Pharmacokinetics of thiopentone: effects of enflurane and nitrous oxide anaesthesia and surgery
Ghoneim, M.M.; Van Hamme, M.J.
British Journal of Anaesthesia 50(12): 1237-1242
1978
ISSN/ISBN: 0007-0912 PMID: 747695 Document Number: 133965
Plasma concentrations of thiopentone following the injection of 3.5 mg kg-1 i.v. were studied in 6 patients who received enflurane and nitrous oxide anesthesia and 6 volunteers. A 3-compartment open model system containing both a shallow and a deep peripheral compartment was identified in all the patients and half of the controls, and a 2-compartment open model was identified for the remaining volunteers. The thiopentone distribution to the tissues was very rapid, the .alpha. and .beta. distribution half-lives averaging 2.5 min and 46.4 min, respectively, for the patient group and 2.8 min and 48.7 min for the control group. The wide distribution of the drug was indicated by the apparent volume of distribution, the means of which varied between 2 and 1.5 times body wt. The mean elimination half-life was 5.1 h for the patients and 5.7 h for the volunteers. The return of the drug to the central compartment from the deep peripheral compartment was the rate-controlling factor in its elimination. Neither enflurane and nitrous oxide anesthesia nor the stress of surgery affected the distribution or clearance of the drug from plasma.