to 8 ml.kg-1, and after fluid administration. Fluid responsiveness was deemed present if cardiac index assessed by transpulmonary thermodilution increased by at least 15% after fluid administration.ResultsThere were 33 patients included, among whom 14 (42%) exhibited cardiac arrhythmia at baseline and 15 (45%) were deemed fluid-responsive. The area under the receiver operating characteristic (ROC) curve of the pulse contour-derived cardiac index change during the Trendelenburg maneuver and the end-expiratory occlusion test were 0.90 (95% CI, 0.80–1.00) and 0.65 (95% CI, 0.46–0.84), respectively. An increase in cardiac index ≥ 8% during the Trendelenburg maneuver enabled diagnosis of fluid responsiveness with sensitivity of 87% (95% CI, 67–100), and specificity of 89% (95% CI, 72–100). The area under the ROC curve of pulse pressure variation and change in pulse pressure variation during the tidal volume challenge were 0.52 (95% CI, 0.24–0.80) and 0.59 (95% CI, 0.31–0.88), respectively.ConclusionsChange in cardiac index during a Trendelenburg maneuver is a reliable test to predict fluid responsiveness in ARDS patients in the prone position, while neither change in cardiac index during end-expiratory occlusion, nor pulse pressure variation during a VT challenge reached acceptable predictive performance to predict fluid responsiveness in this setting.Trial registrationClinicalTrials.gov, NCT01965574. Registered on 16 October 2013. The trial was registered 6 days after inclusion of the first patient.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-017-1881-0) contains supplementary material, which is available to authorized users.

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BackgroundHemodynamic response to prone position (PP) has never been studied in a large series of patients with acute respiratory distress syndrome (ARDS). The primary aim of this study was to estimate the rate of PP sessions associated with cardiac index improvement. Secondary objective was to describe hemodynamic response to PP and during the shift from PP to supine position.MethodsThe study was a single-center retrospective observational study, performed on ARDS patients, undergoing at least one PP session under monitoring by transpulmonary thermodilution. PP sessions performed more than 10 days after ARDS onset, or with any missing cardiac index measurements before (T1), at the end (T3), and after the PP session (T4) were excluded. Changes in hemodynamic parameters during PP were tested after statistical adjustment for volume of fluid challenges, vasopressor and dobutamine dose at each time point to take into account therapeutic changes during PP sessions.ResultsIn total, 107 patients fulfilled the inclusion criteria, totalizing 197 PP sessions. Changes in cardiac index between T1 and T2 (early response to PP) and between T1 and T3 (late response to PP) were significantly correlated (R2 = 0.42, p < 0.001) with a concordance rate amounting to 85%. Cardiac index increased significantly between T1 and T3 in 49 sessions (25% [95% confidence interval (CI95%) 18–32%]), decreased significantly in 46 (23% [CI95% 16–31%]), and remained stable in 102 (52% [CI95% 45–59%]). Global end-diastolic volume index (GEDVI) increased slightly but significantly from 719 ± 193 mL m−2 at T1 to 757 ± 209 mL m−2 at T3 and returned to baseline values at T4. Cardiac index and oxygen delivery decreased slightly but significantly from T3 to T4, without detectable increase in lactate level. Patients who increased their cardiac index during PP had significantly lower CI, GEDVI, global ejection fraction at T1, and received significantly more fluids than patients who did not.ConclusionPP is associated with an increase in cardiac index in 18% to 32% of all PP sessions and a sustained increase in GEDVI reversible after return to supine position. Return from prone to supine position is associated with a slight hemodynamic impairment.Electronic supplementary materialThe online version of this article (10.1186/s13613-018-0464-9) contains supplementary material, which is available to authorized users.