VEXUS and Assessment of Dry Weight of Patients on Hemodialysis

All study participants will undergo a comprehensive array of assessments

Before the midweek session, which will include the following evaluations:

I. Full history taking and clinical assessment A thorough evaluation will include patient age, gender, cause of ESRD, duration of dialysis, and detailed cardiac and pulmonary medical history, including any intradialytic hypotension or hypertension episodes.

At the end of each mid-week session, blood pressure, pulse oximetry measurement, and respiratory symptoms will be assessed in the 2 phases of the study.

II. Laboratory Investigations:

A comprehensive panel of tests will be conducted, including

• Complete blood count (CBC).
• Blood urea (Pre and post-dialysis for Kt/V calculation), serum creatinine and serum albumin.

III. Assessment of dialysis adequacy:

By measurement of Kt/V.

IV. Echocardiography Will be done for all patients in the study V. Ultrafiltration Prescription and Volume Assessment Clinical Determination of Target Ultrafiltration During the clinical assessment phase, target UF will be prescribed based on standard clinical parameters. These include interdialytic weight gain, pre- and post-dialysis body weight, blood pressure trends (any intradialytic hypotension or hypertension episodes), presence of peripheral edema, chest auscultation, pulmonary symptoms, and jugular venous pressure in cmH2O where assessable, and intradialytic symptoms such as hypotension or muscle cramps.

Estimated dry weight will be determined clinically, and target UF will be calculated as the difference between pre-dialysis weight and estimated dry weight. The ultrafiltration rate will be recorded in millilitres per minute per kilogram of body weight.

During the POCUS-guided phase:

LUS Eight-zone examination:

• LUS will be used to assess pulmonary congestion by quantifying B-lines as a marker of extravascular lung water. The presence of multiple B-lines will indicate pulmonary congestion and support adjustment of dry weight and target UF. Conversely, minimal or absent B-lines will suggest euvolemia, prompting avoidance of unnecessary UF escalation to reduce the risk of intradialytic hypotension.

• In this study, each hemithorax is divided into four areas (two anterior, two lateral). For a scan to be considered abnormal, it must meet the following criteria:

  • multiple artefacts per scan (at least three)
  • positive findings in more than one scan per side
  • positive findings bilaterally.

VExUS Score:

• Venous congestion will be evaluated using ultrasound and Doppler-based techniques 30 minutes after the HD session during the POCUS-guided phase.

• The assessment will include:

  1. Measurement of the static diameter of the inferior vena cava (IVC).

     • Normal: IVC less than 20 mm
     • Abnormal: IVC is greater than or equal to 20 mm.

  2. Recording of hepatic venous (HV) flow, classified as follows:

     Normal: Continuous systolic flow greater than diastolic flow Abnormal: Systolic flow less than diastolic flow Severely Abnormal: Systolic flow reversal

  3. Assessment of portal vein (PV) pulsatility using pulsed-wave Doppler. PV patterns include:

     Normal: Continuous flow Abnormal: Pulsatile flow If pulsatile flow is detected, the pulsatility index (PI) will be calculated to assess the severity of the abnormality.

     The PI is determined using the formula: (PVmax -PVmin)/PVmax × 100).

• Measurements will be categorised based on Doppler findings and used to determine the VExUS score (0-3).

Note: The intrarenal flow profile will be omitted from the VExUS score due to its frequent unreliability and inconsistent detectability in previous studies Involving dialysis patients.

- Higher VExUS grades will indicate significant systemic venous congestion and support modification of dry weight and/or increase in target UF, provided hemodynamic stability is maintained. Lower VExUS grades will indicate minimal venous congestion and guide conservative UF strategies when clinically appropriate.

Bio-impedance spectroscopy:

At the end of each phase, all patients' volume status will be assessed by using a Biospace InBody 720 body composition analyzer to be correlated with the results of each phase.

InIntegrated Volume Assessment and Safety Considerations Target UF prescription during the POCUS-guided phase will be based on an integrated assessment combining clinical evaluation, LUS, and VExUS findings. Adjustments to UF and dry weight will be performed gradually and individualised for each patient, with careful attention to patient tolerance and intradialytic hemodynamic stability. Excessive UF rates and intradialytic complications will be actively avoided.