RecruitingNCT07499388

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

Sponsor

Università Politecnica delle Marche

Enrollment

45 participants

Start Date

Mar 1, 2025

Study Type

OBSERVATIONAL

Conditions

Hemodynamic Changes

Summary

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.

Eligibility

Min Age: 18 Years

Inclusion Criteria3

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 Criteria6

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

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Interventions

DRUGFluid 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 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