Intravenous anesthesia


Anesthesia and Pain Medicine. 2001 June 5(2): 107-111
ⓒ Korean Society for Intravenous Anesthesia
Can We Use Yawning as a Landmark of Loss of Consciousness during Anesthesia Induction with Propofol?
Hyun-Hwa Lee, Ho-Yeong Kil, Tae-Hyun Han, Dae-Woo Kim
Department of Anesthesiology, College of Medicine, Hallym University, Seoul, Korea.,Department of Anesthesiology, College of Medicine, Catholic University, Seoul, Korea.

BACKGROUND: Yawning occurs frequently during anesthesia induction and bispectral index has a good relationship with degree of hypnosis caused by propofol. However, it is not known whether yawning could be used as an landmark of loss of consciousness (LOC) during anesthesia induction. For this, we evaluated relationship among bispectral index (BIS), current and effect site concentration of propofol at three different induction mode when yawning is occured during anesthesia induction with propofol.
METHODS: Ninety ASA 1 or 2 adult patients (age: 20 55 years) undergoing minor orthopedic surgery were randomly allocated to one of three groups accordng to induction mode (Group 1: flash, Group 2: 2 min and Group 3: 3 min, n = 30 for each grop). After setting of routine monitors, anesthesia was induced using propofol target controlled infusion (TCI) and loss of consciousness was defined as a loss of eyelash reflex. Incidence of yawning, SpO2, plasma and effect site concentrations of propofol were checked continuously until yawning was occured during induction. For statistical analysis, repeated measured ANOVA test and Spearmann`s r was used.
RESULTS: The incidence of yawning were 37%, 53% and 60% for Group 1, 2 and 3, respectively. Relationships between LOC and BIS were very significant and gradually decreased with longer induction time (r = 0.98, 0.96 and 0.79 for group 1, 2 and 3). No patient showed SpO2 less than 90%.
CONCLUSIONS: We concluded that yawning could be used as a landmark of loss of consciousness when it is occured during anesthesia induction and its incidence was higher at slower induction mode.
Key words : Anesthetics, intravenous, propofol, Anesthetic techniques, TCI, Monitoring, depth of anesthesia, bispectral index, loss of eyelash reflex, yawning
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