title: Ultrasound guidance for difficult peripheral venous access: systematic review and meta-analysis.
abstract: BACKGROUND
  Establishing intravenous access is often vital in an acute hospital setting but can be difficult. Ultrasound-guided cannulation increases success rates in prospective studies. However, these studies have often lacked a comparative group. This systematic review and meta-analysis aimed to determine the clinical effectiveness of Ultrasound-guided peripheral intravenous cannulation compared with the standard technique in patients known to have difficult access.
  
  
  METHODS
  Electronic abstract databases, trial registries, article reference lists and internet repositories were searched using the following search terms: 'peripheral venous cannulation', 'peripheral venous access'. Studies meeting the following criteria were included: randomised controlled trial patients of all ages who required peripheral intravenous access; interventions were Ultrasound-guided versus standard cannulation technique; patients were identified as having difficult venous access; inclusion of at least one defined outcome (procedural success time to cannula placement; number of attempts).
  
  
  RESULTS
  7 trials were identified (289 participants). Ultrasound guidance increases the likelihood of successful cannulation (pooled OR 2.42; 95% CI 1.26 to 4.68; p=0.008). There were no differences in time to successful cannulation, or number of percutaneous skin punctures.
  
  
  CONCLUSIONS
  Ultrasound guidance increases the likelihood of successful peripheral cannulation in difficult access patients. We recommend its use in patients who have difficult venous access, and have failed venous cannulation by standard methods. Further randomised controlled trials (RCTs) with larger sample sizes would be of benefit to investigate if Ultrasound has any additional advantages in terms of reducing the procedure time and the number of skin punctures required for successful venous cannulation.
authors.affiliation: Vascular Research Unit, University Hospital Limerick, Limerick, Ireland.
authors.forename: Grace
authors.initials: G
authors.lastname: Egan
authors.forename: Donagh
authors.initials: D
authors.lastname: Healy
authors.forename: Heidi
authors.initials: H
authors.lastname: O'Neill
authors.forename: Mary
authors.initials: M
authors.lastname: Clarke-Moloney
authors.forename: Pierce A
authors.initials: PA
authors.lastname: Grace
authors.forename: Stewart R
authors.initials: SR
authors.lastname: Walsh
mesh_terms: D002405:Catheterization, Central Venous; D002406:Catheterization, Peripheral / Q000379:methods*; D004636:Emergency Service, Hospital; D006801:Humans; D011677:Punctures / Q000706:statistics & numerical data*; D016032:Randomized Controlled Trials as Topic; D015203:Reproducibility of Results; D013997:Time Factors; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional / Q000379:methods*