This study will evaluate the use of the Venous Excess Ultrasound (VExUS) score to guide fluid management in critically ill ICU patients through a prospective, multi-aim design combining observational and randomized components. The study will be conducted in the medical intensive care unit (MICU), multidisciplinary critical care unit (MCCU), and cardiac care unit (CCU) at UAB.

This study will evaluate the use of the Venous Excess Ultrasound (VExUS) score to guide fluid management in critically ill ICU patients through a prospective, multi-aim design combining observational and randomized components. The study will be conducted in the medical intensive care unit (MICU), multidisciplinary critical care unit (MCCU), and cardiac care unit (CCU) at UAB.

Informed Arm: The treating team receives the patient's VExUS results and management recommendations.

Not-Informed Arm: The treating team remains blinded to all VExUS findings and receives no feedback or recommendations.

Each enrolled patient will undergo two VExUS ultrasound assessments:

Timepoint 1 (enrollment): Two scans are performed by separate operators to assess waveform reliability and inter-user reproducibility.

Timepoint 2 (48-72 hours after enrollment): A single scan is performed along with concurrent collection of serum creatinine, intake/output (I&O) balance, and renal replacement therapy (RRT) status.

Each VExUS exam includes Doppler evaluation of the inferior vena cava, hepatic vein, portal vein, renal cortical artery, and renal cortical vein. Scans are saved to secure UAB SharePoint storage labeled with an auto-incrementing study ID.

Blinding Procedures

To maintain study integrity and minimize bias, multiple layers of blinding will be employed:

Scanner Blinding: Sonographers performing the VExUS scans are blinded to the patient's randomization status and to all prior scan results. They collect and upload de-identified images labeled only by study ID.

Interpreter Blinding: The attending physician interpreting the scans (the "overreader") is blinded to randomization status during the image interpretation phase. The overreader reviews both scans for quality and assigns a VExUS score (0-3) before randomization status is revealed.

Recruiter/Coordinator Role: The research coordinator (unblinded) maintains the randomization list and is responsible for communicating the overread results to the treating team only for patients in the informed arm.

Primary Team Blinding: For patients in the not-informed arm, the primary clinical team will not receive any VExUS scores or recommendations, and no study-related documentation will be visible in the electronic health record (EHR).

Statistical Blinding: Data analysts will remain blinded to treatment arm allocation until after all primary outcomes are recorded.

Communication and Clinical Guidance

For patients in the informed arm, the overreader will generate standardized recommendations based on the VExUS score:

VExUS = 0: Recommend a net positive fluid balance.

VExUS = 1: Recommend a net neutral fluid balance.

VExUS >= 2: Recommend a net negative fluid balance.

These recommendations will be communicated to the treating team via a structured process: documentation in the EHR under the POCUS note and verbal handoff to the resident, fellow, and attending on the primary team.

Data Management and Analysis

Two linked data lists will be maintained:

Master List (PHI-protected): Contains patient identifiers and MRNs, stored on a secure UAB server.

Patient Data List (de-identified): Contains study ID, randomization arm, scan quality, interpreter scores, creatinine values, I&O data, RRT status, ICU-free days, hospital-free days, and mortality.

All ultrasound procedures are noninvasive and adhere to ACEP emergency ultrasound standards. Protected health information will remain secured on institutional servers, and only de-identified data will be used for analysis.

Inclusion Criteria:

• Adults (≥18 years old)
• Admitted to the MICU, MCCU, or CCU within 24 hours of admission
• Acute kidney injury (AKI) (based on Kidney Disease: Improving Global Outcomes (KDIGO) criteria)
• Adequate acoustic windows for a complete VExUS scan

Exclusion Criteria:

• < 18 years old
• pregnant women
• End-stage renal disease (ESRD) or prior renal transplant
• Acute tubular necrosis (ATN) defined by urinalysis (≥2+ protein, ≥2+ blood, ≥1 muddy brown cast, ≥1 RBC cast, or ≥1 dysmorphic RBC)'
• Prior Whipple procedures
• currently incarcerated

To maintain study integrity and minimize bias, multiple layers of blinding will be employed:

Scanner Blinding: Sonographers performing the VExUS scans are blinded to the patient's randomization status and to all prior scan results. They collect and upload de-identified images labeled only by study ID.

Interpreter Blinding: The attending physician interpreting the scans (the "overreader") is blinded to randomization status during the image interpretation phase. The overreader reviews both scans for quality and assigns a VExUS score (0-3) before randomization status is revealed.

Recruiter/Coordinator Role: The research coordinator (unblinded) maintains the randomization list and is responsible for communicating the overread results to the treating team only for patients in the informed arm.

Primary Team Blinding: For patients in the not-informed arm, the primary clinical team will not receive any VExUS scores or recommendations, and no study-related documentation will be visible in