Comparison of electroacupuncture and butorphanol on respiratory and cardiovascular effects and rectal pain threshold after controlled rectal distention in mares.

The research compares the effects of two pain management approaches – electroacupuncture and a drug called butorphanol – on vital signs and pain sensitivity in horses after a rectal distention procedure.

Study Aim and Methodology

• The goal of the study was to compare the effects of electroacupuncture and butorphanol tartrate on hemodynamic (blood pressure and heart rate) and respiratory states, as well as pain tolerance in horses after a controlled rectal distention procedure.
• Eight healthy mares were used in the research. Each horse went through three treatments, administered in a random order with at least a week between each. These treatments were saline solution (the control), butorphanol tartrate, or electroacupuncture (EA).
• For the EA treatment, acupuncture points Bladder 21, 25, and 27 on both sides of the vertebral column, Bai hui, and Stomach 36 (right side only) were specifically targeted.
• To measure the rectal pain threshold, they inserted a balloon in the rectum of each horse and inflated it to pressures less than or equal to 220mm Hg.

Measurement and Findings

• Every five, fifteen, thirty, sixty, ninety, and 120 minutes after the beginning of each treatment, the researchers noted the horse’s rectal temperature, cardiovascular and respiratory states, and compared them to their previous baseline measurements.
• Butorphanol led to the greatest increase in the pain threshold compared to EA. However, the study observed minimal changes in cardiovascular and respiratory states with EA.
• Butorphanol increased heart and respiratory rates, arterial blood pressure, and rectal temperature to a significant degree, although these changes were not of clinical concern.
• After both EA and butorphanol treatments, arterial pH, carbon dioxide tension, bicarbonate concentrations, base excess, packed cell volume (Hct), and concentration of total solids were not significantly different from the baseline measurements.

Conclusions

• The study concluded that both electroacupuncture and butorphanol may be useful methods of providing analgesia (pain relief) for rectal conditions in horses, with the latter having a more pronounced effect on the pain threshold.
• Even though butorphanol led to more significant changes in heart and respiratory rates, arterial blood pressure, and rectal temperature, the changes were not clinically significant. This suggests that either method could be used without causing major shifts in a horse’s vital signs.