Free lidocaine concentrations during continuous epidural anesthesia in geriatric patients.
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.
Fukuda
Taeko
T
Department of Anesthesiology, Institute of Clinical Medicine, and the Department of Pharmacy, Tsukuba University Hospital, Tsukuba University, Ibaraki, Japan. taekof@md.tsukuba.ac.jp
Kakiuchi
Yoshihiro
Y
Miyabe
Masayuki
M
Kihara
Shinichi
S
Kohda
Yukinao
Y
Toyooka
Hidenori
H
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
D000779:Anesthetics, Local; D014662:Vasoconstrictor Agents; D008012:Lidocaine; D004837:Epinephrine