Dose requirement and cardiopulmonary effects of diluted and undiluted propofol for induction of anaesthesia in dogs

Abstract

Objective: To compare anaesthetic induction in healthy dogs using propofol (10 mg mL-1) and diluted propofol (5 mg mL-1). Study design: Prospective, randomized, blinded, clinical study. Animals: Thirty healthy dogs (13 males/17 females), aged 7 - 183 months and weighing between 3.6 - 44.4 Kg. Methods: Following intramuscular sedation (acepromazine 0.02 mg Kg-1 and methadone 0.2 mg Kg-1), propofol (10 mg mL-1) (UP) or diluted propofol (5 mg mL-1) (DP) was administered intravenously by an anaesthetist unaware of the treatment group until tracheal intubation was possible. Sedation, intubation and induction quality were scored. Baseline and postinduction pulse rate (PR), respiratory rate (fR) and systolic (SAP), mean (MAP) and diastolic (DAP) blood pressure were measured and compared. Time to first breath (TTFB) and induction dose were recorded. Data was analysed for normality and Mann-Whitney U or Student’s t tests were performed where adequate. The level of significance was set at p ≤ 0.05. Data was presented as mean ± standard deviation or median (range) as appropriate. Results: The dose of propofol administered to achieve induction was lower in the DP group (2.64 ± 0.47 mg Kg-1) than in the UP group (3.48 ± 1.17 mg Kg-1) (p = 0.02241). No significant difference was observed in baseline and postinduction PR, SAP, MAP, DAP and fR between groups. Difference between baseline and postinduction of the same parameters was not different between groups. TTFB was not different between groups. Sedation was similar between groups. Quality of tracheal intubation was better with UP 0 (0-1) than with DP 1 (0-2) (p = 0.03585), but overall quality of induction was similar between groups [UP 0 (0-1) and DP 0 (0-1), p = 0.5497]. Conclusion and clinical relevance: Diluting propofol reduced the dose required to induce anaesthesia, but did not significantly alter cardiorespiratory parameters associated to it.