title: Pharmacokinetics of isoflurane: uptake in the brain.
abstract: We studied the effect of the inspired isoflurane concentration (C(I)iso) on the pharmacokinetics of isoflurane uptake in the brain by comparing the isoflurane concentration in internal jugular-bulb blood (Jiso) with that in arterial blood (Aiso), and analyzed this by gas chromatography. Sixteen patients (aged 43-76 years) undergoing colorectal surgery were enrolled, and anesthesia was maintained with a constant C(I)iso of either 1% (group 1, n = 8) or 2% (group 2, n = 8) during the 1st hour of isoflurane anesthesia. Under constant volume-controlled ventilation, we measured the C(I)iso and the end-tidal isoflurane concentration (C(E)iso) at the mouthpiece by infrared analysis. Our results demonstrate that it takes 40 min for the brain tissue concentration to equal Aiso for 1% C(I)iso, and 50 min for 2% C(I)iso. The Aiso (and/or Jiso) for 2% C(I)iso was approximately double when compared to that for 1% C(I)iso. Except during the initial wash-in period of the functional residual capacity in the first 3 min, the differences between C(I)iso and C(E)iso revealed that the body uptake of isoflurane for 2% C(I)iso was twice that for 1% C(I)iso. These results demonstrate that the pharmacokinetics of isoflurane uptake in the brain is time-dependent for Jiso to equal Aiso, and the midpoint between Aiso and Jiso (likely representing the isoflurane concentration in brain tissue) was dependent on C(I)iso.
authors.affiliation: Department of Anesthesiology, Tri-Service General Hospital, National Defense Medical Center, No. 161, Section 6 Minchuan E. Road, Taipei, Taiwan.
authors.forename: Chih-Cherng
authors.initials: CC
authors.lastname: Lu
authors.forename: Shung-Tai
authors.initials: ST
authors.lastname: Ho
authors.forename: Jhi-Joung
authors.initials: JJ
authors.lastname: Wang
authors.forename: Chih-Shung
authors.initials: CS
authors.lastname: Wong
authors.forename: Oliver Yao-Pu
authors.initials: OY
authors.lastname: Hu
authors.forename: Sun-Yran
authors.initials: SY
authors.lastname: Chang
authors.forename: Chung-Yuan
authors.initials: CY
authors.lastname: Lin
mesh_terms: D000328:Adult; D018685:Anesthetics, Inhalation / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000378:metabolism*; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D007530:Isoflurane / Q000097:blood / Q000493:pharmacokinetics* / Q000494:pharmacology; D008297:Male; D008875:Middle Aged
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane