The long-term objective of this research program is to improve the understanding of the dose-response relationships of rapidly acting intravenous (IV) anesthetics by describing physiologic factors affecting their pharmacokinetics. The investigators have developed a powerful new pharmacokinetic methodology that enables characterization of blood concentration history from the moment of IV drug administration. The pharmacokinetic analysis uses a recirculatory model which describes the simultaneous disposition of physiologic markers: indocyanine green, blood flow and intravascular space; inulin, free water diffusion and extracellular space; and antipyrine, tissue perfusion and water space. The area under the blood drug concentration vs. time relationship is doubled in halothane-anesthetized (vs. awake) dogs in the first minutes after IV injection due to increased blood flow to tissues with negligible distributional capacity. This observation will be extended by studying the disposition of the three physiologic markers in dogs in several other paradigms of changes in cardiac output and altered distribution of cardiac output due to regional changes in vascular resistance. One study will evaluate the effects of l.7%, 2.6%, and 3.5% isoflurane while the other study will determine the effects of the infusions of phenylephrine, sodium nitroprusside, and dexmedetomidine in awake animals. Thiopental will be administered by a constant rate infusion to young and elderly patients of both sexes and sex- and age-related reactivity differences will be evaluated with a recirculatory pharmacokinetic- pharmacodynamic model. However, drug administration by infusion to obtain proper effect data precludes accurately characterizing the mixing phase of a recirculatory pharmacokinetic model. Thus, antipyrine and ICG will be used as surrogate pharmacokinetic markers to determine the mixing phase kinetics of thiopental during its continuous infusion. Later disposition phases will be determined from blood thiopental concentrations. EEG aperiodic analysis will provide a continuous pharmacodynamic measure.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
2R01GM043776-04A2
Application #
2182177
Study Section
Surgery, Anesthesiology and Trauma Study Section (SAT)
Project Start
1991-01-01
Project End
1999-03-31
Budget Start
1995-04-01
Budget End
1996-03-31
Support Year
4
Fiscal Year
1995
Total Cost
Indirect Cost
Name
Northwestern University at Chicago
Department
Anesthesiology
Type
Schools of Medicine
DUNS #
005436803
City
Chicago
State
IL
Country
United States
Zip Code
60611
Henthorn, T K; Krejcie, T C; Avram, M J (2008) Early drug distribution: a generally neglected aspect of pharmacokinetics of particular relevance to intravenously administered anesthetic agents. Clin Pharmacol Ther 84:18-22
Krejcie, T C; Avram, M J (1999) What determines anesthetic induction dose? It's the front-end kinetics, doctor! Anesth Analg 89:541-4
Krejcie, T C; Avram, M J; Gentry, W B et al. (1997) A recirculatory model of the pulmonary uptake and pharmacokinetics of lidocaine based on analysis of arterial and mixed venous data from dogs. J Pharmacokinet Biopharm 25:169-90
Krejcie, T C; Jacquez, J A; Avram, M J et al. (1996) Use of parallel Erlang density functions to analyze first-pass pulmonary uptake of multiple indicators in dogs. J Pharmacokinet Biopharm 24:569-88
Krejcie, T C; Henthorn, T K; Shanks, C A et al. (1994) A recirculatory pharmacokinetic model describing the circulatory mixing, tissue distribution and elimination of antipyrine in dogs. J Pharmacol Exp Ther 269:609-16
Gentry, W B; Krejcie, T C; Henthorn, T K et al. (1994) Effect of infusion rate on thiopental dose-response relationships. Assessment of a pharmacokinetic-pharmacodynamic model. Anesthesiology 81:316-24;discussion 25A
Henthorn, T K; Krejcie, T C; Shanks, C A et al. (1992) Time-dependent distribution volume and kinetics of the pharmacodynamic effector site. J Pharm Sci 81:1136-8
Henthorn, T K; Avram, M J; Krejcie, T C et al. (1992) Minimal compartmental model of circulatory mixing of indocyanine green. Am J Physiol 262:H903-10