An evaluation of anaesthetic induction in healthy dogs using rapid intravenous injection of propofol or alfaxalone

Objective: To evaluate quality of anaesthetic induction and cardiorespiratory effects following rapid intravenous (IV) injection of propofol or alfaxalone. Study design: Prospective, randomised, blinded clinical study. Animals: Sixty healthy dogs (ASA I/II) anaesthetized for elective surgery or diagnostic procedures. Methods: Premedication was intramuscular acepromazine (0.03 mg kg−1) and meperidine (pethidine) (3 mg kg−1). For anaesthetic induction dogs received either 3 mg kg−1 propofol (Group P) or 1.5 mg kg−1 alfaxalone (Group A) by rapid IV injection. Heart rate (HR), respiratory rate (fR) and oscillometric arterial pressures were recorded prior to induction, at endotracheal intubation and at 3 and 5 minutes post-intubation. The occurrence of post-induction apnoea or hypotension was recorded. Pre-induction sedation and aspects of induction quality were scored using 4 point scales. Data were analysed using Chi-squared tests, two sample t-tests and general linear model mixed effect anova (p < 0.05). Results: There were no significant differences between groups with respect to sex, age, body weight, fR, post-induction apnoea, arterial pressures, hypotension, SpO2, sedation score or quality of induction scores. Groups behaved differently over time with respect to HR. On induction HR decreased in Group P (−2 ± 28 beats minute−1) but increased in Group A (14 ± 33 beats minute−1) the difference being significant (p = 0.047). However HR change following premedication also differed between groups (p = 0.006). Arterial pressures decreased significantly over time in both groups and transient hypotension occurred in eight dogs (five in Group P, three in Group A). Post-induction apnoea occurred in 31 dogs (17 in Group P, 14 in Group A). Additional drug was required to achieve endotracheal intubation in two dogs. Conclusions and clinical relevance: Rapid IV injection of propofol or alfaxalone provided suitable conditions for endotracheal intubation in healthy dogs but post-induction apnoea was observed commonly