Fluid Responsiveness Prediction During Prone Position

Predicting fluid responsiveness is primordial when caring for patients with circulatory shock as it allows correction of preload-dependent low cardiac output states, while preserving patients of the deleterious effects of excessive fluid resuscitation.

Patients with severe acute respiratory distress syndrome (ARDS) treated with prone positioning (PP) are a specific subset of patients, as 1) they frequently present with shock; 2) excessive fluid administration may lead to respiratory worsening due to increased hydrostatic oedema with potential subsequent worse clinical outcome; and 3) all available dynamic tests evaluating fluid responsiveness can only be performed in patients in the supine condition (which in the case of severe ARDS patients in PP occurs only for 8h over 24h). These elements warrant the development of specific tests allowing the clinician to predict fluid responsiveness with enough exactitude when caring for these patients.

We hypothesize that there exists diagnostic heterogeneity in the predictive performance of 4 clinical tests to identify fluid responsiveness in ARDS patients in PP. For the matter of this study, these 4 tests are the Trendelenburg maneuver, the end-expiratory occlusion test, the end-expiratory occlusion test associated with the end-inspiratory occlusion test, and the tidal volume challenge. The diagnostic reference of the study will be the relative change in cardiac index measured by transpulmonary thermodilution before and after a 500 ml fluid bolus, and will allow the adjudication of patients as being fluid responsive or not.

The primary objective of the study is to determine the area under the ROC curve of each of the 4 tests, with their respective 95% confidence interval.

All enrolled patients will perform the 4 tests following a cross-over design and in a randomized sequence, separated by 1-min wash-out periods with return to hemodynamic baseline values, and concluded with the 500-ml fluid bolus. Patients will only participate once. The expected duration of study participation is 30 minutes maximum.


Eligibility Criteria:
Inclusion Criteria:

* adult patient (including patient under protective measures/wardship)
* with ARDS as defined by the Berlin criteria
* in the prone position as per international guidelines
* with a calibrated continuous cardiac output monitoring device
* with a clinical indication for a fluid bolus as prescribed by the clinician in charge, and fulfilling at least 2 clinical criteria: mottles, tachycardia, hypotension, drop in cardiac output, oliguria, high arterial lactate concentration, or any other detailed criterion
* with no respiratory efforts

Exclusion Criteria:

* acute cor pulmonale
* patient treated with veno-venous extra-corporeal membrane oxygenation
* hemorrhagic shock
* Child-Pugh C cirrhosis
* death expected to occur in less than 24h
* decision to withhold or suspend active treatments
* intracranial hypertension
* lower limb amputation
* obstruction of the inferior vena cava
* acute abdominal syndrome
* absence of consent to participate
* pregnancy
* patient previously enrolled in the same study
* lack of affiliation to a social security regimen, as per French legislation
* patient deprived of its liberty