使用局部硬膜外嗎啡與右旋美托密啶於犬隻脊椎手術之止痛效果評估

Abstract

軟骨發育不全犬隻為第一型椎間盤突出（Hansen type I）的好發犬種，第一型椎間盤疾病指的是椎間盤發生退行性（degeneration）變化，其退化的髓核（nucleus pulposus）經退化的纖維環（annulus fibrosus）脫出（herniation），且突出（extrusion）到椎管（vertebral canal）內，造成脊髓的壓迫。其手術治療方式主要為單側椎板切除以達到脊髓減壓的效果。不論小動物或人，最常用來控制術後止痛的是鴉片類（opioid）藥品。鴉片類藥品的止痛效果和其劑量成正相關，使用的劑量越高，止痛效果越強，但也較容易出現副作用。為降低鴉片類的劑量和維持有效的止痛，許多臨床醫師和學者發展出各種新的策略，如合併使用局部、區域性止痛或其他止痛藥物等。 近年來人醫多篇研究報告顯示局部硬膜外（topical epidural）止痛藥物給予有類似硬膜外止痛 （epidural analgesia）的效果和期間（duration）。目前獸醫臨床使用局部硬膜外止痛的資料有限且結果不一，本研究之目的為探討局部硬膜外合併給予嗎啡和右旋美托密啶是否能有一定程度的止痛效果和時間。 本實驗對象為進行單側椎板切除術合併或無預防性椎間盤開窗術之犬隻，在完成單側椎板切除後，實驗組犬隻於椎板切除處覆蓋含嗎啡和右旋美托密啶混合液的止血棉，控制組犬隻於椎板切除處放置含生理食鹽水的止血棉，之後分別在拔管第2、4、6、8、10、12、14、16、20、24、32、40及48小時使用墨爾本大學疼痛量表（The University of Melbourne pain scale，UMPS）和格拉斯哥疼痛量表（Short-form Glasgow composite pain scale，GCPS- SF）評分，如達援救止痛標準（UMPS≧ 6分或GCPS-SF ≧7分）即給予靜脈給予單一劑量吩坦尼（fentanyl）3 μg/kg，接著開始吩坦尼點滴定速給予（constant rate infusion，CRI）。記錄不同組別犬隻的基本資料（包含性別、年齡、體重、品種）、援救止痛 （rescue analgesia）標準時間點、吩坦尼使用總量、最高量和兩種疼痛評估表的疼痛分數等進行統計分析。 實驗結果共有13隻犬隻納入實驗，實驗組7隻，控制組6隻。實驗組和控制組平均援救止痛時間分別為8.29± （2.93）和8± （3.35）小時； UMPS總分分別為51.71± （9.23）和52± （9.17）分，GCPS- SF分別為38.14± （4.98）和34.83± （11.32）分。實驗組和控制組不論援救止痛時間、疼痛總分、單位時間疼痛分數、吩坦尼使用總量或吩坦尼使用最高量皆無顯著差異。樣本數過小、疼痛評估設計不夠敏感、meloxicam止痛效果太強或吩坦尼CRI造成的偽高、偽低分等，都可能影響研究結果，而無法凸顯局部硬膜外止痛效果的因素。 總結使用止血棉負載嗎啡和右旋美托密啶做為局部硬膜外止痛約可提供8小時的止痛時間，但其止痛作用時間、效果等和控制組相比無明顯差異，此部分有待更大規模的研究，評估局部硬膜外止痛於犬隻之真正效用。此外，本實驗結果未見任何懷疑和止血棉使用相關的併發症發生，但其長期放置的安全性仍有待未來研究。

Hansen type I intervertebral disc herniation occurs commonly in chondrodystrophied dogs, and the surgical management is to perform hemilaminectomy to remove the herniated disc material. Multimodal analgesia is usually applied to patients receiving hemilaminectomy. The higher dose of opioids, the stronger analgesia it provides, but the undesirable side effects usually occur subsequently. Recently, topical epidural analgesia had been applied in human and veterinary medicine, which showed effective analgesia with longer duration, compared to the traditional epidural analgesia. The aim of the study is to evaluate the post-operative analgesic effect of topical epidural morphine and dexmedetomidine in dogs underwent hemilaminectomy for thoracolumbar intervertebral disc disease. Dogs underwent hemilaminectomy were included in the study. In most dogs, disc fenestration was also performed. During the surgery, single dose of meloxicam intravenously and fentanyl constant rate infusion (CRI) were administered. At the end of surgery, a hemostatic sponge contained morphine and dexmedetomidine (study group) or saline (control group) was placed on the spinal cord via the hemilaminectomy bone defect. Fentanyl CRI was stopped when extubated. Post-operative pain was evaluated at specific time point after extubation (every 2 hours for the 16 hours, every 4 hours for the following 8 hours, then every 8 hours for the next 24 hours), by using “University of Melbourne Pain Scale” and “Short-form Glasgow Composite Measure Pain Scale”. Fentanyl intravenous bolus followed by CRI was administered when the pain score reached the rescue standard. There were 13 dogs enrolled in the study, 7 in the study group and 6 in the control group. The mean rescue time of the study group was 8.29± (2.93) hour, and 8± (3.35) hour in the control group. The mean total scores of UMPS and GCPS –SF were 51.71± (9.23), 38.14± (4.98) and 52± (9.17), 34.83± (11.32) in the study and control group, respectively. Topical epidural morphine and dexmedetomidine sponge can provide about 8-hour analgesia in the study group, but the analgesic duration and effect seemed similar to the control group. No significant difference was detected between study and control group regarding the time of rescue analgesia, total pain scores, pain scores per time point, and total consumption of fentanyl. However, many biases potentially exist in this study, including small sample size, sensitivity of the pain evaluation, the strong analgesic effect of meloxicam and pain assessment influenced by the side effects of fentanyl CRI. Base on the results in this study, it remained unclear whether there is an advantage to the use of the morphine and dexmedetomidine sponge in dogs receiving hemilaminectomy. Study with large scale and modified design is needed to elucidate the effect of topical epidural analgesia.