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NCT Number: NCT07499388

Assessment of Venous Return During Volume Expansion: a Prospective Observational Study

According to Guyton's model of venous return, the fluids that effectively increase cardiac output are those that, once administered, increase the vascular stressed volume, thereby increasing the mean systemic filling pressure (Pms) without increasing the central venous pressure (CVP). In this way, since the gradient between Pms and CVP increases, venous return-and consequently cardiac output-also increases.

In cases where physiologically ineffective fluids are administered, the situation arises in which, in addition to increasing the stressed volume and thus Pms, CVP also increases. As a result, the gradient between Pms and CVP remains unchanged, and cardiac output does not increase.

The hypothesis is that only a portion of the fluids administered during volume expansion are actually effective in increasing the gradient between Pms and CVP.

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Key information

Conditions

Hemodynamic Changes

Age range

18 year and older

Sex eligibility

All sexes

Study type

Observational

Primary location

AOU delle Marche

Ancona, 60123, Italy

Location status: Recruiting

Location contact

Abele Pr Donati, PhD

CONTACT

[email protected]

0715963858

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Critically ill patients admitted to the intensive care unit
  • Invasive or minimally invasive hemodynamic monitoring
  • Clinical indication for volume expansion with 500 mL of crystalloids

Exclusion criteria

  • Suspected or confirmed pregnancy
  • Clinical conditions that may reduce the reliability of hemodynamic monitoring:
  • Severe aortic stenosis or regurgitation
  • Severe mitral stenosis or regurgitation
  • History of peripheral arterial disease
  • Clinical contraindications to the supine position

Treatment and study plan

Fluid challenge of 500ml of crystalloid

Drug

The mean systemic filling pressure (Pms) will be measured using the transient stop-flow arm technique, a method routinely used in clinical practice. This involves placing a non-invasive blood pressure cuff on the same arm where invasive arterial pressure is monitored via the radial artery. The cuff is inflated for one minute to temporarily occlude blood flow. At the end of this period, the invasive arterial pressure displayed on the monitor reflects the Pms. This brief interruption of blood flow does not pose significant risks to tissue perfusion.

A fluid challenge with 500 mL of crystalloids will then be performed as per clinical indication. Pms will be measured at baseline, after the infusion of 150 mL, 250 mL, 500 mL, and one hour after the end of fluid administration. Central venous pressure (CVP) and cardiac index (CI) will be continuously monitored throughout the fluid challenge.

Patients will be classified as fluid responders if stroke volume (SV) increases by more than

Primary outcomes

  1. Variation of the Venous Return Gradient (Pms - CVP) in Fluid Responders

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To describe the change in the venous return gradient (mean systemic filling pressure minus central venous pressure, Pms - CVP) during volume expansion with 500 mL of crystalloids in fluid responsive patients.

    The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

Secondary outcomes

  1. Venous Return Gradient Variation in Fluid Responders vs Non-Responders

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To compare the change in Pms - CVP between fluid responders and non-responders during volume expansion with 500 mL of crystalloids. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

  2. Venous Return Gradient Variation in the General Population

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To describe the changes in Pms - CVP in the overall study population during volume expansion with 500 mL of crystalloids in fluid responsive patients. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

  3. Cardiac Index Variation in the General Population

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To assess changes in cardiac index in the overall study population during volume expansion with 500 mL of crystalloids. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

  4. Mean Systemic Filling Pressure (Pms) Variation in the General Population

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To evaluate how Pms changes in the overall population during volume expansion with 500 mL of crystalloids. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

  5. Central Venous Pressure (CVP) Variation in the General Population

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To describe how CVP varies in the overall population during volume expansion with 500 mL of crystalloids. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

  6. Cardiac Index Variation in Fluid Responders vs Non-Responders

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To compare cardiac index changes between fluid responders and non-responders during volume expansion with 500 mL of crystalloids. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

  7. Mean Systemic Filling Pressure (Pms) Variation in Fluid Responders vs Non-Responders

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To compare Pms changes between fluid responders and non-responders during volume expansion with 500 mL of crystalloids. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

  8. Central Venous Pressure (CVP) Variation in Fluid Responders vs Non-Responders

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To evaluate CVP changes in fluid responders compared to non-responders during volume expansion with 500 mL of crystalloids. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

  9. Systemic Vascular Resistance (SVR) Variation in Fluid Responders vs Non-Responders

    Time frame: Measurements are taken at baseline, and at 7 minutes and 30 seconds, 12 minutes and 30 seconds, and 25 minutes from the start of crystalloid infusion (corresponding to 150 mL, 250 mL, and 500 mL infused, respectively).

    To describe and compare changes in systemic vascular resistance between fluid responders and non-responders during volume expansion with 500 mL of crystalloids. The fluid challenge is administered according to the clinician's indication. A total of 500 mL of crystalloids is infused over 25 minutes, corresponding to an infusion rate of 1200 mL/h.

Sponsors and collaborators

Lead sponsor

Università Politecnica delle Marche

Other

Registry information

Acronym: PSM-PVC-RITVEN

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Mar 30, 2026
Registry last updated
Mar 30, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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