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

Overview

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.

Interventions

• Drug Fluid challenge of 500ml of crystalloid
  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

Primary outcome measures

• 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).]

Secondary outcome measures (9)

• 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).]
• 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).]
• 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).]
• 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).]
• 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).]
• 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).]
• 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).]
• 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).]
• 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).]

Eligibility criteria

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

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Observational model

Cohort

Study locations

Italy · 1 center

• AOU delle Marche — Ancona

Identifiers

NCT: NCT07499388 · PSM-PVC-VENRET

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗