The Bispectral Index and Modified Observer's Assessment of Alertness/Sedation Scale Comparable to Effect Site Concentration of Propofol in Koreans / 대한마취과학회지

ABSTRACT

BACKGROUND: Propofol has been frequently used for sedation or hypnosis in anesthesia and is relatively accurate in the dose-response relationship for hypnosis. The aim of this study was to define the bispectral index and modified observer's assessment of alertness/sedation (OAA/S) scale at various effect site concentrations (Ce) of propofol in Koreans. METHODS: Fifty premedicated (atropine 0.5 mg, I.M.) adult patients (ASA class I or II, 20 55 yrs) scheduled for elective orthopedic surgery were studied. Propofol was infused until 2 min after the target concentration equilibrated with the effect site concentration (Ce) of propofol using Master TCI. The target concentration of propofol was stepwise increased at intervals of 0.5 microgram/ml until BIS reached 40, BIS and OAA/S at each Ce of propofol were checked. If SpO2 decreased below 90%, oxygen (4 l/min) was given via nasal cannula. RESULTS: BIS was 97.9 +/- 0.2 and OAA/S 5 +/- 0.0 at a Ce of propofol of 0 microgram/ml; the Ce of propofol was 3.5 microgram/ml and OAA/S 0.1 +/- 0.3 at a BIS of 41.1 +/- 2.5. Also, systolic BP at a Ce of propofol above 1.0 microgram/ml and diasolic BP at a Ce of propofol above 1.5 microgram/ml significantly decreased compared to the control (P < 0.05). However, heart rate did not show any difference compared to the control value. Above a 1.0 microgram/ml Ce, fifty-eight percent of patients showed SpO2 < 90%, but there was no incidence of apnea. There were significant correlations between Ce of propofol, BIS and OAA/S. CONCLUSIONS: BIS showed a significant correlation with Ce of propofol (Spearman's r = 1.0) (P < 0.0001). The Ce of propofol was above 3.0 microgram/ml for BIS50.