End-tidal carbon dioxide changes induced by passive leg raising can predict fluid responsiveness in patients on...

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is increasingly used in patients with cardiogenic shock. It results in cardiopulmonary shunting with reduced native cardiac output. Volume expansion is usually administered to increase native cardiac output, in order to improve peripheric perfusion or to avoid thromboembolic complications in cardiac cavities. End-tidal carbon dioxide (EtCO₂) is known to be related to native cardiac output. Our hypothesis was that EtCO₂ changes induced by passive leg raising predict fluid responsiveness in patients under VA-ECMO.

In this prospective, interventional study, patients under VA-ECMO support were included, provided they required volume expansion. The protocol included three sequential steps: (1) Baseline in supine position (2) Passive leg raising (3) Volume expansion in basal position. Hemodynamic parameters were recorded at each step. Fluid responsiveness was defined as a velocity time integral at the left ventricle outflow tract increase of 15% or more after volume expansion. The ability of passive leg raising induced changes in EtCO₂ to predict fluid responsiveness was evaluated with area under the receiver operating characteristics curve (AUC).

41 patients were studied; 58 passive leg raising - volume expansion tests were recorded. Fluid responsiveness was observed in 38 of the 58 measurements (65%). Passive leg raising test has correctly mimicked volume expansion (intraclass correlation coefficient 0.83 [0.73-0.9]). Considering all measurements, AUC of passive leg raising-changes in velocity time integral to predict fluid responsiveness was 0.89 [0.79-0.99] and remained good whatever the basal native cardiac output. Sensitivity and specificity were 92% [85-100] and 80% [69-90] respectively for a threshold of 15%. AUC of passive leg raising-induced changes in EtCO₂ for predicting fluid responsiveness was good (0.98 [0.95-1]) only when basal native cardiac output was ≤ 1 L/min.

Passive leg raising test can predict fluid responsiveness under VA-ECMO. EtCO₂ changes induced by passive leg raising test can be used to detect fluid responsiveness in patients with native cardiac output ≤ 1 L/min under VA-ECMO. This test is easy to perform, reliable and may help to avoid unnecessary and potentially harmful fluid loading.