Cardiovascular and respiratory effects of two doses of fentanyl in the presence or absence of bradycardia in isoflurane-anesthetized dogs.

Abstract

OBJECTIVE:

To compare the cardiopulmonary effects of low and high doses of fentanyl before and after the correction of bradycardia in isoflurane-anesthetized dogs.

STUDY DESIGN:

Prospective, randomized crossover trial.

ANIMALS:

Eight healthy male Beagle dogs weighing 11.1 ± 1.3 kg [mean ± standard deviation (SD)] and aged approximately 1 year.

METHODS:

The dogs were anesthetized with isoflurane [1.3 × minimum alveolar concentration (MAC)] on two occasions and fentanyl was administered intravenously; either low-dose fentanyl, loading dose (33 μg kg-1) and infusion (0.2 μg kg-1 minute-1) or a high-dose, loading dose (102 μg kg-1) and infusion (0.8 μg kg-1 minute-1). Cardiopulmonary variables were measured at three time points in equipotent isoflurane concentrations (1.3 MAC): before fentanyl administration (ISO), during fentanyl-induced bradycardia (ISO-F) and after administration of glycopyrrolate normalized heart rate (ISO-FNHR). Data are mean ± SD.

RESULTS:

Heart rate and cardiac index (CI) decreased and systemic vascular resistance index (SVRI) increased at ISO-F in both treatments. Bradycardia and vasoconstriction at ISO-F were greater in high than in low-dose fentanyl (42 ± 7 versus 57 ± 15 beats minute-1 and 3457 ± 1108 versus 2528 ± 968 dyne second cm-5 m-2), respectively. Oxygen delivery index (DO2I) decreased only during high-dose fentanyl. CI and DO2I were higher in both treatments at ISO-FNHR than at ISO-F; however, they were higher only during the high-dose fentanyl than at ISO. SVRI was higher at ISO-F than at ISO and ISO-FNHR in both treatments, and was higher at ISO-F in the high than in the low-dose treatment.

CONCLUSIONS AND CLINICAL RELEVANCE:

An overall improvement in cardiovascular function of dogs anesthetized with equipotent isoflurane doses (1.3 MAC) was observed after the treatment of bradycardia only with the high-dose fentanyl.

• Authors: Ellen J Williamson, Joao Hn Soares, Natalia Henao-Guerrero, Roberto McAlister Council-Troche, Noah D Pavlisko
• Journal: Veterinary anaesthesia and analgesia (Vet Anaesth Analg) Vol. 45 Issue 4 Pg. 423-431 (07 2018) ISSN: 1467-2995 [Electronic] United States
• PMID: 29716836 (Publication Type: Journal Article, Randomized Controlled Trial)
• Copyright: Copyright © 2018 Association of Veterinary Anaesthetists and American College of Veterinary Anesthesia and Analgesia. Published by Elsevier Ltd. All rights reserved.

Chemical References

• Anesthetics, Inhalation
• Anesthetics, Intravenous
• Isoflurane
• Fentanyl

Topics

• Anesthesia, Inhalation (adverse effects, methods, veterinary)
• Anesthetics, Inhalation (adverse effects)
• Anesthetics, Intravenous (administration & dosage, blood, pharmacology)
• Animals
• Bradycardia (chemically induced, veterinary)
• Cross-Over Studies
• Dog Diseases (physiopathology)
• Dogs
• Dose-Response Relationship, Drug
• Fentanyl (administration & dosage, blood, pharmacology)
• Heart Rate (drug effects)
• Infusions, Intravenous (veterinary)
• Isoflurane (adverse effects)
• Male
• Vascular Resistance (drug effects)
• Vasoconstriction (drug effects)