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-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. 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-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 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.

Effect of midazolam on the quality and duration of anaesthetic recovery in healthy dogs undergoing elective ovariohysterectomy or castration.

OBJECTIVE: To determine whether the use of a single dose of midazolam affects quality and duration of the recovery period in healthy dogs undergoing elective castration or ovariohysterectomy. STUDY DESIGN: Prospective, randomized, placebo-controlled, masked clinical trial. ANIMAL POPULATION: Seventy-four client-owned dogs undergoing neutering. METHODS: Following cage demeanour scoring using a simple descriptive scale (SDS), dogs were premedicated with acepromazine (0.03 mg kg-1) and pethidine (3 mg kg-1) intramuscularly (quadriceps muscle). Twenty minutes later sedation was scored with an SDS. Male dogs were induced with midazolam (0.25 mg kg-1) (group M) or an equivalent amount of Hartmann's solution (group P) and propofol intravenously (IV). Female dogs were induced with propofol alone and were administered midazolam (group M) or Hartmann's solution (group P) 5 minutes before intraoperative manipulation of the first ovary. Anaesthesia was maintained with isoflurane in oxygen. Intraoperative analgesia was provided with morphine (0.3 mg kg-1 IV) prior to the start of surgery. Male dogs were administered intratesticular lidocaine (1 mg kg-1). All dogs were administered meloxicam (0.2 mg kg-1 IV) at the end of the procedure, and recovery was scored with an SDS following extubation and 30 minutes later. Time to extubation, head lift, sternal position and standing and complications during recovery were recorded. Data are presented as median (range). RESULTS: Time to standing was significantly longer in animals in group M [56 (13-179) minutes] than in group P [44 (4-137) minutes], and the early recovery score in group M [3 (2-6)] was overall worse than in group P [3 (1-5)]. Significantly more dogs in group M (n = 30) than in group P (n = 22) displayed hypotension. CONCLUSIONS AND CLINICAL RELEVANCE: The administration of midazolam prolonged time to standing and had a mild negative effect on the quality of recovery in a pooled population of healthy male and female dogs undergoing neutering.