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

Addition of Dexmedetomidine to Ropivacaine-induced Supraclavicular Plexus Block, a Randomized Controlled Study

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.

Brachial plexus block, Dexmedetomidine, Ropivacaine, ultrasound-guided nerve block, supraclavicular brachial plexus block

After a careful aspiration, 1 to 2 mL of normal saline is injected for a distribution in and around the brachial plexus. Additional needle tip repositioning and injections may be needed when the distribution is not attained. Then the study drug (0.5% ropivacaine in a total volume of 20 mL) will be injected with additional fine adjustment of the block needle under continuous ultrasound monitoring.

After skin infiltration with 1-2 mL of lidocaine 2%, a 21-gauge 90-mm spinal needle will be inserted into the brachial plexus sheath using in-plane technique. After a careful aspiration, 1 to 2 mL of normal saline is injected for a distribution in and around the brachial plexus. Additional needle repositioning and injections may be needed when the distribution is not attained. Then the study drug (0.5% ropivacaine plus 30 microg dexmedetomidine in a total volume of 20 mL) will be injected with additional fine adjustment of the block needle under realtime ultrasound monitoring.

Ultrasound-guided supraclavicular brachial plexus block with 0.5% ropivacaine plus low-dose (30 microg) dexmedetomidine

Postoperative pain using visual analog scale (VAS, 0-100, 0 = no pain, 100 = maximum imaginable pain) will be assessed. Duration of analgesia is defined by time between administration of block and the postoperative pain >3.

Noninvasive arterial BP is measured at the non-operated arm. episode of hypotension (30% decrease in mean BP in relation to baseline values) and hypertension (30% increase in mean BP in relation to baseline values) will be recorded.

HR, bradycardia (HR < 50 beats/min), and tachycardia (HR > 100 beats/min) will be recorded at the same time as BP recording.

is defined by pinprick sensation using a 3-point scale (0-2, 0 = normal sensation, 1 = decreased pain sensation to pinprick, 2 = loss of pain sensation to pinprick) in the median nerve locations.

Sensory block of ulnar nerve is defined by pinprick sensation using a 3-point scale (0-2, 0 = normal sensation, 1 = decreased pain sensation to pinprick, 2 = loss of pain sensation to pinprick) in the ulnar nerve locations.

Sensory block of radial nerve is defined by pinprick sensation using a 3-point scale (0-2, 0 = normal sensation, 1 = decreased pain sensation to pinprick, 2 = loss of pain sensation to pinprick) in the radial nerve locations.

Sensory block of musculocutaneous nerve is defined by pinprick sensation using a 3-point scale (0-2, 0 = normal sensation, 1 = decreased pain sensation to pinprick, 2 = loss of pain sensation to pinprick) in the musculocutaneous nerve locations.

Duration of motor block is defined as the time interval between the administration of the block and the recovery of complete motor function of the hand and forearm assessed.

A successful block is defined as surgery without patient discomfort and the need for supplementation of local infiltration or general anesthesia

IV tramadol 50mg will be administered when postoperative pain >3, and be titrated up by 50 mg increments as needed for pain every 4 to 6 hours, with the maximum total dose of 250mg.

The incidence of PONV will be recorded using a 4-point objective score (1 = no PONV;2 = mild nausea, no vomiting; 3 = excessive nausea or vomiting;4 = vomiting ≥2 times).

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

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