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

<span class="paragraphSection"><strong>Background.</strong> 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.<strong>Methods.</strong> 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.<strong>Results.</strong> We identified 32 trials (2007 patients), and found that dexmedetomidine prolonged sensory block (at least 57%, <span style="font-style:italic;">P</span> < 0.0001), motor block (at least 58%, <span style="font-style:italic;">P</span> < 0.0001), and analgesia (at least 63%, <span style="font-style:italic;">P < </span>0.0001) duration. Dexmedetomidine expedited onset for both sensory (at least 40%, <span style="font-style:italic;">P < </span>0.0001) and motor (at least 39%, <span style="font-style:italic;">P < </span>0.0001) blocks. Dexmedetomidine also reduced postoperative oral morphine consumption by 10.2mg [-15.3, -5.2] (<span style="font-style:italic;">P < </span>0.0001), improved pain control, and enhanced satisfaction. In contrast, dexmedetomidine increased odds of bradycardia (3.3 [0.8, 13.5](<span style="font-style:italic;">P = </span>0.0002)), and hypotension (5.4 [2.7, 11.0] (<span style="font-style:italic;">P < </span>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.<strong>Conclusions.</strong> 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.</span>

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