Effects of isoflurane on echocardiographic parameters in healthy dogs

Authors

  • Marlos G Sousa DVM, MS, PhD,

    1. Department of Veterinary Medicine and Surgery, College of Agricultural and Veterinarian Sciences (FCAV), São Paulo State University (UNESP), São Paulo, Brazil
    Search for more papers by this author
  • Roberta Carareto DVM, MS, PhD,

    1. Department of Veterinary Medicine and Surgery, College of Agricultural and Veterinarian Sciences (FCAV), São Paulo State University (UNESP), São Paulo, Brazil
    Search for more papers by this author
  • Andrigo B De-Nardi DVM, MS, PhD,

    1. Department of Veterinary Medicine and Surgery, College of Agricultural and Veterinarian Sciences (FCAV), São Paulo State University (UNESP), São Paulo, Brazil
    Search for more papers by this author
  • Fábio LC Brito DVM, MS, PhD,

    1. Department of Veterinary Medicine and Surgery, College of Agricultural and Veterinarian Sciences (FCAV), São Paulo State University (UNESP), São Paulo, Brazil
    Search for more papers by this author
  • Newton Nunes DVM, MS, PhD,

    1. Department of Veterinary Medicine and Surgery, FCAV, UNESP, São Paulo, Brazil
    Search for more papers by this author
  • Aparecido A Camacho DVM, MS, PhD

    1. Department of Veterinary Medicine and Surgery, FCAV, UNESP, São Paulo, Brazil
    Search for more papers by this author

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°, Jaboticabal, São Paulo, Brazil, CEP 14884-900. E-mail: newton@fcav.unesp.br

Abstract

Objective  To study the echocardiographic effects of isoflurane at an end-tidal concentration approximating 1.0 times the minimum alveolar concentration (MAC) in healthy unpremedicated dogs.

Study design  Prospective experimental trial.

Animals  Sixteen mature mongrel dogs of either sex weighing 11.06 ± 2.72 kg.

Methods  After performing a baseline echocardiogram in the awake animal, anesthesia was induced with increasing inspired concentrations of isoflurane via a face mask until tracheal intubation was possible. Following intubation, the end-tidal concentration was decreased to 1.4% for the rest of the anesthetic period. Serial echocardiograms were recorded at 25, 40, and 55 minutes after the end-tidal concentration was reached.

Results  No changes were observed in heart rate. However, significant decreases were seen in left ventricular end-diastolic diameter (Mean maximal change: 13.8%), interventricular septal thickness during systole (15.2%), interventricular septal thickening fraction (72.2%), left ventricular free wall thickening fraction (63.5%), ejection fraction (39.9%), and fractional shortening (46.7%). In addition, peak flow velocities across mitral, pulmonic, and aortic valves were significantly lower than baseline values. Decreases were also observed in end-diastolic left ventricular volume index (approximately 32.1% from the awake value), stroke index (58.2%), and cardiac index (55.3%) when compared with awake measurements.

Conclusions and clinical relevance  Our results indicate that 1 × MAC isoflurane caused significant myocardial depression in healthy dogs. These changes in myocardial function need to be considered carefully when isoflurane is to be used in dogs with poor cardiovascular reserve.

Ancillary