40 Hz auditory steady-state response and EEG spectral edge frequency during sufentanil anaesthesia.
OBJECTIVE
The auditory steady-state evoked response (ASSR) is an evoked potential which provides a sensitive measure of the effects of general anaesthetics on the brain. We used pharmacokinetic-pharmacodynamic (PK-PD) modelling to compare the effects of sufentanil on the amplitude of the ASSR with its effect on spectral edge frequency (SEF) of the electroencephalogram.


METHODS
Nine patients scheduled for elective cardiac surgery participated. Midazolam (70 micrograms.kg-1 i.m.) was given 60 min before entering the operating room. Anaesthesia was induced with 5 micrograms.kg-1 sufentanil at a rate of 0.83 microgram.kg-1.min-1. The ASSR, SEF and plasma sufentanil concentrations were measured for 30 min after induction of anaesthesia before surgery. The half-life between the central and effect site compartments (t1/2Keo), the 50% inhibitory concentration (IC50) and the slope factor (gamma) were computed.


RESULTS
The amplitude of the ASSR increased during the first three minutes of infusion of sufentanil by up to 40%. This was followed by a rapid decrease between the fourth and fifth minutes to 16% of baseline. The SEF decreased progressively during the first five minutes of infusion to 18% of baseline. Both measures subsequently showed modest recovery. The parameters gamma, IC50 and t1/2Keo for ASSR were (mean +/- SD) 6.0 +/- 3.7, 2.1 +/- 1.2 ng.ml-1 and 7.3 +/- 2.4 min. For SEF the values were 5.9 +/- 5.2, 1.4 +/- 0.7 ng.ml-1 (P < 0.05 compared with ASSR) and 6.8 +/- 2.4 min.


CONCLUSIONS
The sensitivity of ASSR to sufentanil is less than that of the SEF.
Gilron
I
I
Clinical Trials Unit, NIDR, National Institutes of Health, Bethesda, MD 20892, USA.
Plourde
G
G
Marcantoni
W
W
Varin
F
F
D000161:Acoustic Stimulation; D000768:Anesthesia, General; D018681:Anesthetics, General / Q000493:pharmacokinetics; D004569:Electroencephalography / Q000187:drug effects*; D005072:Evoked Potentials, Auditory / Q000187:drug effects*; D005260:Female; D006207:Half-Life; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D017409:Sufentanil / Q000493:pharmacokinetics
D018681:Anesthetics, General; D017409:Sufentanil