Effects of Stellate Ganglion Block on Sedation as Assessed by Bispectral Index in Normal Healthy Volunteers

Abstract

Background: The sympathetic nervous system plays an important role in the arousal response. Recently, the stellate ganglion block (SGB) was found to effectively treat anxiety and night awakening in humans and decrease electroencephalogram (EEG) indices of arousal responses in rat. But, the role of the sympathetic block in human arousal responses has not yet been studied. Objective: We performed this prospective, double-blinded, controlled volunteer study to investigate the sedative effects and bispectral index (BIS) changes of SGB. Study Design: A randomized, double-blind trial. Setting: Single academic medical center. Methods: This study was approved by the Ethics Committee of Kyungpook National University Hospital (ref: KNUH_10-1081) and registered with CRiS (Clinical Research Information Service, http://cris.cdc.go.kr, ref: KCT0000036, 2010. 9.24). Twenty healthy volunteers were enrolled in this study. The volunteers were randomly assigned to one of 2 groups: the SGB group (n = 10) and the sham group (n =10). Volunteers in SGB group received SGB and volunteers in the sham group received a sham procedure. BIS value, heart rate, and blood pressure were measured before and 5, 10, 20, and 30 minutes after the procedure. Observer’s Assessment of Alertness/Sedation (OAA/S) scores were assessed before and 10 and 30 minutes after the intervention. Results: In the SGB group, BIS values and OAA/S scores significantly decreased after the intervention as compared to baseline (P < 0.05). The values were also significantly decreased in the SGB group when compared to the values in sham group after the intervention (P < 0.05). There was a significant change of mean blood pressure 10 to 30 minutes after SGB (P < 0.05). There were no differences in heart rate during study period between groups. Limitations: This study is limited by a relatively small sample size. Conclusions: This study showed that SGB has a sedative effect in normal healthy volunteers, as evidenced by decreased OAA/S scores and BIS values. Key words: Stellate ganglion, sympathetic block, sedation, bisepctral index, EEG, volunteers