Perioperative Medicine  |   January 2017
Does Dexmedetomidine Have a Perineural Mechanism of Action When Used as an Adjuvant to Ropivacaine?: A Paired, Blinded, Randomized Trial in Healthy Volunteers
Author Notes
  • From the Department of Anesthesiology, Zealand University Hospital, Køge, Denmark (J.H.A., O.M.); Department of Anesthesiology, Gentofte Hospital Kildegaardsvej Hellerup, Denmark (U.G.); Department of Anesthesiology, Nykøbing Falster Hospital, Nykøbing Falster, Denmark (H.S.); Department of Anesthesiology, Bispebjerg Hospital, Copenhagen NV, Denmark (J.B.D.); and Department of Anesthesiology, Centre of Head and Orthopedics, Rigshospitalet, Copenhagen East, Denmark (P.J.).
  • Submitted for publication February 25, 2016. Accepted for publication October 4, 2016.
    Submitted for publication February 25, 2016. Accepted for publication October 4, 2016.×
  • Address correspondence to Dr. Andersen: Department of Anesthesiology, University Hospital Zealand, Lykkebækvej 1, 4600 Køge, Denmark. hessel@dadlnet.dk. Information on purchasing reprints may be found at www.anesthesiology.org or on the masthead page at the beginning of this issue. Anesthesiology’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue.
Article Information
Perioperative Medicine / Clinical Science / Pharmacology
Perioperative Medicine   |   January 2017
Does Dexmedetomidine Have a Perineural Mechanism of Action When Used as an Adjuvant to Ropivacaine?: A Paired, Blinded, Randomized Trial in Healthy Volunteers
Anesthesiology 1 2017, Vol.126, 66-73. doi:10.1097/ALN.0000000000001429
Anesthesiology 1 2017, Vol.126, 66-73. doi:10.1097/ALN.0000000000001429
Abstract

Background: Dexmedetomidine used as an adjuvant to local anesthetics may prolong the duration of peripheral nerve blocks. Whether this is mediated by a perineural or systemic mechanism remains unknown. The authors hypothesized that dexmedetomidine has a peripheral mechanism of action.

Methods: The authors conducted a randomized, paired, triple-blind trial in healthy volunteers. All received bilateral saphenous nerve blocks with 20 ml ropivacaine, 0.5%, plus 1 ml dexmedetomidine, 100 µg/ml, in one thigh and 20 ml ropivacaine 0.5% plus 1 ml saline in the other thigh. The primary outcome measure was the duration of block assessed by temperature sensation (alcohol swab). The secondary outcome measure was the duration of block assessed by pinprick, pain during tonic heat stimulation, warmth detection threshold, and heat pain detection threshold.

Results: All 21 enrolled volunteers completed the trial. The mean duration of block assessed by temperature sensation in the leg receiving ropivacaine plus dexmedetomidine was 22 h (95% CI, 21 to 24) compared to 20 h (95% CI, 19 to 21) in the leg receiving ropivacaine plus placebo with a mean difference of 2 h (95% CI, 1 to 3; P = 0.001). The duration of block was also significantly longer in the leg receiving dexmedetomidine when assessed by pinprick, pain during tonic heat stimulation, and warmth detection threshold but not heat pain detection threshold. One participant experienced numbness in an area in the leg receiving dexmedetomidine.

Conclusions: Dexmedetomidine prolongs the duration of a saphenous nerve block by a peripheral mechanism when controlling for systemic effects but not necessarily to a clinically relevant extent.