title: Tensile strength decreases and perfusion pressure of 3-holed polyamide epidural catheters increases in long-term epidural infusion.
abstract: OBJECTIVE
  Epidural analgesia is an established method for pain management. The failure rate is 8% to 12% due to technical difficulties (catheter dislocation and/or disconnection; partial or total catheter occlusion) and management. The mechanical properties of the catheters, like tensile strength and flow rate, may also be affected by the analgesic solution and/or the tissue environment.
  
  
  METHODS
  We investigated the tensile strength and perfusion pressure of new (n=20), perioperatively (n=30), and postoperatively (n=73) used epidural catheters (20-gauge, polyamide, closed tip, 3 side holes; Perifix [B. Braun]). To prevent dislocation, epidural catheters were taped (n=5) or fixed by suture (n=68) to the skin. After removal, mechanical properties were assessed by a tensile-testing machine (INSTRON 4500), and perfusion pressure was measured at flow rates of 10, 20, and 40 mL/h.
  
  
  RESULTS
  All catheters demonstrated a 2-step force transmission. Initially, a minimal increase of length could be observed at 15 N followed by an elongation of several cm at additional forces (7 N). Breakage occurred in the control group at 23.5±1.5 N compared with 22.4±1.6 N in perioperative and 22.4±1.7 N in postoperative catheters (P<0.05). Duration of catheter use had no effect on tensile strength, whereas perfusion pressure at clinically used flow rates (10 mL/h) increased significantly from 19±1.3 to 44±72 mm Hg during long-term (≥7 days) epidural analgesia (P<0.05, analysis of variance). Fixation by suture had no influence on tensile strength or perfusion pressure.
  
  
  CONCLUSIONS
  Epidural catheter use significantly increases the perfusion pressure and decreases the tensile strength.
authors.affiliation: Department of Anesthesiology and Operative Intensive Care, Kantonsspital Lucerne, Switzerland. pascal.kim@ksl.ch
authors.forename: Pascal
authors.initials: P
authors.lastname: Kim
authors.forename: Urs
authors.initials: U
authors.lastname: Meyer
authors.forename: Guido
authors.initials: G
authors.lastname: Schüpfer
authors.forename: Roman
authors.initials: R
authors.lastname: Rukwied
authors.forename: Christoph
authors.initials: C
authors.lastname: Konrad
authors.forename: Helmut
authors.initials: H
authors.lastname: Gerber
mesh_terms: D015360:Analgesia, Epidural / Q000379:methods* / Q000592:standards*; D002404:Catheterization / Q000592:standards; D002408:Catheters, Indwelling / Q000592:standards*; D006801:Humans; D007268:Injections, Epidural / Q000592:standards; D009757:Nylons / Q000592:standards*; D010477:Perfusion / Q000379:methods / Q000592:standards*; D011312:Pressure; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D009757:Nylons