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Efficacy of the A‐line™ AEP monitor as a tool for predicting successful insertion of a laryngeal mask during sevoflurane anesthesia
Author(s) -
Alpiger S.,
HelboHansen H. S.,
Vach W.,
Ording H.
Publication year - 2004
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.0001-5172.2004.00425.x
Subject(s) - medicine , sevoflurane , anesthesia , alarm , airway , mascara , laryngeal mask airway , materials science , composite material
Background: The use of clinical signs for assessing depth of anesthesia is unreliable during periods with little noxious stimulation. A patient may appear adequately anesthetized at one moment at a given level of stimulation, but may later, when facing other more intense stimuli, show signs of insufficient anesthesia. In order to prevent under‐ or overdosing of anesthetics, an anesthesia depth monitor that is able to predict responses to noxious stimulation would therefore be useful. Auditory evoked potentials (AEP) is one of several physiological parameters under investigation. The method has been improved by rapid extraction and conversion of the AEP curve into an index (A‐Line ARX Index™ = AAI). We aimed to determine the clinically required depth of anesthesia, measured by the A‐line™ AEP Monitor, for at least 90% probability of acceptable insertion conditions for a laryngeal mask airway (LMA). Methods: We studied 112 patients anesthetized by mask with increasing concentration of sevoflurane in oxygen. The monitor was programmed to give an alarm at AAI between 15 and 40 according to randomization. When the alarm sounded, the end‐expiratory sevoflurane concentration was recorded and the LMA inserted. Insertion conditions were assessed by an observer blinded to the AAI. Results: The ED 95 and prediction probability (P K ) for AAI were 14.5 (CI 7.4–21.6) and 0.76 (0.66–0.86), respectively, while the ED 95 and P K for expiratory sevoflurane concentration were 4.36% (CI 3.73–4.98) and 0.95 (0.91–0.99). Conclusions: AAI indicates the level of depth of anesthesia necessary for acceptable laryngeal mask insertion conditions. End‐expiratory sevoflurane concentration was the better predictor.