Comparison the Effect of Etomidate vs. Thiopentone on Left Ventricular Strain and Strain Rate at the Time of Anesthesia Induction in Patients Undergoing Elective Coronary Artery Bypass Surgery: A Randomized Double Blind Controlled Trial

AbstractMyocardial strain imaging with speckle tracking echocardiography (STE) is getting popularity because it does not depends on insonation angle and has shown good correlation with intraoperative and postoperative ventricular function in patients with coronary artery disease. The impact of thiopentone and etomidate induction on myocardial function was studied and compared on sixty patients undergoing elective coronary artery bypass grafting. Three loops for each views (apical 4 chamber, apical 2 chamber, and apical long axis ) were acquired at base line (T0) and 1 minute (T1) after induction for offline analysis. In Group T, significant increase in HR from the base line values (67.8 ± 13.8 vs 79.2 ± 15.6, p = 0.001) occurred post induction, where as in Group E it remain near to the base line (71.7 ± 8.3 vs 70.1± 8.9, p = 0.345). A reduction in mean arterial pressure (MAP) was noted in both the groups after the injection of the allocated drug. There was no significant difference in the index of contractility (ICON) (T0 vs T1: 48.7 ± 10.6 vs 47.0 ± 11.7, p = 0.120) in Group E where as in Group T there was a reduction in the ICON value (T0 vs T1: 45.0 ± 10.7 vs 41.0 ± 8.4, p = 0.005). A similar picture was also noted in systemic vascular resistance index. A significant decrease in cardiac index (CI) was seen in Group E (T0 vs T1: 2.7 ± 0.4 vs 2.5 ± 0.4, p = 0.027), however it remain near to the base line in Group T. There occurred no changes in stroke index (SI) in Group E (T0 vs T1: 38.7 ± 6 vs 37.0± 5.3, p = 0.134), where as a significant decrease was noted after injection of thiopental (T0 vs T1: 38.0 ± 6.2 vs 36.1± 4.9, p = 0.049). A significant decline in cardiac performance index (CPI) was also recorded in Group E (T0 vs T1: 0.57 ± 0.15 vs 0.52 ± 0.12, p = 0.032), and not in Group T. There was decrease in left ventricular ejection fraction (LVEF) after the injection of both the drugs (Group E, T0 vs T1: 57 ± 3.7 vs 54± 3.7, p= 0.001; and Group T, T0 vs T1: 57 ± 3.7 vs 54± 3.7, p = 0.001). In Group E, global longitudinal peak systolic strain (GLPSS) showed no change after the injection of the drug (T0 vs T1: −13.2 ± 2.2 vs −13.1± 2.3, p = 0.631). However, a significant decrease in GLPSS (T0 vs T1: −13.5 ± 1.5 vs – 10 ± 1.8, p = 0.001) after injection of thiopental. Longitudinal peak systolic strain rate (LPSSR) was significantly decreased in all echocardiographic views after the injection of respective drugs. However, the decrease in LPSSR was significantly less in Group E in comparison to Group T.To conclude, STE provides accurate and reliable real time quantitative regional and global LV assessment. Use of thiopentone for anesthesia induction is associated with more profound impairment of LV function in comparison to etomidate as assessed by a decreased longitudinal peak systolic strain rate and global longitudinal peak systolic strain. Further studies are warranted to understand the exact clinical impact, which may influence the choice of intravenous induction agent based upon preoperative patient characteristics.