The role of thoracic ultrasound in fluid management in critical care: a narrative review.

Background and Objective: Fluid management remains central to critical care, requiring a careful balance between early resuscitation and the prevention or reversal of pulmonary and systemic congestion. Thoracic ultrasound (TUS) offers real-time, organ-specific assessment of extravascular lung water (EVLW) and pleural effusion, helping clinicians recognize both fluid responsiveness and fluid intolerance-an increasingly relevant distinction in acute respiratory distress syndrome (ARDS), acute heart failure, kidney replacement therapy, and shock. This review synthesizes current evidence on TUS-guided fluid administration and removal and introduces the Fluid Responsiveness & Tolerance, Lung Congestion, Ultrafiltration Optimization, Individualized Therapy, Differentiating Shock (FLUID) framework as a practical bedside reasoning tool emphasizing repeated reassessment rather than prescriptive thresholds. Methods: Narrative review of PubMed, Scopus, and Embase (January 2015 to January 2025), supplemented by landmark earlier articles when clinically relevant. Eligible studies included adult human research, systematic reviews, randomized trials, and consensus statements. Editorials, pediatric, and veterinary studies were excluded. Selection and full-text appraisal were performed independently by two reviewers. Key Content and Findings: TUS provides bedside visualization of pulmonary congestion through B-lines, lung ultrasound scoring, and effusion monitoring, improving detection of EVLW compared with physical examination or central venous pressure. Integrated with focused cardiac and venous Doppler evaluation, TUS supports decisions regarding resuscitation, diuretic escalation, ultrafiltration, or fluid removal in ARDS, heart failure, and shock. Evidence suggests TUS-guided strategies may reduce cumulative fluid balance and rehospitalization in heart failure and may facilitate ventilator liberation, though definitive outcome effects remain under investigation. The FLUID framework structures iterative bedside reasoning without functioning as a prescriptive protocol. Conclusions: TUS is a practical and repeatable tool that enhances individualized fluid management by identifying evolving pulmonary congestion and estimating fluid tolerance. The FLUID framework supports structured clinical integration of ultrasound findings but requires further prospective validation. Future trials and artificial intelligence (AI)-assisted quantification tools may help standardize practice and clarify outcome benefits.