Problems associated with perioperative morphine in horses: a retrospective case analysis.

This research sought to determine the prevalence of side effects caused by the administration of morphine in doses between 100 and 170 micrograms per kilogram during surgery in horses. The study concluded that this dosage does not increase the risk of complications when used for pain relief during surgery, and that morphine is a cost-effective method for providing such relief.

Research Methodology

• This retrospective research was conducted on the medical records of 84 healthy horses, aged between 2 months and 16 years, that underwent surgery at the Royal (Dick) School of Veterinary Studies between 1996 and 2000. The average weight of the horses was approximately 524 kg.
• The horses’ physiologic data and evidence of any surgical complications were compiled from their anesthesia records. All horses in this study were anesthetized with a combination of romifidine, ketamine, diazepam, and halothane, and had either undergone laryngeal surgery or orchiectomy.
• The study population was divided into two groups: those who received morphine (18 horses) and those who did not receive morphine (29 horses). The remaining 37 horses underwent different surgeries and were not included in the statistical analysis due to varying treatment regimens.
• The heart rate, breathing rate, and average arterial pressure of the horses were compared every 15 minutes from 30 to 120 minutes after anesthesia induction.
• Various statistical methods were used to compare the occurrence of intraoperative problems and recovery scores between the two groups.

Findings and Conclusion

• No significant differences were found between the group of horses that received morphine and the group that did not. The incidence of post-operative complications such as erratic movement in a confined space (box-walking) and colic were comparable in both groups.
• The study concluded that administering morphine in doses ranging from 100 to 170 micrograms per kilogram does not increase the risk of complications in horses anesthetized with the aforementioned combination of drugs.
• Based on the findings, the study suggests morphine as an affordable and acceptable method for providing perioperative pain relief in horses, implying that it can be used effectively without significantly increasing risk.