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Last week we discussed the controversy behind the monitoring of anti-Xa level and the risk of bleeding in patients receiving LMWH. Is there any other test that may be helpful in monitoring the coagulation status in patients receiving LMWH?
上周我们讨论了接受LMWH治疗的患者出血危险与抗Xa因子水平监测之间的争论。在监测接受LMWH治疗患者凝血状况还有没有其他检测是有益的？

[每周一问]NO.11之周中问之参考答案
记住ASRA关于轴索麻醉与抗凝指南很重要。指南不推荐监测抗Xa水平或同时的其他实验室检测[1]。
近期的前期研究与血栓弹性描记法（TEG）测定的抗Xa浓度相关[2]。TEG是一全血测量，其检测与凝血相关的所有血液成分的网状结构产物。TEG可以判断凝血强度、凝血块形成、加强及纤溶速度。此外，可以检测血小板功能、血浆因子活性以及凝血功能相关的激活和抑制因素。TEG可以对全身凝血功能状态进行快速、简单的测量，在创伤、心血管及肝脏手术中应用广泛[3-5]。晚近研究中，TEG已经用于研究高危产科病人特别是血小板减少症患者的凝血状况[6-8]。
Klein及其同事证实了在TEG在反应时间（R-time，可检测到血快形成的第一显著水平需要的时间）和K-时间（血块变硬时间）方面与血清抗-Xa因子水平的高峰具有相关性。他们进一步证实，R-time在给与LMWH3天内延长，血清抗-Xa因子呈相应趋势。他们假定了在R-time与抗-Xa因子水平在前2天的相关性，推导出第三天的对LMWH的反应结果有夸大。他们的结论为：TEG在检测LMWH活动是有帮助的，因为其可以测量全部凝血功能并与抗-Xa因子具有相关性。
虽然该项工作是有趣并在将来是有用的，但是其代表的是前期的信息并不能用于临床实践，直到得到进一步的验证。而且，如上所述，在实施局部麻醉前抗-Xa因子测量的有用性尚存在明显争议。

Yesterday we discussed the controversy behind the monitoring of anti-Xa level and the risk of bleeding in patients receiving LMWH. Is there any other test that may be helpful in monitoring the coagulation status in patients receiving LMWH?
It's important to remember that the American Society of Regional Anesthesia (ASRA) guidelines for neuraxial anesthesia and anticoagulation do not recommend monitoring the anti-Xa level or any other laboratory test at the present time (1).
Preliminary work done recently has correlated the anti-Xa concentration with the thromboelastography (2) (TEG-please refer to week of March 26). TEG is a whole blood test that measures the net product of all blood components involved in coagulation. TEG can determine the clot strength, the rate of clot formation/strengthening and fibrinolysis. In addition, it is a test of platelet function, plasma factor activity, and activators and inhibitors of coagulation. TEG is a rapid, simple, and global test of coagulation and has useful applications in trauma, cardiac, vascular and hepatic surgery (3-5). More recently, TEG has been extended to study the coagulation profile in high-risk obstetric patients particularly those with thrombocytopenia (6-8).
Klein and colleagues demonstrated a correlation between the reaction time (R-time or time until the first significant levels of detectable clot formation) and K-time (clot firmness) of the TEG and the peak and through serum anti-Xa levels. They further demonstrated that the R-time was prolonged at the time of the through serum anti-Xa level on day 3 of the administration of LMWH. These authors hypothesized that given the correlation of R-time and anti-Xa levels during the first two days, these results may indicate an exaggerated response to LMWH on day three. Their conclusion was that TEG might have a role in following LMWH activity because it measures the overall coagulation and also because of its correlation with anti-Xa levels.
Although this work is very interesting and may be useful in the future, it represents preliminary information and cannot be used in clinical practice until it is further validated. Furthermore, as mentioned above, there is significant controversy in the usefulness of measuring the anti-Xa level prior to the administration of a regional anesthetic.
Question Author: David Hepner, MD, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham and Women's Hospital, Harvard Medical School
References:
1.  Horlocker TT, Wedel DJ. Neuraxial block and low molecular weight heparin: balancing perioperative analgesia and thromboprophylaxis. Reg Anesth Pain Med 1998:23 Suppl. 7-8.
2.  Klein SM, Slaughter TF, Vail PT, et al. Thromboelastography as a perioperative measure of anticoagulation resulting from low molecular weight heparin: a comparison with anti-Xa concentrations. Anesth Analg 2000;91:1091-5.
3.  Kaufmann CR, Dwyer KM, Crews JD, Dols SJ. The usefulness of thromboelastography in assessment of trauma patient coagulation. The Journal of Trauma 1987;42:716-22.
4.  Kang YG, Martin DJ, Marqueq J, Lewis JH, Bontempo FA, Shaw BW, Starzi TE, Winter PM. Intraoperative changes in blood coagulation and thromboelastographic monitoring in liver transplantation. Anesth Analg 1985;64:888-896.
5.  Tuman KJ, Spiess BD, McCarthy RJ, Ivankovich KD: Comparison of viscoelastic measurements of coagulation after cardiopulmonary bypass. Anesth Analg 1989;69:69-75.
6.  Sharma SK, Philip J, Wilen J. Thromboelastographic changes in healthy parturients and postpartum women. Anesth Analg 1997;85:94-8.
7.  Sharma SK, Vera RL, Stegall WC, Whitten CW. Management of a postpartum coagulopathy using thromboelastography. Journal of Clinical Anesthesia 1997;9:243-7.
8.  Irkujiwsju CEP, Rocke DA, Muray WB, Gouws E, Moodley J, Kenoyer DG, Byrne S. Thromboelastography changes in preeclampsia and eclampsia. Brit J Anaesth 1996;77:556-8.
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