title: Influence of the injection site (L2/3 or L3/4) and the posture of the vertebral column on selective spinal anesthesia for ambulatory knee arthroscopy.
abstract: BACKGROUND
  We tested the hypothesis that selective spinal anesthesia for ambulatory knee arthroscopy can be accomplished with a small dose of bupivacaine at the L3/4 interspace with or without a head-down tilt of 5 degrees when the patients were in the lateral decubitus position.
  
  
  METHODS
  In this double-blind study, 123 patients were randomly allocated to receive spinal anesthesia with 4 mg of hyperbaric bupivacaine inserted at either the L2/3 interspace, while the vertebral column was kept horizontal (L2/3 group), or the L3/4 level, with the vertebral column horizontal (L3/4H) or tilted 5 degrees head-down (L3/4T). At 7 min, an additional head down tilt was used in all groups if the sensory block was inadequate.
  
  
  RESULTS
  In the L3/4T group the sensory block (Th8) reached a significantly higher level 30 min after spinal injection, compared with both the L2/3 (Th10) and L3/4H (Th11) groups. In the L3/4H group, 39% of the patients needed an additional tilt for 3 min at 7 min, compared with 10% (P=0.004) in the L3/4T group. Sacral block developed later and recovered faster (P<0.05) in the L3/4T group compared to the L3/4H group. Home-readiness was achieved equally fast in all groups.
  
  
  CONCLUSIONS
  When producing selective spinal anesthesia, the posture of the vertebral column is a major determinant of both sensory and motor segments to be blocked. A 4-mg dose of hyperbaric bupivacaine at the L3/4 interspace with a 5 degrees head-down tilt of the vertebral column for 6 min is recommended for knee arthroscopy.
authors.affiliation: Department of Anesthesia, Lapland Central Hospital, Rovaniemi, Finland. anna.maija.korhonen@hus.fi
authors.forename: A-M
authors.initials: AM
authors.lastname: Korhonen
authors.forename: J V
authors.initials: JV
authors.lastname: Valanne
authors.forename: R M
authors.initials: RM
authors.lastname: Jokela
authors.forename: P
authors.initials: P
authors.lastname: Ravaska
authors.forename: P
authors.initials: P
authors.lastname: Volmanen
authors.forename: K
authors.initials: K
authors.lastname: Korttila
mesh_terms: D000328:Adult; D000775:Anesthesia, Spinal; D000779:Anesthetics, Local / Q000008:administration & dosage; D001182:Arthroscopy; D015992:Body Mass Index; D002045:Bupivacaine / Q000008:administration & dosage; D004311:Double-Blind Method; D005260:Female; D018475:Head-Down Tilt; D006801:Humans; D007717:Knee / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D009046:Motor Neurons / Q000187:drug effects; D009407:Nerve Block; D010812:Physical Stimulation; D011446:Prospective Studies
chemical_list: D000779:Anesthetics, Local; D002045:Bupivacaine