Examination about stress-level during euthanasia in horses

Abstract

Euthanasia is one of the greatest responsibilities of veterinarian surgeons and should be carried out with the least possible stress for the patient and its owner. Currently, there is little knowledge about the amount of stress horses experience during the process of euthanasia. Serum Cortisol levels have been used to evaluate the stress response in horses, as pain and psychological stress stimulate the hypothalamic-pituitary-adrenal-axis, resulting in Cortisol release from the adrenal gland. In this prospective clinical study, we examined the Cortisol levels during euthanasia in a first attempt to analyze the stress levels our patients experience during this process. Euthanasia was performed in 40 horses and Cortisol levels were measured before sedation and after time of death. Analyzing the data using different groups (horses with colic, orthopedic problems or other diseases; presence or absence of the owner; acute or chronic diseases, and location of euthanasia) there was a smaller increase of Cortisol levels when owners were present (P = 0.04). Furthermore, there were significantly higher values at both measurements of serum Cortisol in horses suffering from colic than in all other horses (before P = 0.002, after P = 0.001). It made no significant difference, whether the horse was euthanized in the stable or in the surgical induction area and no difference were found in terms of the premedication. There were no significant differences in Cortisol levels in horses showing excitations (n = 4), moaning (n = 16) and diffuse muscle twitching (n = 11) during euthanasia. In contrast, a significant increase in Cortisol levels were found in horses with short-term respiration after breathing arrest (n = 4). The median increase was 4.4ng/ml, while it was only 3.6ng/ml in horses without side-effects during euthanasia. A recommendation for the euthanasia in horses was developed on the basis of the obtained data. These recommendations include the presence of the owner during euthanasia. This decreases the stress level for the horse, but a first a clear elucidation regarding the procedure is very important. In addition, the owner should be informed about possible accompanying signs such as muscle twiching or "final gasps". For premedication, a combination of different medications is possible. At our Equine Clinic euthanasia is performed by sedating the horses with xylazine (0.8mg/kg) or xylazine (0.8mg/kg) and butorphanol (0.025 mg/kg), inducing anesthesia using ketamine (2.2 mg/kg) and diazepam (0.02 mg/kg) and euthanizing horses using pentobarbital (80mg/kg).