The Effects of Intrathecal Dexmedetomidine on Spinal Anesthesia Using Diluted Low-Dose Bupivacaine for Transurethral Resection of Prostate in Elderly

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.