Dynamic arterial elastance as a predictor of arterial pressure response to fluid administration: a validation study

Abstract

Introduction: Functional assessment of arterial load by dynamic arterial elastance (Eadyn), defined as the ratio between pulse pressure variation (PPV) and stroke volume variation (SVV), has recently been shown to predict the arterial pressure response to volume expansion (VE) in hypotensive, preload-dependent patients. However, because both SVV and PPV were obtained from pulse pressure analysis, a mathematical coupling factor could not be excluded. We therefore designed this study to confirm whether Eadyn, obtained from two independent signals, allows the prediction of arterial pressure response to VE in fluid-responsive patients.

Methods: We analyzed the response of arterial pressure to an intravenous infusion of 500 ml of normal saline in 53 mechanically ventilated patients with acute circulatory failure and preserved preload dependence. Eadyn was calculated as the simultaneous ratio between PPV (obtained from an arterial line) and SVV (obtained by esophageal Doppler imaging). A total of 80 fluid challenges were performed (median, 1.5 per patient; interquartile range, 1 to 2). Patients were classified according to the increase in mean arterial pressure (MAP) after fluid administration in pressure responders (≥ 10%) and non-responders.

Results: Thirty-three fluid challenges (41.2%) significantly increased MAP. At baseline, Eadyn was higher in pressure responders (1.04 ± 0.28 versus 0.60 ± 0.14; P < 0.0001). Preinfusion Eadyn was related to changes in MAP after fluid administration (R (2) = 0.60; P < 0.0001). At baseline, Eadyn predicted the arterial pressure increase to volume expansion (area under the receiver operating characteristic curve, 0.94; 95% confidence interval (CI): 0.86 to 0.98; P < 0.0001). A preinfusion Eadyn value ≥ 0.73 (gray zone: 0.72 to 0.88) discriminated pressure responder patients with a sensitivity of 90.9% (95% CI: 75.6 to 98.1%) and a specificity of 91.5% (95% CI: 79.6 to 97.6%).

Conclusions: Functional assessment of arterial load by Eadyn, obtained from two independent signals, enabled the prediction of arterial pressure response to fluid administration in mechanically ventilated, preload-dependent patients with acute circulatory failure.

Figures

Figure 1

An illustrative example of the arterial pressure and aortic blood flow recordings is shown. Both signals are integrated into the esophageal Doppler system for analysis: the arterial pressure waveform from the patient’s bedside monitor and the aortic blood flow from the Doppler probe. Dynamic arterial elastance was calculated as the ratio between pulse pressure variation and stroke volume variation. All variables are automatically calculated by the Doppler monitor, which combines the arterial pressure analysis with the usual aortic blood flow measurements.

Figure 2

Individual changes in cardiac output and mean arterial pressure after fluid administration.

Figure 3

Distribution of individual values (open circles) and mean ± SD (lines) of arterial load variables before fluid administration in pressure responders. The dashed line represents the optimal cutoff for dynamic arterial elastance corresponding to maximum Youden index, and dotted lines depict the “gray zone” calculated from bootstrapped 95% confidence interval (0.72 to 0.88). MAP-R, Mean arterial pressure responders defined by increase ≥10%; MAP-NR, Mean arterial pressure non-responders defined by increase <10%. *P <0.0001 for MAP-R vs. MAP-NR.

Figure 4

Linear regression analysis of the relationship between preinfusion dynamic arterial elastance (Eadyn) and changes in arterial pressure induced by fluid administration. DAP: diastolic arterial pressure; MAP: mean arterial pressure; SAP: systolic arterial pressure; PP: arterial pulse pressure.

Figure 5

Comparison of receiver operating characteristic curves for testing the ability of static and dynamic arterial load variables to detect a mean arterial pressure increase ≥10% after volume administration. Dynamic arterial elastance (Eadyn) = area under the receiver operating characteristic curve (AUC): 0.94 (95% CI: 0.86 to 0.98); effective arterial elastance (Ea) = AUC: 0.53 (95% CI: 0.42 to 0.65); systemic vascular resistance (SVR) = AUC: 0.55 (95% CI: 0.44 to 0.66); net arterial compliance (C) = AUC: 0.51 (95% CI: 0.39 to 0.62); preinfusion MAP = AUC: 0.62 (95% CI: 0.50 to 0.72).