Singer M, McNally T, Screaton G, Mackie I, Machin S, Cohen S L
Bloomsbury Institute of Intensive Care Medicine, Department of Medicine, UCL Medical School, London, UK.
Intensive Care Med. 1994;20(3):212-5. doi: 10.1007/BF01704703.
To determine whether premature clotting of haemofiltration circuits could be related to heparin removal across the filter membrane into the ultrafiltrate.
Randomised study using either unfractionated (n = 8) or low molecular weight (n = 7) heparin for anticoagulation of the haemofiltration circuit at 1000 and 600 U/h respectively. Samples were drawn at 1 and 2 h from arterial and venous limbs of the haemofilter circuit for measurement of plasma heparin (as anti-Factor Xa activity), antithrombin III and haematocrit. Ultrafiltrate samples were collected at the same time for measurement of anti-Xa activity.
Intensive care unit.
Patients in acute renal failure requiring haemofiltration.
Both unfractionated and low molecular weight heparin plasma levels were within the range required for therapeutic anticoagulation in all but one patient at 2 h. Ultrafiltrate anti-Xa levels were insignificant. Antithrombin III levels in these critically ill patients were subnormal in 11 of the 15 studies.
Despite their small sizes, neither unfractionated nor low molecular weight heparins cross the haemofilter membrane into the ultrafiltrate in any measurable quantity. Both heparins were present in plasma at a level suitable for therapeutic anticoagulation. Subnormal levels of antithrombin III may be an important factor in determining filter longevity.
确定血液滤过回路的过早凝血是否与肝素通过滤膜进入超滤液有关。
一项随机研究，分别使用普通肝素（n = 8）或低分子量肝素（n = 7）以1000 U/h和600 U/h的剂量对血液滤过回路进行抗凝。在1小时和2小时时从血液滤过回路的动脉和静脉端采集样本，用于测定血浆肝素（以抗Xa因子活性表示）、抗凝血酶III和血细胞比容。同时收集超滤液样本用于测定抗Xa活性。
重症监护病房。
需要进行血液滤过的急性肾衰竭患者。
除一名患者外，所有患者在2小时时普通肝素和低分子量肝素的血浆水平均在治疗性抗凝所需范围内。超滤液中的抗Xa水平不显著。在15项研究中的11项中，这些重症患者的抗凝血酶III水平低于正常。
尽管普通肝素和低分子量肝素体积小，但均不会以任何可测量的量通过血液滤过膜进入超滤液。两种肝素在血浆中的水平均适合治疗性抗凝。抗凝血酶III水平低于正常可能是决定滤器使用寿命的一个重要因素。
