Impaired explicit memory after recovery from propofol/sufentanil anaesthesia is related to changes in the midlatency auditory evoked response.
BACKGROUND
Midlatency auditory evoked responses (MLAER) can distinguish different stages of anaesthesia. We studied MLAER during emergence from propofol/sufentanil anaesthesia in relation to recovery of explicit memory.


METHODS
MLAER were recorded in 29 healthy patients before and during anaesthesia and during emergence until the patients opened their eyes spontaneously. After a structured interview the next day, patients were classified into those with and without explicit memory of the recovery period. Latencies Na, Pa and Nb and the peak-to-peak amplitudes NaPa and PaNb were compared between the groups by multivariate analysis of variance. Results are mean (SD).


RESULTS
At eye opening (37 (12) min after the end of anaesthesia) the latency Nb (47 (5) compared with 41 (5) ms; P < 0.001) was prolonged and the amplitude PaNb (1.3 (0.8) compared with I (0.5) ms; P = 0.012) was greater than the baseline value, respectively. The Nb latency was significantly shorter in patients with explicit memory (49 (2) ms compared with 45 (I); P = 0.041).


CONCLUSIONS
Large intra- and inter-individual variability in the MLAER values limited their ability to predict memory responses in individual patients during emergence from propofol/sufentanil anaesthesia.
Rundshagen
I
I
Department of Anaesthesiology, University Hospital Charité, Campus Charité Mitte, Schumannstrasse 20/21, D-10117 Berlin, Germany.
Schnabel
K
K
Schulte am Esch
J
J
D000293:Adolescent; D000328:Adult; D018686:Anesthetics, Intravenous; D001933:Brain Stem / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D015742:Propofol; D017409:Sufentanil; D013997:Time Factors
D018686:Anesthetics, Intravenous; D017409:Sufentanil; D015742:Propofol