Effects of intravenous acepromazine and butorphanol on propofol dosage for induction of anesthesia in healthy Beagle dogs.

OBJECTIVE: To determine the effects of intravenous (IV) premedication with acepromazine, butorphanol or their combination, on the propofol anesthetic induction dosage in dogs.

STUDY DESIGN: Prospective, blinded, Latin square design.

ANIMALS: A total of three male and three female, healthy Beagle dogs, aged 3.79 ± 0.02 years, weighing 10.6 ± 1.1 kg, mean ± standard deviation.

METHODS: Each dog was assigned to one of six IV treatments weekly: 0.9% saline (treatment SAL), low-dose acepromazine (0.02 mg kg-1 ; treatment LDA), high-dose acepromazine (0.04 mg kg-1 ; treatment HDA), low-dose butorphanol (0.2 mg kg-1 ; treatment LDB), high-dose butorphanol (0.4 mg kg-1 ; treatment HDB); and a combination of acepromazine (0.02 mg kg-1 ) with butorphanol (0.2 mg kg-1 ; treatment ABC). Physiologic variables and sedation scores were collected at baseline and 10 minutes after premedication. Then propofol was administered at 1 mg kg-1 IV over 15 seconds, followed by boluses (0.5 mg kg-1 over 5 seconds) every 15 seconds until intubation. Propofol dose, physiologic variables, recovery time, recovery score and adverse effects were monitored and recorded. Data were analyzed using mixed-effects anova (p < 0.05).

RESULTS: Propofol dosage was lower in all treatments than in treatment SAL (4.4 ± 0.5 mg kg-1 ); the largest decrease was recorded in treatment ABC (1.7 ± 0.3 mg kg-1 ). Post induction mean arterial pressures (MAPs) were lower than baseline values of treatments LDA, HDA and ABC. Apnea and hypotension (MAP < 60 mmHg) developed in some dogs in all treatments with the greatest incidence of hypotension in treatment ABC (4/6 dogs).

CONCLUSIONS AND CLINICAL RELEVANCE: Although the largest decrease in propofol dosage required for intubation was after IV premedication with acepromazine and butorphanol, hypotension and apnea still occurred.