title: Less leakage and dislodgement with a catheter-over-needle versus a catheter-through-needle approach for peripheral nerve block: an ex vivo study.
abstract: OBJECTIVE
  The objective of this study was to compare the catheter-through-needle (CTN) and catheter-over-needle (CON) catheterization techniques ex vivo by measuring leak pressure around the catheter and the catheter's resistance to pulling force.
  
  
  METHODS
  Using an ex vivo porcine limb model, we compared the conventional CTN design with the CON design with respect to the ability to resist leakage at the catheter insertion site under high injection pressure and the force required to withdraw the catheter from tissue. One CON assembly (MultiSet, Pajunk) and three CTN assemblies (Contiplex, B.Braun; StimuCath, Arrow; Stimulong Sono, Pajunk) were studied. Ten porcine hind limbs were used to test leakage and another ten were used to measure withdrawal force. Catheters were placed at angles of 15° and 30° at depths of 3 cm and 5 cm. Leakage was assessed visually at the insertion site, and pressure was measured at the moment leakage occurred. Withdrawal force was measured by pulling the catheter from the tissue.
  
  
  RESULTS
  No evidence of leakage was detected at the CON catheter insertion site at the highest pressure applied (1,000 mmHg) (n = 40). The CON assembly withstood significantly higher injection pressure than the CTN catheters without causing leaks at the catheter insertion site [CON, mean (standard deviation) > 1,000 (0) mmHg; B.Braun, 596 (92) mmHg; Pajunk Stimulong, 615 (107) mmHg; and Arrow, 422 (104) mmHg; P < 0.001 CON vs CTN]. The force required to withdraw the catheter from the porcine limb was greater with CON catheters [3.8 (0.8) N] than with any of the CTN catheters [range, 0.4 (0.2) - 0.8 (0.2) N], depending on depth, angle, and manufacturer (P < 0.001 CON vs CTN).
  
  
  CONCLUSIONS
  In the porcine leg model, CON catheterization provides greater resistance to leakage under high injection pressure and greater holding force in tissue than traditional CTN catheters.
authors.affiliation: Department of Anesthesiology and Pain Medicine, University of Alberta, Edmonton, Canada. btsui@ualberta.ca
authors.forename: Ban C H
authors.initials: BC
authors.lastname: Tsui
authors.forename: Jenkin
authors.initials: J
authors.lastname: Tsui
mesh_terms: D000818:Animals; D002404:Catheterization / Q000379:methods*; D020878:Device Removal; D004867:Equipment Design; D006614:Hindlimb; D009339:Needles; D009407:Nerve Block / Q000379:methods*; D011312:Pressure; D013552:Swine