• Nana Bao, Kejian Shi, YiQuan Wu, Yuting He, Zhengjie Chen, Yuan Gao, Yun Xia, Thomas J Papadimos, Quanguang Wang, and Riyong Zhou.
• Department of Anesthesiology, the First Affiliated Hospital of Wenzhou Medical University, South Baixiang, Wenzhou City, 325000, Zhejiang Province, China.
• BMC Anesthesiol. 2022 Jun 7; 22 (1): 176.

BackgroundTo study the respective peripheral and systemic mechanisms of action of dexmedetomidine, as adjuvant to regional anesthesia, we compared dexmedetomidine added to ropivacaine for mid-forearm nerve blocks, to either systemic-only dexmedetomidine, and to a control with no dexmedetomidine.MethodsSixty patients undergoing hand surgery were randomly divided into three groups (n = 20 per group). Each group underwent a triple-nerve (median, radial and ulnar) mid-forearm blocks with 0.75% ropivacaine. In the DexP group, 60 µg of dexmedetomidine were added to the anesthetic mixture, while in the DexIV group, they were intravenously infused. Normal saline as a placebo was used, either as adjuvant, or intravenously. All patients underwent also a supraclavicular block with 1.5% lidocaine for tourniquet pain. The main outcomes were the duration of analgesia and the duration of sensory blockade separately for each nerve termination of the upper limb, and the duration of motor blockade of the upper limb. Tolerance was assessed by blood pressure and heart rate, and the report of adverse events.ResultsDuration of analgesia was longer in the DexP group, in comparison to the two other groups (P < 0.001), while it was similar in the DexIV and the control group. For cutaneous territories targeted by the three mid-forearm blocks, the between-group differences behaved similarly. For the other cutaneous territories (musculocutaneous and posterior brachial cutaneous nerves), duration of sensory blockade was shorter in the control group than in the two dexmedetomidine groups. For duration of motor blockade, the between-group differences behaved similarly. Both blood pressure and heart rate were reduced in the DexP and the DexIV groups, compared to the control.ConclusionsDexmedetomidine used as an adjuvant to regional anesthesia may act mostly though a perineural mechanism, especially for the sensory aspects of anesthesia. A systemic action might however explain other clinical effects.Trial RegistrationChiCTR-IOR-17011149 , date of registration: 16/04/2017.© 2022. The Author(s).

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