title: Does the site of injection distal to the greater trochanter make a difference in lateral sciatic nerve blockade?
abstract: The two components of the sciatic nerve become more distant from one another in their course down the lower limb. This may have clinical implications if a small volume of local anesthetic is used with a single injection technique. In this prospective, randomized, double-blind study, we compared two different injection sites, 20 cm and 30 cm distal to the greater trochanter, in terms of onset time and success rate of sciatic nerve blockade after a single injection of 20 mL of 1.5% mepivacaine. Fifty patients undergoing foot surgery were randomly allocated to receive a lateral sciatic nerve blockade using one of 2 levels: 20 cm distal to the greater trochanter (group proximal; n = 25) and 30 cm distal to the greater trochanter (group distal; n = 25). Twenty milliliters of 1.5% mepivacaine was injected after a flexion plantar response was obtained at <0.5 mA. Time required for onset of sensory and motor blockade of the foot was recorded. Success rate was defined as complete sensory and motor blockade in all sciatic nerve distributions associated with a pain-free surgery. Onset of complete sensory and motor blockade was faster in group proximal (12 +/- 7 min and 15 +/- 8 min, respectively) compared with group distal (19 +/- 9 min and 23 +/- 9 min; P < 0.05). Group proximal also had a more frequent success rate compared with group distal (88% versus 56%, respectively; P < 0.05). It is concluded that in lateral sciatic nerve blockade, a more proximal approach to the sciatic nerve predicts a shorter onset time and more frequent success than a more distal injection site when a single injection and a small volume of local anesthetic is used.
  
  
  CONCLUSIONS
  In lateral sciatic nerve blockade, a more proximal approach to the sciatic nerve provides shorter onset times and more frequent success than a more distal injection site when a single injection of 20 mL of mepivacaine 1.5% is used.
authors.affiliation: *Department of Anesthesiology, Hospital Clínico Universitario de Santiago, Spain; and †Department of Anesthesiology, Yale University School of Medicine, New Haven, Connecticut.
authors.forename: Manuel
authors.initials: M
authors.lastname: Taboada
authors.forename: Jaime
authors.initials: J
authors.lastname: Rodríguez
authors.forename: Sabela
authors.initials: S
authors.lastname: Del Rio
authors.forename: Juan
authors.initials: J
authors.lastname: Lagunilla
authors.forename: Javier
authors.initials: J
authors.lastname: Carceller
authors.forename: Julián
authors.initials: J
authors.lastname: Álvarez
authors.forename: Peter G
authors.initials: PG
authors.lastname: Atanassoff
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004311:Double-Blind Method; D005269:Femur; D006801:Humans; D007267:Injections; D008619:Mepivacaine / Q000008:administration & dosage*; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D011446:Prospective Studies; D012584:Sciatic Nerve
chemical_list: D008619:Mepivacaine