title: The effects of different inspired oxygen fractions on gas exchange and Tei-index of myocardial performance in propofol-anesthetized dogs.
abstract: OBJECTIVE
  To evaluate the influence of different inspired oxygen fractions (FiO2) on pulmonary oxygen exchange and Tei-index of myocardial performance in propofol-anesthetized dogs.
  
  
  METHODS
  Prospective crossover, randomized, experimental trial.
  
  
  METHODS
  Eight adult dogs weighing 8.6 ± 1.8 kg.
  
  
  METHODS
  The animals were anesthetized on five occasions, receiving either an FiO2 = 1.0 (F100), 0.8 (F80), 0.6 (F60), 0.4 (F40) or 0.21 (F21). Propofol was used for induction (6.45 ± 0.69 mgkg(-1) IV) followed by a continuous rate infusion (CRI, 0.7 mgkg(-1) minute(-1)). The dogs breathed spontaneously. The initial measurements of arterial partial pressures of oxygen (PaO2) and carbon dioxide (PaCO2), arterial hemoglobin saturation (SaO2), heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), stroke index (SI), pre-ejection period (PEP) and left ventricular ejection time (LVET) were performed 30 minutes after beginning the CRI (T0) and then, at 15-minute intervals (T15-T60). From these measurements the following were calculated; alveolar oxygen partial pressure (PAO2), alveolar-arterial oxygen gradient (AaDO2), arterial oxygen partial pressure/inspired oxygen fraction ratio (PaO2/FiO2), arterial-to-alveolar oxygen tension ratio (PaO2/PAO2), respiratory index (RI), oxygen delivery (D·O2), PEP/LVET ratio, isovolumic relaxation time (IVRT) and Tei-index.
  
  
  RESULTS
  At T30, PaCO2 in F100 was higher than in F21. The AaDO2 mean in F100 was greater than in other treatments. PaO2/FiO2 in F21 was lower than F100 and F80 at T0 and than in F80 and F60 at T15. At T15, PaO2/PAO2 and RI in F100 were higher than in F80, F60 and F21. At T30, PaO2/PAO2 in F21 was lower than in F100 and F60. At T30, PEP/LVET in F100 was higher than F80, F40 and F21, which was lower than F80 and F40.
  
  
  CONCLUSIONS
  The Tei-index and cardiovascular parameters are not affected by different FiO2.
  
  
  CONCLUSIONS
  An FiO2 of 1.0 and 0.21 impaired respiratory efficiency.
authors.affiliation: Department of Veterinary Medicine and Surgery, Veterinary Surgery Postgraduate Program, College of Agricultural and Veterinary Sciences, Universidade Estadual Paulista Júlio de Mesquita Filho, Jaboticabal, SP, Brazil.
authors.forename: Patrícia C
authors.initials: PC
authors.lastname: Ferro Lopes
authors.forename: Newton
authors.initials: N
authors.lastname: Nunes
authors.forename: Marlos G
authors.initials: MG
authors.lastname: Sousa
authors.forename: Celina Td
authors.initials: CT
authors.lastname: Nishimori
authors.forename: Roberta
authors.initials: R
authors.lastname: Carareto
authors.forename: Paulo Sérgio P
authors.initials: PS
authors.lastname: Dos Santos
authors.forename: Aparecido A
authors.initials: AA
authors.lastname: Camacho
mesh_terms: D000771:Anesthesia, Intravenous / Q000379:methods / Q000662:veterinary; D018686:Anesthetics, Intravenous; D000818:Animals; D004285:Dogs; D005260:Female; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology; D008297:Male; D010102:Oxygen Inhalation Therapy / Q000662:veterinary; D015742:Propofol; D011659:Pulmonary Gas Exchange / Q000502:physiology*
chemical_list: D018686:Anesthetics, Intravenous; D015742:Propofol
keywords: cardiac function; monitoring; total intravenous anesthesia; venous admixture