Rapid determination of anti-heparin/platelet factor 4 antibody titers in the diagnosis of heparin-induced thrombocytopenia

PURPOSE: Heparin-induced thrombocytopenia is mediated by antibodies directed against the heparin-platelet factor 4 (heparin/PF4) complex. Our aim was to investigate whether rapid measurement of anti-heparin/PF4 antibodies could improve the diagnostic workup of patients with suspected heparin-induced thrombocytopenia. METHODS: We examined 148 consecutive patients in our laboratory between January 1995 and June 2001 for suspected heparin-induced thrombocytopenia. Clinical data allowed retrospective assessment of the likelihood of heparin-induced thrombocytopenia. Antibodies against the heparin/PF4 complex were detected by a rapid particle gel immunoassay. RESULTS: Anti-heparin/PF4 antibodies were detected in 69 (47%) of the 148 patients, at dilution titers from 1 to 256. Clinically "likely" or "very likely" heparin-induced thrombocytopenia was significantly more common in patients with titers >or=4 (95% [39/41]) than in those with undetectable antibodies (13% [9/70]; P <0.0001), a titer of 1 (18% [4/22]; P <0.0001), or a titer of 2 (33% [2/6]; P = 0.001). All 19 samples with a positive platelet aggregation test had anti-heparin/PF4 antibody titers of at least 4, including 15 samples with titers >or=32. Thromboembolic complications in heparin-treated patients were significantly more prevalent in patients with titers >or=4 (63% [26/41]) than in those with undetectable antibodies (8% [6/79]; P <0.0001) or a titer of 1 (9% [2/22]; P <0.0001). Of the 11 patients with a titer of 1 who were maintained on heparin, none developed worse thrombocytopenia or thromboembolic complications. CONCLUSION: Anti-heparin/PF4 antibody titers, which can be measured rapidly and reproducibly using a particle gel immunoassay, can be used as a confirmatory test to complement a clinical likelihood score among patients with suspected heparin-induced thrombocytopenia.     

阻抑eIF-4E对大肠腺癌LS-174T细胞乙酰肝素酶mRNA及其翻译表达水平的影响

目的:确定阻抑结肠癌LS-174T细胞中过量表达的真核细胞起始因子-4E(eukaryoticinitiationfactor-4E,eIF-4E)是否促进乙酰肝素酶(heparanase)mRNA的降解,并改变其翻译表达水平。方法:应用脂质体包裹与eIF-4EmRNA翻泽起始点互补的asODN,转染处理人大肠腺癌细胞LS-174T。使用Westernblot和RT-PCR方法分别检测eIF-4E被阻抑后其转录和翻译水平的改变。乙酰肝素酶mRNA在细胞内水平采用Northernblot定量检测,其蛋白表达水平改变采用Westernblot检测。结果:asODN经脂质体转染LS-174T细胞后,eIF-4E基因表达明显受到抑制,其蛋白表达产物也显著下降。伴随eIF-4E被阻抑表达,Northernblot结果显示乙酰肝素酶mRNA水平下降,且其蛋白翻译表达量也降低。结论:阻抑eIF-4E影响LS-174T细胞乙酰肝素酶mRNA稳定、促使其降解,并降低乙酰肝素酶表达。     

Effect of sustained heparin release from PCL/chitosan hybrid small-diameter vascular grafts on anti-thrombogenic property and endothelialization

Thrombus formation and subsequent occlusion are the main reasons for the failure of small-diameter vascular grafts. In this study, a hybrid small-diameter vascular graft was developed from synthetic polymer poly(ε-caprolactone) (PCL) and natural polymer chitosan (CS) by the co-electrospinning technique. Heparin was immobilized on the grafts through ionic bonding between heparin and CS fibers. The immobilization was relatively stable, and heparin could continuously release from the grafts for more than 1 month. Heparin functionalization evidently improved the hemocompatibility of the PCL/CS vascular grafts, which was illustrated by the reduced platelet adhesion and prolonged coagulation time (activated partial thromboplastin time, prothrombin time and thromboplastin time) as shown in the human plasma assay, and was further confirmed by the ex vivo arteriovenous shunt experiment. In vitro cell proliferation assay showed that heparin can promote the growth of human umbilical vein endothelial cells, while moderately inhibiting the proliferation of vascular smooth muscle cells, a main factor for neointimal hyperplasia. Implantation in rat abdominal aorta was performed for 1 month. Results indicate that sustained release of heparin provided optimal anti-thrombogenic effect by reducing thrombus formation and maintaining the patency. Furthermore, heparin functionalization also enhanced in situ endothelialization, thereby preventing the occurrence of restenosis. In conclusion, it provides a facile and useful technique for the development of heparinized medical devices, including vascular grafts.     

Hemocompatibility of a Miniaturized Extracorporeal Membrane Oxygenation and a Pumpless Interventional Lung Assist in Experimental Lung Injury

Extracorporeal membrane oxygenation (ECMO) is used for most severe acute respiratory distress syndrome cases in specialized centers. Hemocompatibility of devices depends on the size and modification of blood contacting surfaces as well as blood flow rates. An interventional lung assist using arteriovenous perfusion of a low-resistance oxygenator without a blood pump (Novalung, Hechingen, Germany) or a miniaturized ECMO with reduced filling volume and a diagonal blood pump (Deltastream, Medos AG, Stolberg, Germany) could optimize hemocompatibility. The aim of the study was to compare hemocompatibility with conventional ECMO. Female pigs were connected to extracorporeal circulation for 24 h after lavage induced lung injury (eight per group). Activation of coagulation and immune system as well as blood cell damage was measured. A P value <0.05 was considered significant. Plasmatic coagulation was slightly activated in all groups demonstrated by increased thrombin-anti-thrombin III-complex. No clinical signs of bleeding or thromboembolism occurred. Thrombelastography revealed decreased clotting capacities after miniaturized ECMO, probably due to significantly reduced platelet count. These resulted in reduced dosage of intravenous heparin. Scanning electron microscopy of oxygenator fibers showed significantly increased binding and shape change of platelets after interventional lung assist. In all groups, hemolysis remained negligible, indicated by low plasma hemoglobin concentration. Interleukin 8 and tumor necrosis factor-α concentration as well as leukocyte count remained unchanged. Both devices demonstrated adequate hemocompatibility for safe clinical application, although a missing blood pump did not increase hemocompatibility. Further studies seem necessary to analyze the influence of different blood pumps on platelet drop systematically.     

The Use of Bivalirudin for Cardiopulmonary Bypass Anticoagulation in Pediatric Heparin‐Induced Thrombocytopenia Patients

Infants with heparin‐induced thrombocytopenia (HIT) represent a challenging and high‐risk group of patients when they require cardiopulmonary bypass (CPB). Bivalirudin offers many potential pharmacologic advantages over other nonheparin anticoagulants for such patients. We describe our protocol for the use of bivalirudin in a 5‐month‐old infant undergoing stage 2 Norwood for hypoplastic left heart syndrome. The patient was a 5‐ month‐old, 6‐kg infant who developed HIT after a bowel resection complicating initial Norwood stage 1. After sternotomy and dissection had been redone, the child received an initial dose of bivalirudin of 1.0 mg/kg and 0.5 mg/kg 5 min later. The CPB circuit was primed with 50 mg/kg bivalirudn/400 cc volume. With the initiation of CPB, a continuous infusion of 2.5 mg/kg bivalirudin was begun. Activated clotting time (ACT) was targeted for over 400 s, with an examination prior to bypass and each 15 min thereafter. Bivalirudin was discontinued with separation from bypass and during modified ultrafiltration (MUF). The ACT was 286 s after the initial 1 mg/kg bolus and 597 s after the second 0.5 mg/kg bolus and initiation of CPB. At a rate of 2.5 mg/kg/min, ACT ranged between 461 and 597 s. At the completion of MUF, the ACT was 316 s. The ACT was 214 s 20 min after MUF. No clots were noted in the CPB circuit, and good hemostasis was achieved within 10 min after MUF was completed. Incision to closure time was 160 min; time from completion of MUF to sternal closure was 30 min. Post‐MUF, 60 cc of processed cell saver blood was reinfused, and no clotting factors were required. Chest tube output was 10, 10, 3, and 4 ccs, respectively, at hours 1–4 post operation. Bivalirudin provides effective anticoagulation in infants requiring CPB in the presence of HIT. Bivalirudin's efficacy is effectively monitored by ACT, and, after CPB, its short half‐life and ability to be ultrafiltered facilitate the ability to achieve hemostasis in a timely fashion.     

Glomerular Capillary Hemorrhage Induced in Rats by Diagnostic Ultrasound with Gas–Body Contrast Agent Produces Intratubular Obstruction

Glomerular capillary hemorrhage (GCH) induced by ultrasonic cavitation during diagnostic imaging represents a unique contrast agent–related nephron injury. Consequences of GCH during 1.5-MHz diagnostic ultrasound with contrast agent were examined by histologic methods in rats. Definity was infused at 10 μl/kg/min for 5 min at the start of 8 min of intermittent image-exposure, with 2.3 MPa in situ peak rarefactional pressure amplitude. Kidney samples were taken for histology at 5 min, 30 min, 4 h, 2 d, 1 week and 4 weeks post exposure. In addition, samples were taken at 4 h from groups treated with heparin or aminocaproic acid. GCH was found in 61% of glomeruli in the center of the scan plane 5 min after exposure, which declined (p < 0.05) to 36.3% after 4 h. The width of Bowman's space was significantly increased for glomeruli with GCH relative to glomeruli without GCH (p < 0.05), consistent with tubular obstruction. Antibody staining revealed fibrin clotting in Bowman's space in 4-h samples and this persisted in the 2-d samples. Heparin reduced and aminocaproic acid increased the GCH seen in 4-h samples. Tubular dilation was evident with injury to the epithelium after 2 d. After one week, areas of inflammatory cell infiltration were present. After four weeks, areas of interstitial fibrosis were revealed by Masson's trichrome stain. The consequences of GCH induced by diagnostic ultrasound with contrast agents include rupture of glomerular capillaries, procoagulant activity resulting in intratubular obstruction, and the potential for progression of the resulting tubular injury toward interstitial fibrosis. (E-mail: douglm@umich.edu)     

早期应用微量肝素治疗小儿全身炎性反应综合征的临床观察

目的观察早期应用微量肝素治疗全身炎性反应综合征（SIRS）危重患儿的临床效果。方法将符合诊断标准的53例患儿随机分为两组，对照组26例，给予治疗原发病及保护重要脏器等综合治疗；治疗组27例，在综合治疗基础上早期加用微量肝素皮下注射，每次5—10U／kg，每6h重复1次，连用3d。结果两组治疗后Pt升高，CRP下降；治疗组Pt升高、CRP下降比对照组更显著（P〈0．01）；治疗组与对照组比较，Pt回升时间明显缩短[（28±9）h对（55±14）h，P〈0．01]，SIRS纠正时间≤3d所占比例明显增高，多脏器功能不全（MODS）、弥散性血管内凝血．（DIC）的发生率显著减少，病死率明显降低（P〈0．05或〈0．01）。结论微量肝素早期干预可缩短危重患儿SIRS持续时间，降低MODS、DIC的发生率及病死率。     

刺五加注射液联合低分子肝素治疗原发性肾病综合征的研究

目的观察刺五加注射液联合低分子肝素治疗原发性肾病综合征的疗效及安全性。方法对照组常规应用泼尼松加刺五加注射液及其他常规对症治疗,观察组在对照组用药的基础上加用低分子肝素皮下注射。2组治疗前后分别检测24 h尿蛋白、血浆白蛋白、总胆固醇、三酰甘油、血液流变学、凝血酶原时间(PT)、部分凝血酶时间(APTT)、凝血酶时间(TT)、血小板计数,并观察临床症状改善情况及有无出血倾向。结果经4周治疗,2组患者临床症状减轻或消失,观察组总有效率96%,对照组88%(P<0.01)。治疗后2组患者尿蛋白减少,血浆白蛋白升高,血液黏度降低(P<0.05或0.01),观察组优于对照组(P<0.05或0.01);2组患者中无一例出血倾向。结论刺五加注射液联合低分子肝素治疗原发性肾病综合征可以更好地改善患者的高凝状态,降低血液黏度,减轻蛋白尿,升高血浆白蛋白,并有很好的安全性。     

肝素表面处理人工晶状体在并发性白内障手术中应用疗效观察

目的探讨肝素表面处理人工晶状体在并发性白内障患者手术中应用的疗效。方法106例(152只眼)并发性白内障患者中随机抽取98只眼为研究组(A),植入HQ-201HEP型肝素表面处理人工晶状体;54只眼为对照组(B),植入MA-60MB型人工晶状体。比较术后视力、眼压、前房闪辉、房水细胞、虹膜后粘连、后囊膜混浊等结果。结果研究组(A)中98只眼有前房闪辉30只眼(30.6%),房水细胞阳性26只眼(26.5%),虹膜后粘连17只眼(17.3%),后囊膜混浊2只眼(2.04%),高眼压2只眼(2.04%)。而对照组(B)54只眼有前房闪辉42只眼(77.8%),房水细胞阳性43只眼(79.6%),虹膜后粘连24只眼(44.4%),后囊膜混浊7只眼(12.7%),高眼压6只眼(11.1%)。结论临床研究发现肝素表面处理人工晶状体在减轻眼内炎症反应、异物反应、细胞在人工晶状体表面沉着(前房闪辉、房水细胞、虹膜后粘连、后囊膜混浊)等方面优于对照组,尤其对于有葡萄膜炎病史、青光眼术后、局部和全身应用类固醇激素者尤为适合,可减轻高眼压和前房出血的发生。     

肝素与高龄PCI术后上消化道大出血

目的:探讨高龄患者PCI术后使用肝素发生上消化道出血的危险性及注意事项.方法:比较普通肝素与低分子肝素的使用剂量、观测指标及各自特点.结果:高龄患者,尤合并消化道疾病者,PCI术后使用肝素易发生上消化道出血.结论:拟行PCI术的患者,尤高龄者,应行全面的评估,特别是消化道疾病史.在应用肝素时应酌减剂量及严密监测实验室指标,以便及时防治,避免发生严重并发症.