title: Combined spinal-epidural anesthesia for outpatient surgery. Dose-response characteristics of intrathecal isobaric lidocaine using a 27-gauge Whitacre spinal needle.
abstract: BACKGROUND
  Combined spinal-epidural anesthesia (CSE) may offer theoretic advantages for outpatient surgery, because it produces the rapid onset of spinal anesthesia, with the option to extend the blockade with an epidural catheter. In this study, the authors attempted to determine an appropriate initial dose of a short-acting local anesthetic, 2% lidocaine, to administer for outpatient knee arthroscopy using CSE.
  
  
  METHODS
  Data were collected from 90 patients undergoing outpatient knee arthroscopy. Using a double-blinded, prospective study design, patients were randomly assigned to receive CSE with an initial dose of intrathecal 2% lidocaine of 40, 60, or 80 mg. A 27-G 4 11/16-inch Whitacre needle was placed through a 17-G Weiss needle. Onset and regression of sensory anesthesia and motor blockade were measured by a blinded observer at frequent intervals.
  
  
  RESULTS
  All 90 patients had adequate anesthesia. Durations of thoracic and lumbar sensory and lower limb motor blockade were significantly shorter in the 40-mg group compared with the 60- or 80-mg groups (P < 0.0002 Mantel-Cox, Survivorship Analysis). Indices of neural blockade resolved 30-40 min more rapidly in the 40-mg group than in either the 60- or 80-mg group. Times to urinate, site upright in a chair, take oral fluids, and be discharged were all significantly shorter (between 30 and 60 min) in the 40-mg group compared with the 60- and 80-mg groups (P < 0.01). Seven patients required intraoperative epidural supplementation: three in the 40-mg group, three in the 60-mg group, and one in the 80-mg group.
  
  
  CONCLUSIONS
  Combined spinal-epidural anesthesia with a 40-mg initial intrathecal dose of lidocaine provided reliable anesthesia for knee arthroscopy. Duration of spinal anesthesia with lidocaine was dose related.
authors.affiliation: Department of Anesthesiology, Hospital for Special Surgery, Cornell University Medical College, New York, New York 10021, USA.
authors.forename: W F
authors.initials: WF
authors.lastname: Urmey
authors.forename: J
authors.initials: J
authors.lastname: Stanton
authors.forename: M
authors.initials: M
authors.lastname: Peterson
authors.forename: N E
authors.initials: NE
authors.lastname: Sharrock
mesh_terms: D000293:Adolescent; D000328:Adult; D000556:Ambulatory Surgical Procedures; D000775:Anesthesia, Spinal; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007278:Injections, Spinal; D008012:Lidocaine / Q000008:administration & dosage*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies
chemical_list: D008012:Lidocaine