ISSN:
1573-2614
Keywords:
Anesthesia: general, depth
;
Fentanyl
;
Isoflurane
;
Nitrous oxide
;
Monitoring: anesthetic depth
;
EEG
Source:
Springer Online Journal Archives 1860-2000
Topics:
Computer Science
,
Medicine
Notes:
Abstract Objective. Our objective was to evaluate the performance of the EEG as an indicator of anesthetic depth by measuring EEG prediction of movement response to surgical stimuli.Methods. While using 5 different combinations of isoflurane, 70% N2O, and fentanyl, we measured the EEG of 246 patients during pelvic laparoscopy and observed their movement responses to opening stimuli (defined as skin incision, CO2 needle insertion, or trocar insertion) and also to closing stimuli (defined as sutures during incision closure). The EEG was expressed asF95, the frequency in hertz below which resides 95% of the power in the EEG frequency spectrum. The relations betweenF95 and movement response were expressed as logistic regression curves.F95-response logistic regression curves, which are analogous to dose-response curves, were calculated for each of the 2 stimuli administered during each of the 5 anesthetic techniques. The prediction of patient responsiveness byF95 was tested using β (beta), a measure of the slope of anF95-response logistic curve. The presence of shifts among theF95-response logistic curves was tested using the differences inF95 values between curves. Hypothesis tests used a level of significance ofP = 0.05.Main Results. The slopes of theF95-response logistic regression curves showed a statistically significant ability to predict movement response to stimuli for 9 of the 10 combinations of stimuli and anesthetic techniques. We did not calculate anF95-response logistic curve for the tenth combination because it contained burst suppression, which our EEG analysis method was not designed to process. TheF95-response logistic curves were shifted relative to each other, and the shifts were affected by the type of stimulus and the combination of anesthetic agents. Referenced to opening curves, the mean shift of the closing curves was ± 4.2 ± 0.3 Hz (mean ± SD). With increasing doses of fentanyl, the use of 70% N2O, or both, the curves shifted to higher values ofF95; the range in shifts was 0.2 to 8.1 Hz. The slope β values of theF95-response logistic curves and the shifts among the curves were similar to the β values and shifts that might be expected from changes in anesthetic agent doses.Conclusions. The EEG, expressed asF95, predicted movement response to surgical stimuli during combinations of isoflurane, 70% N2O, and fentanyl. TheF95-response curves shifted upward on the frequency scale for the less intense stimuli and for anesthetic techniques using 70% N2O, fentanyl, or both.F95 prediction of movement response appeared to be related to anesthetic agent doses. OurF95-response curves may provide helpful guidelines for usingF95 to titrate the administration of anesthetic agents and for assessing the depth of general anesthesia.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02078133
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