title: Determination of the EC50 of levobupivacaine for femoral and sciatic perineural infusion after total knee arthroplasty.
abstract: BACKGROUND
  Infusion of local anaesthetic through femoral and sciatic catheters is an accepted method of providing pain relief after knee arthroplasty. However, the minimum effective concentration of perineural local anaesthetics is not known.
  
  
  METHODS
  Twenty-four patients received femoral and sciatic perineural infusions of levobupivacaine in order to prevent pain relief after total knee arthroplasty. The primary endpoint of the study was patient request for analgesic rescue for anterior or posterior knee pain within the first 36 h of perineural infusion. Treatment was determined by the method of sequential allocation, with a dosing interval of 0.002% w/v.
  
  
  RESULTS
  Thirteen patients did not require rescue analgesia for anterior knee pain and 16 patients did not require rescue analgesia for posterior knee pain. Median duration of failed blocks until rescue analgesia was 25 h (24-27 h) for the femoral block and 27 h (24-29 h) for the sciatic block. The minimum concentration at which patients did not require rescue analgesia was 0.024% for the femoral nerve and 0.014% for the sciatic nerve. Comparison of EC(50) showed that local anaesthetic requirements were significantly (P=0.03) higher by a factor of 1.25 (95% CI 1.03-1.55) for the femoral compared with the sciatic nerve.
  
  
  CONCLUSIONS
  The EC(50) for femoral perineural infusion is greater than the EC(50) for sciatic perineural infusion.
authors.affiliation: University Department of Anaesthesia, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK. g.a.mcleod@dundee.ac.uk
authors.forename: G A
authors.initials: GA
authors.lastname: McLeod
authors.forename: J
authors.initials: J
authors.lastname: Dale
authors.forename: D
authors.initials: D
authors.lastname: Robinson
authors.forename: M
authors.initials: M
authors.lastname: Checketts
authors.forename: M O
authors.initials: MO
authors.lastname: Columb
authors.forename: J
authors.initials: J
authors.lastname: Luck
authors.forename: C
authors.initials: C
authors.lastname: Wigderowitz
authors.forename: D
authors.initials: D
authors.lastname: Rowley
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000779:Anesthetics, Local / Q000008:administration & dosage*; D019645:Arthroplasty, Replacement, Knee; D002045:Bupivacaine / Q000008:administration & dosage / Q000031:analogs & derivatives; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005267:Femoral Nerve; D006801:Humans; D007719:Knee Joint / Q000503:physiopathology; D000077554:Levobupivacaine; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods; D010147:Pain Measurement / Q000379:methods; D010149:Postoperative Pain / Q000517:prevention & control*; D016059:Range of Motion, Articular / Q000187:drug effects; D012584:Sciatic Nerve
chemical_list: D000779:Anesthetics, Local; D000077554:Levobupivacaine; D002045:Bupivacaine