The Effect of Depth of Anaesthesia on the Severity of Mitral Insufficiency by Transesophageal Echocardiography

Abstract

Background The assessment of mitral regurgitation (MR) is complex and complicated by the dynamic nature of this valvular abnormality. Intraoperative transesophageal echocardiography (TEE) is a well-established tool that is used to assess the mitral regurgitation (MR) before and after mitral valve reconstruction. Objectives This study conducted in the National Heart Institute in Cairo aimed at assessing the effect of depth of anaesthesia guided by bispectral index on the severity of mitral insufficiency as measured by transesophageal echocardiography. Patients and Methods This study was conducted in the National Heart Institute in Cairo. The study was conducted for a period of about six months after the approval from Ethical committee. Informed oral consent for every patient was obtained. Prospective observational cross-sectional study with a random sample of 20 patients at National Heart Institute. A sample size of at least 15 data pairs achieves 80% power to reject the null hypothesis of zero effect size when the population effect size is 0.80 and the significance level (alpha) is 0.05 using a two-sided paired ttest. Adult patients undergoing elective cardiac surgery in National Heart Institute. Results The MR severity decreased at a deeper anaesthesia at low BIS than at a shallower anaesthesia at high BIS in patients with organic MR. Eight patients out of twenty patients (40% with organic MR) showed a + 1 grade of improvement in MR grade, by semi-quantitively measuring maximal JA and VC width. Improvement in mitral regurge severity thought to be secondary to unloading effect of general anaesthesia on left ventricle causing a decrease in afterload, preload, and left ventricular dimensions. This study demonstrated that, a comparison between deep anaesthesia and shallow anaesthesia using BIS showed there is a significant reduction in multiple parameters of MR severity assessment secondary to unloading effect of general anaesthesia on left ventricle caused by a decrease in both afterload and preload. Conclusion This reduction in MR severity appeared to be significant enough to modify intraoperative decisions regarding valve surgery by underestimation of valve severity. Thus, strong consideration should be given to thorough preoperative assessment of MR severity, rather than relying on intraoperative findings.