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Free Lidocaine Concentrations During Continuous Epidural Anesthesia in Geriatric Patients
  1. Taeko Fukuda, M.D.,
  2. Yoshihiro Kakiuchi, Ph.D.,
  3. Masayuki Miyabe, M.D.,
  4. Shinichi Kihara, M.D.,
  5. Yukinao Kohda, Ph.D. and
  6. Hidenori Toyooka, M.D.
  1. From the Department of Anesthesiology, Institute of Clinical Medicine (T.F., M.M., S.K., H.T.), and the Department of Pharmacy (Y.K., Y.K.), Tsukuba University Hospital, Tsukuba University, Ibaraki, Japan.
  1. Reprint requests: Taeko Fukuda, M.D., Department of Anesthesiology, Institute of Clinical Medicine, Tsukuba University, Tsukuba-city, Ibaraki 305-8575, Japan. E-mail: taekof{at}


Background and Objectives 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.

  • Epidural anesthesia
  • Free lidocaine

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