Bispectral and spectral entropy indices at propofol-induced loss of consciousness in young and elderly patients.
BACKGROUND
Bispectral (BIS) and state/response entropy (SE/RE) indices have been widely used to estimate depth of anaesthesia and sedation. In adults, independent of age, adequate and safe depth of anaesthesia for surgery is usually assumed when these indices are between 40 and 60. Since the EEG is changing with increasing age, we investigated the impact of advanced age on BIS, SE, and RE indices during induction.


METHODS
BIS and SE/RE indices were recorded continuously in elderly (> or =65 yr) and young (< or =40 yr) surgical patients who received propofol until loss of consciousness (LOC) using stepwise increasing effect-site concentrations. LOC was defined as an observer assessment of alertness/sedation score <2, corresponding to the absence of response to mild prodding or shaking.


RESULTS
We analysed 35 elderly [average age, 78 yr (range, 67-96)] and 34 young [35 (19-40)] patients. At LOC, all indices were significantly higher in elderly compared with young patients: BIS(LOC), median 70 (range, 58-91) vs 58 (40-70); SE(LOC), 71 (31-88) vs 55.5 (23-79); and RE(LOC), 79 (35-96) vs 59 (25-80) (P<0.001 for all comparisons). With all three monitors, only a minority of elderly patients lost consciousness within a 40-60 index range: two (5.7%) with BIS and RE each, and seven (20%) with SE. In young patients, the respective numbers were 20 (58.8%) for BIS, 13 (38.2%) for SE, and nine (26.5%) for RE.


CONCLUSIONS
In adults undergoing propofol induction, BIS, SE, and RE indices at LOC are significantly affected by age.
Lysakowski
C
C
Division of Anaesthesiology, University Hospitals of Geneva, rue Gabrielle Perret-Gentil 4, CH-1211 Geneva 14, Switzerland. christopher.lysakowski@hcuge.ch
Elia
N
N
Czarnetzki
C
C
Dumont
L
L
Haller
G
G
Combescure
C
C
Tramèr
M R
MR
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D018686:Anesthetics, Intravenous / Q000008:administration & dosage / Q000494:pharmacology*; D003243:Consciousness / Q000187:drug effects*; D004334:Drug Administration Schedule; D004569:Electroencephalography / Q000187:drug effects / Q000295:instrumentation / Q000379:methods; D019277:Entropy; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D016343:Monitoring, Intraoperative / Q000379:methods*; D015742:Propofol / Q000008:administration & dosage / Q000494:pharmacology*; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult
D018686:Anesthetics, Intravenous; D015742:Propofol