Background: Blood pressure is controlled by stroke volume and afterload. Arterial load is an effective measure of afterload because it represents all extracardiac factors that oppose left ventricular ejection. Dynamic arterial elastance (Ea_dyn; pulse pressure variation over stroke volume variation) is a dynamic parameter of arterial load that can be continuously monitored. Ea_dyn was reported to predict mean arterial pressure (MAP) responsiveness after a fluid challenge.

Objective: To assess whether Ea_dyn can predict MAP responsiveness in acute respiratory distress syndrome (ARDS) patients ventilated with low tidal volume.

Materials and Methods: The authors performed a prospective study of diagnostic test accuracy in adult ARDS patients with acute circulatory failure and fluid responsiveness. All patients received continuous blood pressure monitoring via an arterial line connected to a Flotrac™ transducer and Vigileo™ monitor. When the attending physicians decided to load intravenous fluid, the authors recorded the pulse pressure variation over stroke volume variation and other hemodynamic parameters before and after fluid bolus. MAP responsiveness was defined as increased MAP of 10% or more from baseline after fluid challenge.

Results: Twenty-three events were included. Nine events (39.13%) were MAP-responsive. Cardiac output, heart rate, and stroke volume were similar in both MAP-responder and MAP-non-responder groups. Baseline MAP, diastolic blood pressure, and pulse pressure were significantly different after fluid challenge in the MAP-responder group. Ea_dyn of the pre-infusion phase failed to predict MAP responsiveness after fluid challenge (area under the curve 0.603, 95% confidence interval 0.38 to 0.798).

Conclusion: Arterial load parameters, including Ea_dyn, derived from non-calibrated pulse contour analysis failed to predict MAP responsiveness in ARDS patients with low tidal volume ventilation.

Keywords: Acute respiratory distress syndrome, Dynamic arterial elastance, Mean arterial pressure, Pulse contour analysis

DOI: doi.org/10.35755/jmedassocthai.2020.07.10601

Received 30 Sep 2019 | Revised 17 Apr 2020 | Accepted 22 Apr 2020