Ultrasound-Guided Mini Fluid Challenge via Velocity–Time Integral to Assess Fluid Responsiveness in Upper Gastrointestinal Bleeding: A Prospective Quasi-Experimental Feasibility Study

Background: Acute upper gastrointestinal bleeding (UGIB) remains a leading cause of emergency department (ED) admission and carries a mortality of 5–10%. Static hemodynamic parameters perform poorly as predictors of fluid responsiveness, exposing patients either to under-resuscitation or to the harms of fluid overload. The mini fluid challenge (MFC), in which a 100 mL bolus is used to elicit a measurable change in the left ventricular outflow tract velocity–time integral (ΔVTI), is a validated dynamic test in intensive care but has not been evaluated in undifferentiated ED haemorrhagic shock. We aimed to determine whether ΔVTI-guided resuscitation is feasible at the bedside in UGIB and to explore how ΔVTI relates to in-hospital mortality. Methods: Prospective, single-centre, randomised quasi-experimental comparative study conducted between February 2024 and February 2025. Adults presenting with UGIB were allocated by treatment period, and credentialed emergency physicians to an ultrasound-guided protocol group (UGPG) or a standard care protocol group (SCPG). ΔVTI was measured in both groups but was disclosed to the treating team only in UGPG; in SCPG, it was recorded offline and analysed post hoc. The primary outcome was the feasibility of ΔVTI acquisition; the association of ΔVTI with in-hospital mortality was a secondary, exploratory outcome. Results: Eighty-five patients were enrolled (UGPG n = 47; SCPG n = 38). ΔVTI acquisition was completed within the intended time window in all enrolled patients, establishing bedside feasibility. Across the whole cohort, ΔVTI discriminated non-survivors poorly (AUC 0.55, 95% CI 0.44–0.66), and its performance differed markedly by group: AUC 0.83 (95% CI 0.67–0.93) in SCPG versus 0.69 (95% CI 0.54–0.82) in UGPG. In SCPG, non-survivors had substantially higher ΔVTI than survivors (58.6 ± 30.5% vs. 28.4 ± 30.9%; p = 0.030), a pattern consistent with persistent, uncorrected fluid responsiveness. In UGPG, the association ran in the opposite direction, mortality being concentrated among ΔVTI < 10% non-responders (p = 0.020). Conclusions: ΔVTI-guided resuscitation is feasible in the ED management of UGIB. The direction of the ΔVTI–mortality association differed according to whether ΔVTI was visible to clinicians, generating the testable hypothesis that unrecognised fluid responsiveness contributes to death in standard care. These findings are hypothesis-generating only: the small sample and the low number of events preclude any causal inference and require confirmation in an adequately powered, randomised, etiology-stratified trial.