Caudal epidural analgesia is a well-established therapeutic modality for pain alleviation in horses. Additionally, epidural analgesia could potentially be a complementary diagnostic tool for confirmation of pain-related conditions in horses presenting with nonspecific signs of poor performance or rideability issues. To use the epidural as a diagnostic tool, the administered medications should provide efficient analgesia without accompanying adverse effects. Therefore, the objectives of the current study were to evaluate the analgesic properties and effects on locomotor function, mentation and physical examination parameters of caudal epidural co-administration of methadone and morphine in horses. Five mares received a caudal epidural injection of 0.1 mg/kg bwt methadone and 0.1 mg/kg bwt morphine diluted to a total volume of 4.4 mL/100 kg. Before and several times thereafter, horses were subjected to mechanical nociceptive threshold evaluation, physical examination, assessment of mentation and locomotor function examination. Horses were assigned ataxia scores (0–4) by a group of inexperienced raters (three senior-year veterinary students) and a group of experienced raters (two board-certified internal medicine specialists) that assessed the locomotor examinations either live or video-based. The epidural co-administration of methadone and morphine resulted in clinically relevant and statistically significant increases of horses’ tolerance to mechanical noxious stimuli at the coccygeal, perineal, sacral, lumbar and thoracic regions. Analgesia was evident after 4.4 h and lasted at least 5 h. Regional differences in the onset of analgesia reflected a cranial spread of the analgesic solution. No horses showed signs of gait disturbances; the overall median ataxia score was 0 at all times; and the average difference in scores between two randomly selected raters for a random horse at a random time point was 0.377 indicating high inter-rater agreement. There were no adverse changes of mentation and physical examination parameters. Observed side effects included signs of decreased frequency of defaecation, generalised sweating, and pruritus.

中文翻译：

---

马的尾端硬膜外联合使用美沙酮和吗啡：镇痛特性评估及其对运动功能、精神状态和体格检查参数的影响

尾部硬膜外镇痛是一种行之有效的缓解马疼痛的治疗方式。此外，硬膜外镇痛可能是一种补充诊断工具，用于确认表现不佳或骑乘性问题的非特异性迹象的马的疼痛相关状况。为了使用硬膜外麻醉作为诊断工具，所施用的药物应提供有效的镇痛，而不会伴随有副作用。因此，本研究的目的是评估马的尾部硬膜外联合给药美沙酮和吗啡的镇痛特性和对运动功能、精神和体格检查参数的影响。五匹母马接受了 0.1 mg/kg bwt 美沙酮和 0.1 mg/kg bwt 吗啡的尾部硬膜外注射，稀释至总体积为 4.4 mL/100 kg。在此之前和之后数次，对马进行机械伤害感受阈值评估、体格检查、精神评估和运动功能检查。一组缺乏经验的评估者（三名高年级兽医学生）和一组经验丰富的评估者（两名获得董事会认证的内科专家）对马进行了共济失调评分 (0-4)，他们通过现场或视频方式评估了运动检查. 美沙酮和吗啡的硬膜外联合给药导致马对尾骨、会阴、骶骨、腰椎和胸椎区域的机械性伤害性刺激的耐受性在临床上和统计学上显着增加。4.4 小时后镇痛明显并持续至少 5 小时。镇痛开始的区域差异反映了镇痛溶液的颅内扩散。没有马出现步态紊乱的迹象；共济失调总分中位数始终为 0；在随机时间点对一匹随机马的两个随机选择的评分者之间的平均得分差异为 0.377，表明评分者之间的一致性很高。精神状态和体格检查参数无不良变化。观察到的副作用包括排便频率降低、全身出汗和瘙痒的迹象。精神状态和体格检查参数无不良变化。观察到的副作用包括排便频率降低、全身出汗和瘙痒的迹象。精神状态和体格检查参数无不良变化。观察到的副作用包括排便频率降低、全身出汗和瘙痒的迹象。