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

Abstract

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 pressures, 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.