Evaluation of two different radiotherapy anaesthetic protocols for dogs: a randomized clinical crossover trial

To describe alfentanil-propofol admixture for induction of anaesthesia for canine radiotherapy and compare it to alfentanil-atropine followed by propofol induction in terms of heart rate (HR), mean arterial pressure (MAP), recovery duration and quality.

Prospective, masked, randomized clinical crossover trial.

A group of 40 client-owned dogs anaesthetized from October 2017 to June 2018.

Dogs were randomly assigned to be administered one of two protocols. For both protocols, IV preanaesthetic medication was given 30 seconds before rapid IV administration of a set volume of induction agent, with further induction agent administered as needed to permit intubation. For protocol ADMIX, the preanaesthetic medication was 0.04 mL kg^-1 0.9% sodium chloride and the induction agent was 0.2 mL kg^-1 propofol-alfentanil admixture. For protocol ATRO, the preanaesthetic medication was 10 μg kg^-1 alfentanil with 12 μg kg^-1 atropine (0.04 mL kg^-1 total volume) and the induction agent was 0.2 mL kg^-1 propofol. Anaesthesia was maintained with sevoflurane. Cardiorespiratory variables, agitation, hypotension, or inadequate depth of anaesthesia requiring supplemental boluses of propofol or increased vaporizer settings were recorded. Time to extubation, sternal recumbency and walking was noted. Videos were recorded for recovery quality scoring. Owner questionnaires gave feedback about recoveries at home. The other protocol was administered for the next radiotherapy session.

The only significantly different variable between protocols was mean HR during anaesthesia, which was lower in ADMIX (p < 0.001). Hypotension was recorded in seven (17.5%) dogs in ATRO and three (7.5%) in ADMIX, with an association (p < 0.005) between ATRO and hypotension. Owners reported animals recovered 'normal' behaviour and appetite by the next morning.

Both protocols were acceptable for dogs undergoing radiotherapy, with minimal differences in anaesthetic quality, recovery duration and quality. Although MAP did not differ overall, the incidence of hypotension was higher in ATRO.