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

Abstract

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.

Keywords: echocardiography, transoesophageal; monitoring, intraoperative; myocardial contraction; phenylephrine.