Ultrasound-Guided Mini Fluid Challenge via Velocity-Time Integral to Assess Fluid Responsiveness in Upper...

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.