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

ObjectiveTo compare a propofol continuous rate infusion (CRI) with a target-controlled infusion (TCI) in dogs.Study designRandomized prospective double-blinded clinical study.AnimalsA total of 38 healthy client-owned dogs.MethodsDogs premedicated intramuscularly with acepromazine (0.03 mg kg^–1) and an opioid (pethidine 3 mg kg^–1, morphine 0.2 mg kg^–1 or methadone 0.2 mg kg^–1) were allocated to P-CRI group (propofol 4 mg kg^–1 intravenously followed by CRI at 0.2 mg kg^–1 minute^–1), or P-TCI group [propofol predicted plasma concentration (Cp) of 3.5 μg mL^–1 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.ResultsOverall, 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^–1, 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 relevanceBoth 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.