British Journal of Anaesthesia, 2003, Vol. 91, No. 3 341-346
© 2003 The Board of Management and Trustees of the British Journal of Anaesthesia
Clinical Investigations |
Bispectral index changes following etomidate induction of general anaesthesia and orotracheal intubation
1 Department of Anaesthesia and Intensive Care and 2 Department of Surgery, University Paris V—René Descartes, Hôpital Cochin, Assistance Publique—Hôpitaux de Paris, 27 rue du Faubourg Saint Jacques, F-75679 Paris Cedex 14, France. 3 Anaesthesiology Laboratory, Université Paris-Sud, Hôpital de Bicêtre, 78 Avenue du Géneral Leclerc, F-94275 Le Kremlin Bicêtre Cedex, France
Corresponding author. E-mail: claude.lentschener@cch.ap-hop-paris.fr
Background. 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.
Methods. 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.
Results. 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.
Conclusions. Etomidate induction doses do not predict the time for BIS to decrease to 50 as this variable varies markedly following three etomidate dose regimen.
Br J Anaesth 2003; 91: 341–6
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