title: Does dexamethasone have a perineural mechanism of action? A paired, blinded, randomized, controlled study in healthy volunteers.
abstract: BACKGROUND
  Dexamethasone prolongs block duration. Whether this is achieved via a peripheral or a central mechanism of action is unknown. We hypothesized that perineural dexamethasone added as an adjuvant to ropivacaine prolongs block duration compared with ropivacaine alone, by a locally mediated effect when controlled for a systemic action.
  
  
  METHODS
  We performed a paired, blinded, randomized trial, including healthy men. All subjects received bilateral blocks of the saphenous nerve with ropivacaine 0.5%, 20 ml mixed with dexamethasone 2 mg in one leg and saline in the other, according to randomization. The primary outcome was the duration of sensory block assessed by temperature discrimination in the saphenous nerve distribution. Secondary outcomes were sensory block assessed by mechanical discrimination, pain response to tonic heat stimulation, and warmth and heat pain detection thresholds.
  
  
  RESULTS
  We included 20 subjects; one had a failed block and was excluded from the paired analysis. Block duration was not statistically significantly longer in the leg receiving dexamethasone when assessed by temperature discrimination (primary outcome, estimated median difference 1.5 h, 95% confidence interval -3.5 to 0, P=0.050). For all other outcomes, the duration was statistically significantly longer in the leg receiving dexamethasone, but the median differences were <2.0 h. Individual subject analysis revealed that only eight subjects had a block prolongation of at least 2 h in the leg receiving dexamethasone perineurally.
  
  
  CONCLUSIONS
  Perineural administration of dexamethasone 2 mg showed a modest and inconsistent effect of questionable clinical relevance on block duration.
  
  
  BACKGROUND
  NCT01981746.
authors: Department of Anaesthesia, Centre of Head and Orthopaedics, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark pia.therese.jaeger@regionh.dk.
authors: P
authors: P
authors: Jæger
authors: Department of Anaesthesia, Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors: U
authors: U
authors: Grevstad
authors: Department of Anaesthesia, Centre of Head and Orthopaedics, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark.
authors: Z J
authors: ZJ
authors: Koscielniak-Nielsen
authors: Department of Research and Development, Division of Emergencies and Critical Care, Oslo University Hospital, Oslo, Norway.|Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
authors: A R
authors: AR
authors: Sauter
authors: Department of Anaesthesia, Gentofte Hospital, University of Copenhagen, Copenhagen, Denmark.
authors: J K
authors: JK
authors: Sørensen
authors: Department of Anaesthesia, Bispebjerg and Frederiksberg Hospitals, University of Copenhagen, Copenhagen, Denmark.
authors: J B
authors: JB
authors: Dahl
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage; D000779:Anesthetics, Local / Q000008:administration & dosage; D003907:Dexamethasone / Q000494:pharmacology*; D004359:Drug Therapy, Combination / Q000379:methods; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D007866:Leg / Q000294:innervation*; D008297:Male; D009407:Nerve Block / Q000379:methods*; D010146:Pain / Q000188:drug therapy*; D012016:Reference Values; D000077212:Ropivacaine; D016037:Single-Blind Method; D013997:Time Factors; D055815:Young Adult
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D005938:Glucocorticoids; D000077212:Ropivacaine; D003907:Dexamethasone
keywords: anaesthetics; dexamethasone; local; lower extremity; nerve block