Effect of benzodiazepines on the dose of alfaxalone needed for endotracheal intubation in healthy dogs.

OBJECTIVE: To evaluate the dose-sparing effect of midazolam or diazepam on the dose of alfaxalone required to achieve endotracheal intubation in premedicated dogs.

STUDY DESIGN: Prospective, randomized, 'blinded', controlled clinical trial.

ANIMALS: Ninety healthy dogs anaesthetized for elective surgery or diagnostic procedures.

METHODS: Saline (0.1 mL kg-1 ), or midazolam or diazepam (0.2, 0.3, 0.4 or 0.5 mg kg-1 ) intravenously (IV) was randomly assigned; investigators were unaware of group designation. After premedication with IV acepromazine 0.01 mg kg-1 and methadone 0.2 mg kg-1 , the degree of sedation was assessed. Alfaxalone (0.5 mg kg-1 ) was administered IV, followed by the assigned treatment. Further alfaxalone was administered until endotracheal intubation could be performed. Ease of endotracheal intubation, pulse rate and arterial blood pressure were assessed. General linear models were used to examine the effect of treatment drug and dose on induction dose of alfaxalone with Tukey's post hoc tests. Incidence of adverse reactions was assessed with chi-square tests.

RESULTS: There were no significant differences between groups with regard to demographic data or sedation. Median (range) induction dose of alfaxalone in the saline group was 0.74 (0.43-1.26) mg kg-1 compared with 0.5 (0.46-0.75) mg kg-1 and 0.5 (0.42-1.2) mg kg-1 for the midazolam and diazepam groups, respectively. Midazolam 0.3 and 0.5 mg kg-1 (p = 0.005 and 0.044, respectively) and diazepam 0.4 mg kg-1 (p = 0.032) reduced the alfaxalone dose compared with saline. Adverse effects were not significantly different between groups. Midazolam 0.2, 0.3, 0.4 and 0.5 mg kg-1 (p < 0.044, p = 0.001, p = 0.007, p = 0.044, respectively) and diazepam 0.2 and 0.5 mg kg-1 (p = 0.025 and p = 0.025) improved intubation score compared with saline.

CONCLUSION AND CLINICAL RELEVANCE: Midazolam 0.3 and 0.5 mg kg-1 and diazepam 0.4 mg kg-1 coadministered at anaesthetic induction allow alfaxalone dose reduction in healthy dogs. Use of benzodiazepines improved the ease of endotracheal intubation.