The Use of Pulse Pressure Variation and Stroke Volume Variation in Spontaneously Breathing Patients to Assess Dynamic Arterial Elastance and to Predict Arterial Pressure Response to Fluid Administration

BACKGROUND: Dynamic arterial elastance (Ea(dyn)), defined as the pulse pressure variation (PPV) to stroke volume variation (SVV) ratio, has been suggested as a predictor of the arterial pressure response to fluid administration. In this study, we assessed the effectiveness of Ea(dyn) to predict the arterial blood pressure response to a fluid challenge (FC) in preload-dependent, spontaneously breathing patients. METHODS: Patients admitted postoperatively and monitored with the Nexfin monitor (BMEYE, Amsterdam, The Netherlands) were enrolled in the study. Patients were included in the analysis if they were spontaneously breathing and had an increase in cardiac output >= 10% during an FC. Patients were classified according to the increase in mean arterial blood pressure (MAP) after FC into MAP-responders (MAP increase >= 10%) and MAP-nonresponders (MAP increase < 10%). Ea(dyn) was continuously calculated from the PPV and SVV values obtained from the monitor. RESULTS: Thirty-four FCs from 26 patients were studied. Seventeen FCs (50%) induced a positive MAP response. Preinfusion Ea(dyn) was significantly higher in MAP-responders (1.39 +/- 0.41 vs 0.85 +/- 0.23; P = 0.0001). Preinfusion Ea(dyn) predicted a positive MAP response to FC with an area under the receiver-operating characteristic curve of 0.92 +/- 0.04 of standard error (95% confidence interval, 0.78-0.99; P < 0.0001). A preinfusion Ea(dyn) value >= 1.06 (gray zone: 0.9-1.15) discriminated MAP-responders with a sensitivity and specificity of 88.2% (approximate 95% confidence interval, 64%-99%), respectively. CONCLUSIONS: Noninvasive Ea(dyn), defined as the PPV to SVV ratio, predicted the arterial blood pressure increase to fluid administration in spontaneously breathing, preload-dependent patients.