title: The Shamrock lumbar plexus block: A dose-finding study.
abstract: BACKGROUND
  The Shamrock technique is a new method for ultrasound-guided lumbar plexus blockade. Data on the optimal local anaesthetic dose are not available.
  
  
  OBJECTIVE
  The objective of this study is to estimate the effective dose of ropivacaine 0.5% for a Shamrock lumbar plexus block.
  
  
  METHODS
  A prospective dose-finding study using Dixon's up-and-down sequential method.
  
  
  METHODS
  University Hospital Orthopaedic Anaesthesia Unit.
  
  
  METHODS
  Shamrock lumbar plexus block performance and block assessment were scheduled preoperatively. Ropivacaine 0.5% was titrated with the Dixon and Massey up-and-down method using a stepwise change of 5 ml in each consecutive patient. Combined blocks of the femoral, the lateral femoral cutaneous and the obturator nerve were prerequisite for a successful lumbar plexus block.
  
  
  METHODS
  Thirty patients scheduled for lower limb orthopaedic surgery completed the study.
  
  
  METHODS
  The minimum effective anaesthetic volume of ropivacaine 0.5% (ED50) to achieve a successful Shamrock lumbar plexus block in 50% of the patients. Further analysis of the data was performed with a logistic regression model to calculate ED95 and to estimate the effective doses for a sensory lumbar plexus block not requiring a motor block of the femoral nerve.
  
  
  RESULTS
  The Dixon and Massay estimate of the ED50 was 20.4 [95% confidence interval (95% CI) 13.9 to 30.0] ml ropivacaine 0.5%. The logistic regression estimate of the ED95 was 36.0 (95% CI 19.7 to 52.2) ml ropivacaine 0.5%. For a sensory lumbar plexus block, the ED50 was 17.1 (95% CI 12.3 to 21.9) ml and the ED95 was 25.8 (95% CI 18.6 to 33.1) ml.
  
  
  CONCLUSIONS
  A volume of 20.4 ml ropivacaine 0.5% provided a successful Shamrock lumbar plexus block in 50% of the patients. A volume of 36.0 ml would be successful in 95% of the patients.
  
  
  BACKGROUND
  ClinicalTrials.gov identifier NCT01956617.
authors.affiliation: From the Division of Emergencies and Critical Care, Department of Anaesthesiology, Oslo University Hospital Rikshospitalet (ARS, KU, GN, LR), Department of Anaesthesiology, Lovisenberg Diakonale Hospital, Oslo, Norway (HTL), Department of Anaesthesia and Intensive Care Medicine, Aarhus University Hospital, Aarhus (TFB), Department of Anaesthesia and Intensive Care Medicine, Roskilde Hospital, University of Copenhagen, Copenhagen, Denmark (JB), and Oslo Centre for Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway (AHP).
authors.forename: Axel R
authors.initials: AR
authors.lastname: Sauter
authors.forename: Kyrre
authors.initials: K
authors.lastname: Ullensvang
authors.forename: Geir
authors.initials: G
authors.lastname: Niemi
authors.forename: Håvard T
authors.initials: HT
authors.lastname: Lorentzen
authors.forename: Thomas Fichtner
authors.initials: TF
authors.lastname: Bendtsen
authors.forename: Jens
authors.initials: J
authors.lastname: Børglum
authors.forename: Are Hugo
authors.initials: AH
authors.lastname: Pripp
authors.forename: Luis
authors.initials: L
authors.lastname: Romundstad
mesh_terms: D000328:Adult; D000368:Aged; D000577:Amides / Q000008:administration & dosage*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006785:Hospitals, University; D006801:Humans; D016015:Logistic Models; D035002:Lower Extremity / Q000601:surgery; D008160:Lumbosacral Plexus; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D019637:Orthopedic Procedures / Q000379:methods*; D000077212:Ropivacaine
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine