title: Novel pulsatile cerebrospinal fluid model to assess pressure manometry and fluid sampling through spinal needles of different gauge: support for the use of a 22 G spinal needle with a tapered 27 G pencil-point tip.
abstract: BACKGROUND
  Parallel-walled spinal needles ≤ 22 G are routinely used for lumbar puncture, despite a reported ≥ 32% incidence of post-dural puncture headache. A tapered spinal needle (22 G shaft, 27 G tip) is in use in our institution. We hypothesized that despite the smaller dural puncture hole, this needle has similar cerebrospinal fluid (CSF) pressure equilibration times and CSF sampling times to a standard 22 G needle and assessed a range of spinal needles using an experimental pulsatile CSF reservoir.
  
  
  METHODS
  The pulsatile CSF reservoir had an oscillating pressure varying between 25 and 15 cm H(2)O at a cycle frequency of 80 s(-1). We tested seven parallel-walled spinal needles (18-27 G) and the tapered 22/27 G needle. CSF pressure was measured every 2 s by manometry. The time to collect 1 ml CSF samples was measured. Saline 0.9% and mannitol 20% were tested separately. One-way ANOVA with Bonferroni post-hoc test was used to compare 22G, 27G and 22/27G needles.
  
  
  RESULTS
  The mean [standard deviation (sd)] CSF pressure equilibration time (saline) was 40.7 (6.4), 108.7 (6.1), and 51.3 (4.6) s for the 22, 27, and 22/27 G needles (P< 0.0001 for comparisons between 27 G and other needles). The mean (sd) CSF sampling time (saline) was 40.3 (3.1), 225.3 (10.0), and 63.0 (5.2) s for the 22, 27, and 22/27 G needles (P< 0.0001 for comparisons between 27 G and other needles, and P= 0.019 between 22 and 22/27 G needles). Saline was different from mannitol for both measurements and all needles (P< 0.0001).
  
  
  CONCLUSIONS
  A 22/27 G tapered spinal needle has similar flow properties to the 22 G needle, despite a 27 G tip.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Hadassah Hebrew University Medical Center, Jerusalem, Israel. yginosar@netvision.net.il
authors.forename: Y
authors.initials: Y
authors.lastname: Ginosar
authors.forename: Y
authors.initials: Y
authors.lastname: Smith
authors.forename: T
authors.initials: T
authors.lastname: Ben-Hur
authors.forename: J M
authors.initials: JM
authors.lastname: Lovett
authors.forename: T
authors.initials: T
authors.lastname: Clements
authors.forename: Y D
authors.initials: YD
authors.lastname: Ginosar
authors.forename: E M
authors.initials: EM
authors.lastname: Davidson
mesh_terms: D015170:Cerebrospinal Fluid Pressure / Q000502:physiology*; D002648:Child; D004867:Equipment Design; D006801:Humans; D008365:Manometry / Q000379:methods; D008959:Models, Neurological; D009339:Needles / Q000009:adverse effects; D051299:Post-Dural Puncture Headache / Q000209:etiology / Q000517:prevention & control; D011673:Pulsatile Flow / Q000502:physiology; D012212:Rheology; D013129:Spinal Puncture / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods