Minimally invasive intraoperative estimation of left-ventricular end-systolic elastance with phenylephrine as loading intervention.

BACKGROUND Left-ventricular end-systolic elastance (Ees) is an index of cardiac contractility, but the invasive nature of its assessment has limited perioperative application. We explored the feasibility of a minimally invasive method of Ees estimation for perioperative assessment of cardiac function and evaluated the suitability of phenylephrine as a loading intervention. METHODS In 17 surgical patients, Ees was determined as the slope of the end-systolic pressure-volume relation, which was obtained from non-invasive or invasive continuous arterial pressure measurements and left-ventricular volume determinations using transoesophageal echocardiography (TOE). Ees was determined using as loading interventions preload reduction by inferior vena cava compression (IVCC) and afterload increase by phenylephrine administration. RESULTS Median invasive Ees determined with phenylephrine estimated 1.05 (0.59-1.21) mm Hg ml(-1) and with IVCC 0.58 (0.31-1.13) mm Hg ml(-1). Bland-Altman analysis to evaluate the level of agreement between minimally invasive and invasive Ees estimation revealed a bias of -0.03 (0.12) mm Hg ml(-1) with limits of agreement from -0.27 to 0.21 mm Hg ml(-1) and the percentage error was 33%. Agreement between Ees obtained with phenylephrine and IVCC revealed a bias of 0.15 (0.69) mm Hg ml(-1) with limits of agreement from -1.21 to 1.51 mm Hg ml(-1) and a percentage error of 149%. CONCLUSIONS It is feasible to determine Ees combining continuous non-invasive arterial pressure measurements and left-ventricular volume determinations with TOE. However, administration of phenylephrine cannot substitute IVCC as a loading intervention, indicating that estimation of Ees in the intraoperative setting remains a challenge.