Spinal block is the most common anesthetic technique for transurethral resection of
prostatectomy (TURP). Most patients undergoing TURP are elderly and frequently present with
cardiopulmonary and endocrine diseases. Low-dose local anesthetic is commonly administer to
limit the block level to minimize the hemodynamic changes. However, sometimes it may not
provide an adequate level of sensory block. Thus, intrathecal additive is frequently
administer with local anesthetic to improve analgesic effect.

Dexmedetomidine(DXM), a selective 2-adrenoreceptor agonist, has been used in the epidural
space in humans without any reports of neurological deficits. Previous clinical studies
showed that intravenous dexmedetomidine administration prolonged the sensory and motor blocks
of bupivacaine spinal analgesia. But clinical studies about the use of intrathecal DXM with
local anesthesia in humans are scarce in the literature. Kanazi et al. found that 3μg DXM
added to 12 mg spinal bupivacaine produced the significant short onset of sensory and motor
block as well as significantly longer duration of sensory and motor block than bupivacaine.
And Al-Mustafa et al. reported that intrathecal dexmedetomidine as an adjuvant to 12.5mg
bupivacaine in spinal anesthesia has a dose dependant effect on the onset and regression of
sensory and motor block.

In our previous study, low-dose diluted bupivacaine 5 mg provided sufficient anesthetic level
when opioid was added with local anesthetic. However, opioid-induced side effects, such as
pruritus, nausea, or vomiting, could be an obstacle in common use. The aim of this study is
to evaluate whether DXM-low-dose bupivacaine spinal anesthesia can provide the effective
spinal anesthesia and postoperative analgesia with minimal side effect compare to the local
anesthetic only group.

This study was conducted in a randomized, double-blind, controlled fashion. Patients were
randomly allocated to DXM group or Saline group. DMT group received hyperbaric bupivacaine
0.5% (1.2 ml) (6 mg) in dextrose 8% solution + DMT 0.3 ml (3 µg)－in total, bupivacaine 0.4%
(1.5 ml) intrathecally and Saline group received hyperbaric bupivacaine 0.5% (1.2 ml) (6 mg)
in dextrose 8% solution + normal saline 0.3 ml －in total, bupivacaine 0.4% (1.5 ml)
intrathecally. After spinal block, the level of sensory block, defined as the dermatomal
segment with loss of pain sensation to pin-prick with a 22 G hypodermic needle and cold
sensation to alcohol swab was measured every 2 min after intrathecal injection. The
investigators recorded the peak sensory block level, time to peak block level from
intrathecal injection, blood pressure and heart rate, and analgesic supplementation during
operation. The maximum motor block level was assessed according to the modified Bromage
scale. During postoperative period, the frequency of analgesic requirement, time to the first
analgesic request, and pain scores were evaluated by blind investigator.