A randomized trial of anesthetic induction agents in patients with coronary artery disease and left ventricular dysfunction

Abstract

The deleterious effects of anesthetic agents in patients suffering from coronary artery disease are well known. The risk increases when a patient has compromised ventricular function. There is a paucity of literature regarding the choice of the suitable agent to avoid deleterious effects in such patients. The use of etomidate and propofol has been considered superior to other intravenous anesthetic agents in these groups of patients. The aim of the present study is to compare the hemodynamic effects of anesthesia induction with etomidate, thiopentone, propofol, and midazolam in patients with coronary artery disease and left ventricular dysfunction. This randomized clinical trail was conducted at the All Indian Institute of Medical Sciences, New Delhi, India. Sixty patients with coronary artery disease and left ventricular dysfunction (ejection fraction < 45%) scheduled for elective coronary artery bypass surgery participated in this study. After stabilization baseline hemodynamic data stroke volume variation and systemic vascular resistance index were recorded for all patients (Flo Trac TM sensor with Vigileo cardiac output monitor used for hemodynamic monitoring). The patients were randomly alloted to one of the four groups and the intravenous induction agent was administered for over 60-90 seconds (Group E--Etomidate 0.2 mg/Kg; Group M--Midazolam 0.15 mg/Kg; Group T--Thiopentone 5 mg/Kg; Group P--Propofol 1.5 mg/Kg). Hemodynamic data were recorded at one minute intervals starting from induction till seven minutes after intubation,--the end point of the present study. There was a significant decrease in the heart rate in comparison to the baseline(-7 to -15%, P = 0.001), mean arterial pressure (-27 to -32%, P = 0.001), cardiac index (-36 to -38%, P = 0.001), and stroke volume index (-27 to -34%, P = 0.001) after induction in all four groups. The hemodynamic response was similar in all the four groups. There was no significant change in central venous pressure and stroke volume variation (SVV) during induction and intubation, while the effects on the systemic vascular resistance index (SVRI) were variable. The midazolam group was the most effective in preventing intubation stress (tachycardia,hypertension). The change from baseline values in heart rate (+ 4%, P = 0.12) and mean arterial pressure (-1%, P = 0.77) after intubation were not statistically significant in the midazolam group. The etomidate group was the least effective of all the four groups in minimizing stress response, with statistically significant increase from baseline in both heart rate (P = 0.001) and mean arterial pressure (P = 0.001) at 1 minute after intubation. All the four anesthetic agents were acceptable for induction in patients with coronary artery disease and left ventricular dysfunction despite a 30-40% decrease in the cardiac index. Clinician experience along with knowledge of the potential interactions (e.g., premedication, concurrent opioid use) is needed to determine hemodynamic stability during anesthetic induction in these patients with ventricular dysfunction.