title: Triple-blind randomized clinical trial of time until sensory change using 1.5% mepivacaine with epinephrine, 0.5% bupivacaine, or an equal mixture of both for infraclavicular block.
abstract: OBJECTIVE
  Practitioners mix faster-onset, intermediate-duration local anesthetics (LAs) with slower-onset, long-duration LAs to get fast peripheral nerve block (PNB) onset and long duration. We hypothesized that 1.5% mepivacaine (with epinephrine) (mepivacaine) or 1.5% mepivacaine (with epinephrine) mixed with 0.5% bupivacaine (mixed) would reduce PNB sensory onset by 20% or more versus 0.5% bupivacaine alone (bupivacaine).
  
  
  METHODS
  Patients (n = 93) having arm surgery were randomized to 1 of the 3 LA groups. Infraclavicular PNB was administered using 1 of 3 LAs; afterward, PNB sensory (motor) onset, duration, and other outcomes were assessed. Subjects, physicians, and the biostatistician were blinded until study completion.
  
  
  RESULTS
  Median (interquartile range) PNB sensory onset (in minutes) was as follows: mepivacaine, 3 (3-6); mixed, 6 (3-6); and bupivacaine, 6 (3-12) (P = 0.0085). Mepivacaine PNB sensory onset was not faster than mixed (P = 0.57), but mixed was faster than bupivacaine (P = 0.0035). More mixed group patients achieved PNB sensory onset (0.81) versus the bupivacaine group (0.54) at 6 mins. Median (interquartile range) PNB motor onset (in minutes) was as follows: mepivacaine, 15 (12-18); mixed, 17 (12-21); and bupivacaine, 21 (12-24) (P < 0.0001). Median sensory and motor PNB duration (in minutes) was as follows: mepivacaine, 281 and 320; mixed, 439 and 556; and bupivacaine, 850 and 1109. Sensory (motor) PNB duration was shorter with mepivacaine versus mixed (P < 0.0001, P = 0.034), and mixed was shorter versus bupivacaine (P = 0.0243, P = 0.034).
  
  
  CONCLUSIONS
  Mixing 1.5% mepivacaine (with epinephrine) with 0.5% bupivacaine speeds up PNB sensory (motor) onset compared with 0.5% bupivacaine alone.
authors.affiliation: Department of Anesthesia, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA 52242, USA. john-laur@uiowa.edu
authors.forename: John J
authors.initials: JJ
authors.lastname: Laur
authors.forename: Emine Ozgur
authors.initials: EO
authors.lastname: Bayman
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Foldes
authors.forename: Richard W
authors.initials: RW
authors.lastname: Rosenquist
mesh_terms: D000322:Adrenergic Agonists / Q000008:administration & dosage*; D000328:Adult; D019162:Anesthetics, Combined / Q000008:administration & dosage*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D002045:Bupivacaine / Q000008:administration & dosage*; D016009:Chi-Square Distribution; D004311:Double-Blind Method; D004837:Epinephrine / Q000008:administration & dosage*; D006801:Humans; D007484:Iowa; D053208:Kaplan-Meier Estimate; D008619:Mepivacaine / Q000008:administration & dosage*; D008875:Middle Aged; D009043:Motor Activity / Q000187:drug effects; D009407:Nerve Block / Q000379:methods*; D012684:Sensory Thresholds / Q000187:drug effects*; D013997:Time Factors; D034941:Upper Extremity / Q000294:innervation* / Q000601:surgery
chemical_list: D000322:Adrenergic Agonists; D019162:Anesthetics, Combined; D000779:Anesthetics, Local; D008619:Mepivacaine; D002045:Bupivacaine; D004837:Epinephrine