Dynamic arterial elastance to predict arterial pressure response to volume loading in preload-dependent patients

Abstract

IntroductionHemodynamic resuscitation should be aimed at achieving not only adequate cardiac output but also sufficient mean arterial pressure (MAP) to guarantee adequate tissue perfusion pressure. Since the arterial pressure response to volume expansion (VE) depends on arterial tone, knowing whether a patient is preload-dependent provides only a partial solution to the problem. The objective of this study was to assess the ability of a functional evaluation of arterial tone by dynamic arterial elastance (Eadyn), defined as the pulse pressure variation (PPV) to stroke volume variation (SVV) ratio, to predict the hemodynamic response in MAP to fluid administration in hypotensive, preload-dependent patients with acute circulatory failure.MethodsWe performed a prospective clinical study in an adult medical/surgical intensive care unit in a tertiary care teaching hospital, including 25 patients with controlled mechanical ventilation who were monitored with the Vigileo® monitor, for whom the decision to give fluids was made because of the presence of acute circulatory failure, including arterial hypotension (MAP ≤65 mmHg or systolic arterial pressure <90 mmHg) and preserved preload responsiveness condition, defined as a SVV value ≥10%.ResultsBefore fluid infusion, Eadyn was significantly different between MAP responders (MAP increase ≥15% after VE) and MAP nonresponders. VE-induced increases in MAP were strongly correlated with baseline Eadyn (r2 = 0.83; P < 0.0001). The only predictor of MAP increase was Eadyn (area under the curve, 0.986 ± 0.02; 95% confidence interval (CI), 0.84-1). A baseline Eadyn value >0.89 predicted a MAP increase after fluid administration with a sensitivity of 93.75% (95% CI, 69.8%-99.8%) and a specificity of 100% (95% CI, 66.4%-100%).ConclusionsFunctional assessment of arterial tone by Eadyn, measured as the PVV to SVV ratio, predicted arterial pressure response after volume loading in hypotensive, preload-dependent patients under controlled mechanical ventilation.

Functional haemodynamic monitoring

“…If the arterial circuit becomes stiffer, then for the same stroke volume change, arterial pulse pressure will change more and vice versa. Using this approach, Monge et al [29] assessed the effect of volume loading on arterial pressure in hypotensive septic shock patients whose PPV predicted that they were volume responsive. All patients increased their cardiac output, as expected, in response to the fluid challenge, but only those patients with normal or increased Ea also increased their arterial pressure.…”

Evaluation of contractility and postloading in the intensive care unit

“…This algorithm has not yet been validated in the clinical setting. Lastly, Monge Garcia et al 14 have recently published a study in which Eadyn was found to predict the response to volume expansion in preload-dependent patients with acute circulatory failure. An Eadyn value of 0.89 differentiates those patients who will increase their mean blood pressure by 15% after the administration of volume, with a sensitivity of 94% and a specificity of 100%.…”

“…The presence of a decreased or increased vasomotor tone would cause the Eadyn value to be smaller or greater than 1, respectively. 3,13,14 The relationship between Ees and Ea, which represents ventricle-arterial ''coupling'', has been used even in animal experimentation and in some clinical protocols for evaluating the mechanical-energy properties of the left ventricle. 15…”

Applied Physiology at the Bedside to Drive Resuscitation Algorithms

“…A decrease in central arterial compliance causes a decrease in PPV/SVV ratio. Furthermore, Monge et al 53 showed that critically ill patients who were both volume responsive (defined as a PPV > 15% or SVV > 10%) and hypotensive had a PPV/SVV ratio of at least 0.9. When these patients were given a fluid challenge they remained hypotensive despite an increase in cardiac output.…”