title: The effect of mixing 1.5% mepivacaine and 0.5% bupivacaine on duration of analgesia and latency of block onset in ultrasound-guided interscalene block.
abstract: BACKGROUND
  Short- and long-acting local anesthetics are commonly mixed to achieve nerve blocks with short onset and long duration. However, there is a paucity of data on advantages of such mixtures. We hypothesized that a mixture of mepivacaine and bupivacaine results in a faster onset than does bupivacaine and in a longer duration of blockade than does mepivacaine.
  
  
  METHODS
  Sixty-four patients undergoing arthroscopic shoulder surgery (ages 18 to 65 years; ASA physical status I-II) with ultrasound-guided interscalene brachial plexus block as the sole anesthetic were studied. The subjects were randomized to receive 1 of 3 study solutions: 30 mL of mepivacaine 1.5%, 30 mL of bupivacaine 0.5%, or a mixture of 15 mL each of bupivacaine 0.5% and mepivacaine 1.5%. The block onset time and duration of motor and sensory block were assessed.
  
  
  RESULTS
  Onset of sensory block in the axillary nerve distribution (superior trunk) was similar among the 3 groups (8.7 ± 4.3 minutes for mepivacaine, 10.0 ± 5.1 minutes for bupivacaine, and 11.3 ± 5.3 minutes for the combination group; P = 0.21 between all groups). The duration of motor block for the combination group (11.5 ± 4.7 hours) was between that of the bupivacaine (16.4 ± 9.4 hours) and mepivacaine (6.0 ± 4.2 hours) groups (P = 0.03 between bupivacaine and combination groups; P = 0.01 between mepivacaine and combination groups). Duration of analgesia was the shortest with mepivacaine (4.9 ± 2.4 hours), longest with bupivacaine (14.0 ± 6.2 hours), and intermediate with the combination group (10.3 ± 4.9 hours) (P < 0.001 for mepivacaine vs. combination group; P = 0.01 for bupivacaine vs. combination group).
  
  
  CONCLUSIONS
  For ultrasound-guided interscalene block, a combination of mepivacaine 1.5% and bupivacaine 0.5% results in a block onset similar to either local anesthetic alone. The mean duration of blockade with a mepivacaine-bupivacaine mixture was significantly longer than block with mepivacaine 1.5% alone but significantly shorter than the block with bupivacaine 0.5% alone.
authors.affiliation: St. Luke's-Roosevelt Hospital Center, 1111 Amsterdam Avenue, New York, NY 10025, USA. jeffgadsden@gmail.com
authors.forename: Jeff
authors.initials: J
authors.lastname: Gadsden
authors.forename: Admir
authors.initials: A
authors.lastname: Hadzic
authors.forename: Kishor
authors.initials: K
authors.lastname: Gandhi
authors.forename: Ali
authors.initials: A
authors.lastname: Shariat
authors.forename: Daquan
authors.initials: D
authors.lastname: Xu
authors.forename: Thomas
authors.initials: T
authors.lastname: Maliakal
authors.forename: Vijay
authors.initials: V
authors.lastname: Patel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000698:Analgesia / Q000379:methods*; D019162:Anesthetics, Combined / Q000008:administration & dosage*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D001182:Arthroscopy; D001917:Brachial Plexus / Q000000981:diagnostic imaging / Q000187:drug effects*; D002045:Bupivacaine / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008619:Mepivacaine / Q000008:administration & dosage*; D008875:Middle Aged; D009043:Motor Activity / Q000187:drug effects; D009407:Nerve Block; D009519:New York City; D010149:Postoperative Pain / Q000209:etiology / Q000517:prevention & control; D011930:Reaction Time; D012677:Sensation / Q000187:drug effects; D012782:Shoulder / Q000294:innervation / Q000601:surgery; D013997:Time Factors; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional; D055815:Young Adult
chemical_list: D019162:Anesthetics, Combined; D000779:Anesthetics, Local; D008619:Mepivacaine; D002045:Bupivacaine