Comparison of fentanyl and alfentanil in combination with atropine for premedication of dogs undergoing radiotherapy.

OBJECTIVE

To evaluate the effects of two opioid-based premedication protocols on propofol requirement, time to recovery and occurrence of post-anaesthetic vocalization, paddling, nystagmus and dysphoria in dogs anaesthetized for radiotherapy.

STUDY

DESIGN

Blinded, randomized, crossover clinical study.

ANIMALS: A total of 22 client-owned dogs, each serving as their own control.

METHODS

Dogs were randomly assigned to one of two intravenous premedication protocols on their first radiotherapy session, and the other on their second session. Premedication consisted of atropine (10 μg kg-1) mixed with equipotent doses of either alfentanil (10 μg kg-1, group AA) or fentanyl (2.5 μg kg-1, group FA), followed by propofol induction and maintenance with sevoflurane in oxygen. Cardiorespiratory variables and observation of dysphoria and nystagmus were recorded after premedication and during recovery. Time elapsed from discontinuation of sevoflurane to tracheal extubation, sternal position and walking were also recorded (minutes).

RESULTS

The proportion of dogs showing dysphoria and nystagmus was not different between treatments at any time point. With both treatments, heart rate (mean ± standard deviation) decreased after premedication (82 ± 27 and 93 ± 27 beats minute-1 in groups AA and FA, respectively) compared with baseline (117 ± 23 and 112 ± 26 beats minute-1 in groups AA and FA, respectively; p < 0.001). Propofol dose did not differ between treatments (3.8 ± 1.7 and 4.3 ± 1.3 mg kg-1 in groups AA and FA, respectively). Time to extubation was shorter with treatment AA (5.3 ± 2.1 minutes) compared with treatment FA (6.2 ± 2.3 minutes; p = 0.049), while time to sternal recumbency and walking did not differ between treatments.

CONCLUSIONS AND CLINICAL RELEVANCE: Since the two protocols produced comparable clinical effects and were both found suitable for dogs undergoing repeated radiotherapy, fentanyl is recommended over alfentanil in countries where it is licensed.