Nowadays, we are seeing many patients that arrive for pre-anesthesia testing and are receiving anticoagulation. Last week we discussed the management of anticoagulation prior to surgical procedures and during pregnancy and this week we will be discussing the guidelines for the performance of neuraxial anesthesia and analgesia in anticoagulated patients. Today, we will be discussing the performance of regional anesthesia in these patients.
You are ready to anesthetize a 54 year-old male scheduled to undergo a total knee replacement. The patient has a history of recurrent deep venous thrombosis and had an episode of pulmonary embolism. He was taking warfarin until 4 days prior to the date of surgery and would prefer a regional anesthetic. .
1. Is it safe to perform a regional anesthetic under these conditions?
2. Does it make a difference if a patient is also taking nonsteroidal antiinflammatory drugs (NSAIDs) for his arthritis pain along with warfarin?
3. How about if the warfarin was just started the night before the surgery as prophylaxis for deep venous thrombosis. Why might this be done and does it affect your plans for a regional anesthetic?
抗凝患者的轴索麻醉与镇痛使用指南
平常我们遇到很多正在使用抗凝药物而又需要进行麻醉前评估的患者。本周讨论抗凝患者的轴索麻醉与镇痛使用情况。今天，我们讨论此类患者的局部（区域）麻醉的实施。
准备对一接受全膝置换术的54岁的男性患者实施麻醉。该患者近期有深静脉血栓病史，并曾经出现过肺栓赛。其接受华发林治疗持续到术前4天，并要求实施区域麻醉。
1. 在该情况下实施区域麻醉是否安全？
2. 如果该患者在使用华发林治疗的同时，为缓解关节炎疼痛同时服用NSAIDs药物治疗，麻醉是否有区别？
3. 如果为了预防肾静脉血栓，华发林只是在手术前晚使用，这样做是否影响你实施区域阻滞，为什么？
[每周一问]NO.8之参考答案
1.在该情况下实施区域麻醉是否安全？
在华发林治疗停止后，在几乎所有患者INR恢复到1.5需要4天时间[1]。然而，每个患者之间存在部分差异性，因此在麻醉实施前最安全的方法是检测INR。美国局部麻醉协会（ASRA）关于轴索麻醉和抗凝药物的公开声明强调，对于使用慢性口服抗凝药的患者，抗凝治疗必须停止，在实施轴索麻醉前必须检测INR。
2.如果该患者在使用华发林治疗的同时，为缓解关节炎疼痛同时服用NSAIDs药物治疗，麻醉是否有区别？
ASRA指南强调，同时使用影响其他凝血机制成分的药物可增加出血并发症的危险，但是对于INR可无影响。虽然没有特定的指南指导，但是仍然强调在放置硬膜外导管时应该考虑药物间的相互作用[2]。
3.如果为了预防深静脉血栓，华发林只是在手术前晚使用，这样做是否影响你实施区域阻滞，为什么？
一些矫形外科医师在术前晚开始给患者使用首次剂量的华发林，以试图在术后早期能使INR达到1.7~2.0。致死性肺栓塞是膝关节置换术最严重并发症之一，其发生仅次于深静脉血栓（DVT）。全膝置换术伴随的血管壁损伤、静脉淤滞和机体高凝状态促成了DVT的形成[3]。预防性使用抗凝剂减少了这些并发症的危险。低剂量预防性使用华发林被证明与高剂量使用具有相同的效果，并减少了出血性并发症的发生率。Ⅶ因子是在使用华发林之后首先衰竭的凝血因子，因为其半衰期只有4-6小时。因此即使华发林的抗凝效果（PT或INR）在其首次给于后的24-36小时没有显现，实施区域阻滞前12小时使用华发林的患者Ⅶ因子已经被耗尽。ASRA指南推荐检查INR，仅在实施区域阻滞前的24小时给于华发林或者在麻醉穿刺前给于第二次剂量的华发林的时候推荐INR。
[每周一问]No.8-Performance of Neuraxial Anesthesia and Analgesia in Anticoagulated Patients之英文参考答案
Is it safe to perform a regional anesthetic under these conditions?
After warfarin therapy is stopped, it takes about four days for the INR to reach 1.5 in almost all patients (1). However, there is some variability from patient to patient and the safest route is to measure the INR prior to the performance of the anesthetic. The American Society of Regional Anesthesia (ASRA) Consensus Statement on Neuraxial Anesthesia and Anticoagulation states that for patients on chronic oral anticoagulation, the anticoagulant therapy must be stopped and the INR measured prior to initiation of neuraxial block (2).
Does it make a difference if a patient is also taking nonsteroidal antiinflammatory drugs (NSAIDs) for his arthritis pain along with warfarin?
The ASRA guidelines state that the concurrent use of medications that affect other components of the clotting mechanisms may increase the risk of bleeding complications and do so without influencing the INR. Although there are no specific guidelines given, it is stated that one should reflect on these drug interactions when an epidural catheter is being considered for a patient (2).
How about if the warfarin was just started the night before the surgery as prophylaxis for deep venous thrombosis. Why might this be done and does it affect your plans for a regional anesthetic?
Many orthopedic surgeons start the first dose of warfarin the night before surgery in an attempt to achieve a target INR of 1.7-2.0 earlier in the postoperative period. Fatal pulmonary embolism is one of the most catastrophic complications of knee replacement surgery and occurs secondary to the development of deep venous thrombosis (DVT). Vessel wall damage, venous stasis and a hypercoagulable state following total knee replacements contribute to the formation of DVTs (3). Prophylactic anticoagulation decreases the risks of these complications. Low-dose warfarin prophylaxis has been demonstrated to be as effective as higher doses for thromboprophylaxis, with a decreased incidence of bleeding complications. Factor VII is the first factor that is depleted upon initiation of warfarin therapy as it has only a half-time of 4-6 hours. Therefore it is likely to be depleted on a patient that has taken warfarin 12 hours prior to the administration of a regional anesthetic, even if the anticoagulant effect of warfarin (PT or INR) is not apparent for 24-36 hours after its first administration. The ASRA guidelines recommend an International Normalized Ratio (INR, see last week for details) only when the warfarin was administered 24 hours prior to the administration of a regional anesthetic or if a second dose of warfarin was administered prior to the needle insertion (2).
Question Author: David Hepner, MD, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School
References:
1. Hirsh J, Levine M. Prevention of venous thrombosis in patients undergoing orthopaedic surgical procedures. Br J Clin Pract 1989;65:2-8.
2. Enneking KF, Benzon HT. Oral anticoagulants and regional anesthesia: A perspective. Reg Anesth Pain Med 1998:23 Suppl.
3. Miric A, Lombardi P, Sculco TP. Deep vein thrombosis prophylaxis: a comprehensive approach for total hip and total knee arthroplasty patient populations. Am J Orthop 2000;29:269-74.
Site Editor: Stephen B. Corn, M.D. and B. Scott Segal, M.D.
Department of Anesthesia, Harvard Medical School
Founders and Editors-in-Chief: Stephen B. Corn, M.D. and B. Scott Segal, M.D.
Department of Anesthesiology, Perioperative and Pain Medicine, Harvard Medical School 
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