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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
NONE
Enrollment
96
Bed tilting from the +13° position to the -13° position for 60 seconds. Evaluator: relative change in continuous cardiac index between baseline, and the highest value observed during the maneuver
End-expiratory pause performed on the ventilator, and maintained for 15 seconds. Evaluator: relative change in continuous cardiac index between baseline, and the value observed in the last 5 seconds of the respiratory pause
End-inspiratory pause performed on the ventilator, and maintained for 15 seconds. Evaluator: relative change in continuous cardiac index between baseline, and the value observed in the last 5 seconds of the respiratory pause. The evaluator is calculated as the sum of the relative change in cardiac index observed during the end-expiratory pause and that of the end-inspiratory pause. Hence, for this test, the evaluator will be coupled with that of intervention 2 (end-expiratory occlusion test).
Increase in tidal volume set on the ventilator from 6 ml.kg-1 of predicted body weight, to 8 ml.kg-1 for 60 seconds. Evaluator: difference in the pulse pressure variation measured at 6 ml.kg-1 and at 8 ml.kg-1.
After the 4 tests, the patient will receive a 500-ml fluid bolus of crystalloids in less than 15 minutes. Evaluator (reference method): cardiac index measured by transpulmonary thermodilution before and immediately after the fluid bolus. Patients with a relative change in cardiac index \> 15% will be identified as being fluid responders, and the others as non-responders.
CHU Gabriel Montpied
Clermont-Ferrand, France
NOT_YET_RECRUITINGHôpital de la Croix Rousse, Hospices Civils de Lyon
Lyon, France
RECRUITINGCHU de Nice - l'Archet 1
Nice, France
NOT_YET_RECRUITINGCHU Nice - Pasteur 2
Nice, France
NOT_YET_RECRUITINGArea under the ROC curve (AUROC) of the evaluated tests.
The AUROC will be determined for each of the 4 clinical tests evaluated in this study. The reference method to define the AUROC to design the curve will be the fluid responsive status (responder vs. non-responder) as determined by the fluid bolus. For each test, the AUROC will be accompanied with its 95% confidence interval.
Time frame: 30 minutes
Comparison of diagnostic performance of the evaluated tests.
For this outcome measure, the AUROCs will be determined as for the primary outcome measure. The AUROCs will be compared using the Delong's method, with adjustments for the repetition of measurements in a single patient.
Time frame: 30 minutes
Diagnostic performance metrics of each test
Sensitivity, specificity, positive predictive value, negative predictive value and likelihood ratios of the evaluated tests, computed for the optimal diagnostic threshold determined using the Youden J index of the ROC curve. The optimal threshold will only be computed for AUROCs significantly different from 0.5.
Time frame: 30 minutes
Weighted diagnostic performance of each test
Sensitivity, specificity, positive predictive value, negative predictive value and likelihood ratios of the evaluated tests, computed for the optimal diagnostic threshold determined using the Youden J index of the ROC curve, and adjusted using weighting based on the clinical tradeoff of the subsequent fluid bolus on hemodynamic benefit vs. the respiratory risk. The optimal threshold will only be computed for AUROCs significantly different from 0.5.
Time frame: 30 minutes
Grey zone area of the optimal diagnostic threshold of each test
Determination of the boundaries of a grey zone around the value of the optimal threshold of each test, in which the diagnostic performance is deemed clinically insufficient (excessive misclassification risk due to lack of discrimination). The grey zone around the optimal threshold will only be computed for AUROCs significantly different from 0.5.
Time frame: 30 minutes
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