Metabolic and hormonal responses to neuroleptanalgesia (etorphine and acepromazine) in the horse.

This study examines the changes in blood composition and hormone levels in horses that are given etorphine and acepromazine, painkillers often used in surgical procedures. The researchers found evidence of increased hormonal and metabolic activity, which could potentially cause complications, such as irregular heart rhythms.

Introduction to the Research

• The research aims to investigate how administration of certain drugs — etorphine and acepromazine — in horses results in changes in their metabolic and hormonal reactions. Etorphine and acepromazine are neuroleptic analgesics often used to manage pain in veterinary medicine.
• The study specifically examines the changes in the horses’ haematocrit, blood glucose, lactate, plasma non-esterified fatty acids (NEFA), insulin, cortisol, and venous blood pH.

Observations and Findings

• The researchers observed an increase in various components of the horse’s blood after administration of the drugs. There was a notable rise in haematocrit, blood glucose, blood lactate, and plasma NEFA.
• Of these, the rise in plasma NEFA was especially remarkable after injection of the antagonist diprenorphine. This is significant as it might contribute to the production of cardiac arrhythmias – irregular heart rhythms that could prove dangerous.
• Plasma insulin levels were found to be reduced at the end of the surgical procedure. Alongside the other changes and the profuse sweating observed in the horses, these are indirect signs of intense sympathetic activation – part of the body’s response to stress or danger.

Other Factors Considered

• Plasma cortisol levels did not change significantly in the horses. The results varied widely among individual horses, making it difficult to establish a clear pattern.
• The pH of the horses’ venous blood decreased, reflecting the increase in lactate levels and venous carbon dioxide tension – a measure of the amount of carbon dioxide gas dissolved in the blood, and an indicator of lung function.

Conclusion

• This research provides useful insights into how etorphine and acepromazine affect horses’ physiologies. The findings could have crucial implications for the use of these drugs in horse surgeries, especially as the study highlights potential risk factors such as cardiac arrhythmias.