OBJECTIVETo investigate the effect of cerebral state index (CSI) in measuring the level of sedation during target controlled infusion (TCI) of propofol in patients of different ages.

METHODSForty ASA class I-II patients undergoing general anesthesia were divided into group A (65 to 79 years old, n=20) and group B (20 to 55 years, n=20). The sedation level was assessed using OAA/S scale. Anesthesia was induced with TCI of propofol. The target effect-site concentration (CE) was set initially at 0.5 µg/ml followed by increments of 0.5 µg/ml every 5 min until 5 min after the patients lost consciousness and did not respond to pain stimulation (OAA/S=0). OAA/S score was recorded every 20 s, and MAP, HR, SPO(2) and CSI were recorded. Spearman correlation coefficient between OAA/S score and CSI and their prediction probabilities (Pk) were calculated. The values of CE(05), CE(50), CE(95) and CSI(05), CSI(50), CSI(95) at loss of verbal contact (LVC) (OAA/S=2) and loss of consciousness (LOC) (OAA/s≤1) were also calculated.

RESULTSCSI was well correlated to the sedation depth. The values of CE(50) and CSI50 were 1.3 µg/ml and 69.7 at LVC in group A, and were 1.8 µg/ml and 65.9 at LVC in group B, respectively. The values of CE(50) and CSI(50) were 1.5 µg/ml and 64.3 at LOC in group A, as compared to 2.5 µg/ml and 54.8 at LOC in group B, respectively. When the OAA/S scale was lower than 3, the CSI values in group A were significantly higher than those in group B (P<0.05).

CONCLUSIONCSI can effectively and rapidly distinguish the level of sedation in different age groups. At the same OAA/S scale, the target effect-site concentration in the elderly is obviously lower than that in the young patients, but CSI values were significantly higher in the elderly than in the young patients during TCI of propofol.