Assessment of Venous Return During Volume Expansion: a Prospective Observational Study (PSM-PVC-RITVEN)

March 23, 2026 updated by: Abele Donati, MD, Università Politecnica delle Marche

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.

Study Overview

Status

Recruiting

Conditions

Intervention / Treatment

Study Type

Observational

Enrollment (Estimated)

45

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Italy
      • Ancona, Italy, 60123
        • Recruiting
        • Aou Delle Marche
        • Contact:

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Critically ill patients

Description

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

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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.
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).

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
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.
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).
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.
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).
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.
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).
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.
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).
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.
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).
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.
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).
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.
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).
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.
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).
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.
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).

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Università Politecnica delle Marche

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

March 1, 2025

Primary Completion (Estimated)

July 1, 2026

Study Completion (Estimated)

July 1, 2026

Study Registration Dates

First Submitted

April 18, 2025

First Submitted That Met QC Criteria

March 23, 2026

First Posted (Actual)

March 30, 2026

Study Record Updates

Last Update Posted (Actual)

March 30, 2026

Last Update Submitted That Met QC Criteria

March 23, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Additional Relevant MeSH Terms

Other Study ID Numbers

  • PSM-PVC-VENRET

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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