Evaluation of natriuresis-guided depletion after cardiac surgery: protocol for a single-centre, open-label, randomised controlled trial-the EASY-CS study.

Introduction: Fluid overload (FO) is a common complication following cardiac surgery with cardiopulmonary bypass (CPB) and is associated with increased morbidity and mortality. Loop diuretics, particularly furosemide, are widely used to promote sodium and water excretion, but their postoperative use remains largely empirical. International guidelines recommend early assessment of diuretic response using spot urinary sodium concentration, traditionally measured by automated laboratory analysers. Recent advances now enable bedside measurement of natriuresis using point-of-care (POC) urinary sodium sensors. This trial aims to determine whether real-time bedside natriuresis monitoring using a POC device can guide safer and more effective diuretic strategies in the postoperative management of FO.

Materials and methods: The EASY-CS trial is a prospective, single-centre, open-label, randomised controlled trial designed to evaluate whether a natriuresis-guided furosemide titration protocol improves diuresis within 48 hours following cardiac surgery with CPB. A total of 102 adult patients undergoing elective cardiac surgery with CPB and requiring postoperative intravenous (IV) furosemide for FO will be randomised in a 1:1 ratio to either standard care (n=51; furosemide titration based on clinical judgement) or a natriuresis-guided arm (n=51), in which furosemide dosing is adjusted according to urinary sodium concentration. All patients will receive an initial 20 mg dose of IV furosemide. In the intervention group, urinary sodium will be measured every 6 hours using a POC sodium sensor (LAQUAtwin Na⁺ metre, Horiba, Japan). If the spot urinary sodium is <70 mmol/L, the furosemide dose will be doubled at the next administration, up to a maximum of 200 mg per bolus. The primary endpoint is cumulative urine output at 48 hours post-randomisation.Secondary outcomes include urinary sodium concentration and urine output at 24 hours, natriuresis at 48 hours, and the venous excess ultrasound score at 48 hours, as determined by transthoracic echocardiography. The study will also assess total loop diuretic dose administered, cumulative fluid balance over 48 hours and the incidence of postoperative complications at day 30, including cardiovascular, renal, respiratory and gastrointestinal events. Safety endpoints include the presence of hypotension, hypokalaemia or acute kidney injury before each diuretic administration. Randomisation will be stratified by EuroSCORE II (<4% vs ≥4%) and baseline serum creatinine (<100 vs≥100 µmol/L). Recruitment has not yet started.

Ethics and dissemination: Ethical approval has been obtained from the Institutional Review Board (IRB) of Amiens University hospital (IRB-ID: 2025-A00925-44). The study's results will be disseminated through peer-reviewed publications and presentations at national and international conferences.

Trial registration number: ClinicalTrials.gov Identifier: NCT07077772.