title: A randomized, observer-blinded determination of the median effective volume of local anesthetic required to anesthetize the sciatic nerve in the popliteal fossa for stimulating and nonstimulating perineural catheters.
abstract: OBJECTIVE
  Stimulating perineural catheters are developed to overcome technical problems of nonstimulating catheters, but their efficacy remains controversial. However, no volume-response study has compared success rates between stimulating and nonstimulating catheters. This study of stimulating versus nonstimulating catheters compares the minimal effective volume required to successfully block the sciatic nerve in 50% of patients scheduled for unilateral hallux valgus repair.
  
  
  METHODS
  Patients underwent unilateral sciatic nerve block in the popliteal fossa with mepivacaine 1.5%, using either a stimulating (STIM group) or a nonstimulating (NONSTIM group) popliteal catheter. The volume of mepivacaine started at 20 mL and was increased or decreased by increments of 2 mL in subsequent patients, depending on the efficacy of the block in the previous patient, using the technique of up-down sequential allocation described by Dixon (Neurosci Biobehav Rev. 1991;15:47-50). Minimum effective volumes of local anesthetic were calculated using the formula of Dixon. Efficacy of block was defined by a complete sensory-motor block in the cutaneous distributions of the sciatic nerve associated with a pain-free surgery.
  
  
  RESULTS
  Twenty-four patients were included in each group. Median effective volume blocking the sciatic nerve was significantly lower (P < 0.05) in the STIM group (2.7 mL; 95% confidence interval, 0.5-4.9 mL) compared with the NONSTIM group (16.6 mL; 95% confidence interval, 15.2-18.0 mL).
  
  
  CONCLUSIONS
  Stimulating popliteal catheters dramatically decrease the volume required to block the sciatic nerve in 50% of patients, compared with nonstimulating catheters.
authors: Department of Anesthesiology and Intensive Care, Centre Clinical, 2 chemin de Frégeneuil, Soyaux 16800, France. xavier.paqueron@orange.fr
authors: Xavier
authors: X
authors: Paqueron
authors: Patrick
authors: P
authors: Narchi
authors: Jean-Xavier
authors: JX
authors: Mazoit
authors: François
authors: F
authors: Singelyn
authors: Alain
authors: A
authors: Bénichou
authors: Philippe
authors: P
authors: Macaire
mesh_terms: D000779:Anesthetics, Local / Q000008:administration & dosage*; D002406:Catheterization, Peripheral / Q000295:instrumentation / Q000379:methods; D002408:Catheters, Indwelling; D005260:Female; D006215:Hallux Valgus / Q000601:surgery; D006801:Humans; D008297:Male; D008619:Mepivacaine / Q000008:administration & dosage*; D008875:Middle Aged; D009407:Nerve Block / Q000295:instrumentation / Q000379:methods*; D012584:Sciatic Nerve / Q000502:physiology*
chemical_list: D000779:Anesthetics, Local; D008619:Mepivacaine