title: Evidence basis for ultrasound-guided block characteristics: onset, quality, and duration.
abstract: OBJECTIVE
  This systematic review summarizes existing evidence for superior onset, quality, and duration of block for ultrasound (US) guidance versus other techniques for nerve localization.
  
  
  METHODS
  MEDLINE was systematically searched from 1966 to September 2009 for randomized controlled trials (RCTs) comparing US guidance to another technique for peripheral nerve blocks.
  
  
  RESULTS
  Sixteen RCTs were identified for upper-extremity peripheral nerve blocks and 8 for lower extremity. Jadad scores for quality of RCT ranged from 1 to 5, with a median of 2. For upper-extremity blocks, 9 (60%) of 15 RCTs reported faster onset of block, 4 (25%) of 16 reported better quality of block, and 1 (17%) of 6 reported longer duration of block with US. Only 1 RCT reported that US was inferior in any outcome. For lower-extremity blocks, 5 (71%) of 7 RCTs reported faster onset, 5 (63%) of 8 reported better quality, and none of 3 RCTs reported longer duration of blocks. No RCTs reported that US was inferior in any outcome.
  
  
  CONCLUSIONS
  There is level 1b evidence to make a grade A recommendation that US guidance provides a modest improvement in block onset and quality of peripheral nerve blocks. Ultrasound is rarely inferior to other techniques.
authors.affiliation: Departments of Anesthesiology, Hospital for Special Surgery, Weill College of Medicine of Cornell University, New York, NY 10021, USA. liusp@hss.edu
authors.forename: Spencer S
authors.initials: SS
authors.lastname: Liu
authors.forename: Justin
authors.initials: J
authors.lastname: Ngeow
authors.forename: Raymond S
authors.initials: RS
authors.lastname: John
mesh_terms: D019317:Evidence-Based Medicine; D006801:Humans; D009407:Nerve Block / Q000295:instrumentation / Q000592:standards*; D016032:Randomized Controlled Trials as Topic; D013997:Time Factors; D004561:Transcutaneous Electric Nerve Stimulation; D018084:Ultrasonography, Interventional