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.
Highlights
The passive leg-raising (PLR) maneuver provides a dynamic assessment of fluid responsiveness inducing a reversible increase in cardiac preload
All the patients had sinus rhythm, transient supraventricular extrasystoles were observed during the study in some patients (13%)
Effects of passive leg-raising maneuver Overall, the PLR maneuver increased cardiac output (CO) by 15.9 ± 9.1%, stroke volume (SV) by 15.5 ± 10.2%, Corrected flow time (FTc) by 8.4 ± 6%, mean arterial pressure (MAP) by 5.4% (IQR: 1.3 to 10.2%; 95% Confidence interval (CI): 1.8 to 7.6%; P < 0.0001), arterial pulse pressure (PP) by 10.1% (IQR: 2.3 to 21.8; P < 0.0001), and Partial end-tidal CO2 pressure (PETCO2) by 5.32 ± 3.09%
Summary
The passive leg-raising (PLR) maneuver provides a dynamic assessment of fluid responsiveness inducing a reversible increase in cardiac preload. The abrupt transfer of blood contained in the venous reservoir of the legs and splanchnic compartment while moving the patient from a semirecumbent to supine position with legs elevated increases cardiac preload as a ‘self-. This regard, several monitoring techniques have been proposed for this purpose: echocardiography [2,3,7], arterial pulse contour analysis [8,9], bioreactance [10], esophageal Doppler [1,11,12], and so on. PETCO2 has been suggested as a noninvasive alternative for continuous assessment of CO in different shock states [20]
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