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Systemic dexmedetomidine is not as efficient as perineural dexmedetomidine in prolonging an ulnar nerve block
  1. Jakob Hessel Andersen1,
  2. Pia Jaeger2,
  3. Ulrik Grevstad3,
  4. Stine Estrup1,
  5. Anja Geisler1,
  6. Frederik Vilhelmsen1,
  7. Jorgen B Dahl4,
  8. Gunnar Hellmund Laier5,
  9. Brian M Ilfeld6 and
  10. Ole Mathiesen1
  1. 1 Department of Anesthesiology, Zealand University Hospital, Koege, Denmark
  2. 2 Department of Anesthesiology, Rigshospitalet, Kobenhavn, Denmark
  3. 3 Department of Anesthesiology, Gentofte Hospital, Hellerup, Denmark
  4. 4 Department of Anesthesiology, Bispebjerg Hospital, Kobenhavn, Denmark
  5. 5 Production Research and Innovation, Region Zealand, Soroe, Denmark
  6. 6 Division of Regional Anesthesia and Acute Pain Medicine, Department of Anesthesiology, University of California, San Diego, La Jolla, USA
  1. Correspondence to Dr Jakob Hessel Andersen, Department of Anesthesiology, Zealand University Hospital, Køge 4600, Denmark; hessel{at}


Background We tested the joint hypotheses that both perineural and systemic dexmedetomidine prolong the duration of an ulnar nerve block (UNB) compared with ropivacaine alone and that systemic dexmedetomidine is noninferior compared with perineural dexmedetomidine in block prolongation.

Methods We performed bilateral UNBs in 22 healthy volunteers on two separate days. On the first day, each arm was randomized to either 4 mL ropivacaine 5 mg/mL+1 mL dexmedetomidine 100 µg/mL (Perineural) or 4 mL ropivacaine 5 mg/mL+1 mL saline (Systemic). On the subsequent treatment day, each arm was randomized to 1 mL of saline plus 4 mL of ropivacaine at either 7.5 mg/mL(HiRopi) or 5 mg/mL (NoDex). The primary outcome measure was the duration of sensory block assessed by mechanical discrimination.

Results Mean sensory block duration was longer in both the Perineural (14.4 hours, 95% CI 13.1 to 15.6) and Systemic treatments (9.2 hours, 95% CI 8.6 to 9.8) compared with the NoDex treatment (7.1 hours, 95% CI 6.6 to 7.6) (p<0.0001 for both). Systemic dexmedetomidine was inferior (not noninferior) compared with perineural dexmedetomidine, as the 95% CI of the difference (mean difference 5.2 hour, 95% CI 4.2 to 6.1) exceeded the noninferiority limit of 3.6 hour. Onset time did not differ among the groups. The other test modalities demonstrated similar block durations as the primary outcome.

Conclusions Adding dexmedetomidine perineurally to ropivacaine doubles the duration of an UNB. Systemic dexmedetomidine also prolongs the duration of UNB, but has less of an effect compared with the perineural route.

Trial registration number NCT03222323.

  • adjuvants
  • pharmaceutic
  • anesthesia
  • conduction
  • anesthetic
  • local
  • dexmedetomidine
  • nerve block

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  • Funding This trial was supported by the DAnish Society of Anesthesia and Intensive care Medicine (DASAIM) and Region Zealand Research Foundation.

  • Competing interests BMI’s institution has received funding and/or product for his research from Myoscience, Epimed, Ferrosan Medical, Infutronics, Teleflex Medical, SPR Therapeutics, and Heron Therapeutics. The rest of the authors declare no conflicts of interest.

  • Patient consent for publication Not required.

  • Ethics approval The Regional Ethics Committee of Region Zealand, Denmark.

  • Provenance and peer review Not commissioned; externally peer reviewed.