title: Evidence basis for using perineural dexmedetomidine to enhance the quality of brachial plexus nerve blocks: a systematic review and meta-analysis of randomized controlled trials.
abstract: BACKGROUND
  Dexmedetomidine has been proposed as a perineural local anaesthetic (LA) adjunct to prolong peripheral nerve block duration; however, results from our previous meta-analysis in the setting of brachial plexus block (BPB) did not support its use. Many additional randomized trials have since been published. We thus conducted an updated meta-analysis.
  
  
  METHODS
  Randomized trials investigating the addition of dexmedetomidine to LA compared with LA alone (Control) in BPB for upper extremity surgery were sought. Sensory and motor block duration, onset times, duration of analgesia, analgesic consumption, pain severity, patient satisfaction, and dexmedetomidine-related side-effects were analysed using random-effects modeling. We used ratio-of-means (lower confidence interval [point estimate]) for continuous outcomes.
  
  
  RESULTS
  We identified 32 trials (2007 patients), and found that dexmedetomidine prolonged sensory block (at least 57%, P < 0.0001), motor block (at least 58%, P < 0.0001), and analgesia (at least 63%, P < 0.0001) duration. Dexmedetomidine expedited onset for both sensory (at least 40%, P < 0.0001) and motor (at least 39%, P < 0.0001) blocks. Dexmedetomidine also reduced postoperative oral morphine consumption by 10.2mg [-15.3, -5.2] (P < 0.0001), improved pain control, and enhanced satisfaction. In contrast, dexmedetomidine increased odds of bradycardia (3.3 [0.8, 13.5](P = 0.0002)), and hypotension (5.4 [2.7, 11.0] (P < 0.0001)). A 50-60µg dexmedetomidine dose maximized sensory block duration while minimizing haemodynamic side-effects. No patients experienced any neurologic sequelae. Evidence quality for sensory block was high according to the GRADE system.
  
  
  CONCLUSIONS
  New evidence now indicates that perineural dexmedetomidine improves BPB onset, quality, and analgesia. However, these benefits should be weighed against increased risks of motor block prolongation and transient bradycardia and hypotension.
authors.affiliation: Department of Anaesthesia, University of Toronto, Toronto, Canada.|Department of Anaesthesia, St. Michael's Hospital, University of Toronto, Toronto, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Vorobeichik
authors.affiliation: Department of Anaesthesia, University of Toronto, Toronto, Canada.|Department of Anaesthesia, Women's College Hospital, Toronto, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Brull
authors.affiliation: Department of Anaesthesia, University of Toronto, Toronto, Canada abdallahf@smh.ca.|Department of Anaesthesia, St. Michael's Hospital, University of Toronto, Toronto, Canada.|The Li Ka Shing Knowledge Institute, University of Toronto, Toronto, Canada.
authors.forename: F W
authors.initials: FW
authors.lastname: Abdallah
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage; D065527:Brachial Plexus Block / Q000379:methods*; D020927:Dexmedetomidine / Q000009:adverse effects / Q000494:pharmacology*; D006801:Humans; D016032:Randomized Controlled Trials as Topic
chemical_list: D000779:Anesthetics, Local; D020927:Dexmedetomidine
keywords: adjunct; adjuvant; axillary; brachial plexus block; infraclavicular; interscalene; nerve block; perineural dexmedetomidine; regional anaesthesia; sensory block; supraclavicular