Increase in Central Venous Pressure During Passive Leg Raising Cannot Detect Preload Unresponsiveness

Area of Science:

• Critical Care Medicine
• Hemodynamics
• Echocardiography

Background:

• Assessing fluid responsiveness is crucial in critically ill patients.
• Passive leg raising (PLR) is a non-invasive method to predict fluid responsiveness.
• Central venous pressure (CVP) changes during PLR have been proposed as a predictor, analogous to fluid challenge rules.

Purpose of the Study:

• To investigate if an increase in CVP during PLR can predict preload unresponsiveness.
• To determine if a specific CVP increase threshold (≥ 4 mmHg) during PLR can identify patients who will not respond to fluids.

Main Methods:

• Prospective study including critically ill patients undergoing PLR for fluid responsiveness assessment.
• Central venous pressure (CVP) and left ventricular outflow tract velocity-time integral (VTI) were measured before and during PLR.
• VTI was measured using transthoracic echocardiography.

Main Results:

• No significant difference in CVP changes during PLR was observed between fluid responders and non-responders (3 ± 2 mmHg vs 3 ± 2 mmHg).
• An increase in CVP ≥ 4 mmHg during PLR did not reliably predict preload unresponsiveness (AUC = 0.59).
• Varying the CVP increase threshold (≥ 3 mmHg or ≥ 5 mmHg) did not improve prediction accuracy.

Conclusions:

• A marked increase in CVP during PLR is insufficient to identify preload unresponsiveness.
• Direct measurement of cardiac output or its surrogates during PLR is mandatory for accurate interpretation.
• Relying solely on CVP changes during PLR can lead to misinterpretation of fluid responsiveness.