title: Effects of acute normovolemic hemodilution on ventriculoarterial coupling in dogs.
abstract: BACKGROUND
  Acute normovolemic hemodilution (ANH) causes a decrease in systemic vascular resistance. Similar to vasodilating drugs, ANH might modify ventriculoarterial coupling. Left ventricular elastance (Ees), effective arterial elastance (Ea), stroke work (SW), and pressure volume area (PVA) were used as indicators to examine the effects of ANH on this coupling.
  
  
  METHODS
  After institutional approval eight dogs were anesthetized with isoflurane and subjected to measurements including aortic pressure, left ventricular (LV) pressure, and LV volume. Left ventricular volume was measured with a conductance catheter. Ees was determined as the slope of the end-systolic pressure-volume relationship. Ea was determined as the ratio of LV end-systolic pressure to stroke volume. Ventriculoarterial coupling was evaluated as the ratio of Ees to Ea. Mechanical efficiency, another criterion for ventriculoarterial coupling, was calculated as the ratio of SW to PVA. Data are expressed as mean+/-SD, and P<0.05 was considered significant.
  
  
  RESULTS
  Normovolemic exchange of 50 ml kg-1 of blood for 6% hydroxyethyl starch (ANH50) reduced hemoglobin concentration from 12.8+/-3.0 g dl-1 to 6.4+/-1.3 g dl-1. Acute normovolemic hemodilution 50 did not change Ees significantly although it significantly decreased Ea. Left ventricular elastance/Ea did not change after ANH (1.0+/-0.4 at baseline and 1.2+/-0.5 at ANH50). Acute normovolemic hemodilution 50 significantly increased SW and PVA, preventing SW/PVA from changing significantly after ANH (0.57+/-0.10 at baseline and 0.62+/-0.14 at ANH50).
  
  
  CONCLUSIONS
  Before ANH, ventriculoarterial coupling was so matched as to maximize SW at the expense of the work efficiency. This relation was preserved at ANH50.
authors.affiliation: Department of Anesthesiology, Tokushima University School of Medicine, Japan. jnozaki@clin.med.tokushima-u.ac.jp
authors.forename: J
authors.initials: J
authors.lastname: Nozaki
authors.forename: H
authors.initials: H
authors.lastname: Kitahata
authors.forename: K
authors.initials: K
authors.lastname: Tanaka
authors.forename: S
authors.initials: S
authors.lastname: Kawahito
authors.forename: S
authors.initials: S
authors.lastname: Oshita
mesh_terms: D000465:Algorithms; D000758:Anesthesia; D000818:Animals; D001158:Arteries / Q000502:physiology*; D001784:Blood Gas Analysis; D001794:Blood Pressure / Q000502:physiology; D001810:Blood Volume / Q000502:physiology; D004285:Dogs; D004548:Elasticity; D005260:Female; D006321:Heart / Q000502:physiology*; D006438:Hemodilution / Q000009:adverse effects*; D008297:Male; D013318:Stroke Volume / Q000502:physiology; D016276:Ventricular Function; D016277:Ventricular Function, Left / Q000502:physiology