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 (f(R)) 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, f(R), post-induction apnoea, arterial pres-sures, hypotension, SpO(2), 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.