Assessment of fluid responsiveness with end-tidal carbon dioxide using a simplified passive leg raising maneuver: a prospective observational study.
BACKGROUND
Assessing fluid responsiveness is important in the management of patients with hemodynamic instability. Passive leg raising (PLR) is a validated dynamic method to induce a transient increase in cardiac preload and predict fluid responsiveness. Variations in end-tidal carbon dioxide (ETCO2) obtained by capnography correlate closely with variations in cardiac output when alveolar ventilation and carbon dioxide production are kept constant. In this prospective observational study, we tested the hypothesis that variations in ETCO2 induced by a simplified PLR maneuver can track changes in the cardiac index (CI) and thus predict fluid responsiveness.


METHODS
A five-minute standardized PLR maneuver was performed in 90 paralyzed hemodynamically stable cardiac surgical patients receiving mechanical ventilation. Cardiac index was measured by thermodilution before and one minute after PLR. End-tidal CO2 measurements using capnography were obtained during the entire PLR maneuver. Fluid responsiveness was defined as a 15% increase in the CI. The Chi square test and Student's t test were used to compare responders and non-responders. Logistic regression analyses were then performed to determine factors of responsiveness.


RESULTS
There were no differences between responders and non-responders in demographic and baseline hemodynamic variables. Fluid responsiveness was associated with an ETCO2 variation (ΔETCO2) of ≥ 2 mmHg during PLR [odds ratio (OR), 7.3; 95% confidence interval (CI), 2.7 to 20.2; P < 0.01; sensitivity 75%]. A low positive predictive value (54%) and a high negative predictive value (NPV) (86%) were observed. No other clinical or hemodynamic predictors were associated with fluid responsiveness. A logistic regression model established that a combination of ΔETCO2 ≥ 2 mmHg and a change in systolic blood pressure ≥ 10 mmHg induced by passive leg raising was predictive of fluid responsiveness (OR, 8.9; 95% CI, 2.5 to 32.2; P = 0.005).


CONCLUSIONS
Use of a passive leg raising maneuver to induce variation in ETCO2 is a noninvasive and useful method to assess fluid responsiveness in paralyzed cardiac surgery patients receiving mechanical ventilation. Given its high NPV, fluid responsiveness is unlikely if a passive leg raising maneuver induces ΔETCO2 of < 2 mmHg.
Department of Anesthesiology, Montreal Heart Institute, Université de Montréal, 5000 Belanger Street, Montreal, QC, H1T 1C8, Canada.
Francis
F
Toupin
Department of Anesthesiology, Montreal Heart Institute, Université de Montréal, 5000 Belanger Street, Montreal, QC, H1T 1C8, Canada.
Ariane
A
Clairoux
Department of Anesthesiology, Montreal Heart Institute, Université de Montréal, 5000 Belanger Street, Montreal, QC, H1T 1C8, Canada.
Alain
A
Deschamps
Department of Anesthesiology, Montreal Heart Institute, Université de Montréal, 5000 Belanger Street, Montreal, QC, H1T 1C8, Canada.
Jean-Sébastien
JS
Lebon
The Department of Cardiac Surgery, Montreal Heart Institute, Université de Montréal, Montreal, QC, Canada.
Yoan
Y
Lamarche
The Department of Social & Preventive Medicine, School of Public Health, Université de Montréal, Montreal, QC, Canada.
Jean
J
Lambert
Montreal Health Innovations Coordinating Center (MHICC), Montreal, QC, Canada.
Annik
A
Fortier
Department of Anesthesiology, Montreal Heart Institute, Université de Montréal, 5000 Belanger Street, Montreal, QC, H1T 1C8, Canada. andre.denault@gmail.com.|Department of Anesthesiology and Critical Care Division, Montreal Heart Institute, Montreal, QC, Canada. andre.denault@gmail.com.
André Y
AY
Denault
D000368:Aged; D015992:Body Mass Index; D019296:Capnography; D002245:Carbon Dioxide / Q000378:metabolism*; D002302:Cardiac Output; D005260:Female; D005440:Fluid Therapy / Q000379:methods*; D006439:Hemodynamics; D006801:Humans; D007866:Leg; D008297:Male; D011446:Prospective Studies; D012121:Respiration, Artificial; D013815:Thermodilution
D002245:Carbon Dioxide