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Keywords:

  • alfaxalone;
  • dogs;
  • fentanyl;
  • heart rate;
  • propofol

Abstract

Objective

To compare the effect of alfaxalone and propofol on heart rate (HR) and blood pressure (BP) after fentanyl administration in healthy dogs.

Study design

Prospective, randomised clinical study.

Animals

Fifty healthy client owned dogs (ASA I/II) requiring general anaesthesia for elective magnetic resonance imaging for neurological conditions.

Methods

All dogs received fentanyl 7 μg kg−1 IV and were allocated randomly to receive either alfaxalone (n = 25) or propofol (n = 25) to effect until endotracheal (ET) intubation was possible. Heart rate and oscillometric BP were measured before fentanyl (baseline), after fentanyl (Time F) and after ET intubation (Time GA). Post-induction apnoea were recorded. Data were analysed using Fisher's exact test, Mann Whitney U test and one-way anova for repeated measures as appropriate; p value <0.05 was considered significant.

Results

Dogs receiving propofol showed a greater decrease in HR (−14 beat minute−1, range −47 to 10) compared to alfaxalone (1 beat minute−1, range −33 to 26) (p = 0.0116). Blood pressure decreased over the three time periods with no difference between groups. Incidence of post-induction apnoea was not different between groups.

Conclusion

Following fentanyl administration, anaesthetic induction with propofol resulted in a greater negative chronotropic effect while alfaxalone preserved or increased HR.

Clinical relevance

Following fentanyl administration, HR decreases more frequently when propofol rather than alfaxalone is used as induction agent. However, given the high individual variability and the small change in predicted HR (−7.7 beats per minute after propofol), the clinical impact arising from choosing propofol or alfaxalone is likely to be small in healthy animals. Further studies in dogs with myocardial disease and altered haemodynamics are warranted.