title: Risk evaluation for needle-nerve contact related to electrical nerve stimulation in a porcine model.
abstract: BACKGROUND
  For performing peripheral nerve blocks, the risk for needle-nerve contact (NNC) as an adverse event for low and high current thresholds has not yet been clearly defined when nerve stimulator guided techniques were applied. This experimental study aimed to investigate the risk of NNCs when applying stimulation currents between 0.1 and 2 mA (in increments of 0.1 mA).
  
  
  METHODS
  Brachial plexus nerves were exposed surgically in five anesthetized pigs. An insulated needle connected to a nerve stimulator was placed at 10 mm distance to the targeted nerves. Current intensity was adjusted according to randomization (0.1-2.0 mA, increments of 0.1 mA). The needle tip was advanced toward the nerve until a motor response was elicited. The frequencies of NNCs for each of the adjusted current intensities were noted. Risks of NNCs were calculated according to the analysis of 95% confidence intervals (95% CI).
  
  
  RESULTS
  We executed 2000 needle placements with stimulation currents ranging from 0.1 to 2.0 mA. The risks for NNC at low current intensities were 0.85 (95% CI, 0.77-0.91) for 0.3 mA and 0.5 (95% CI, 0.4-0.6) for 0.5 mA, respectively. For high current intensities, risks of 0.13 (95% CI, 0.07-0.21) for 0.9 mA and 0.01 (95% CI, 0-0.05) for 1.1 mA were calculated.
  
  
  CONCLUSIONS
  In this experimental animal study, a relevant reduction in the risk of NNCs could be observed when high current intensities (0.9-1.1 mA) were applied compared to low current intensities (0.3-0.5 mA).
authors.affiliation: Department of Anaesthesiology and Critical Care, University Hospital Gießen-Marburg, Philipps-University Marburg, Marburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Vassiliou
authors.affiliation: Institute of Medical Biometry and Epidemiology, Philipps-University Marburg, Marburg, Germany.
authors.forename: H-H
authors.initials: HH
authors.lastname: Müller
authors.affiliation: Department of Anaesthesiology and Critical Care, University Hospital Gießen-Marburg, Philipps-University Marburg, Marburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Limberg
authors.affiliation: Department of Anaesthesiology and Critical Care, University General Hospital Valencia, Valencia, Spain.
authors.forename: J
authors.initials: J
authors.lastname: De Andres
authors.affiliation: Department of Anaesthesiology and Critical Care, University Hospital Gießen-Marburg, Philipps-University Marburg, Marburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Steinfeldt
authors.affiliation: Department of Anaesthesiology and Critical Care, University Hospital Gießen-Marburg, Philipps-University Marburg, Marburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Wiesmann
mesh_terms: D000818:Animals; D001917:Brachial Plexus / Q000502:physiology*; D004558:Electric Stimulation; D005260:Female; D009339:Needles; D009407:Nerve Block / Q000009:adverse effects*; D012306:Risk; D013552:Swine