Addition of Dexmedetomidine to Ropivacaine-induced Supraclavicular Block (ADRIB Trial)

Dexmedetomidine, an alpha 2-adrenoreceptor agonist, has been found to exerts an excellent influences on the filed of perineural block. It could shorten the onset time and prolong the duration of the nerve block and improved postoperative pain. However, Dexmedetomidine-induced bradycardia or hypotension has recently attracted considerable attention because of potentially grave consequences, including sinus arrest and refractory cardiogenic shock. A low dose may help minimize cardiovascular risks associated with dexmedetomidine. However, few studies have addressed the clinical effects of low-dose dexmedetomidine as an perineural adjuvant. The present study was designed to test the hypothesis that low-dose dexmedetomidine added to ropivacaine would safely enhance the duration of analgesia without adverse effects when compared with ropivacaine alone. Investigators will conduct a single-center, prospective, randomized, triple-blind, controlled trial in patients undergoing elective forearm and hand surgery under ultrasound-guided supraclavicular brachial plexus block using either ropivacaine or ropivacaine plus low-dose dexmedetomidine. The primary outcome is self-reported duration of analgesia . Secondary outcomes include onset time and duration of motor and sensory block, total postoperative analgesics, and safety assessment (adverse effects and postoperative abnormal sensation).

Dexmedetomidine, an alpha 2-adrenoreceptor agonist, has been found to exerts an excellent influences on the filed of perineural block. It could shorten the onset time and prolong the duration of the nerve block and improved postoperative pain. However, Dexmedetomidine-induced bradycardia or hypotension has recently attracted considerable attention because of potentially grave consequences, including sinus arrest and refractory cardiogenic shock. Although meta-analysis showed that perineural dexmedetomidine as a local anaesthetic adjuvant for neuraxial and peripheral nerve blocks produced reversible bradycardia in only 7% of brachial plexus block patients and no effect on the incidence of hypotension, various clinical studies reported a significant decrease in heart rate. A low dose may help minimize cardiovascular risks associated with dexmedetomidine. However, few studies have addressed the clinical effects of low-dose dexmedetomidine as an perineural adjuvant. The present study was designed to test the hypothesis that low-dose dexmedetomidine, which till today has not been reported in the literature, added to ropivacaine for brachial plexus block would safely enhance the duration of analgesia without adverse effects when compared with ropivacaine alone. Investigators will conduct a single-center, prospective, randomized, triple-blind, controlled trial in patients undergoing elective forearm and hand surgery under ultrasound-guided supraclavicular brachial plexus block using either 20 mL of 0.5% ropivacaine or 0.5% ropivacaine plus 30 microg dexmedetomidine. The primary outcome is self-reported duration of analgesia . Secondary outcomes include onset time and duration of motor and sensory block, total postoperative analgesics, and safety assessment (adverse effects including cardiovascular inhibitions and postoperative abnormal sensation). Data will be collected and analyzed in a blinded fashion.

Eligibility Criteria:
Inclusion Criteria:

* Surgery: elective forearm and hand surgery under ultrasound-guided supraclavicular brachial plexus block
* American Society of Anesthesiologist(ASA) physical status of Ⅰ to III
* Age between 18 to 60 years old

Exclusion Criteria:

* Having an ongoing another clinical trials
* Taking antihypertensive drugs such as methyldopa, clonidine and other α2 receptor agonist
* Peripheral neuropathy
* Cerebrovascular disease
* Psychiatric disease
* Coagulopathies
* Pregnant women
* Liver and kidney dysfunction
* Heart failure
* Known allergy or hypersensitive reaction to dexmedetomidine or anesthetic
* Patient refusal