Predictive value of trendelenburg position and carotid ultrasound for fluid responsiveness in patients on VV-ECMO with acute respiratory distress syndrome in the prone position

Fluid administration is widely used to treat hypotension in patients undergoing veno-venous extracorporeal membrane oxygenation (VV-ECMO). However, excessive fluid administration may lead to fluid overload can aggravate acute respiratory distress syndrome (ARDS) and increase patient mortality, predicting fluid responsiveness is of great significance for VV-ECMO patients. This prospective single-center study was conducted in a medical intensive care unit (ICU) and finally included 51 VV-ECMO patients with ARDS in the prone position (PP). Stroke volume index variation (ΔSVI), pulse pressure variation (PPV), stroke volume variation (SVV), baseline carotid corrected flow time (FTc_Baseline), and respirophasic variation in carotid artery blood flow peak velocity (ΔVpeak_CA) were taken before and after the Trendelenburg position or volume expansion. Fluid responsiveness was defined as a 15% or more increase in stroke volume index as assessed by transthoracic echocardiography after the volume expansion (VE). In our study, 33 patients (64.7%) were identified as fluid responders. Stroke volume index variation induced by the Trendelenburg position (ΔSVI_Trend), FTc_Baseline, and ΔVpeak_CA demonstrated superior predictive performance of fluid responsiveness. ΔSVI_Trend had an AUC of 0.89 (95% CI, 0.80-0.98) with an optimal threshold of 14.5% (95% CI, 12.5-21.5%), with the sensitivity and specificity were 82% (95% CI, 66-91%) and 83% (95% CI, 61-94%). FTc_Baseline had an AUC of 0.87 (95% CI, 0.76-0.98) with an optimal threshold of 332ms (95% CI, 318-335ms), the sensitivity and specificity were 85% (95% CI, 69-93%) and 83% (95% CI, 61-94%), respectively. ΔVpeak_CA showed an AUC of 0.83 (95% CI, 72-95), with a 10% optimal threshold (95% CI, 9-13%), sensitivity was 82% (95% CI, 66-91%) and specificity 78% (95% CI, 55-91%). ΔSVI_Trend, FTc_Baseline and ΔVpeak_CA could effectively predict fluid responsiveness in VV-ECMO patients with ARDS in the PP. Compared to ΔSVI_Trend and ΔVpeak_CA, FTc_Baseline is easier and more direct to acquire, and it does not require Trendelenburg position or VE, making it a more accessible and efficient option for assessing fluid responsiveness.