Comparison of auditory evoked potentials and the A-line ARX Index for monitoring the hypnotic level during sevoflurane and propofol induction.
BACKGROUND
Extraction of the middle latency auditory evoked potentials (AEP) by an auto regressive model with exogenous input (ARX) enables extraction of the AEP within 1.7 s. In this way, the depth of hypnosis can be monitored at almost real-time. However, the identification and the interpretation of the appropriate signals of the AEP could be difficult to perform during the anesthesia procedure. This problem was addressed by defining an index which reflected the peak amplitudes and latencies of the AEP, developed to improve the clinical interpretation of the AEP. This index was defined as the A-line Arx Index (AAI).


METHODS
The AEP and AAI were compared with the Modified Observers Assessment of Alertness and Sedation Scale (MOAAS) in 24 patients scheduled for cardiac surgery, anesthetized with propofol or sevoflurane.


RESULTS
When comparing the AEP peak latencies and amplitudes and the AAI, measured at MOAAS level 5 and level 1, significant differences were achieved. (mean(SD) Nb latency: MOAAS 5 51.1 (7.3) ms vs. MOAAS 1: 68.6 (8.1) ms; AAI: MOAAS 5 74.9 (13.3) vs. MOAAS 1 20.7 (4.7)). Among the recorded parameters, the AAI was the best predictor of the awake/anesthetized states.


CONCLUSIONS
We conclude that both the AAI values and the AEP peak latencies and amplitudes correlated well with the MOAAS levels 5 (awake) and 1 (anesthetized).
Litvan
H
H
Hospital Santa Creu i Sant Pau, Barcelona and Polytechnic University of Catalonia, Spain. hlitvan@hsp.santpau.es
Jensen
E W
EW
Revuelta
M
M
Henneberg
S W
SW
Paniagua
P
P
Campos
J M
JM
Martínez
P
P
Caminal
P
P
Villar Landeira
J M
JM
D000758:Anesthesia; D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D006348:Cardiac Surgical Procedures; D005072:Evoked Potentials, Auditory; D006801:Humans; D008738:Methyl Ethers; D015742:Propofol; D011930:Reaction Time; D000077149:Sevoflurane; D012815:Signal Processing, Computer-Assisted; D014474:Unconsciousness
D018685:Anesthetics, Inhalation; D018686:Anesthetics, Intravenous; D008738:Methyl Ethers; D000077149:Sevoflurane; D015742:Propofol