Recently many studies reported that intraoperative dexmedetomidine administration undergoing
spinal anesthesia give a satisfactory sedation in elderly patients and cause less respiratory
depressions compared other sedatives(e.g. benzodiazepine) But the optimal dose of
dexmedetomidine for sedative effect in elderly patients undergoing spinal anesthesia was not
got general consensus.

The investigators hypothesized that the dose requirements would be lower than in elderly
patients than young patients. Furthermore, intrathecal small dose opioids enhance the
analgesia provided by bupivacaine due to synergistic effects and it would reduce the dose of
dexmedetomidine.

The purpose of this study was to determine the dose of dexmedetomidine to provide
satisfactory sedation undergoing spinal anesthesia with or without additive small dose
intrathecal opioids.

Elderly patients(65~85 years old) undergoing TURP or TURB were enrolled in this
single-blinded study. Forty patients were randomly assigned to receive intrathecal hyperbaric
bupivacaine 6mg coadministered with 20mcg fentanyl or placebo normal saline 0.4cc. After the
induction (bilateral T10 sensory level to pinprick within 5 mins of intrathecal drug
administration), continuous intravenous dexmedetomidine was started in dose of 0.8, 0.6, 0.5,
0.4, 0.3, or 0.2mcg. Successful sedation was defined as OASS score 3 or 4 within 20 minutes
of dexmedetomidine infusion. The dose of dexmedetomidine was selected for each patient
according to an up and down method. Intraoperative arterial pressure, heart rate, and
bispectral index was compared. Postoperative pain score, the time for the regression of
sensory and motor was recorded for further analysis.