title: Free lidocaine concentrations during continuous epidural anesthesia in geriatric patients.
abstract: OBJECTIVE
  To evaluate the effects of aging on lidocaine pharmacokinetics, the plasma concentrations of total and free lidocaine and its metabolites were measured during continuous thoracic epidural anesthesia in middle-aged (age 41 +/- 9 years, n = 7) and elderly (age 72 +/- 2 years, n = 7) male patients.
  
  
  METHODS
  After establishment of general anesthesia, 7 mL 1.5% lidocaine with epinephrine 1:200,000 was injected into the epidural space and subsequently infused at a rate of 5 mL/h for 5 hours. Plasma concentrations of total and free lidocaine, monoethylglycinexylidide (MEGX), and glycinexylidide (GX) were measured at 10, 15, 20, 30, 45, 60, 90, 120, 150, 180, 240, and 300 minutes after initial lidocaine injection using high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection.
  
  
  RESULTS
  The elderly group showed a stronger upward trend in the corrected free lidocaine concentrations and lower corrected total MEGX concentrations than the middle-aged group.
  
  
  CONCLUSIONS
  Lidocaine metabolite activity in the elderly male patients was lower than that in the middle-aged male patients. Free lidocaine concentration is prone to increase in elderly patients. Caution must be exercised during continuous thoracic epidural anesthesia combined with general anesthesia in geriatric patients.
authors.affiliation: Department of Anesthesiology, Institute of Clinical Medicine, and the Department of Pharmacy, Tsukuba University Hospital, Tsukuba University, Ibaraki, Japan. taekof@md.tsukuba.ac.jp
authors.forename: Taeko
authors.initials: T
authors.lastname: Fukuda
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kakiuchi
authors.forename: Masayuki
authors.initials: M
authors.lastname: Miyabe
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kihara
authors.forename: Yukinao
authors.initials: Y
authors.lastname: Kohda
authors.forename: Hidenori
authors.initials: H
authors.lastname: Toyooka
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000378:metabolism; D000767:Anesthesia, Epidural; D000779:Anesthetics, Local / Q000097:blood*; D002851:Chromatography, High Pressure Liquid; D004837:Epinephrine / Q000494:pharmacology; D006801:Humans; D008012:Lidocaine / Q000097:blood*; D008175:Lung Neoplasms / Q000188:drug therapy; D008297:Male; D008479:Mediastinal Neoplasms / Q000601:surgery; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D013056:Spectrophotometry, Ultraviolet; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects
chemical_list: D000779:Anesthetics, Local; D014662:Vasoconstrictor Agents; D008012:Lidocaine; D004837:Epinephrine