title: Influence of cardiac output on plasma propofol concentrations during constant infusion in swine.
abstract: BACKGROUND
  As propofol is a high-clearance drug, plasma propofol concentrations can be influenced by cardiac output (CO), which can easily change in response to several factors. If propofol is metabolized in the lungs, the difference between pulmonary and arterial propofol concentrations might also be affected by CO. The objective of the current study was to assess how much plasma propofol concentrations are affected by CO and to determine how much the lungs take part in propofol elimination and in concentration changes affected by CO in anesthetized swine.
  
  
  METHODS
  Thirteen swine were studied. Propofol was administered via a peripheral vein at a rate of 6 mg x kg(-1) x h(- 1), and blood samples were simultaneously collected from pulmonary and femoral arteries at 0, 2, 3.5, 5, 7, 10, 20, and 30 min and at 20-min intervals up to 270 min. After 90 min of sampling (baseline 1), CO increased in response to a continuous infusion of dobutamine (20 microg x kg(-1) x min(- 1); high-CO state); the infusion was then stopped, and CO was allowed to return to baseline (baseline 2). Finally, CO decreased with the administration of propranolol (2.0-4.0 mg administered intravenously; low-CO state). Each hemodynamic status was maintained for 1 h.
  
  
  RESULTS
  As CO increased 36% from baseline 1, plasma propofol concentrations decreased by 18% from baseline 1, and as CO decreased 42% from baseline 1, plasma propofol concentrations increased by 70% from baseline 1. Plasma propofol concentrations can be expressed by the following equation: plasma propofol concentration (micrograms per milliliter) = 6.51/CO (l/min) + 1.11 (r = 0.78, P < 0.0001). No significant differences were observed between plasma propofol concentrations in pulmonary and femoral arteries in any state, and CO caused no apparent differences between pulmonary and arterial propofol concentrations.
  
  
  CONCLUSIONS
  An inverse relation was observed between CO and propofol concentrations. The lungs appear to have a minor effect on plasma propofol concentrations during constant infusion in anesthetized swine.
authors.affiliation: Department of Anesthesiology and Intensive Care, Hamamatsu University School of Medicine, Handayama, Hamamatsu, Japan. tadkur@hama-med.ac.jp
authors.forename: Tadayoshi
authors.initials: T
authors.lastname: Kurita
authors.forename: Koji
authors.initials: K
authors.lastname: Morita
authors.forename: Tomiei
authors.initials: T
authors.lastname: Kazama
authors.forename: Shigehito
authors.initials: S
authors.lastname: Sato
mesh_terms: D018686:Anesthetics, Intravenous / Q000097:blood*; D000818:Animals; D002302:Cardiac Output; D005263:Femoral Artery / Q000378:metabolism; D007262:Infusions, Intravenous; D015742:Propofol / Q000008:administration & dosage / Q000097:blood*; D011651:Pulmonary Artery / Q000378:metabolism; D013552:Swine
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol