Effect of Fentanyl Infusion on Heart Rate Variability and Anaesthetic Requirements in Isoflurane-Anaesthetized Horses

Controversy continues to surround the use of opioids in equine anaesthesia, with variable effects reported. This blinded clinical study aimed to investigate the influence of a low-dose fentanyl continuous rate infusion (CRI) on isoflurane requirements, parasympathetic tone activity (PTA), and anaesthetic parameters in horses during general anaesthesia. All of the twenty-two horses included in the research underwent a standard anaesthetic protocol. Eleven horses in the fentanyl group (Group F) received a loading dose of fentanyl at 6 µg/kg, followed by a CRI of 0.1 µg/kg/min during anaesthesia. A further 11 horses in the control group (Group C) received equivalent volumes of normal saline. Anaesthetic parameters and PTA index were recorded during anaesthesia. The achieved mean fentanyl plasma concentration was 6.2 ± 0.83 ng/mL. No statistically significant differences between groups were found in isoflurane requirements, MAP values, and mean dobutamine requirements. However, horses in Group F required a significantly lower dose of additional ketamine to maintain a sufficient depth of anaesthesia. Significantly higher PTA values were found in the fentanyl group. Further research is warranted to determine the limitations of PTA monitoring, and the influence of various anaesthetics on its values.

Evaluation of different premedicants in canine anaesthesia

Fifteen experimental trials were made in fifteen dogs in three different groups to study the degree of sedation produced by different premedicants, to evaluate and to compare their effects on various clinical parameters including different reflexes in dogs. These animals were premedicated with xylazine (1.1mg/kg), atropine (0.05mg/kg)-xylazine (1.1mg/kg) and diazepam (0.2mg/kg)-xylazine (1.1mg/kg) to observe their effect on different clinical and anaesthetic parameters. Diazepam-xylazine combination produced deep sedation while mild sedation was recorded with atropine-xylazine premedication. Respiration rate, heart rate and rectal temperature significantly decreased (P<0.05) in dogs of all three groups after fifteen minutes of premedication. Diazepam-xylazine produced marked reduction (P<0.05) on clinical parameters while atropine-xylazine produced mild to moderate reduction (P<0.05) on clinical parameters in dogs. All experimental dogs in different groups were anaesthetized with ketamine hydrochloride after fifteen minutes of premedication. The respiration rate, heart rate and rectal temperature reduced significantly (P<0.05) in xylazine-ketamine, atropinexylazine- ketamine and diazepam-xylazine-ketamine combination at 5, 10 and 15 min after induction when compared with pre-induction control values. The longest duration of anaesthesia (61.6 minutes) was obtained with diazepam-xylazine-ketamine combination while the shortest anaesthetic period (28.4 minutes) was observed in xylazine-ketamine combination. Diazepam-xylazine-ketamine combination produced longest recovery period (56.4 minutes) while the shortest recovery period (46.2 minutes) was observed with xylazineketamine combination. Atropine-xylazine-ketamine combination appears to be a safe combination for anaesthesia in dogs.Res. Agric. Livest. Fish.4(3): 209-214, December 2017