title: Adductor Canal Block With 10 mL Versus 30 mL Local Anesthetics and Quadriceps Strength: A Paired, Blinded, Randomized Study in Healthy Volunteers.
abstract: OBJECTIVE
  Adductor canal block (ACB) is predominantly a sensory nerve block, but excess volume may spread to the femoral triangle and reduce quadriceps strength. We hypothesized that reducing the local anesthetic volume from 30 to 10 mL may lead to fewer subjects with quadriceps weakness.
  
  
  METHODS
  We performed a paired, blinded, randomized trial including healthy men. All subjects received bilateral ACBs with ropivacaine 0.1%; 10 mL in 1 leg and 30 mL in the other leg. The primary outcome was the difference in number of subjects with quadriceps strength reduced by more than 25% from baseline in 2 consecutive assessments. Secondary outcomes were quadriceps strength as a percentage of baseline at predefined time points, functional outcome assessed by the 30-Second Chair Stand Test (1 leg at a time), and sensory block. Clinicaltrials.gov Identifier: NCT01981746.
  
  
  RESULTS
  We included and analyzed 26 subjects. For either volume, 2 subjects had a reduction in quadriceps strength by more than 25% from baseline (difference, 0%; 95% confidence interval, -13 to 13; P > 0.999). Similarly, we found no significant differences between volumes in quadriceps strength at any of the predefined time points or in sensory block. The only statistically significant difference between volumes was found in the 30-Second Chair Stand Test at 2 hours (P = 0.02), but this difference had disappeared at 4 hours (P = 0.06).
  
  
  CONCLUSIONS
  Varying the volume of ropivacaine 0.1% used for ACB between 10 and 30 mL did not have a statistically significant or clinically relevant impact on quadriceps strength.
authors.affiliation: From the *Department of Anaesthesia, Centre of Head and Orthopaedics, Copenhagen University Hospital, Rigshospitalet; and †Department of Anaesthesia, Bispebjerg and Frederiksberg Hospitals, Copenhagen University Hospital, Copenhagen, Denmark.
authors.forename: Pia
authors.initials: P
authors.lastname: Jæger
authors.forename: Zbigniew J
authors.initials: ZJ
authors.lastname: Koscielniak-Nielsen
authors.forename: Karen Lisa
authors.initials: KL
authors.lastname: Hilsted
authors.forename: Maria Louise
authors.initials: ML
authors.lastname: Fabritius
authors.forename: Jørgen B
authors.initials: JB
authors.lastname: Dahl
mesh_terms: D000328:Adult; D000577:Amides / Q000008:administration & dosage*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D001340:Autonomic Nerve Block / Q000379:methods*; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D053580:Muscle Strength / Q000187:drug effects* / Q000502:physiology; D052097:Quadriceps Muscle / Q000187:drug effects* / Q000502:physiology; D000077212:Ropivacaine; D016037:Single-Blind Method; D055815:Young Adult
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine