Changes in CO₂-Derived Variables, Induced by Passive Leg Raising Test, Detect Preload Responsiveness in Mechanically...

Area of Science:

• Critical Care Medicine
• Cardiovascular Physiology
• Hemodynamic Monitoring

Background:

• Fluid responsiveness assessment is crucial in critically ill patients.
• CO2-derived variables are potential markers for fluid responsiveness.
• Passive leg raising (PLR) is a non-invasive method to assess preload responsiveness.

Purpose of the Study:

• To investigate if PLR-induced changes in CO2-derived variables can detect preload responsiveness.
• To evaluate central venous-arterial carbon dioxide partial pressure (P(cv-a)CO2) and the P(cv-a)CO2/C(a-cv)O2 ratio as markers.

Main Methods:

• 30 mechanically ventilated patients with acute circulatory failure underwent PLR testing.
• Hemodynamic variables, left ventricular outflow tract velocity-time integral (VTI), and CO2-derived variables were measured.
• Preload responsiveness was defined as a ≥10% increase in VTI during PLR.

Main Results:

• 50% of patients were preload responsive.
• Changes in P(cv-a)CO2 and P(cv-a)CO2/C(a-cv)O2 correlated with VTI changes and differed significantly between responders and non-responders.
• A PLR-induced decrease in P(cv-a)CO2 was significantly associated with preload responsiveness (AUC 0.89).

Conclusions:

• PLR-induced changes in P(cv-a)CO2 and P(cv-a)CO2/C(a-cv)O2 correlate with VTI changes in mechanically ventilated ICU patients.
• The change in P(cv-a)CO2 effectively detects preload responsiveness assessed by PLR.
• P(cv-a)CO2 can serve as an indirect marker for guiding fluid resuscitation when cardiac output measurement is not feasible.