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Fluid Responsiveness in Laparoscopic Surgery: End-Expiratory Occlusion Test Versus Mini-Fluid Challenge

Sponsor: University Of Perugia

Summary

Background Fluid management is central to perioperative care, but only about half of surgical patients increase their stroke volume after a fluid challenge. Dynamic indices such as pulse pressure variation and stroke volume variation are often unreliable during laparoscopy, because of low tidal volume ventilation and carbon dioxide (CO2) pneumoperitoneum. Functional hemodynamic tests may overcome these limitations. In the Mini fluid chAllenge aNd End-expiratory occlusion test to assess flUid responsiveness in the opeRating room (MANEUVER) study (NCT03808753), conducted in open abdominal surgery, the mini-fluid challenge predicted fluid responsiveness well, whereas the end-expiratory occlusion test did not. Pneumoperitoneum raises intra-abdominal pressure instead of abolishing it, so these results cannot be extrapolated to laparoscopy. Design FLUID-LAP is a prospective, multicenter, observational diagnostic-accuracy cohort study conducted in four Italian centers and reported according to the Standards for Reporting of Diagnostic Accuracy (STARD) 2015 statement. Each patient is their own control: both index tests and the reference standard are performed in sequence in the same patient during a period of stable intraoperative hemodynamics, so the resulting receiver operating characteristic (ROC) curves are correlated. The study replicates the design of MANEUVER, changing only the surgical setting. Ventilation (volume-controlled, 7 ml/kg predicted body weight), the reference fluid challenge and uncalibrated pulse-contour monitoring are the same, to allow direct comparison with the open-abdomen data. Procedures Tests are performed under standardized baseline conditions (stable pneumoperitoneum and position, unchanged ventilation, no recent drug changes or surgical manipulation, arterial waveform checked with a square-wave test). The order of the two index tests is chosen by the attending anesthesiologist, is recorded for every patient, and is analyzed as a pre-specified covariate. A 3-minute return to steady state separates the tests. The complete 4 ml/kg fluid challenge is given after both tests. The maneuvers are already part of routine goal-directed practice, and no treatment decision is dictated by the protocol. Patient safety always prevails over the protocol. Analysis The primary analysis compares the areas under the ROC curves (AUC) of the two tests using the DeLong test. The expected AUCs are 0.90 for the mini-fluid challenge and 0.75 for the end-expiratory occlusion test. With 80% power and a two-sided alpha of 0.05, 87 evaluable patients are required; 104 will be enrolled to allow for 15% attrition (26 per center). Pre-specified analyses address the mathematical coupling between the mini-fluid challenge and the reference challenge, the effect of test order, and subgroups by intra-abdominal pressure and patient position.

Official title: FLUID Responsiveness in LAParoscopic Surgery: A Prospective, Multicentre, Observational Diagnostic-accuracy Cohort Study Comparing the End-expiratory Occlusion Test and the Mini-fluid Challenge for the Prediction of Fluid Responsiveness During Laparoscopic Surgery

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