title: Method of preload reduction during LVPVR analysis of systolic function: airway pressure elevation and vena cava occlusion.
abstract: BACKGROUND
  A graded preload reduction during analysis of the left ventricular pressure-volume relationship (LVPVR) is required for derivation of end-systolic elastance (Ees) and preload recruitable stroke work (PRSW). The authors aimed to measure serial changes in these systolic function parameters before and during planned circulatory interventions using two different methods of preload alteration: a positive airway pressure plateau (APP) and inferior vena cava occlusion (IVCO).
  
  
  METHODS
  In eight animals, measurements were made at 38 degrees, 30 degrees, 32 degrees, 34 degrees, and posthypothermia 38 degrees C. In an additional eight animals, isoflurane, adrenaline, and aorta occlusion (balloon catheter occluder) were administered in series, each with a preintervention control measurement. Left ventricular volume was measured by conductance. Paired measurements of the systolic function parameters Ees and PRSW, each derived with two preload methods, were analyzed for bias.
  
  
  RESULTS
  Circulatory alterations were achieved with the temperature, isoflurane, adrenaline, and aorta occlusion interventions. Measured changes in Ees and PRSW from control to intervention showed a strong correlation and no significant bias for APP in relation to IVCO. The APP-derived absolute values for Ees and PRSW demonstrated a consistent positive bias compared with IVCO.
  
  
  CONCLUSIONS
  The APP method for preload reduction during LVPVR analysis detected changes in Ees and PRSW during the circulatory interventions in this model that were not different than those detected using another preload reduction method, IVCO. APP and IVCO are not interchangeable methods for preload reductions during LVPVR absolute quantitation of systolic function, and each needs to be used serially.
authors.affiliation: Department of Anesthesiology, Umeå University Hospital, Umeå, Sweden. michael.haney@anestesi.umu.se
authors.forename: Michael F
authors.initials: MF
authors.lastname: Haney
authors.forename: Göran
authors.initials: G
authors.lastname: Johansson
authors.forename: Sören
authors.initials: S
authors.lastname: Häggmark
authors.forename: Björn
authors.initials: B
authors.lastname: Biber
mesh_terms: D000704:Analysis of Variance; D018685:Anesthetics, Inhalation / Q000494:pharmacology*; D000818:Animals; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D007530:Isoflurane / Q000494:pharmacology*; D013318:Stroke Volume / Q000187:drug effects*; D013552:Swine; D013599:Systole / Q000187:drug effects*
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane