Bispectral index changes following etomidate induction of general anaesthesia and orotracheal intubation

• Published in: British journal of anaesthesia : BJA Vol. 91; no. 3; pp. 341 - 346
• Main Authors: Lallemand, M.-A., Lentschener, C., Mazoit, J.-X., Bonnichon, P., Manceau, I., Ozier, Y.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.09.2003; Oxford University Press; Oxford Publishing Limited (England)
• Subjects: Adult; Aged; anaesthesia; anaesthesia, depth; anaesthesia, general; anaesthetic techniques; anaesthetic techniques, induction; anaesthetics i.v; anaesthetics i.v, etomidate; analgesia; Anesthesia, General - methods; Anesthetics, Intravenous - administration & dosage; Anesthetics, Intravenous - pharmacology; Anesthetics. Neuromuscular blocking agents; Biological and medical sciences; bispectral index; Blinking - drug effects; complications; complications, intubation tracheal; depth; Dose-Response Relationship, Drug; Double-Blind Method; Electroencephalography - drug effects; etomidate; Etomidate - administration & dosage; Etomidate - pharmacology; Female; Hemodynamics - drug effects; Humans; induction; intubation tracheal; Intubation, Intratracheal; Male; Medical sciences; Middle Aged; monitoring; monitoring, bispectral index; Monitoring, Intraoperative - methods; Neuropharmacology; Pharmacology. Drug treatments; Prospective Studies; monitoring, bispectral index; complications, intubation tracheal; anaesthetics i.v, etomidate; analgesia; anaesthesia, general; anaesthesia, depth; anaesthetic techniques, induction; anaesthesia, depth; anaesthesia, general; anaesthetic techniques, induction; anaesthetics i.v, etomidate; complications, intubation tracheal; analgesia; monitoring, bispectral index; Human; Imidazole derivatives; general; anaesthetic techniques; Induction; bispectral index; induction; anaesthetics i.v; General anesthesia; Electroencephalography; Spectral analysis; Etomidate; etomidate; complications; General anesthetic; depth; anaesthesia; intubation tracheal; analgesia; monitoring; Intubation; Trachea; Monitoring; anaesthesia
• ISSN: 0007-0912; 1471-6771
• DOI: 10.1093/bja/aeg175

Etomidate-associated hypnosis has only been studied using standard clinical criteria and raw EEG variables. We conducted a BIS-based investigation of etomidate induction of general anaesthesia. Thirty hydroxyzine-premedicated ASA I patients were randomly allocated to receive etomidate 0.2, 0.3, or 0.4 mg kg−1 intravenously over 30 s. The BIS was continuously recorded. A tourniquet was placed on a lower limb to record purposeful movements and myoclonia. Tracheal intubation was facilitated using rocuronium 0.6 mg kg−1 when the BIS value was 50. The times to disappearance of the eyelash reflex, to a decrease in the BIS to 50, and to tracheal intubation were compared. The BIS values 30 s following tracheal intubation, and mean arterial pressure (MAP) and heart rate (HR) at all time points were also recorded. The BIS value decreased to 50 for tracheal intubation with no purposeful movement in all but one patient in the 0.2 mg kg−1 group. There was no difference between the etomidate groups (0.2, 0.3, and 0.4 mg kg−1) in regards to time to loss of the eyelash reflex (103 (67), 65 (34), 116 (86) s, P=0.2), or to a decrease in BIS to 50 (135 (81), 82 (36), 150 (84) s, P=0.1). Also, the BIS value 30 s after intubation (41 (10), 37 (4), 37 (4), P=0.4), and plasma etomidate concentrations (161 [29–998], 308 [111–730], 310 [90–869] ng ml−1, P=0.2) did not differ between groups. The time to loss of the eyelash reflex was 12–140 s shorter than the time to a decrease in BIS to 50 in three patients in each group who received etomidate 0.2 and 0.4 mg kg−1, and in four patients who received 0.3 mg kg−1. No awareness was recorded. MAP and HR increases following tracheal intubation were comparable between groups. Etomidate induction doses do not predict the time for BIS to decrease to 50 as this variable varies markedly following three etomidate dose regimen.