Comparison between continuous rate infusion and target-controlled infusion of propofol in dogs: a randomized clinical trial.

Objective: To compare a propofol continuous rate infusion (CRI) with a target-controlled infusion (TCI) in dogs.

Study Design: Randomized prospective double-blinded clinical study.

Animals: A total of 38 healthy client-owned dogs.

Methods: Dogs premedicated intramuscularly with acepromazine (0.03 mg kg) and an opioid (pethidine 3 mg kg, morphine 0.2 mg kg or methadone 0.2 mg kg) were allocated to P-CRI group (propofol 4 mg kg intravenously followed by CRI at 0.2 mg kg minute), or P-TCI group [propofol predicted plasma concentration (Cp) of 3.5 μg mL for induction and maintenance of anaesthesia via TCI]. Plane of anaesthesia, heart rate, respiratory rate, invasive blood pressure, oxygen haemoglobin saturation, end-tidal carbon dioxide and body temperature were monitored by an anaesthetist blinded to the group. Numerical data were analysed by unpaired t test or Mann-Whitney U test, one-way analysis of variance and Dunnett's post hoc test. Categorical data were analysed with Fisher's exact test. Significance was set for p < 0.005.

Results: Overall, propofol induced a significant incidence of relative hypotension (mean arterial pressure 20% below baseline, 45%), apnoea (71%) and haemoglobin desaturation (65%) at induction of anaesthesia, with a higher incidence of hypotension and apnoea in the P-CRI than P-TCI group (68% versus 21%, p = 0.008; 84% versus 58%, p = 0.0151, respectively). Propofol Cp was significantly higher at intubation in the P-CRI than P-TCI group (4.83 versus 3.5 μg mL, p < 0.0001), but decreased during infusion, while Cp remained steady in the P-TCI group. Total propofol administered was similar between groups.

Conclusions And Clinical Relevance: Both techniques provided a smooth induction of anaesthesia but caused a high incidence of side effects. Titration of anaesthesia with TCI caused fewer fluctuations in Cp and lower risk of hypotension compared with CRI.