Fentanyl for co-induction of propofol anesthesia in dogs premedicated with morphine

Abstract

The aim of the present study was to evaluate the effectiveness of fentanyl to reduce the induction dose of propofol and the quality of induction in dogs premedicated with morphine. The sedative effect promoted by morphine and its action on some physiological variables were also investigated. Twenty-two healthy dogs had their baseline values (BL) of the physiological variables and the degree of sedation recorded. Then, received morphine (0.3 mg/kg) intramuscularly. Ten minutes after morphine administration (T10), all variables were reassessed. Dogs were randomly assigned to receive intravenously: fentanyl (2.5 µg/kg) or saline (3.0 mL), followed by propofol (2 mg/kg/minute), groups FP and SP, respectively. The dose of propofol required for intubation and the quality of anesthetic induction were recorded. Morphine administration resulted in vomiting and no sedation. Heart rate significantly decreased at T10 in FP and in SP groups, compared to BL. The total dose of propofol used for anesthetic induction was 6.4 ± 1.7 and 5.8 ± 1.6 [mean ± standard deviation] mg/kg in FP and SP, respectively, with no differences between groups (P > 0.05). The quality of anesthetic induction score was excellent in all groups. During anesthetic induction, some dogs had apnea and muscle stiffness. Fentanyl was not effective in reducing the propofol requirement in the anesthetic induction of dogs premedicated with morphine. Anesthetic induction was excellent in both groups, and may be accompanied by apnea and muscle stiffness. Morphine resulted in no sedation, minimal changes in physiological parameters and vomiting.