Investigating the Efficacy of Dexmedetomidine as an Adjuvant to Local Anesthesia in Brachial Plexus Block A Systematic Review and Meta-Analysis of 18 Randomized Controlled Trials Nasir Hussain, MSc,* Vincent Paul Grzywacz, BS,* Charles Andrew Ferreri,† Amit Atrey, MD, MSc, FRCS,‡ Laura Banfield, MLIS,§ Naum Shaparin, MD,|| and Amaresh Vydyanathan, MD§ Background and Objectives: Dexmedetomidine has been thought to be an effective adjuvant to local anesthetics in brachial plexus blockade. We sought to clarify the uncertainty that still exists as to its true efficacy. Methods: A meta-analysis of randomized controlled trials was conducted to assess the ability of dexmedetomidine to prolong the duration and hasten the onset of motor and sensory blockade when used as an adjuvant to local anesthesia for brachial plexus blockade versus using local anesthesia alone (control). A search strategy was created to identify eligible articles in MEDLINE, EMBASE, and The Cochrane Library. The methodological quality for each included study was evaluated using the Cochrane Tool for Risk of Bias. Results: Eighteen randomized controlled trials were included in this meta- analysis (n = 1092 patients). The addition of dexmedetomidine significantly reduced sensory block time onset time by 3.19 minutes (95% confidence in- terval [CI], -4.60 to -1.78 minutes; I 2 = 95%; P < 0.00001), prolonged sen- sory block duration by 261.41 minutes (95% CI, 145.20–377.61 minutes; I 2 = 100%; P < 0.0001), reduced the onset of motor blockade by 2.92 minutes (95% CI, -4.37 to -1.46 minutes; I 2 = 96%, P < 0.0001), and prolonged mo- tor block duration by 200.90 minutes (CI, 99.24–302.56 minutes; I 2 = 99%; P = 0.0001) as compared with control. Dexmedetomidine also signifi- cantly prolonged the duration of analgesia by 289.31 minutes (95% CI, 185.97–392.64 minutes; I 2 = 99%; P < 0.00001). Significantly more patients experienced intraoperative bradycardia with dexmedetomidine (risk difference [RD], 0.06; 95% CI, 0.00–0.11; I 2 = 72%; P = 0.03); however, there was no difference in the incidence of intraoperative hypotension (RD, 0.01; 95% CI, -0.02 to 0.04; I 2 = 3%; P = 0.45). It is important to note that all studies reported that intraoperative bradycardia was either transient in nature or reversible, when needed, with the administration of intravenous atropine. Conclusions: Dexmedetomidine has the ability to hasten the onset and prolong the duration of blockade when used as an adjuvant to local anes- thesia for brachial plexus blockade. Considering an analgesic effect to be either decreased pain, a longer duration of analgesic block, or decreased opioid consumption, the addition of dexmedetomidine to local anesthetics for brachial plexus blockade was found to significantly improve analgesia in all 18 included studies. However, patients receiving dexmedetomidine should be continuously monitored for the potentially harmful but reversible adverse effect of intraoperative bradycardia. Level of Evidence: Therapeutic, level I. (Reg Anesth Pain Med 2017;42: 184–196) U pper-extremity surgeries are a commonly performed proce- dure in the United States. Most of these surgeries are in the ambulatory setting where pain after surgery and adverse effects of opioid administration remain significant factors in postopera- tive recovery and discharge. Upper-extremity regional anesthetic techniques, using brachial plexus blockade, have been shown to reduce adverse effects related to opioid administration, improve patient satisfaction, and provide significantly improved analgesia immediately following these surgeries. 1 Brachial plexus blockade is typically administered as a single injection or as a continuous peripheral nerve block via a catheter. Continuous peripheral nerve blocks, although effective, have been associated with complications such as pump malfunction, catheter dislodgement, and fluid leakage. 2 Thus, they remain unsuitable in many ambulatory surgical settings. While single injections of local anesthetics are free of these complications, they can suffer from suboptimal duration of analgesia and can negatively impact the postoperative experience. 3 To remedy this shortcoming, vari- ous adjuvant drugs have been used in combination with local an- esthetics to prolong the duration of analgesia. The commonly used adjuvants remain clonidine and dexamethasone; however, each of these has also been found to have its own shortcomings. In comparison to the above, dexmedetomidine has been found to be a more potent and effective adjuvant for brachial plexus blockade. 4,5 Its use has been thought to increase the dura- tion of blockade; however, common adverse effects such as brady- cardia, hypotension, and significant respiratory depression have been reported. 6 The recent increase in use of dexmedetomidine as an adjuvant warrants further investigation into its efficacy and safety in this role. Abdallah and Brull 7 recently conducted a meta-analysis on this topic; however, since that publication, there have been 14 new randomized trials conducted on this popular topic, thus allowing us to gain greater insights into the role of dexme- detomidine as an adjuvant for brachial plexus blockade. Given the continued uncertainty of dexmedetomidine's ability to pro- long the duration of brachial plexus blockade, we undertook this meta-analysis to evaluate current evidence of its efficacy. There- fore, the primary objective of this meta-analysis is to evaluate the effectiveness of dexmedetomidine at prolonging the duration of motor and sensory blockade when used as an adjuvant to local anesthesia for brachial plexus blockade versus using local anes- thesia alone (control) in adult patients (≥18 years old) undergoing upper-limb procedures. In addition, we hope to further explore the adverse events profile of dexmedetomidine to gain greater in- sights into its safety. From the *Central Michigan University College of Medicine, Mt Pleasant; and †University of Michigan College of Literature, Sciences, and the Arts, Ann Ar- bor, MI; ‡Department of Orthopaedics, St Michael's Hospital, Toronto; and §Health Sciences Library, McMaster University, Hamilton, Ontario, Canada; and ||Department of Anesthesia, Montefiore Medical Center, Bronx, NY. Accepted for publication November 21, 2016. Address correspondence to: Nasir Hussain, MD (Cand), MSc, Central Michigan University College of Medicine, CMED Bldg, 1280S E Campus St, Mt Pleasant, MI 48859 (e‐mail: nasir.hussain@cmich.edu). The authors declare no conflict of interest. Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.rapm.org). Copyright © 2017 by American Society of Regional Anesthesia and Pain Medicine ISSN: 1098-7339 DOI: 10.1097/AAP.0000000000000564 REGIONAL ANESTHESIA AND ACUTE PAIN REVIEW ARTICLE 184 Regional Anesthesia and Pain Medicine • Volume 42, Number 2, March-April 2017 Copyright © 2017 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.