Fluid boluses are often administered to patients in shock as a first-line intervention to increase cardiac output. Previous literature states, however, that only 50% of patients in shock will respond to a fluid bolus.
Several validated techniques exist to distinguish which patients will respond to a fluid bolus and which will not; one method is the passive leg raise (PLR) maneuver (more on PLR here). A drawback to PLR is that it requires direct measurement of cardiac output, either by invasive hemodynamic monitoring or using advanced bedside ultrasound techniques.
Another technique to quantify changes in cardiac output is through measurement of end-tidal CO2 (ETCO2). The benefits of measuring ETCO2 is that it can be continuously measured and can be performed non-invasively on mechanically ventilated patients.
A 5% or greater increase in end-tidal CO2 (ETCO2) following a PLR maneuver has been found to be a good predictor of fluid responsiveness with reliability similar to invasive measures.
