Effective arterial elastance as a predictor of fluid responsiveness in patients with septic shock：a prospective observational study

Abstract Background Assessment of fluid responsiveness is essential in the resuscitation of patients with septic shock. Effective arterial elastance (Ea) is a lumped index of arterial load; however, its ability to predict fluid responsiveness in these patients remains unknown. Methods This prospective observational study was conducted in the intensive care unit of Zhejiang Cancer Hospital. All enrolled patients underwent a 500mL fluid challenge (FC), and hemodynamic parameters, including cardiac output (CO) and mean arterial pressure (MAP), were recorded using the PiCCO system. Fluid responsiveness was defined as an increase in CO of > 10% after the fluid challenge, and arterial pressure responsiveness as an increase in MAP of > 10%. Receiver operating characteristic (ROC) curve was performed to evaluate the predictive ability of Ea. Correlations between Ea and FC-induced changes in CO and MAP were assessed. Results Forty-one patients were analysed, of whom 20 (49%) were fluid responders. Baseline Ea was significantly higher in fluid responders than in fluid nonresponders [2.43 (2.07–4.04) vs 1.82 (1.61–2.47) mmHg/mL, p = 0.022]. Baseline Ea predicted fluid responsiveness with an area under the curve (AUC) of 0.710 (95% CI: 0.549–0.870, p = 0.022) and an optimal cut-off value of 2.00 mmHg/mL (sensitivity: 80%; specificity: 62%), but lacked predictive ability for arterial pressure responsiveness (AUC = 0.583, 95% CI: 0.361–0.781, p = 0.427). FC-induced percentage change in CO (ΔCO%) was moderately correlated with baseline Ea (ρ = 0.45, p = 0.004), whereas the percentage change in MAP (ΔMAP%) was not (ρ = −0.28, p = 0.080). Among the fluid responders, 15 (75%) were arterial pressure nonresponders. In this subgroup, Ea decreased significantly after the fluid challenge [1.91 (1.67–2.45) vs 2.43 (2.07–4.29) mmHg/mL, p = 0.001], and the percentage change in Ea (ΔEa%) was strongly correlated with both ΔCO% (ρ = −0.65, p = 0.002) and ΔMAP% (r = 0.67, p = 0.001). Conclusion In patients with septic shock, baseline Ea > 2.00 mmHg/mL predicts fluid responsiveness but not arterial pressure responsiveness. A significant decrease in Ea after a fluid challenge may explain the dissociation between fluid responsiveness and arterial pressure responsiveness.