Quantification of Systemic Congestion by Ultrasound As a Predictor of Weaning Failure From Mechanical Ventilation
Trial Snapshot
- Phase
- Not Applicable
- Status
- Not yet recruiting
- Sponsor
- Enrollment
- 350
- Primary Endpoint
- Weaning failure
Study Overview
Brief Summary
Mechanical ventilation is an essential, life-saving therapy in the ICU, allowing critically ill patients to rest and recover. Transitioning patients back to spontaneous breathing-known as weaning-is clinically challenging. The first attempt, the Spontaneous Breathing Trial (SBT), fails in 10-30% of cases. Identifying the mechanisms behind failure is crucial, as unsuccessful weaning prolongs ICU stay and increases the risk of reintubation, which worsens prognosis. The SCOUT study aims to improve prediction and management of weaning failure.
The main objective of the study is to evaluate whether a specific ultrasound-based method, the Venous Excess Ultrasound Score (VExUS), can predict failure of weaning from mechanical ventilation. A key pathophysiological factor is systemic venous congestion. When a patient initiates an SBT, the increased respiratory effort shifts venous return and may precipitate cardiovascular decompensation with pulmonary fluid accumulation, termed weaning-induced pulmonary edema (WIPO). Notably, this may occur even in patients without known cardiac disease.
Detecting clinically relevant congestion before SBT is difficult. Fluid balance and body weight are imprecise, physical examination lacks sensitivity, and biomarkers such as NT-proBNP have limited predictive capacity. VExUS offers a promising, non-invasive approach by directly assessing venous flow patterns in major veins (inferior vena cava, hepatic, portal, and renal veins), providing an estimation of systemic venous pressure and congestion. The central hypothesis is that elevated VExUS grades prior to SBT will identify patients at high risk of failure, enabling proactive optimization and potentially improving outcomes.
SCOUT is designed as a prospective, multicenter, observational study. Standard clinical management of mechanical ventilation and weaning remains unchanged. After informed consent, baseline data will be obtained immediately before SBT, including vital signs, ventilator parameters, blood sampling, and three non-invasive ultrasound assessments: cardiac, pulmonary, and VExUS. During the 30-120-minute SBT, the patient breathes with reduced ventilatory support while their clinical tolerance is evaluated. At the end of the SBT, selected measurements are repeated. Weaning failure is defined as: early termination of SBT due to intolerance, need for invasive or non-invasive ventilation within 48 h after extubation, or death within 48 h. Data are anonymized and stored securely (REDCap) in compliance with Spanish and EU data protection regulations.
The study is low-risk and provides no direct individual benefit, but may benefit future ICU patients by improving weaning strategies and prognostication.
Detailed Description
- Protocol overview and Rationale Weaning patients from invasive mechanical ventilation represents a significant daily challenge within the intensive care unit (ICU). The process is complex, and failure can lead to prolonged ventilation, increased morbidity, and worsened patient outcomes. The "Quantification of Systemic Congestion by Ultrasound As a Predictor of Weaning Failure from Mechanical Ventilation (SCOUT)" study is a prospective investigation designed to evaluate a novel, non-invasive method for identifying patients at high risk of weaning failure before a trial is even attempted.
The core clinical problem addressed by this study is the high incidence of weaning failure, which occurs in 10-30% of patients. While respiratory complications are a common cause, up to 30% of failures are attributed to cardiovascular origins. A key mechanism in these cases is systemic congestion, which can lead to weaning-induced pulmonary edema (WIPO). This condition occurs when the physiological stress of a spontaneous breathing trial (SBT) causes a rapid shift of fluid into the central circulation, overwhelming cardiac capacity and flooding the lungs, even in patients without a prior history of heart failure.
Current methods for assessing a patient's fluid status and risk of congestion have significant limitations. Clinicians often rely on metrics such as cumulative fluid balances, daily weight changes, physical examination findings, and biomarkers. However, these tools have proven to be insufficiently reliable or specific for accurately predicting which patients will develop WIPO during an SBT. While tools like echocardiography are useful for diagnosing pulmonary edema after it has already occurred, they have not demonstrated utility in identifying at-risk patients beforehand. Similarly, pulmonary ultrasound can detect lung edema (B-lines) but not identify high risk patients before it occurs.
This study will investigate the Venous Excess Ultrasound (VExUS) grading system as a predictive tool. VExUS is a novel, point-of-care ultrasound protocol that provides a comprehensive assessment of systemic venous congestion. It integrates ultrasound measurements of the inferior vena cava with Doppler flow patterns in the hepatic veins, portal vein, and intrarenal veins to generate a score that quantifies the degree of venous congestion.
Given that systemic congestion is a central mechanism in WIPO, a tool that can reliably measure it at the bedside holds immense potential. VExUS provides real-time, repeatable information, allowing for dynamic patient monitoring. The central justification for this study is that by using the VExUS score to assess a patient before initiating an SBT, clinicians may be able to identify those at high risk of cardiovascular-related weaning failure. This proactive identification would allow for targeted therapeutic measures to be implemented preemptively, thereby improving a patient's readiness for weaning, reducing the likelihood of failure, and minimizing the consequences associated with prolonged mechanical ventilation. This clinical rationale underpins the study's formal hypotheses and objectives. 2. Study Hypotheses and Objectives
Study Design
- Study Type
- Interventional
- Allocation
- Na
- Intervention Model
- Single Group
- Primary Purpose
- Diagnostic
- Masking
- None
Eligibility Criteria
- Ages
- 18 Years to — (Adult, Older Adult)
- Sex
- All
- Accepts Healthy Volunteers
- No
Inclusion Criteria
- •Patients aged > 18 years.
- •Admitted to an Intensive Care Unit (ICU).
- •Requiring invasive mechanical ventilation for more than 48 hours.
- •Meeting the center's standard criteria to begin weaning and undergo an SBT.
Exclusion Criteria
- •Inadequate ultrasound window for assessment.
- •Presence of "do not reintubate" orders.
- •Patients with a tracheostomy.
- •Presence of atrial fibrillation.
- •Diagnosed liver cirrhosis (portal hypertension).
- •Absence of qualified personnel to perform the ultrasound at the time of the SBT.
- •Denial of informed consent.
Arms & Interventions
Ultrasound study
Prior to SBT: A complete set of pulmonary, cardiac, and VExUS ultrasounds will be performed and stored for later analysis by blinded experts.
At the end of SBT: repeat pulmonary and cardiac ultrasounds
Intervention: point of care ultrasound (Diagnostic Test)
Outcomes
Primary Outcomes
Weaning failure
Time Frame: From the start of the spontaneous breathing trail to 48 hours after
The primary objective of the SCOUT study is: To evaluate the utility of VExUS to predict weaning failure from mechanical ventilation. Defining the Weaning Failure A patient is considered to have met the primary outcome if they experience any one of the following events: * The Spontaneous Breathing Trial (SBT) is interrupted due to clinical intolerance, requiring reconnexion to mechanical ventilation. * The patient is extubated but requires rescue with mechanical ventilation (either invasive or non-invasive) within the subsequent 48 hours. * The patient is extubated and dies within the subsequent 48 hours.
Utility of the VExUS score for predicting the failure of weaning from mechanical ventilation
Time Frame: From the start of the spontaneous breathing trial to the next 48 hours
The primary objective of the SCOUT study is: To evaluate the utility of VExUS to predict weaning failure from mechanical ventilation. A patient is considered to have met the primary outcome (weaning failure) if they experience any one of the following events: * The Spontaneous Breathing Trial (SBT) is interrupted due to clinical intolerance, requiring reconnexion to mechanical ventilation. * The patient is extubated but requires rescue with mechanical ventilation (either invasive or non-invasive) within the subsequent 48 hours. * The patient is extubated and dies within the subsequent 48 hours.
Secondary Outcomes
No secondary outcomes reported