Effects of xylazine on cecal mechanical activity and cecal blood flow in healthy horses.

This research describes a study on the effects of various dosages of xylazine on the cecal mechanical activity, blood flow, arterial pressure and heart rates in horses. Larger dosages were shown to decrease cecal motility for longer periods of time and all dosages caused transient hypertension and bradycardia, followed by hypotension.

Study Objectives and Methodology

• The research was aimed at understanding the influence of xylazine, a commonly used equine sedative, on the cecal mechanical activity (the movement of the cecum which is a part of the horse’s gut), arterial blood flow in the cecum, carotid arterial pressure, and heart rate in horses.
• Six healthy horses were selected for the research. Three different dosages of xylazine (1.1 mg/kg, 0.55 mg/kg, and 0.275 mg/kg) were intravenously administered to the horses.
• Observations were made 30 minutes prior to the administration and continued for two hours post-administration.

Key Findings

• Xylazine administration had a significant effect on the cecal mechanical activity of the horses. The effect was dosage-dependent, with higher dosages resulting in more pronounced effects.
• The highest dosage (1.1 mg/kg) reduced the mean motility index (a measure of gut movement) of the circular and longitudinal muscle layers for all the four 30-minute periods observed post-administration.
• The 0.55 mg/kg dosage caused a reduction in the motility index during the first and second 30-minute periods, while the smallest dosage (0.275 mg/kg) affected only the first 30-minute period after administration.
• All dosages of xylazine caused a decrease in cecal arterial blood flow, with values significantly lower than baseline at two and four minutes after administration in all dosages, and also eight minutes after administration in the two higher dosages.
• Irrespective of the dosage, xylazine administration resulted in transient hypertension (a temporary increase in blood pressure) and a slower heart rate (bradycardia), followed by lower-than-normal blood pressure (hypotension).

Implications of the Findings

• The findings suggest that xylazine, as a sedative, impacts the gut movement and blood parameters in horses in a dosage-dependent manner. These need to be taken into consideration when using xylazine clinically.
• Hypertension and bradycardia induced on administration of xylazine, irrespective of the dosage, indicate potential cardiovascular effects that warrant further research.