Passive leg raising can predict fluid responsiveness in patients placed on venovenous extracorporeal membrane oxygenation

Introduction: In ICUs, fluid administration is frequently used to treat hypovolaemia. Because volume expansion (VE) can worsen acute respiratory distress syndrome (ARDS) and volume overload must be avoided, predictive indicators of fluid responsiveness are needed. The purpose of this study was to determine whether passive leg raising (PLR) can be used to predict fluid responsiveness in patients with ARDS treated with venovenous extracorporeal membrane oxygenation (ECMO). Methods: We carried out a prospective study in a university hospital surgical ICU. All patients with ARDS treated with venovenous ECMO and exhibiting clinical and laboratory signs of hypovolaemia were enrolled. We measured PLR-induced changes in stroke volume (Delta PLRSV) and cardiac output (Delta PLRCO) using transthoracic echocardiography. We also assessed PLR-induced changes in ECMO pump flow (Delta PLRPO) and PLR-induced changes in ECMO pulse pressure (Delta PLRPP) as predictors of fluid responsiveness. Responders were defined by an increase in stroke volume (SV) > 15% after VE. Results: Twenty-five measurements were obtained from seventeen patients. In 52% of the measurements (n = 13), SV increased by > 15% after VE (responders). The patients' clinical characteristics appeared to be similar between responders and nonresponders. In the responder group, PLR significantly increased SV, cardiac output and pump flow (P < 0.001). Delta PLRSV values were correlated with VE-induced SV variations (r(2) = 0.72, P = 0.0001). A 10% increased Delta PLRSV predicted fluid responsiveness with an area under the receiver operating characteristic curve (AUC) of 0.88 +/- 0.07 (95% confidence interval (CI95): 0.69 to 0.97; P < 0.0001), 62% sensitivity and 92% specificity. On the basis of AUCs of 0.62 +/- 0.11 (CI95: 0.4 to 0.8; P = 0.31) and 0.53 +/- 0.12 (CI95: 0.32 to 0.73, P = 0.79), respectively, Delta PLRPP and Delta PLRPO did not predict fluid responsiveness. Conclusions: In patients treated with venovenous ECMO, a > 10% Delta PLRSV may predict fluid responsiveness. Delta PLRPP and Delta PLRPO cannot predict fluid responsiveness.