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This study investigated the effect of intrathecal fentanyl on the dose of propofol during sedation guided by Cerebral State Index monitoring. Seventy patients were randomly assigned to receive either fentanyl 25 microg (n = 35) or normal saline (n = 35) with hyperbaric bupivacaine 12.5 mg for spinal anaesthesia. Propofol was infused to maintain a Cerebral State Index value of 65-75 for 30 min. The propofol infusion time and dose required to reach a Cerebral State Index value of 75 were recorded together with the time required to reach a Cerebral State Index value higher than 90 after cessation of sedation. The onset time for sedation was faster and the recovery time was slower in the fentanyl group compared to those in the saline group (p = 0.018 and 0.027, respectively). The propofol doses required for onset and maintenance of sedation were significantly lower in the fentanyl group compared to those in the control group (p = 0.018 and < 0.001, respectively). In conclusion, adding intrathecal fentanyl 25 microg during spinal anaesthesia significantly reduced the dose of propofol required for sedation and prolonged the subsequent recovery time.

Prolongation of the corrected QT (QTc) interval is associated with various anaesthetic drugs. The QTc prolongation may become more exacerbated during laryngoscopy and intubation, which is possibly caused by sympathetic stimulation. The aim of this study was to investigate the effects of fentanyl on the QTc interval during propofol induction in healthy patients. The patients were randomly allocated to receive either fentanyl (n = 25) or saline (n = 25) before induction. The QTc interval was significantly prolonged immediately after intubation in control group compared to preceding values, but it did not change in the fentanyl group. The number of patients with the prolonged QTc interval exceeding 20 ms immediately after intubation compared to the baseline values was 14 in the control group and seven in the fentanyl group. In conclusion, pretreatment with fentanyl 2 microg x kg(-1) significantly attenuated QTc prolongation associated with laryngoscopy and tracheal intubation during propofol induction.