Dynamic arterial elastance obtained using arterial signal does not predict an increase in arterial pressure after a volume expansion in the operating room
Résumé
INTRODUCTION: Dynamic arterial elastance (Eadyn) is defined as the ratio between pulse pressure variations (PPV) and stroke volume variations (SVV). Eadyn has been proposed to predict an increase in mean arterial pressure (MAP) after volume expansion with conflicting results. The aim of the present study was to test the reliability of Eadyn in hypotensive patients (MAP\textless65mmHg) in the operating room (OR). PATIENTS AND METHODS: The study pooled data from 51 patients. They were included after the induction of anaesthesia and before skin incision. Eadyn, MAP and stroke volume (FloTrac\texttrademark, Vigileo\texttrademark, Edwards Lifesciences, Irvine,CA) were recorded before and after volume expansion (500mL starch 6% given over 10minutes). Pressure-responders were defined as an increase MAP>=15% after volume expansion. Changes in MAP were predicted using the area under the curves (AUC) with their 95% Confidence Interval (95%CI) derived from Receiver Operating Characteristic curves. RESULTS: Seventeen patients responded to volume expansion. Heart rate, PPV, SVV and Eadyn were similar between pressure-responders and non-responders. Baseline values of stroke volume, cardiac output and MAP were lower in responders. Volume expansion induced significant variations in stroke volume, cardiac output, SVV and PPV, but not in Eadyn. Baseline Eadyn failed to predict MAP increase (AUC=0.53, 95%CI=0.36-0.70, P\textgreater0.05) and was not correlated with volume expansion-induced changes in MAP (P\textgreater0.05). In preload responsive patients (changes in SV>=15% after volume expansion, n=24), the AUC was 0.54 (95%CI=0.29-0.78; P\textgreater0.05). CONCLUSION: In the present study performed in the OR and in hypotensive patients, Eadyn obtained using arterial signal was unable to predict an increase in MAP after volume expansion.