Non-invasive assessment of fluid responsiveness by changes in partial end-tidal CO 2 pressure during a passive leg-raising maneuver

Abstract

Background: The 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 CO 2 pressure (PETCO 2) have been demonstrated to be tightly correlated with changes in CO during constant ventilation and stable tissue CO 2 production (VCO 2). In this study we tested the hypothesis that, assuming a constant VCO 2 and under fixed ventilation, PETCO 2 can track changes in CO induced by PLR and can be used to predict fluid responsiveness. Methods: Thirty-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. Results: PLR-induced increases in CO and PETCO 2 were strongly correlated (R 2 = 0.79; P <0.0001). The areas under the receiver-operating characteristics (ROC) curve for a PLR-induced increase in CO and PETCO 2 (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 PETCO 2 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%). Conclusion: Induced changes in PETCO 2 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 CO 2 production. © 2012 Monge Garcia et al.