Objective To investigate the cardiorespiratory, nociceptive and endocrine effects of the combination of propofol and remifentanil, in dogs sedated with acepromazine.
Study design Prospective randomized, blinded, cross-over experimental trial.
Animals Twelve healthy adult female cross-breed dogs, mean weight 18.4 ± 2.3 kg.
Methods Dogs were sedated with intravenous (IV) acepromazine (0.05 mg kg−1) followed by induction of anesthesia with IV propofol (5 mg kg−1). Anesthesia was maintained with IV propofol (0.2 mg kg−1 minute−1) and remifentanil, infused as follows: R1, 0.125 μg kg−1 minute−1; R2, 0.25 μg kg−1 minute−1; and R3, 0.5 μg kg−1 minute−1. The same dogs were administered each dose of remifentanil at 1-week intervals. Heart rate (HR), mean arterial pressure (MAP), respiratory rate (fR), end tidal CO2 (Pe′CO2), arterial hemoglobin O2 saturation, blood gases, and rectal temperature were measured before induction, and 5, 15, 30, 45, 60, 75, 90, and 120 minutes after beginning the infusion. Nociceptive response was investigated by electrical stimulus (50 V, 5 Hz and 10 ms). Blood samples were collected for plasma cortisol measurements. Statistical analysis was performed by anova (p < 0.05).
Results In all treatments, HR decreased during anesthesia with increasing doses of remifentanil, and increased significantly immediately after the end of infusion. MAP remained stable during anesthesia (72–98 mmHg). Antinociception was proportional to the remifentanil infusion dose, and was considered satisfactory only with R2 and R3. Plasma cortisol concentration decreased during anesthesia in all treatments. Recovery was smooth and fast in all dogs.
Conclusions and clinical relevance Infusion of 0.25–0.5 μg kg−1 minute−1 remifentanil combined with 0.2 mg kg−1 minute−1 propofol produced little effect on arterial blood pressure and led to a good recovery. The analgesia produced was sufficient to control the nociceptive response applied by electrical stimulation, suggesting that it may be appropriate for performing surgery.