title: Alterations in aortic wave reflection with vasodilation and vasoconstriction in anaesthetized dogs.
abstract: BACKGROUND
  Using the reservoir-wave approach, we studied wave propagation, reflection, and re-reflection in the canine aorta with administrations of sodium nitroprusside (NP) and methoxamine (Mtx).
  
  
  METHODS
  In 8 anaesthetized dogs, excess pressures were calculated from pressure and flow measurements at 4 locations along the aorta; wave intensity analysis was employed to identify wavefronts and the type of waves.
  
  
  RESULTS
  NP (intravenous; 14 μg/min) decreased mean aortic pressure from 80 ± 3 mm Hg to 48 ± 1 mm Hg; Mtx (intravenous; 10 μg/min) increased mean pressure from 80 ± 3 mm Hg to 104 ± 4 mm Hg. NP increased negative reflection near the kidneys (reflection coefficient: -0.33 vs -0.18; P < 0.01) and produced new negatively reflecting sites just beyond the arch and in the proximal femoral arteries, consistent with a vasodilating effects of nitrates on conducting arteries. Mtx negated negative reflection from near the kidneys (-0.02 vs -0.17; P < 0.01) and increased positive femoral reflection (0.38 vs 0.26; P < 0.01). The large reflected compression wave was re-reflected from the closed aortic valve to produce a prominent increase in middiastolic pressure in the distal aorta.
  
  
  CONCLUSIONS
  The reservoir-wave approach explains decreasing diastolic pressure without positing waves that travel at near-infinite velocities and reveals the pressure changes that are uniquely due to wave motion.
authors.affiliation: Department of Medicine, Fu Jen Catholic University, New Taipei City, Taiwan. 078625@mail.fju.edu.tw
authors.forename: Jiun-Jr
authors.initials: JJ
authors.lastname: Wang
authors.forename: J Christopher
authors.initials: JC
authors.lastname: Bouwmeester
authors.forename: Israel
authors.initials: I
authors.lastname: Belenkie
authors.forename: Nigel G
authors.initials: NG
authors.lastname: Shrive
authors.forename: John V
authors.initials: JV
authors.lastname: Tyberg
mesh_terms: D000768:Anesthesia, General; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000503:physiopathology*; D062186:Arterial Pressure; D004195:Disease Models, Animal; D004285:Dogs; D006973:Hypertension / Q000175:diagnosis / Q000503:physiopathology*; D008729:Methoxamine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*; D014665:Vasodilator Agents / Q000494:pharmacology
chemical_list: D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D008729:Methoxamine