Non-invasive assessment of fluid responsiveness by changes in partial end-tidal CO2 pressure during a passive leg-raising maneuver

Abstract

BackgroundThe passive leg-raising (PLR) maneuver provides a dynamic assessment of fluid responsiveness inducing a reversible increase in cardiac preload. Since its effects are sudden and transitory, a continuous cardiac output (CO) monitoring is required to appropriately assess the hemodynamic response of PLR. On the other hand, changes in partial end-tidal CO2 pressure (PETCO2) have been demonstrated to be tightly correlated with changes in CO during constant ventilation and stable tissue CO2 production (VCO2). In this study we tested the hypothesis that, assuming a constant VCO2 and under fixed ventilation, PETCO2 can track changes in CO induced by PLR and can be used to predict fluid responsiveness.MethodsThirty-seven mechanically ventilated patients with acute circulatory failure were monitored with the CardioQ-ODM esophageal Doppler. A 2-minutes PLR maneuver was performed. Fluid responsiveness was defined according to CO increase (responders ≥ 15%) after volume expansion.ResultsPLR-induced increases in CO and PETCO2 were strongly correlated (R2 = 0.79; P < 0.0001). The areas under the receiver-operating characteristics (ROC) curve for a PLR-induced increase in CO and PETCO2 (0.97 ± 0.03 SE; CI 95%: 0.85 to 0.99 and 0.94 ± 0.04 SE; CI 95%: 0.82 to 0.99; respectively) were not significantly different. An increase ≥ 5% in PETCO2 or ≥ 12% in CO during PLR predicted fluid responsiveness with a sensitivity of 90.5% (95% CI: 69.9 to 98.8%) and 95.2% (95% CI: 76.2 to 99.9%), respectively, and a specificity of 93.7% (95% CI: 69.8 to 99.8%).ConclusionInduced changes in PETCO2 during a PLR maneuver could be used to track changes in CO for prediction of fluid responsiveness in mechanically ventilated patients with acute circulatory failure, under fixed minute ventilation and assuming a constant tissue CO2 production.

Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine

“…Accordingly, changes in cardiac output by at least 10–15 % (to ascertain that these changes are not due to measurement variability) are used to define a positive response to fluids [ 77 ]. When cardiac output is not measured, surrogate measurements can be used, such as changes in end-tidal CO 2 in mechanically ventilated patients [ 78 , 79 ]. Alternatively, resolution of the signs of preload dependency indicates a positive response to fluids.…”

Prediction of fluid responsiveness: an update

“…An original and totally non-invasive method is to measure the PLR-induced increase in end-tidal carbon dioxide (CO 2 ) [69–71]. This technique requires that the patient has perfectly stable mechanical ventilation, in order to be sure that the changes in end-tidal CO 2 are only related to changes in cardiac output.…”

Assessment of volume responsiveness during mechanical ventilation: recent advances

“…This aspect is particularly true in septic patients in whom capillary leak may account for an attenuation of the PLR effects after one minute, as already described [22]. This is why clinical studies that have tested the value of PLR to predict volume responsiveness used real-time hemodynamic measurements, such as aortic blood flow measured by esophageal Doppler [22,41], pulse contour analysis-derived cardiac output [16,26,42], cardiac output measured by bioreactance [43,44] or endotracheal bioimpedance cardiography [45], subaortic blood velocity measured by echocardiography [46-48], ascending aortic velocity measured by suprasternal Doppler [49] and, more recently, end-tidal carbon dioxide [50,51]. …”