兽研引言
疼痛是一种不愉快的感官和情绪体验，显著影响动物健康和福利[1]。在兽医患者中，疼痛会诱导神经生物学反应，可能损害生理稳定性、恢复和整体生活质量。因此，有效的疼痛识别和管理是现代兽医实践的基本组成部分[2]。
在兽医学中，疼痛识别和管理尤其具有挑战性，因为动物无法用语言表达其主观体验[3]。近几十年来，疼痛评估工具、物种特异性疼痛量表和循证镇痛指南的重大进展已将疼痛评估确立为临床评估的重要组成部分以及兽医学中的“第四生命体征”[4–6]。
当代镇痛策略强调多模式方法，结合具有不同作用机制的药物，最常见的是阿片类药物和非甾体抗炎药（NSAIDs），以提高镇痛疗效并减少不良反应[7, 8]。
阿片类镇痛药因其强效镇痛作用、可逆性和可预测的药效动力学，是兽医麻醉中围手术期疼痛管理的基石[2, 9, 10]。然而，欧洲各国阿片类药物的可及性差异很大，因为监管限制和可获得性可能限制其在临床实践中的常规使用[11]。
尽管近年来对兽医疼痛管理的科学兴趣大幅增加，但研究仍表明小动物医学中的镇痛实践并不一致[12]。评估围手术期和慢性疼痛管理的国际调查显示，兽医专业人员对镇痛原则的认识和接受度不断提高；然而，在知识、药物可获得性和多模式镇痛方案的持续实施方面仍存在差距[13–27]。
兽医学中阿片类镇痛药的可获得性和使用不仅受临床因素影响，还受国家法规和市场供应的影响。尽管拉脱维亚遵循欧盟关于兽药产品的立法，但阿片类药物的采购、储存、记录保存和处方在国家层面受到监管。此外，2019年美沙酮相对较新地进入拉脱维亚兽医市场，扩大了伴侣动物可用的阿片类镇痛药范围。因此，拉脱维亚的阿片类药物可获得性和使用模式可能不一定反映西欧国家报告的情况。区域数据对于识别各国特有的趋势和兽医疼痛管理的障碍至关重要。尽管近期研究评估了斯洛文尼亚、意大利、加拿大和巴西等国的镇痛实践和对疼痛管理的态度，但拉脱维亚和波罗的海地区目前缺乏可比数据[13, 17, 21, 25]。此外，尽管阿片类药物在当代多模式镇痛方案和国际疼痛管理指南中发挥核心作用，但这些研究均未专门关注该地区小动物实践中的阿片类药物使用模式[1, 28–32]。因此，可能影响临床实践中阿片类药物使用的因素，包括药物可获得性的区域差异、专业经验和手术活动，仍然特征不明。
因此，本研究的主要目的是评估拉脱维亚兽医的阿片类药物可获得性、阿片类药物使用模式和围手术期疼痛管理实践。次要目的是调查阿片类药物可获得性与手术病例量、专业经验年限、地理区域和疼痛评估实践之间的关联。研究假设为：（1）完全μ-阿片受体激动剂将更频繁地用于重度疼痛，而部分激动剂将优先用于轻至中度疼痛；（2）手术病例量较高的诊所将报告芬太尼和美沙酮等强效阿片类药物的可获得性更高；（3）毕业年限较少的兽医将报告更容易获得强效阿片类药物，并更频繁地使用标准化疼痛评估工具。据我们所知，本研究是波罗的海地区首个同时考察伴侣动物兽医手术病例量、专业经验、地理位置和阿片类药物选择之间关联的全国性调查。通过在全国兽医队列中考察这些因素，本研究提供了对拉脱维亚阿片类药物使用和围手术期疼痛管理实践的更广泛理解。
材料与方法
伦理批准
本研究经拉脱维亚生命科学与技术大学（拉脱维亚叶尔加瓦）动物福利与保护伦理委员会审查批准（批准号：LLU_Dzaep_2022-5；批准日期：2022年10月11日）。本研究按照涉及人类参与者研究的机构伦理指南开展，并符合适用的国家伦理行为和数据保护要求。参与调查完全自愿。在访问问卷之前，所有参与者均获得了关于研究目的、预计完成时间、保密措施以及所收集数据预期用途的信息。所有受访者在参与前均获得了电子知情同意。未收集任何个人可识别信息，包括姓名、电子邮件地址或IP地址。所有回复在分析前均经过匿名化处理，并存储在仅调查人员可访问的受密码保护的安全电子数据库中。参与者可在提交回复前的任何时间退出调查，且不会受到任何处罚。数据仅以汇总形式进行分析和报告，以确保受访者的保密性和隐私。
研究期间和地点
本调查在拉脱维亚全国范围内以电子方式实施。在线问卷通过Google Forms以电子方式实施，回复收集时间为2023年12月1日至2024年1月1日。调查结束后，数据于2024年1月至4月期间导出、进行完整性筛查、清理和统计分析。
研究设计
采用结构化问卷进行了一项横断面在线调查。符合条件的参与者为在拉脱维亚执业的持证兽医。调查通过Google Forms实施，并由拉脱维亚兽医协会和拉脱维亚兽医教育中心通过电子邮件和社交媒体渠道以电子方式分发。研究期间分发了一次提醒以鼓励参与。仅纳入完整填写的问卷。回复收集时间为2023年12月1日至2024年1月1日。调查回复以电子表格（MS Excel for Windows）形式下载。数据收集时间为2023年12月1日至2024年1月1日。
数据收集
参与调查为自愿性质，未提供任何报酬或激励。在开始填写问卷之前，受访者已被告知研究目的、预计完成时间（15–20分钟）以及数据收集的匿名性质。所有参与者在完成调查前均获得了电子知情同意。未收集任何个人可识别信息，包括姓名、电子邮件地址或IP地址。调查回复存储在仅调查人员可访问的受密码保护的电子数据库中。数据以汇总形式进行分析以保护参与者保密性。受访者可在每页末尾使用返回按钮查看和修改其答案。调查由24道多项选择题组成。
问卷
问卷基于先前发表的评估伴侣动物疼痛管理实践和阿片类药物使用的调查编制，并进行了调整以反映拉脱维亚当地临床实践[10, 13, 17, 21–23, 33–35]，且在分发前未经过正式验证。
问卷由六个部分组成，涉及以下领域：人口学和专业背景、临床实践中阿片类药物的可获得性和使用、物种特异性阿片类药物使用、阿片类药物使用指征和从业者认知、疼痛管理实践和不良反应，以及基于疼痛严重程度的药物选择。补充材料1提供了问卷条目和回答选项的详细概述。未应用条目加权；所有问卷条目对分析的贡献均等，未根据相对重要性进行调整。
统计分析
调查回复采用描述性和推断性统计进行分析。分类变量计算频率和百分比。对于多项回答题，每个回答选项独立分析并报告为选择该选项的受访者比例；因此，百分比可能超过100%。
分类变量之间的关联，包括手术活动、阿片类药物可获得性和疼痛评估方法，采用独立性卡方检验进行评估，并计算Cramer's V作为效应量指标。有序变量之间的关联，如专业工作年限与阿片类药物可获得性，采用Spearman秩相关系数（ρ）进行评估。进行二元logistic回归以进一步评估专业经验与芬太尼和美沙酮可获得性之间的关系。计算比值比（ORs）及其95%置信区间（CIs），并使用Nagelkerke's R²和Hosmer–Lemeshow拟合优度检验评估模型拟合。统计显著性设定为p < 0.05。
数据管理和描述性分析使用Microsoft Excel（Microsoft Corporation, Redmond, WA, USA）进行，回归分析使用基于Python的统计计算进行。
结果
应答率和样本代表性
在拉脱维亚兽医协会967名注册会员中（数据由拉脱维亚国家兽医协会于2024年提供），共有101人参与了调查，参与率为10.4%。该样本约占拉脱维亚估计687名活跃执业兽医的14.7%（据欧洲兽医联合会报告），而该国总人口约为190万。
受访者的人口学与职业特征
共回收拉脱维亚各地受访者填写的完整问卷101份。大多数回复（57%，57/101）来自在里加及周边地区执业的兽医，而4%（4/101）来自库尔泽梅地区（表1）。
Table 1. Demographic and professional characteristics of respondents (n = 101).
| Characteristic | n (%) |
|---|---|
| Region of practice | |
| Rīga and surrounding region | 57 (56.4) |
| Zemgale | 19 (18.8) |
| Vidzeme | 13 (12.9) |
| Latgale | 7 (6.9) |
| Kurzeme | 4 (4.0) |
| Years of professional experience | |
| 0–5 years | 30 (28.7) |
| 6–15 years | 34 (33.7) |
| 16–20 years | 9 (7.9) |
| >20 years | 28 (27.7) |
| Practice typeᵃ | |
| Small-animal practice | 82 (81.2) |
| Exotic animal practice | 10 (9.9) |
| Farm animal practice | 10 (9.9) |
| Equine practice | 4 (4.0) |
| Animals treated per month | |
| ≤100 | 45 (43.6) |
| 100–200 | 36 (35.6) |
| 300–500 | 12 (11.9) |
| >500 | 8 (6.9) |
| Surgical activity (% of patients undergoing surgery) | |
| 0–10% | 32 (30.7) |
| 10–20% | 37 (36.6) |
| 30–50% | 28 (27.7) |
| >50% | 4 (4.0) |
大多数参与者（82.7%，n=83）报告主要从事小动物执业。此外，部分受访者报告在主要执业之外还诊治其他物种，包括异宠或非传统伴侣动物（10.2%，10/101）、农场动物（10.2%，10/101）和马匹患者（4.1%，4/101）。
大多数受访者（43.6%，44/101）报告每月诊治最多100只动物，而35.6%（36/101）每月诊治100–200只动物。报告的动物诊治数量最高的是里加及周边地区，该地区每月诊治超过500只动物的执业机构报告更为频繁（6.9%，7/101）。
阿片类药物的可及性
80%（81/101）的受访者报告在临床实践中常规使用阿片类药物。在强效阿片类药物中，54.1%（55/101）的受访者报告可获得μ-阿片受体激动剂美沙酮，其次是芬太尼（45.9%，46/101）。芬太尼的可及性主要在里加及周边地区报告（24.8%，25/101），其次是泽姆加莱（9.9%，10/101）。维泽梅和库尔泽梅地区的可及性明显较低（各2%；2/101），而拉特加莱地区未报告可及性（0/101）（图1）。
[图：受访兽医（n = 101）中芬太尼可及性的地区分布。]
仅12.9%（13/101）的受访者临床实践报告使用吗啡。83.5%（84/101）的受访者报告可获得部分阿片受体激动剂丁丙诺啡。在低效价阿片类药物和部分μ-阿片受体激动剂中，布托啡诺在大多数地区最为常用（84.7%，86/101），而曲马多（52.9%，53/101）在特定地区更为普遍，尤其是里加及周边地区。
阿片受体拮抗剂纳洛酮在43.2%（44/101）的兽医执业机构中可及。在报告芬太尼可及的执业机构中，84.6%（33/39）可获得纳洛酮；在报告美沙酮可及的执业机构中，73.9%（34/46）可获得纳洛酮，表明大多数可获得这些阿片类药物的诊所同时也备有其拮抗剂（图2）。
[图：所有受访诊所及报告芬太尼或美沙酮可及的诊所中纳洛酮的可及性。]
工作年限与阿片类药物可及性的关系
大多数受访者为从业年限<15年的较年轻执业者。分析显示，从业年限与报告的芬太尼和美沙酮可及性之间存在负相关（图3和图4）。毕业时间较近的兽医更可能报告可获得芬太尼，而从业年限>20年者报告的可及性最低。
[图：受访兽医中按从业年限划分的芬太尼可及性。]
从业年限与芬太尼可及性之间观察到显著负相关（Spearman's ρ = −0.275，p = 0.0059），表明毕业年限较短的兽医更可能报告可获得芬太尼。逻辑回归分析证实了这一关联。从业年限增加与芬太尼可及性几率降低相关（OR=0.60，95% CI：0.41–0.88，p=0.008）。模型拟合可接受（Nagelkerke R² = 0.10；Hosmer–Lemeshow p = 0.642）。相比之下，工作年限与美沙酮可及性之间未观察到显著关联（Spearman's ρ = −0.079，p = 0.436）。逻辑回归同样显示从业年限对美沙酮可及性无显著影响（OR = 0.86，95% CI：0.62–1.21，p = 0.400）。模型拟合统计表明解释力有限（Nagelkerke R²=0.01；Hosmer–Lemeshow p = 0.556）。
[图：受访兽医中按从业年限划分的美沙酮可及性。]
手术活动与阿片类药物可及性之间的关联
在兽医实践中进行外科手术的频率与芬太尼和美沙酮的可获得性之间观察到显著关联。与执行较少外科手术的诊所相比，外科手术占病例量30-50%的诊所更频繁地报告这些阿片类药物的可获得性。
卡方分析表明，外科活动与芬太尼可获得性之间存在显著关联（χ² = 15.39，p = 0.0015）。效应量为中等（Cramer's V=0.39），表明外科病例量较高的诊所更可能报告芬太尼的可获得性。外科活动与美沙酮可获得性之间也观察到显著关联（χ² (3) = 17.50，p = 0.0006）。效应量为中等（Cramer's V = 0.42），提示执行外科手术比例较高的诊所中美沙酮的可获得性更高。
对有关外科手术中阿片类药物使用应答的分析显示，最常报告的挑战与人为错误和记录保存（62.4%，63/101）以及法律和文档要求（40.6%，41/101）相关。较少见的，受访者提到药物可获得性或采购困难（13.9%，14/101）以及储存要求（12.9%，13/101）。
物种特异性阿片类药物使用
最常报告的阿片类药物是丁丙诺啡（42.0%，42/101）和布托啡诺（32.1%，32/101），其次是美沙酮（19.8%，20/101）。对问题12应答的分析揭示了不同物种间阿片类药物使用的不同模式。芬太尼（21.8%，22/101）和曲马多（15.8%，16/101）在犬中最常报告，而布托啡诺（21.8%，22/101）和丁丙诺啡（22.8%，23/101）在犬和猫中均常报告。
美沙酮在犬和猫中均有报告，犬中报告率较高（14.9%，15/101），犬猫联合诊所中为（16.8%，17/101）。相比之下，吗啡很少使用，大多数受访者（7.9%，8/101）表示未使用。
阿片类药物使用指征与认知
兽医报告将阿片类药物用于各种临床目的，其中治疗性疼痛管理（47.6%，48/101）、术中镇痛（45.2%，46/101）和术后疼痛控制（33.3%，34/101）是最常选择的指征。此外，21.4%（22/101）的受访者报告在姑息治疗环境中使用阿片类药物。
当被问及在哪些外科手术中给予阿片类药物时，55.1%（56/101）的受访者表示在所有列出的干预措施中均使用。在各项手术中，阿片类药物最常报告用于软组织手术（43.6%，44/101）和去势或卵巢子宫切除术（42.3%，43/101），其次是牙科和口腔手术（35.9%，36/101）和骨科手术（21.8%，22/101）。
曲马多的使用在不同外科活动水平的从业者中存在差异。在10-20%的登记动物接受手术的诊所中最常报告（34.4%，11/101），其次是30-50%（28.1%，9名受访者）和0-10%（25.0%，8名受访者）。只有一小部分（6.3%，2名受访者）外科病例量超过50%的诊所报告使用曲马多。
96.6%（98/101）的受访者对将阿片类药物引入兽医实践给予了积极评价。总计62.4%（63/101）的受访者评价其疼痛评估和阿片类药物使用知识为足够但需要改进。
当被问及如何评估动物的疼痛时，62.6%（62/99）的受访者报告主要依赖自身的临床经验。此外，48.4%（46/95）报告查阅科学文献或从研讨会和会议获得的知识，33.0%（33/100）报告使用疼痛量表和世界小动物兽医协会（WSAVA）疼痛评估指南，29.7%（30/101）依赖同事的经验。受访者可选择多个选项（图5）。
[图：动物疼痛评估所使用的方法。]
独立性卡方检验表明，专业经验年限与疼痛评估方法之间存在显著关联（χ² = 27.18，df = 12，p = 0.0073；Cramer's V = 0.303）。在拥有0-5年专业经验的兽医中，41%报告使用正式疼痛量表和WSAVA指南，而经验>20年的兽医中有50%报告主要依赖个人临床经验。
疼痛管理实践与不良反应
镇静是清醒动物中观察到的最常见不良反应（61.0%，62/101）。其他报告的不良反应包括流涎（41.5%，42/101）、喘息（37.8%，38/101）以及以发声和不安为特征的烦躁不安（36.6%，37/101）。23.2%（23/101）的受访者报告心动过缓和低血压，3.7%（4/101）报告呕吐。在麻醉期间给予阿片类药物时，58.9%（59/101）的受访者报告心动过缓。35.6%（36/101）的病例报告低血压，28.8%（29/101）报告低体温和呼吸抑制。表2提供了与阿片类药物给药相关不良反应的详细概述。51.1%（52/101）的受访者将阿片类药物与NSAIDs联合使用，主要用于急性疼痛的管理。
Table 2. Reported adverse effects associated with opioid administration in small animals under different clinical conditions.
| Clinical context | Adverse effect | Respondents reporting adverse effect, n (%) |
|---|---|---|
| Conscious animals | Sedation | 62 (61.0) |
| Hypersalivation | 42 (41.5) | |
| Panting | 38 (37.8) | |
| Dysphoria (vocalization, restlessness) | 37 (36.6) | |
| Bradycardia and hypotension | 23 (23.2) | |
| Vomiting | 4 (3.7) | |
| During anesthesia | Bradycardia | 59 (58.9) |
| Hypotension | 36 (35.6) | |
| Hypothermia | 29 (28.8) | |
| Respiratory depression | 29 (28.8) |
根据疼痛严重程度选择药物
布托啡诺（29.7%，30/101）和丁丙诺啡（14.9%，15/101）是报告用于轻度疼痛最常见的阿片类药物。曲马多（5.9%，6/101）和美沙酮（2.0%，2/101）的报告频率较低。在中度疼痛病例中，23.8%（24/101）的受访者报告使用丁丙诺啡，其次是布托啡诺（11.9%，12/101）和美沙酮（10.9%，11/101）。芬太尼（39.6%，40/101）和美沙酮（31.7%，32/101）是报告用于治疗重度疼痛最频繁的阿片类药物。26.7%（27/101）的受访者报告使用丁丙诺啡，而10.9%（11/101）报告使用吗啡。表3提供了根据感知疼痛严重程度选择阿片类药物的详细概览。
Table 3. Opioid selection according to perceived pain severity in dogs and cats among surveyed veterinarians.
| Pain severity | Opioid | Respondents selecting opioid, n (%) |
|---|---|---|
| Mild pain | Butorphanol | 30 (29.7) |
| Buprenorphine | 15 (14.9) | |
| Tramadol | 6 (5.9) | |
| Methadone | 2 (2.0) | |
| Moderate pain | Buprenorphine | 24 (23.8) |
| Butorphanol | 12 (11.9) | |
| Methadone | 11 (10.9) | |
| Severe pain | Fentanyl | 40 (39.6) |
| Methadone | 32 (31.7) | |
| Buprenorphine | 27 (26.7) | |
| Morphine | 11 (10.9) |
讨论
研究结果概述
本研究基于101名受访者的数据，评估了拉脱维亚兽医的阿片类药物使用模式和疼痛评估实践。据我们所知，这是首次系统性地专门调查拉脱维亚小动物临床实践中对阿片类药物使用的态度、疼痛感知及镇痛策略。尽管应答率不高（10.4%），但参与者的人口学和专业分布表明，研究结果可为当前临床实践提供有意义的见解。
若干发现值得特别关注。首先，强效阿片类药物的可及性存在显著地区差异，芬太尼和美沙酮主要在里加及周边地区报告，该国其他地区报告频率明显较低。其次，从业年限与芬太尼可及性和疼痛评估实践均相关，提示在采用循证镇痛方法方面存在代际差异。第三，超过半数受访者报告美沙酮可及，尽管其进入拉脱维亚兽医市场相对较晚，表明其已快速融入临床实践。总之，这些发现为影响拉脱维亚兽医疼痛管理的因素提供了重要见解。
尽管近期没有专门研究拉脱维亚小动物兽医实践中阿片类药物使用的研究，但从评估兽医对伴侣动物疼痛管理方法的国际调查中可以推断出类似趋势。总体而言，这些研究表明，阿片类药物的使用受临床医生对疼痛的认知、监管限制、药物可及性以及各实践机构对镇痛总体重视程度的影响[17, 21, 27, 36]。
根据疼痛严重程度选择阿片类药物
拉脱维亚兽医的阿片类药物选择反映了根据疼痛严重程度的适当区分。关于重度疼痛，芬太尼（39.6%，40/101）和美沙酮（31.7%，32/101）是报告最频繁的阿片类药物，而丁丙诺啡（26.7%，27/101）和吗啡（10.9%，11/101）报告频率较低。这些发现表明，阿片类药物选择总体符合当代镇痛原则和围手术期镇痛的國際建议，其中布托啡诺最常用于轻度疼痛，丁丙诺啡用于中度疼痛，芬太尼和美沙酮用于重度疼痛[37, 38]。
这些发现支持我们的第一个假设，即纯μ-阿片受体激动剂将更频繁地用于重度疼痛，而部分激动剂将优先用于轻度至中度疼痛。
阿片类药物可及性与地区差异
阿片类药物引入兽医实践被绝大多数人认为是有益的，96.6%（98/101）的受访者报告镇痛和动物福利得到改善。只有一小部分兽医认为阿片类药物可及性具有负面或无影响。这种强烈的专业共识强化了阿片类药物作为有效疼痛管理核心组成部分的作用，并与提倡在多模式镇痛方案中使用阿片类药物的国际建议相一致。
阿片类药物是拉脱维亚兽医临床实践中急性疼痛管理的基本组成部分，这与其他国家的研究结果一致[21, 27]。然而，其可获得性因地区和执业类型而存在显著差异。芬太尼和美沙酮在手术病例量较高的诊所（≥30%的注册动物）中可获得性显著更高，凸显了手术活动与强效阿片类药物采购之间的密切关系。这一观察结果与国际证据一致，表明μ-阿片受体激动剂的可及性在围手术期镇痛需求较大的执业机构中最高[37, 39]。
地理差异十分显著：芬太尼和美沙酮主要在里加及周边地区可获得，其次是泽姆加莱，而在维泽梅和库尔泽梅可获得性极低，在拉特加莱则完全不可获得。这些模式可能反映了转诊结构和复杂外科手术在城市中心的集中。尽管可能性较低，但不能排除农村地区的麻醉标准和镇痛实践可能有所不同，值得进一步研究。小动物兽医执业机构在里加及周边地区的集中可能进一步导致了这些观察到的差异。
多种因素可能促成这些地区差异。兽医转诊中心和开展高级外科手术的执业机构主要集中在较大的城市区域（里加和叶尔加瓦），这可能增加对强效阿片类药物的需求，并为其储存和给药所需的基础设施提供合理性。经济因素也可能影响采购决策，尤其是在手术病例量较低的小型诊所。此外，遵守管制药品法规需要行政和记录保存程序，这可能对小型执业机构构成更大负担。尽管这些解释仍属推测，但研究结果表明强效镇痛药的可及性在全国范围内可能并不均衡。
吗啡的可获得性明显较低，仅有12.9%的受访者报告使用，这与新西兰早期的调查形成对比，在新西兰的调查中吗啡仍是最常用的阿片类药物[27]。这种差异的部分原因可能是2019年美沙酮进入拉脱维亚兽医市场，导致处方偏好逐渐转变。澳大利亚、斯洛文尼亚、意大利和瑞士也报告了类似的转变，在这些国家美沙酮、丁丙诺啡和布托啡诺已成为小动物临床的首选阿片类药物[9, 16, 22, 25]。
布托啡诺和丁丙诺啡在拉脱维亚兽医中的广泛使用与国际趋势一致，可能反映了其良好的安全性特征、许可状态和历史可获得性。在拉脱维亚，布托啡诺在较长时期内未被归类为管制物质，这促进了其常规使用。与纯μ-阿片受体激动剂相比，部分激动剂通常与较低的呼吸抑制和心动过缓风险相关，这可能进一步解释了其受欢迎程度[40, 41]。此外，丁丙诺啡肌内注射给药的便利性和较长的镇痛持续时间也增强了其临床吸引力[42, 43]。
报告同时备有纳洛酮的诊所比例较高，表明对阿片类药物安全性和不良反应应对准备有适当的认识。大多数储备芬太尼或美沙酮的执业机构报告了纳洛酮的可获得性，反映了这些环境中负责任的阿片类药物管理。
阿片类药物使用的人口学和临床决定因素
大多数受访者是从业经验不足15年的年轻从业者，这一人口学特征与澳大利亚和泰国进行的调查相当[9, 26]。观察到的从业年限与芬太尼可获得性之间的负相关表明镇痛实践存在代际转变。这一趋势可能反映了过去十年中兽医培训期间对阿片类药物药理学、多模式镇痛和循证疼痛管理的接触增加。
从业年限较少的兽医更可能报告获得芬太尼，这可能反映了课程改革和对继续教育的更多参与[44]。在过去十年中，兽医课程越来越强调麻醉学、镇痛和循证疼痛管理，这可能有助于新近培训的从业者对强效阿片类药物的使用更加熟悉和自信。相比之下，美沙酮的可获得性未显示类似的关联，表明其使用可能更多地受法规和后勤因素的影响，而非仅受代际培训的影响。对输液泵和高级监测设备的要求可能进一步限制了芬太尼在小型或低病例量诊所中的使用。
手术量与阿片类药物可获得性之间的强关联进一步证实了临床需求在塑造镇痛实践中的作用。执行高比例手术操作的诊所显著更有可能储备芬太尼和美沙酮，支持这些药物在围手术期疼痛管理中的核心作用[45]。相反，手术量较低的诊所可能对管制镇痛药的投入重视不足，可能导致疼痛管理标准的差异。
物种特异性偏好与手术情境
研究识别出明显的物种相关阿片类药物选择模式。芬太尼和曲马多主要用于犬，而布托啡诺和丁丙诺啡在犬和猫患者中的分布较为均衡。吗啡使用频率较低，这与国际上关于临床偏好下降和小动物实践中可获得性有限的报告一致。
曲马多的使用随手术活动而变化，在中等手术量的诊所中患病率较高，而在高手术量实践中使用减少。这一模式可能反映了临床医生对替代镇痛药的熟悉程度、感知疗效和可及性方面的差异。然而，支持曲马多在犬中疗效的证据仍不一致。实验和临床研究表明术中镇痛效果有限，而术后益处已有报道，尤其是当曲马多作为多模式方案的一部分使用时[46, 47]。
相比之下，曲马多在猫中似乎能提供一致的术后镇痛。随机临床试验已证明其在常规手术后的有效疼痛控制，尤其是与NSAIDs联合使用时[48, 49]。这些发现突出了曲马多镇痛效用的物种特异性，并强调了定制镇痛方案的重要性。
观察到的手术活动与芬太尼和美沙酮可获得性之间的关联支持了我们的第二个假设，即手术量较高的诊所会报告更容易获得强效阿片类药物。
疼痛评估实践与代际差异
疼痛评估方法的差异在不同代际之间表现明显。较近期毕业的兽医更倾向于使用结构化工具，如经过验证的疼痛量表和WSAVA指南，而经验更丰富的临床医生主要依赖临床判断。尽管这一关联的强度有限，但它与多项国际调查的结果一致[9, 50, 51]。
常规疼痛评分的障碍，包括时间限制、培训不足和评估工具的感知僵化，在文献中已被一致报道[29, 52]。然而，年轻从业者对循证资源使用的增加表明疼痛评估正逐渐向标准化转变，继续教育在促进这一转变中发挥着关键作用。
经验较少的兽医中疼痛量表使用的增加和报告的芬太尼可获得性更高，与我们的第三个假设关于镇痛实践中的代际差异一致。
观察到的疼痛评估实践中的代际差异可能反映了近几十年来兽医教育的变化和对循证疼痛管理的日益重视。然而，仅三分之一的受访者报告使用正式疼痛量表，表明仍有相当大的改进空间。侧重于疼痛识别、实施经过验证的疼痛评估工具和多模式镇痛策略的继续教育举措，可能有助于在临床实践中更广泛地采用标准化疼痛管理方法。
不良反应与阿片类药物使用认知
报告的不良反应与已知的阿片类药物药效动力学一致。镇静是清醒动物中最常见的不良反应，其次是流涎、喘气和烦躁不安。心血管效应，包括心动过缓和低血压，报告频率较低，而呼吸抑制不常见。这些发现与既往研究一致，强调了阿片类药物给药期间警惕监测的重要性，尤其是在麻醉状态下[38, 53]。
关于阿片类药物安全性的误解仍然存在。多项调查显示，对物种特异性不良反应的认识有限，这可能导致对阿片类药物使用的犹豫[20, 54]。这些观察结果强调了针对性教育的必要性，以提高我们对阿片类药物药理学的理解并促进有信心的循证镇痛使用。
临床意义
总体而言，拉脱维亚兽医在阿片类药物的选择上体现了根据疼痛严重程度进行适当区分的原则，部分激动剂主要用于轻至中度疼痛，而强效μ-阿片受体激动剂则保留用于重度疼痛。非甾体抗炎药的广泛联合使用进一步支持了多模式镇痛策略的采用，这与国际指南一致。综合来看，这些发现表明，尽管拉脱维亚的阿片类药物使用和疼痛管理实践总体符合循证原则，但在可及性、培训和疼痛评估方面仍存在差异。通过继续教育、政策举措和改善镇痛资源可及性来弥补这些差距，可能有助于促进兽医实践中疼痛管理标准的统一。
从动物福利的角度来看，强效阿片类镇痛药可及性不均衡可能导致不同地区兽医患者可获得的疼痛管理选择存在差异。尽管阿片类药物仅是多模式镇痛的一个组成部分，但全μ-阿片受体激动剂可及性有限可能降低接受大手术或经历重度疼痛患者的镇痛方案灵活性。因此，持续努力改善循证疼痛管理策略的可及性，有可能在国家层面提升动物福利结局。
本研究结果凸显了加强拉脱维亚兽医疼痛管理的若干机会。首先，应通过本科教育和继续专业发展项目鼓励更广泛地实施经过验证的疼痛评估工具。其次，传播国家或国际疼痛管理指南可能有助于促进不同地区镇痛实践更加一致。最后，进一步评估影响阿片类药物可及性的因素，特别是在报告芬太尼和美沙酮可及性有限的地区，可能有助于识别影响围手术期镇痛提供的实际或监管障碍。
局限性
解读本研究结果时应考虑若干局限性。首先，应答率相对较低（10.4%），且参与为自愿性质，存在选择偏倚的可能性。对麻醉、镇痛或疼痛管理特别感兴趣的兽医可能更有可能参与，可能导致对阿片类药物可及性、阿片类药物使用和循证疼痛管理实践的高估。此外，与其他地理区域相比，来自里加及周边地区的受访者比例过高。由于无法获得未应答者的人口学信息，无法对无应答偏倚进行正式评估。此外，调查通过电子邮件和社交媒体以电子方式分发，并非所有兽医都可能常规使用这些沟通渠道。
其次，本研究依赖自我报告数据，因此存在社会期望偏倚和回忆偏倚。受访者可能报告了被认为符合专业期望的实践，特别是在疼痛评估和阿片类药物使用方面，而对不良反应和处方实践的回忆可能并不完善。没有客观指标（如处方记录、管制药品库存或患者病例日志）可用于核实；因此，研究结果反映的是报告的临床实践而非直接观察到的临床实践。此外，未评估患者层面的结局、镇痛疗效和福利指标。
最后，问卷改编自既往发表的调查，但在分发前未经过正式验证。问卷仅由封闭式问题组成，未包含开放式定性条目，无法进行混合方法分析。此外，未收集关于阿片类药物给药方案、给药途径、芬太尼恒速输注与推注给药、治疗持续时间以及局部或区域麻醉使用的信息。尽管存在这些局限性，本研究首次提供了拉脱维亚兽医阿片类药物可及性、阿片类药物使用模式和疼痛评估实践的国家概览，并识别了值得进一步研究的重要地区和代际趋势。
结论
本研究通过对101名受访者的全国性调查，评估了拉脱维亚兽医的阿片类药物使用和围手术期疼痛管理实践。主要结果显示阿片类药物采用率高（80%每日使用），其中丁丙诺啡和布托啡诺最为可及，芬太尼/美沙酮在里加及周边地区手术量大的实践中更为常用。出现了显著的代际差异，年轻兽医报告芬太尼可及性更高且更频繁使用标准化疼痛量表。地区差异明显，多模式镇痛（尤其是联合非甾体抗炎药）较为常见，但正式疼痛评分仍未充分利用（33%）。
这些发现凸显了需要有针对性的干预措施，以缩小阿片类药物可及性和标准化疼痛评估方面的地区和代际差距。改善农村地区强效阿片类药物的可及性，结合循证方案的继续教育，可以提升动物福利，并使拉脱维亚的实践更紧密地与国际指南接轨。
这是波罗的海地区首个将阿片类药物使用模式与手术病例量、专业经验和疼痛评估实践相结合进行考察的全国性调查，提供了有价值的国别基线数据。
适度的应答率（10.4%）以及可能存在的选择偏倚（偏向有兴趣的受访者）、城市从业者比例过高、依赖自我报告数据以及问卷缺乏验证，限制了结果的普遍性。未评估患者结局和客观指标（如处方记录）。
有必要开展更大规模、应答率更高的研究，对实践进行客观验证，纳入定性见解，并评估患者层面的结局。在教育干预和阿片类药物获取政策变化后进行的纵向评估，可进一步为拉脱维亚及更广泛波罗的海地区兽医疼痛管理的改进提供信息。
拉脱维亚的阿片类药物选择总体上与当代镇痛原则一致，按疼痛严重程度有明确区分，且多模式镇痛使用广泛。然而，明显的地区差异、最佳实践采纳方面的代际差异以及标准化疼痛评估工具利用不足，表明仍存在持续差距。通过教育、改善获取途径和政策支持来解决这些问题，对于确保全国范围内一致、高质量的围手术期疼痛管理和更好的动物福利结局至关重要。
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作者贡献
LV：构思和设计研究，开发问卷，收集和分析数据，进行统计分析，解释研究结果，并起草稿件。AV和LK：参与研究设计，解释结果，并对稿件进行严格修订。所有作者均已阅读并批准最终稿件。
致谢
作者衷心感谢拉脱维亚生命科学与技术大学通过内部研究项目DG5（编号3.2.-10/207）提供的财政支持，该项目题为“三种不同镇痛方案在犬中的疗效比较”。作者还感谢拉脱维亚兽医协会和拉脱维亚兽医教育中心分发调查问卷并协助招募参与者。
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参考文献
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INTRODUCTION
Pain is an unpleasant sensory and emotional experience that significantly affects animal health and welfare [1]. In veterinary patients, pain induces neurobiological responses that may compromise physiological stability, recovery, and overall quality of life. Consequently, effective pain recognition and management are fundamental components of modern veterinary practice [2].
Pain recognition and management are particularly challenging in veterinary medicine because animals cannot verbally communicate their subjective experiences [3]. In recent decades, significant advances in pain assessment tools, species-specific pain scales, and evidence-based analgesic guidelines have established pain assessment as an essential component of clinical evaluation and the “fourth vital sign” in veterinary medicine [4–6].
Contemporary analgesic strategies emphasize multimodal approaches combining drugs with different mechanisms of action, most commonly opioids and non-steroidal anti-inflammatory drugs (NSAIDs), to improve analgesic efficacy and reduce adverse effects [7, 8].
Opioid analgesics represent a cornerstone of perioperative pain management in veterinary anesthesia owing to their potent analgesic effects, reversibility, and predictable pharmacodynamics [2, 9, 10]. However, access to opioid medications varies considerably across European countries, as regulatory restrictions and availability may limit their routine use in clinical practice [11].
Although scientific interest in veterinary pain management has increased substantially in recent years, studies continue to indicate that analgesic practices in small animal medicine remain inconsistent [12]. International surveys evaluating perioperative and chronic pain management have demonstrated increasing awareness and acceptance of analgesic principles among veterinary professionals; however, persistent gaps remain in knowledge, drug availability, and the consistent implementation of multimodal analgesic protocols [13–27].
The availability and use of opioid analgesics in veterinary medicine are influenced not only by clinical considerations but also by national regulations and market availability. Although Latvia follows European Union legislation on veterinary medicinal products, opioid procurement, storage, record-keeping, and prescription are regulated at the national level. In addition, the relatively recent introduction of methadone to the Latvian veterinary market in 2019 expanded the range of available opioid analgesics for companion animals. As a result, patterns of opioid availability and use in Latvia may not necessarily reflect those reported in Western European countries. Regional data are essential to identify country-specific trends and barriers to veterinary pain management. Although recent studies have evaluated analgesic practices and attitudes toward pain management in countries such as Slovenia, Italy, Canada, and Brazil, comparable data are currently lacking for Latvia and the Baltic region [13, 17, 21, 25]. Furthermore, none of these studies have specifically focused on opioid use patterns in small animal practice within this region despite the central role of opioids in contemporary multimodal analgesic protocols and international pain management guidelines [1, 28–32]. Consequently, factors that may influence opioid use in clinical practice, including regional differences in drug availability, professional experience, and surgical activity, remain poorly characterized.
Therefore, the primary objective of this study was to evaluate opioid availability, opioid use patterns, and perioperative pain management practices among veterinarians in Latvia. Secondary objectives were to investigate associations between opioid availability and surgical caseload, years of professional experience, geographic region, and pain assessment practices. It was hypothesized that: (1) full μ-opioid receptor agonists would be used more frequently for severe pain, whereas partial agonists would be preferred for mild-to-moderate pain; (2) practices with higher surgical caseloads would report greater availability of potent opioids such as fentanyl and methadone; and (3) veterinarians with fewer years since graduation would report greater access to potent opioids and more frequent use of standardized pain assessment tools. To the best of our knowledge, this study is the first national survey in the Baltic region to simultaneously examine associations between surgical caseload, professional experience, geographic location, and opioid selection among companion animal veterinarians. By examining these factors within a national cohort of veterinarians, this study provides a broader understanding of opioid use and perioperative pain management practices in Latvia.
MATERIALS AND METHODS
Ethical approval
This study was reviewed and approved by the Animal Welfare and Protection Ethics Council of the Latvia University of Life Sciences and Technologies, Jelgava, Latvia (Approval No. LLU_Dzaep_2022-5; approved on October 11, 2022). The study was conducted in accordance with the institutional ethical guidelines for research involving human participants and complied with the applicable national requirements for ethical conduct and data protection. Participation in the survey was entirely voluntary. Before accessing the questionnaire, all participants were provided with information regarding the study objectives, estimated completion time, confidentiality measures, and intended use of the collected data. Electronic informed consent was obtained from all respondents before participation. No personally identifiable information, including names, email addresses, or IP addresses, was collected. All responses were anonymized before analysis and stored in a secure, password-protected electronic database accessible only to the investigators. Participants could discontinue the survey at any time before submitting their responses without penalty. Data were analyzed and reported only in aggregate form to ensure respondent confidentiality and privacy.
Study period and location
The survey was administered electronically across Latvia. The online questionnaire was administered electronically via Google Forms, and responses were collected between December 1, 2023, and January 1, 2024. Following survey closure, the data were exported, screened for completeness, cleaned, and statistically analyzed between January and April 2024.
Study design
A cross-sectional online survey was conducted using a structured questionnaire. Eligible participants were licensed veterinarians practicing in Latvia. The survey was administered via Google Forms and distributed electronically by the Latvian Veterinary Association and the Latvian Veterinary Education Center through email and social media channels. One reminder was distributed during the study period to encourage participation. Only fully completed questionnaires were included. Responses were collected between December 1, 2023, and January 1, 2024. Survey responses were downloaded as an electronic spreadsheet (MS Excel for Windows). Data collection took place between December 1, 2023, and January 1, 2024.
Data collection
Participation in the survey was voluntary, and no compensation or incentives were provided. Before beginning the questionnaire, respondents were informed about the study objectives, the estimated completion time (15–20 min), and the anonymous nature of data collection. Electronic informed consent was obtained from all participants prior to survey completion. No personally identifiable information, including names, email addresses, or IP addresses, was collected. Survey responses were stored in a password-protected electronic database accessible only to the investigators. Data were analyzed in aggregated form to preserve participant confidentiality. Respondents could review and modify their answers using a back button at the end of each page. The survey consisted of 24 multiple-choice questions.
Questionnaire
The questionnaire was developed based on previously published surveys evaluating pain management practices and opioid use in companion animals, with adaptations to reflect local clinical practice in Latvia [10, 13, 17, 21–23, 33–35], and was not formally validated prior to distribution.
The questionnaire consisted of six sections addressing the following domains: demographic and professional background, availability and use of opioids in clinical practice, species-specific opioid use, indications for opioid use and practitioner perceptions, pain management practices and adverse effects, and drug selection based on pain severity. Supplementary Material 1 provides a detailed overview of the questionnaire items and response options. Item weighting was not applied; all questionnaire items contributed equally to the analysis, without adjusting for relative importance.
Statistical analysis
Survey responses were analyzed using descriptive and inferential statistics. Frequencies and percentages were calculated for categorical variables. For multiple-response questions, each response option was analyzed independently and reported as the proportion of respondents selecting that option; therefore, percentages could exceed 100%.
Associations between categorical variables, including surgical activity, opioid availability, and pain assessment methods, were evaluated using the chi-square test of independence, with Cramer’s V calculated as a measure of effect size. Associations between ordinal variables, such as years of professional experience, and opioid availability were assessed using Spearman’s rank correlation coefficient (ρ). Binary logistic regression was performed to further evaluate the relationship between professional experience and the availability of fentanyl and methadone. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated, and model fit was assessed using Nagelkerke’s R² and the Hosmer–Lemeshow goodness-of-fit test. Statistical significance was set at p < 0.05.
Data management and descriptive analyses were performed using Microsoft Excel (Microsoft Corporation, Redmond, WA, USA), and regression analyses were conducted using Python-based statistical computations.
RESULTS
Response rate and sample representativeness
Of the 967 registered members of the Veterinary Association of Latvia (data provided by the National Association of Latvian Veterinarians in 2024), 101 participated in the survey, corresponding to a participation rate of 10.4%. This sample represents approximately 14.7% of the estimated 687 actively practicing veterinarians in Latvia, as reported by the Federation of Veterinarians of Europe, within a national population of approximately 1.9 million.
Demographic and professional characteristics of respondents
A total of 101 completed questionnaires were returned by the respondents across Latvia. Most responses (57%, 57/101) were submitted by veterinarians practicing in Rīga and surrounding regions, whereas 4% (4/101) were from the Kurzeme region (Table 1).
Table 1. Demographic and professional characteristics of respondents (n = 101).
| Characteristic | n (%) |
|---|---|
| Region of practice | |
| Rīga and surrounding region | 57 (56.4) |
| Zemgale | 19 (18.8) |
| Vidzeme | 13 (12.9) |
| Latgale | 7 (6.9) |
| Kurzeme | 4 (4.0) |
| Years of professional experience | |
| 0–5 years | 30 (28.7) |
| 6–15 years | 34 (33.7) |
| 16–20 years | 9 (7.9) |
| >20 years | 28 (27.7) |
| Practice typeᵃ | |
| Small-animal practice | 82 (81.2) |
| Exotic animal practice | 10 (9.9) |
| Farm animal practice | 10 (9.9) |
| Equine practice | 4 (4.0) |
| Animals treated per month | |
| ≤100 | 45 (43.6) |
| 100–200 | 36 (35.6) |
| 300–500 | 12 (11.9) |
| >500 | 8 (6.9) |
| Surgical activity (% of patients undergoing surgery) | |
| 0–10% | 32 (30.7) |
| 10–20% | 37 (36.6) |
| 30–50% | 28 (27.7) |
| >50% | 4 (4.0) |
Most participants (82.7%, n=83) reported working primarily in small animal practice. In addition, some respondents reported providing care for other species alongside their primary practice, including exotic or nontraditional companion animals (10.2%, 10/101), farm animals (10.2%, 10/101), and equine patients (4.1%, 4/101).
Most respondents (43.6%, 44/101) reported treating up to 100 animals per month, while 35.6% (36/101) treated 100–200 animals per month. The highest number of animals treated was reported in Rīga and surrounding regions, where practices managing more than 500 animals per month (6.9%, 7/101) were more frequently reported.
Availability of opioids
Regular use of opioids in clinical practice was reported by 80% (81/101) of respondents. Among potent opioids, the μ-opioid receptor agonist methadone was reported as available by 54.1% (55/101) of respondents, followed by fentanyl (45.9%, 46/101). Fentanyl availability was reported predominantly in Rīga and surrounding regions (24.8%, 25/101), followed by Zemgale (9.9%, 10/101). Availability was considerably lower in the Vidzeme and Kurzeme regions (2% each; 2/101), whereas no availability was reported in Latgale (0/101) (Figure 1).
[图：Regional distribution of fentanyl availability among surveyed veterinarians (n = 101).]
Morphine use was reported in only 12.9% (13/101) of the respondents’ clinical practices. The partial opioid agonist buprenorphine was reported by 83.5% (84/101) of the respondents. Among lower-potency opioids and partial μ-opioid receptor agonists, butorphanol was the most commonly available across most regions (84.7%, 86/101), while tramadol (52.9%, 53/101) showed greater prevalence in specific areas, particularly Rīga and surrounding regions.
Naloxone, an opioid antagonist, was available in 43.2% (44/101) of veterinary practices. Naloxone was available in 84.6% (33/39) of practices reporting fentanyl availability and 73.9% (34/46) of practices reporting methadone availability, indicating that most clinics with access to these opioids also maintained access to their antagonists (Figure 2).
[图：Naloxone availability among all surveyed practices and among practices reporting fentanyl or methadone availability.]
Relationship between work experience and opioid availability
Most respondents were younger practitioners with <15 years of professional experience. The analysis revealed a negative association between the years of professional experience and the reported availability of fentanyl and methadone (Figures 3 and 4). Veterinarians who had graduated more recently were more likely to report access to fentanyl, whereas those with >20 years of experience reported the lowest access.
[图：Fentanyl availability according to years of professional experience among surveyed veterinarians.]
A significant negative correlation was observed between years of professional experience and fentanyl availability (Spearman’s ρ = −0.275, p = 0.0059), indicating that veterinarians with fewer years since graduation were more likely to report access to fentanyl. Logistic regression analysis confirmed this association. Increasing years of professional experience were associated with lower odds of fentanyl availability (OR=0.60, 95% CI: 0.41–0.88, p=0.008). The model demonstrated an acceptable fit (Nagelkerke R² = 0.10; Hosmer–Lemeshow p = 0.642). In contrast, no significant association was observed between work experience and methadone availability (Spearman’s ρ = −0.079, p = 0.436). Logistic regression similarly showed no significant effect of professional experience on methadone availability (OR = 0.86, 95% CI: 0.62–1.21, p = 0.400). Model fit statistics indicated limited explanatory power (Nagelkerke R²=0.01; Hosmer–Lemeshow p = 0.556).
[图：Methadone availability according to years of professional experience among surveyed veterinarians.]
Association between surgical activity and opioid availability
A significant association was observed between the frequency of surgical procedures performed in veterinary practice and the availability of fentanyl and methadone. Practices in which surgical procedures accounted for 30–50% of the caseload more frequently reported the availability of these opioids compared with practices that perform fewer surgical procedures.
Chi-square analyses demonstrated a significant association between surgical activity and the availability of fentanyl (χ² = 15.39, p = 0.0015). The effect size was moderate (Cramer’s V=0.39), indicating that practices with higher surgical caseloads were more likely to report fentanyl availability. A significant association was also observed between surgical activity and methadone availability (χ² (3) = 17.50, p = 0.0006). The effect size was moderate (Cramer’s V = 0.42), suggesting greater methadone availability in practices that perform a higher proportion of surgical procedures.
Analysis of responses concerning opioid use in surgical procedures revealed that the most frequently reported challenges were associated with human error and record-keeping (62.4%, 63/101), as well as legal and documentation requirements (40.6%, 41/101). Less frequently, respondents cited difficulties with drug availability or procurement (13.9%, 14/101) and storage requirements (12.9%, 13/101).
Species-specific opioid use
The most frequently reported opioids were buprenorphine (42.0%, 42/101) and butorphanol (32.1%, 32/101), followed by methadone (19.8%, 20/101). Analysis of responses to Question 12 revealed distinct patterns of opioid use across species. Fentanyl (21.8%, 22/101) and tramadol (15.8%, 16/101) were most frequently reported in dogs, whereas butorphanol (21.8%, 22/101) and buprenorphine (22.8%, 23/101) were commonly reported in both dogs and cats.
Methadone was reported in both dogs and cats, with higher reporting rates in dogs (14.9%, 15/101) and in combined dog–cat practices (16.8%, 17/101). In contrast, morphine was rarely used, with most respondents (7.9%, 8/101) indicating that it was not used.
Indications for opioid use and perceptions
Veterinarians reported using opioids for various clinical purposes, with therapeutic pain management (47.6%, 48/101), intraoperative analgesia (45.2%, 46/101), and postoperative pain control (33.3%, 34/101) being the most frequently selected indications. In addition, 21.4% (22/101) of respondents reported using opioids in palliative care settings.
When asked about the surgical procedures during which opioids were administered, 55.1% (56/101) of respondents indicated their use during all listed interventions. Among the individual procedures, opioids were most frequently reported for soft tissue surgeries (43.6%, 44/101) and castration or ovariohysterectomy (42.3%, 43/101), followed by dental and oral procedures (35.9%, 36/101) and orthopedic surgeries (21.8%, 22/101).
Tramadol use varied across practitioners with different levels of surgical activity. It was most frequently reported in practices where 10–20% of registered animals underwent surgery (34.4%, 11/101), followed by 30–50% (28.1%, 9 respondents), and 0–10% (25.0%, 8 respondents). Only a small proportion (6.3%, 2 respondents) of practices involving surgical caseloads exceeding 50% reported tramadol use.
A positive assessment of the introduction of opioids into veterinary practice was reported by 96.6% (98/101) of respondents. In total, 62.4% (63/101) of respondents evaluated their knowledge of pain assessment and opioid use as adequate, but in need of improvement.
When asked how pain is assessed in animals, 62.6% (62/99) of respondents reported relying primarily on their own clinical experiences. In addition, 48.4% (46/95) reported consulting scientific literature or knowledge obtained from seminars and conferences, 33.0% (33/100) reported using pain scales and the World Small Animal Veterinary Association (WSAVA) pain assessment guidelines, and 29.7% (30/101) relied on their colleagues’ experiences. Respondents were able to select more than one option (Figure 5).
[图：Methods used for pain assessment in animals.]
A chi-square test of independence demonstrated a significant association between years of professional experience and pain assessment methods (χ² = 27.18, df = 12, p = 0.0073; Cramer’s V = 0.303). Among veterinarians with 0–5 years of professional experience, 41% reported using formal pain scales and the WSAVA guidelines, whereas 50% of those with >20 years of experience reported relying primarily on personal clinical experience.
Pain management practices and adverse effects
Sedation was the most common adverse effect (61.0%, 62/101) observed in conscious animals. Other reported adverse effects included hypersalivation (41.5%, 42/101), panting (37.8%, 38/101), and dysphoria characterized by vocalizations and restlessness (36.6%, 37/101). Bradycardia and hypotension were reported by 23.2% (23/101) of respondents, while vomiting was reported by 3.7% (4/101). When opioids were administered during anesthesia, bradycardia was reported by 58.9% (59/101) of respondents. Hypotension was reported in 35.6% (36/101) of cases, while hypothermia and respiratory depression were reported by 28.8% (29/101). Table 2 provides a detailed overview of the adverse effects associated with opioid administration. Opioids were combined with NSAIDs by 51.1% (52/101) of respondents, primarily for the management of acute pain.
Table 2. Reported adverse effects associated with opioid administration in small animals under different clinical conditions.
| Clinical context | Adverse effect | Respondents reporting adverse effect, n (%) |
|---|---|---|
| Conscious animals | Sedation | 62 (61.0) |
| Hypersalivation | 42 (41.5) | |
| Panting | 38 (37.8) | |
| Dysphoria (vocalization, restlessness) | 37 (36.6) | |
| Bradycardia and hypotension | 23 (23.2) | |
| Vomiting | 4 (3.7) | |
| During anesthesia | Bradycardia | 59 (58.9) |
| Hypotension | 36 (35.6) | |
| Hypothermia | 29 (28.8) | |
| Respiratory depression | 29 (28.8) |
Drug selection for pain based on severity
Butorphanol (29.7%, 30/101) and buprenorphine (14.9%, 15/101) were the most commonly reported opioids for mild pain. Tramadol (5.9%, 6/101) and methadone (2.0%, 2/101) were reported less frequently. In cases of moderate pain, buprenorphine was reported by 23.8% (24/101) of respondents, followed by butorphanol (11.9%, 12/101) and methadone (10.9%, 11/101). Fentanyl (39.6%, 40/101) and methadone (31.7%, 32/101) were the most frequently reported opioids used to treat severe pain. Buprenorphine was reported by 26.7% (27/101) of respondents, while morphine was reported by 10.9% (11/101). Table 3 provides a detailed overview of the opioid selection according to perceived pain severity.
Table 3. Opioid selection according to perceived pain severity in dogs and cats among surveyed veterinarians.
| Pain severity | Opioid | Respondents selecting opioid, n (%) |
|---|---|---|
| Mild pain | Butorphanol | 30 (29.7) |
| Buprenorphine | 15 (14.9) | |
| Tramadol | 6 (5.9) | |
| Methadone | 2 (2.0) | |
| Moderate pain | Buprenorphine | 24 (23.8) |
| Butorphanol | 12 (11.9) | |
| Methadone | 11 (10.9) | |
| Severe pain | Fentanyl | 40 (39.6) |
| Methadone | 32 (31.7) | |
| Buprenorphine | 27 (26.7) | |
| Morphine | 11 (10.9) |
DISCUSSION
Overview of findings
This study evaluated the patterns of opioid use and pain assessment practices among veterinarians in Latvia, based on data obtained from 101 respondents. To the best of our knowledge, this is the first systematic investigation focusing specifically on attitudes toward opioid use, pain perception, and analgesic strategies in small animal practices in Latvia. Although the response rate was modest (10.4%), the demographic and professional distribution of the participants suggests that the findings provide meaningful insights into the current clinical practice.
Several findings warrant particular attention. First, substantial regional differences were observed in the availability of potent opioids, with fentanyl and methadone reported predominantly in Rīga and surrounding regions and considerably less frequently in other parts of the country. Second, years of professional experience were associated with both fentanyl availability and pain assessment practices, suggesting generational differences in the adoption of evidence-based analgesic approaches. Third, methadone was reported as available by more than half of respondents despite its relatively recent introduction to the Latvian veterinary market, indicating rapid integration into clinical practice. Together, these findings provide important insights into factors influencing veterinary pain management in Latvia.
Although no recent studies have exclusively examined opioid use in small veterinary practices in Latvia, comparable trends can be inferred from international surveys that evaluate veterinarians’ approaches to pain management in companion animals. Collectively, these investigations indicate that opioid utilization is influenced by clinician perceptions of pain, regulatory constraints, drug availability, and the overall emphasis placed on analgesia within individual practices [17, 21, 27, 36].
Opioid selection according to pain severity
Opioid selection among Latvian veterinarians reflects appropriate differentiation according to pain severity. Regarding severe pain, fentanyl (39.6%, 40/101) and methadone (31.7%, 32/101) were the most frequently reported opioids, whereas buprenorphine (26.7%, 27/101) and morphine (10.9%, 11/101) were reported less frequently. These findings indicate that opioid selection generally aligned with contemporary analgesic principles and international recommendations for perioperative analgesia, with butorphanol most commonly reported for mild pain, buprenorphine for moderate pain, and fentanyl and methadone for severe pain [37, 38].
These findings support our first hypothesis that full μ-opioid receptor agonists would be selected more frequently for severe pain, whereas partial agonists would be preferred for mild-to-moderate pain.
Opioid availability and regional variation
The introduction of opioids into veterinary practice was overwhelmingly perceived as beneficial, with 96.6% (98/101) of respondents reporting improvements in analgesia and animal welfare. Only a small proportion of the veterinarians considered opioid availability to have a negative or no impact. This strong professional consensus reinforces the role of opioids as a central component of effective pain management and aligns with international recommendations advocating their use in multimodal analgesic protocols.
Opioids are a fundamental component of acute pain management in Latvian veterinary practice, consistent with findings from other countries [21, 27]. However, their availability markedly varies across regions and practice profiles. Fentanyl and methadone were significantly more likely to be available in clinics with higher surgical caseloads (≥ 30% of registered animals), highlighting the close relationship between surgical activity and the procurement of potent opioids. This observation is consistent with international evidence demonstrating that access to μ-opioid receptor agonists is greatest in practices with substantial perioperative analgesic demand [37, 39].
Geographical disparities were pronounced: fentanyl and methadone were predominantly available in Rīga and the surrounding regions, followed by Zemgale, while availability was minimal in Vidzeme and Kurzeme and absent in Latgale. These patterns likely reflect referral structures and the concentration of complex surgical procedures in urban centers. Although less likely, it cannot be ruled out that anesthetic standards and analgesic practices may differ in more rural settings, warranting further investigation. The concentration of small animal veterinary practices in Rīga and the surrounding regions may further contribute to these observed differences.
Several factors may contribute to these regional differences. Veterinary referral centers and practices performing advanced surgical procedures are concentrated primarily in larger urban areas (Rīga and Jelgava), which may increase demand for potent opioids and justify the infrastructure required for their storage and administration. Economic considerations may also influence purchasing decisions, particularly in smaller clinics with lower surgical caseloads. In addition, compliance with controlled-drug regulations requires administrative and record-keeping procedures that may represent a greater burden for smaller practices. Although these explanations remain speculative, the findings suggest that access to potent analgesics may not be uniform throughout the country.
Morphine availability was notably low, reported by only 12.9% of respondents, in contrast to earlier surveys from New Zealand, in which morphine remained the most commonly used opioid [27]. This discrepancy may be partly explained by the introduction of methadone to the Latvian veterinary market in 2019, which led to a gradual shift in prescription preferences. Similar transitions have been reported in Australia, Slovenia, Italy, and Switzerland, where methadone, buprenorphine, and butorphanol have emerged as the preferred opioids in small animal practice [9, 16, 22, 25].
The widespread use of butorphanol and buprenorphine among Latvian veterinarians is consistent with international trends and likely reflects their favorable safety profiles, licensing status, and historical availability. In Latvia, butorphanol was not classified as a controlled substance for an extended period, which facilitates its routine use. Partial agonists are generally associated with a lower risk of respiratory depression and bradycardia compared with pure μ-opioid agonists, which may further explain their popularity [40, 41]. Additionally, the ease of intramuscular administration and longer analgesic duration of buprenorphine contribute to its clinical appeal [42, 43].
The high proportion of clinics reporting concurrent access to naloxone indicates appropriate awareness of opioid safety and preparedness for adverse effects. Naloxone availability was reported by most practices stocking fentanyl or methadone, reflecting responsible opioid stewardship in these settings.
Demographic and clinical determinants of opioid use
Most respondents were younger practitioners with <15 years of professional experience, a demographic profile comparable to that of surveys conducted in Australia and Thailand [9, 26]. The observed negative association between years of professional experience and fentanyl availability suggests a generational shift in analgesic practice. This trend may reflect the increased exposure to opioid pharmacology, multimodal analgesia, and evidence-based pain management during veterinary training over the past decade.
Veterinarians with fewer years of professional experience are more likely to report access to fentanyl, potentially reflecting curricular changes and greater engagement in continuing education [44]. Over the past decade, veterinary curricula have increasingly emphasized anesthesiology, analgesia, and evidence-based pain management, which may contribute to greater familiarity and confidence in the use of potent opioids among more recently trained practitioners. In contrast, methadone availability did not show a similar association, suggesting that its use may be influenced more strongly by regulatory and logistic factors than by generational training alone. The requirements for infusion pumps and advanced monitoring equipment may further limit the use of fentanyl in smaller- or lower-volume clinics.
The strong association between surgical caseload and opioid availability reinforces the role of clinical demand in shaping analgesic practices. Clinics that perform a high proportion of surgical procedures are significantly more likely to stock fentanyl and methadone, supporting the central role of these agents in perioperative pain management [45]. Conversely, practices with lower surgical volumes may underprioritize investment in controlled analgesics, potentially contributing to disparities in pain management standards.
Species-specific preferences and surgical context
Clear species-related patterns of opioid selection were identified. Fentanyl and tramadol were predominantly used in dogs, whereas butorphanol and buprenorphine were more evenly distributed among canine and feline patients. Morphine use was infrequent, consistent with international reports of declining clinical preference and limited availability in small-animal practice.
Tramadol use varied according to surgical activity, with a higher prevalence in clinics with moderate surgical caseloads and reduced use in high-volume surgical practices. This pattern may reflect differences in clinicians’ familiarity with, perceived efficacy of, and access to alternative analgesics. However, evidence supporting the efficacy of tramadol in dogs remains inconsistent. Experimental and clinical studies have indicated limited intraoperative analgesic effects, whereas modest postoperative benefits have been reported, particularly when tramadol is used as part of multimodal protocols [46, 47].
In contrast, tramadol appears to provide consistent postoperative analgesia in cats. Randomized clinical trials have demonstrated effective pain control following routine surgery, especially when combined with NSAIDs [48, 49]. These findings highlight the species-specific nature of the analgesic utility of tramadol and underscore the importance of tailoring analgesic protocols.
The observed association between surgical activity and fentanyl and methadone availability supports our second hypothesis that practices with higher surgical caseloads would report greater access to potent opioids.
Pain assessment practices and generational differences
Differences in pain assessment approaches were evident across generations. Veterinarians who had graduated more recently were more likely to use structured tools, such as validated pain scales and the WSAVA guidelines, whereas more experienced clinicians predominantly relied on clinical judgment. Although the strength of this association was modest, it mirrors the findings of multiple international surveys [9, 50, 51].
Barriers to routine pain scoring, including time constraints, limited training, and the perceived rigidity of assessment tools, have been consistently reported in the literature [29, 52]. Nevertheless, the increasing use of evidence-based resources among younger practitioners suggests a gradual shift toward standardized pain assessment, with continued education playing a crucial role in facilitating this transition.
The increased use of pain scales and greater reported fentanyl availability among less experienced veterinarians are consistent with our third hypothesis regarding generational differences in analgesic practices.
The observed generational differences in pain assessment practices may reflect changes in veterinary education and increased emphasis on evidence-based pain management during recent decades. Nevertheless, only one-third of respondents reported using formal pain scales, indicating considerable scope for improvement. Continuing education initiatives focusing on pain recognition, implementation of validated pain assessment tools, and multimodal analgesic strategies may facilitate broader adoption of standardized approaches to pain management in clinical practice.
Adverse effects and perceptions of opioid use
The reported adverse effects were consistent with known opioid pharmacodynamics. Sedation was the most frequently observed effect in the conscious animals, followed by hypersalivation, panting, and dysphoria. Cardiovascular effects, including bradycardia and hypotension, have been reported less frequently, whereas respiratory depression is uncommon. These findings are consistent with those of previous studies and emphasize the importance of vigilant monitoring during opioid administration, especially under anesthesia [38, 53].
Misconceptions regarding opioid safety persist. Several surveys have demonstrated a limited awareness of species-specific adverse effects that may contribute to hesitation in opioid use [20, 54]. These observations underscore the need for targeted education to improve our understanding of opioid pharmacology and promote confident evidence-based analgesic use.
Clinical implications
Overall, opioid selection among Latvian veterinarians reflected appropriate differentiation according to pain severity, with partial agonists predominantly used for mild-to-moderate pain and potent μ-opioid agonists reserved for severe pain. The widespread concurrent use of NSAIDs further supports the adoption of multimodal analgesic strategies, which is consistent with international guidelines. Taken together, these findings suggest that, while opioid use and pain management practices in Latvia generally align with evidence-based principles, disparities in access, training, and pain assessment remain. Addressing these gaps through continued education, policy initiatives, and improved access to analgesic resources may help promote uniform standards of pain management across veterinary practices.
From an animal welfare perspective, unequal access to potent opioid analgesics may contribute to variation in pain management options available to veterinary patients across regions. Although opioids represent only one component of multimodal analgesia, limited access to full μ-opioid receptor agonists may reduce the flexibility of analgesic protocols for patients undergoing major surgical procedures or experiencing severe pain. Therefore, continued efforts to improve access to evidence-based pain management strategies have the potential to enhance animal welfare outcomes at a national level.
The findings of this study highlight several opportunities to strengthen veterinary pain management in Latvia. First, wider implementation of validated pain assessment tools should be encouraged through undergraduate education and continuing professional development programs. Second, dissemination of national or international pain management guidelines may help promote more consistent analgesic practices across regions. Finally, further evaluation of factors influencing opioid availability, particularly in regions reporting limited access to fentanyl and methadone, may help identify practical or regulatory barriers affecting the provision of perioperative analgesia.
Limitations
Several limitations should be considered when interpreting the findings of this study. First, the response rate was relatively modest (10.4%), and participation was voluntary, introducing the possibility of selection bias. Veterinarians with a particular interest in anesthesia, analgesia, or pain management may have been more likely to participate, potentially resulting in an overestimation of opioid availability, opioid use, and evidence-based pain management practices. In addition, respondents from Rīga and the surrounding regions were overrepresented compared with those from other geographic regions. Formal assessment of non-response bias was not possible because demographic information regarding non-respondents was unavailable. Furthermore, the survey was distributed electronically via email and social media, and not all veterinarians may routinely use these communication channels.
Second, the study relied on self-reported data and was therefore subject to social desirability and recall bias. Respondents may have reported practices perceived as professionally desirable, particularly regarding pain assessment and opioid use, while recollection of adverse effects and prescribing practices may have been imperfect. No objective measures, such as prescription records, controlled-drug inventories, or patient case logs, were available for verification; therefore, the findings reflect reported rather than directly observed clinical practice. In addition, patient-level outcomes, analgesic efficacy, and welfare indicators were not evaluated.
Finally, the questionnaire was adapted from previously published surveys but was not formally validated before distribution. It consisted exclusively of closed-ended questions and did not include open-ended qualitative items, preventing mixed-methods analysis. Furthermore, information regarding opioid dosing regimens, routes of administration, fentanyl constant rate infusion versus bolus administration, treatment duration, and the use of local or regional anesthesia was not collected. Despite these limitations, this study provides the first national overview of opioid availability, opioid use patterns, and pain assessment practices among veterinarians in Latvia and identifies important regional and generational trends that warrant further investigation.
CONCLUSION
This study evaluated opioid use and perioperative pain management practices among veterinarians in Latvia through a national survey of 101 respondents. Key results showed high adoption of opioids (80% daily use), with buprenorphine and butorphanol most available and fentanyl/methadone more common in high-surgical-volume practices in Rīga and surrounding regions. Significant generational differences emerged, with younger veterinarians reporting greater fentanyl availability and more frequent use of standardized pain scales. Regional disparities were pronounced, and multimodal analgesia (especially with NSAIDs) was common, though formal pain scoring remained underutilized (33%).
These findings highlight the need for targeted interventions to reduce regional and generational gaps in opioid access and standardized pain assessment. Improved availability of potent opioids in rural areas, combined with continuing education on evidence-based protocols, could enhance animal welfare and align Latvian practices more closely with international guidelines.
This is the first national survey in the Baltic region to examine opioid patterns alongside surgical caseload, professional experience, and pain assessment practices, providing valuable country-specific baseline data.
The modest response rate (10.4%) and potential selection bias toward interested respondents, overrepresentation of urban practitioners, reliance on self-reported data, and lack of validation of the questionnaire limit generalizability. Patient outcomes and objective measures (e.g., prescription records) were not assessed.
Larger studies with higher response rates, objective verification of practices, inclusion of qualitative insights, and evaluation of patient-level outcomes are warranted. Longitudinal assessments following educational interventions and policy changes regarding opioid access could further inform improvements in veterinary pain management across Latvia and the broader Baltic region.
Opioid selection in Latvia generally aligned with contemporary analgesic principles, with clear differentiation by pain severity and widespread multimodal use. However, marked regional disparities, generational differences in adoption of best practices, and underutilization of standardized pain assessment tools indicate persistent gaps. Addressing these through education, improved access, and policy support will be essential to ensure consistent, high-quality perioperative pain management and better animal welfare outcomes nationwide.
DATA AVAILABILITY
The supplementary data are available from the corresponding author upon reasonable request.
GENERATIVE AI DECLARATION
The authors used OpenAI to assist with language editing and to improve the clarity and structure of the manuscript. All AI-assisted content was critically reviewed, revised, and verified by the authors, who take full responsibility for the accuracy, originality, and integrity of the final manuscript.
AUTHORS’ CONTRIBUTIONS
LV: Conceived and designed the study, developed the questionnaire, collected and analyzed the data, performed the statistical analyses, interpreted the findings, and drafted the manuscript. AV and LK: Contributed to the study design, interpreted the results, and critically revised the manuscript. All authors have read and approved the final manuscript.
ACKNOWLEDGMENTS
The authors gratefully acknowledge financial support from the Latvia University of Life Sciences and Technologies through the internal research project DG5 (No. 3.2.-10/207), entitled "Comparison of the efficacy of three different analgesia protocols in dogs." The authors also thank the Latvian Veterinary Association and the Latvian Veterinary Education Center for distributing the survey questionnaire and facilitating participant recruitment.
COMPETING INTERESTS
The authors declare that they have no competing interests.
PUBLISHER’S NOTE
Veterinary World remains neutral with regard to jurisdictional claims in the published institutional affiliations.
REFERENCES
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Associated Data
Data Availability Statement
The supplementary data are available from the corresponding author upon reasonable request.