• Maya Keplinger, Peter Marhofer, Stephan C Kettner, Daniela Marhofer, Oliver Kimberger, and Markus Zeitlinger.
• From the Department of Anaesthesia, Intensive Care Medicine and Pain Therapy (MK, PM, SCK, DM, OK), and Department of Clinical Pharmacology (MK, MZ), Medical University of Vienna, Vienna, Austria.
• Eur J Anaesthesiol. 2015 Nov 1; 32 (11): 790-6.

BackgroundPrevious data have indicated the efficacy of dexmedetomidine as an additive to peripheral regional anaesthesia. There are no pharmacodynamic data regarding the addition of dexmedetomidine to local anaesthetics for perineural administration.ObjectiveThe objective of this study is to assess the dose-dependency of dexmedetomidine when injected with ropivacaine for peripheral nerve blockade.DesignA randomised, triple-blind, controlled study in volunteers.SettingDepartment of Clinical Pharmacology, Medical University of Vienna.ParticipantsTwenty-four volunteers.InterventionsAll volunteers received an ulnar nerve block with 22.5 mg ropivacaine alone (R), or mixed with 50 (RD50), 100 (RD100) or 150 μg (RD150) dexmedetomidine.Main Outcome MeasuresThe primary outcome was the duration of complete sensory block to pinprick and time to complete recovery of pinprick. Secondary outcomes included block success and onset time, motor block, haemodynamic parameters and sedation level.ResultsThere was a significant dose-dependent (P < 0.0001) increase in the mean duration (SD) of sensory block with dexmedetomidine: R: 8.7 (1.5) h, RD50: 16.4 (4.0) h, RD100: 20.4 (2.8) h and group RD150: 21.2 (1.7) h. Sedation was also enhanced in a dose-dependent (P < 0.001) manner. Two volunteers each receiving 150 μg dexmedetomidine had postblock paraesthesia for 72 h.ConclusionDexmedetomidine mixed with ropivacaine produces a dose-dependent prolongation of sensory block and clinically relevant dose-dependent sedation. Dexmedetomidine 100 μg may represent a balance between efficacy and sedation.

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