title: Epidural bolus injection with alkalinized lidocaine improves blockade of the first sacral segment--a brief report.
abstract: OBJECTIVE
  It has been reported that the addition of epinephrine and/or bicarbonate to local anesthetic enhances the depth of epidural blockade and that initial partial bolus injection results in greater caudal spread. We evaluated the anesthetic effects of lidocaine with epinephrine and/or bicarbonate injected into the epidural space by bolus or catheter injection.
  
  
  METHODS
  Forty-four patients undergoing epidural anesthesia with 17 mL of 2% lidocaine containing 1:200,000 epinephrine at L4-5 or L5-S1 were randomly divided into four groups. Lidocaine was administrated via epidural catheter [lidocaine catheter (LC) group] or Tuohy needle (lidocaine bolus group), lidocaine-bicarbonate was administrated via catheter (lidocaine-bicarbonate catheter group) or needle [lidocaine-bicarbonate bolus (LBB) group]. Pain threshold after repeated electrical stimulation was performed at L2 and S1 regions. Motor blockade was evaluated using the Bromage scale. Sympathetic blockade was assessed with plethysmographic waveforms from the toe.
  
  
  RESULTS
  The pain threshold of the S1 dermatome in LBB group was significantly higher than in the lidocaine only groups, however, differences in the pain threshold at the L2 dermatome among the groups were insignificant. The onset of sensory blockade in the S1 dermatome in the LBB group was significantly shorter than in the LC group. Significantly greater motor blockade was achieved in the lidocaine-bicarbonate groups than in the lidocaine-only groups. The amplitude of plethysmographic waveforms significantly increased within each group.
  
  
  CONCLUSIONS
  Epidural bolus injection of lidocaine-bicarbonate with epinephrine improves the pain threshold and speeds the onset of the blockade of the first sacral region.
authors.affiliation: Second Department of Anesthesiology, Toho University School of Medicine, Tokyo, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Arakawa
authors.forename: Yukio
authors.initials: Y
authors.lastname: Aoyama
authors.forename: Yoko
authors.initials: Y
authors.lastname: Ohe
mesh_terms: D000759:Adjuvants, Anesthesia; D000328:Adult; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local; D001340:Autonomic Nerve Block; D001639:Bicarbonates; D002021:Buffers; D004558:Electric Stimulation; D004837:Epinephrine; D005260:Female; D006801:Humans; D008012:Lidocaine; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons / Q000187:drug effects; D009407:Nerve Block; D017288:Pain Threshold / Q000187:drug effects; D010991:Plethysmography; D020671:Posterior Horn Cells / Q000187:drug effects; D014662:Vasoconstrictor Agents
chemical_list: D000759:Adjuvants, Anesthesia; D000779:Anesthetics, Local; D001639:Bicarbonates; D002021:Buffers; D014662:Vasoconstrictor Agents; D008012:Lidocaine; D004837:Epinephrine