Duration and depth of anaesthesia after administration of a single dose of etomidate combined with remifentanil in healthy patients: a survey and a randomised controlled double-blind pilot study

Background: Etomidate is a hypnotic agent frequently used to induce general anaesthesia, primarily in frail patients and in emergency situations. The depth of etomidate-induced general anaesthesia in healthy patients is currently poorly studied. Objectives: The purpose of this study was to evaluate the depth and duration of general anaesthesia by bispectral analysis of the electroencephalogram following the administration of an induction dose of etomidate, combined with remifentanil. We also aimed to gain insight into the attitudes of French-speaking-Belgian anaesthesiologists regarding the use of etomidate. Design: Prospective, randomised, controlled, double-blind, single-centre trial, pilot study. Setting: A university hospital, CUB Erasme, Brussels, Belgium, between 11 January and 08 April 2022 Methods: Healthy patients (ASA score I/II), < 75 years (n=18) scheduled for minor stomatological, cervico-facial or reconstructive surgery were included. Patients were randomly assigned to receive either 0.2 mg/kg (n=8) or 0.3 mg/kg (n=10) of etomidate as an induction bolus. Main Outcome Measures: Practices regarding the use of etomidate were assessed using online survey. We evaluated the onset of general anaesthesia (clinically and time for bispectral index <60) and the duration of an “adequate” depth of general anaesthesia (bispectral index 40-60). Results: Most of the ninety-six responding anaesthetists believe that etomidate is not very effective or ineffective for inducing general anaesthesia in healthy patients. When used, the common dosage of etomidate for induction ranges from 0.2 mg/kg to 0.3 mg/kg. The onset time of general anaesthesia was similar between the two groups. Patients who received 0.3 mg/kg spent a longer time within adequate depth of anaesthesia (396 ± 175 sec) compared with the lower dose of 0.2 mg/kg (156 ± 91 sec) (p<0.01) Conclusion: Most anaesthesiologists express concerns regarding the low efficacy of etomidate when administered as a hypnotic agent in healthy patients. Our findings suggest that etomidate can induce a general anaesthesia of adequate depth, of which the duration double when administered using bolus of 0.3 mg/kg compared with 0.2 mg/kg. Trial Registration: ClinicalTrials.gov ID : NCT05862753