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 Type
OBSERVATIONAL
Enrollment
45
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
AOU delle Marche
Ancona, Italy
RECRUITINGVariation of the Venous Return Gradient (Pms - CVP) in Fluid Responders
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.
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 Fluid Responders vs Non-Responders
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.
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
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.
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
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.
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
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.
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
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.
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
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.
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
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.
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
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.
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
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.
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).
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