The effects of different inspired oxygen fractions on gas exchange and Tei-index of myocardial performance in propofol-anesthetized dogs

Authors

  • Patrícia C Ferro Lopes,

    1. 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
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  • Newton Nunes,

    Corresponding author
    1. 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
    • Correspondence: Newton Nunes, Departamento de Clínica e Cirurgia Veterinária, Faculdade de Ciências Agrárias e Veterinárias, Universidade Estadual Paulista, Via de Acesso Professor Paulo Donato Castellane, s/n°, CEP: 14884-900 Jaboticabal, SP, Brazil. E-mail: newton@fcav.unesp.br

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  • Marlos G Sousa,

    1. 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
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  • Celina TD Nishimori,

    1. 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
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  • Roberta Carareto,

    1. 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
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  • Paulo Sérgio P dos Santos,

    1. Department of Veterinary Medicine Surgery and Animal Reproduction, College of Agricultural and Veterinary Sciences, Universidade Estadual Paulista Júlio de Mesquita Filho, Araçatuba, SP, Brazil
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  • Aparecido A Camacho

    1. 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
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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.

Study design

Prospective crossover, randomized, experimental trial.

Animals

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 (math formulaO2), 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.

Conclusion

The Tei-index and cardiovascular parameters are not affected by different FiO2.

Clinical Relevance

An FiO2 of 1.0 and 0.21 impaired respiratory efficiency.

Ancillary