Levine M N, Hirsh J
Baillieres Clin Haematol. 1990 Jul;3(3):545-54. doi: 10.1016/s0950-3536(05)80018-6.
In recent years there has been an explosion of clinical trials evaluating low molecular weight (LMW) heparin both in the prevention of venous thrombosis and in the treatment of established venous thrombosis. Results to date would indicate that LMW heparin is an effective method of prophylaxis and has a negligible risk of bleeding, provided the anti-factor Xa levels 4-6 h after injection do not exceed 0.2 units/ml. There is suggestive evidence that, if LMW heparin is given in doses which produce anti-factor Xa levels of more than 0.4 units/ml, there is an increased risk of perioperative bleeding in surgical patients. Although three studies have reported that LMW heparin is more effective than standard unfractionated low dose heparin in the prevention of venous thrombosis, further studies evaluating risks and benefits are required. The promising experimental findings that LMW heparin produces less bleeding for equivalent antithrombotic efficacy has yet to be established in man. Results of clinical trials in neurosurgical patients, patients undergoing knee surgery and patients undergoing cardiac surgery may establish whether LMW heparin is advantageous in such patients at very high risk for bleeding. Finally, the early results from randomized trials suggest that LMW heparins are effective in the treatment of established venous thrombosis, but further trials are required.
近年来，评估低分子量（LMW）肝素在预防静脉血栓形成以及治疗已形成的静脉血栓方面的临床试验呈爆发式增长。迄今为止的结果表明，LMW肝素是一种有效的预防方法，并且只要注射后4 - 6小时的抗Xa因子水平不超过0.2单位/毫升，出血风险就可忽略不计。有提示性证据表明，如果给予LMW肝素的剂量导致抗Xa因子水平超过0.4单位/毫升，手术患者围手术期出血风险会增加。尽管有三项研究报告称，在预防静脉血栓形成方面，LMW肝素比标准的未分级低剂量肝素更有效，但仍需要进一步评估风险和益处的研究。LMW肝素在等效抗血栓疗效下出血更少这一有前景的实验结果在人体中尚未得到证实。神经外科患者、接受膝关节手术的患者和接受心脏手术的患者的临床试验结果可能会确定LMW肝素在此类出血风险极高的患者中是否具有优势。最后，随机试验的早期结果表明，LMW肝素在治疗已形成的静脉血栓方面是有效的，但仍需要进一步试验。
