title: Withdrawal forces of lumbar spinal catheters: no dependence on body position.
abstract: BACKGROUND
  Spinal catheters, because of their smaller diameter, have lower tensile strength than epidural catheters. This study was designed to measure the withdrawal forces needed to remove lumbar spinal catheters and to determine whether patient position affects withdrawal forces.
  
  
  METHODS
  Eighty-two patients with a 24-gauge spinal catheter placed midline at the lumbar L3/4 or L4/5 level were randomly assigned to catheter removal either in flexed lateral or sitting position. Withdrawal forces were measured using a tension spring balance.
  
  
  RESULTS
  Mean withdrawal force was 0.91 N (95% CI: 0.73, 1.09) with extremes up to 5 N. Withdrawal force in the flexed lateral position was 1.04 N (95% CI: 0.73, 1.34) or in the sitting position was 0.78 N (95% CI: 0.59, 0.97). The 95% CI for the difference of the means was -0.62 N, 0.10 N. Thus, the absolute mean difference between the positions can be assumed to be smaller than 0.62 N. Neither the length of the spinal catheter under the skin or in the subarachnoid space, nor BMI influenced withdrawal force.
  
  
  CONCLUSIONS
  Withdrawal force of spinal catheters is not influenced by body position during catheter removal, length of catheter under skin, or BMI.
authors.affiliation: Department of Special Anaesthesia and Pain Control, Vienna Medical University, General Hospital Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria.
authors.forename: A
authors.initials: A
authors.lastname: Michalek-Sauberer
authors.forename: M J
authors.initials: MJ
authors.lastname: Oehmke
authors.forename: G
authors.initials: G
authors.lastname: Scharbert
authors.forename: K
authors.initials: K
authors.lastname: Neumann
authors.forename: S A
authors.initials: SA
authors.lastname: Kozek-Langenecker
authors.forename: E
authors.initials: E
authors.lastname: Deusch
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000775:Anesthesia, Spinal / Q000295:instrumentation; D002406:Catheterization, Peripheral / Q000295:instrumentation*; D020878:Device Removal; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology; D008297:Male; D008422:Materials Testing / Q000379:methods; D008875:Middle Aged; D011187:Posture; D011446:Prospective Studies; D013129:Spinal Puncture / Q000295:instrumentation*; D013314:Stress, Mechanical