Thoughts and Progress

The constant-pressure filtration (CPF) method has been developed to assess blood microemboli (BME) in terms of their ability to occlude microvascular flow. Previous reports suggest that the method is sensitive to the effects of platelet stimulation and to blood-pumping conditions. BME production and heparin activity were studied in bovine and human blood pumped by a Pellethane ventricle with Pellethane molded valves connected via smooth quick-connects to a Pellethane horseshoe-shaped reservoir. In each experiment, blood was collected into heparin by cardiac puncture from a stunned animal or by venepuncture from a human donor. The blood from each donor was filled into three ventricle-reservoir systems (50 cc ventricle and 1,500 cc reservoir for the bovine blood, and 20 cc ventricle and 150 cc reservoir for the human blood). One of the systems received aspirin (ASA; 25 mg/dl) shortly after the onset of pumping, whereas the other two served as pumping and non-pumping controls. The blood was pumped in a full-fill/full-eject mode for up to 10 h. BME concentration was measured by the CPF method in which the blood was filtered through 20-microns pore filters at 20 mm Hg for 10 s, and the flowrate curves were evaluated from occlusion model. Heparin activity was measured by the activated partial thromboplastin time (APTT) test. In the early period after the onset of pumping, the BME concentration increased, whereas the APTT decreased from an initial value of greater than 250 s, with the relative rate of change for both the BME and the APTT being the following: pumping control greater than pumping ASA blood greater than quiescent control.(ABSTRACT TRUNCATED AT 250 WORDS)     

低分子量肝素在血液透析中的应用

为探讨低分子量肝素在血液透析中的抗凝作用，选择血液透析患者６０例、１５００例次，分成两组。一组透析中使用肝素抗凝，另一组使用低分子量肝素（ＣＸ）抗凝，分别测量凝血时间、凝血酶原时间、活化部分凝血活酶时间及血小板，进行对照研究。结果发现，ＣＸ比肝素能更有效地抗凝，又能减少出血倾向，透析器复用次数明显增加，活化部分凝血活酶时间降低（Ｐ＜０．０１）。表明低分子量肝素特别适用于有出血倾向者，可代替肝素在血液透析中应用。     

阿加曲班与肝素在维持性血液透析患者抗凝治疗中的比较

目的 比较两种不同的抗凝方法在维持性血液透析(hemodialysis,HD)患者中的抗凝效果以及对患者凝血功能的影响.方法 选取40例维持性血液透析患者,先后采用不同的抗凝剂,一次使用肝素抗凝(肝素组),一次使用阿加曲班抗凝(阿加曲班组).监测患者治疗前血路管动脉端、治疗中2h血路管动、静脉端、治疗结束后1h活化部分凝血活酶时间(activated partial thromboplastin time,APTT),治疗过程中管路和透析器凝血情况,治疗后穿刺点压迫止血平均时间及组织器官24h内有无出血情况(包括鼻出血、牙龈出血、结膜出血、皮下出血点和黑便等).结果 阿加曲班组HD治疗中APTT明显延长,达到HD抗凝治疗要求,与HD治疗前相比,差异有统计学意义(P＜0.01);阿加曲班组与肝素组相比,治疗中2h及治疗后1h的APTT差异有统计学意义(P＜0.01);阿加曲班组与肝素组治疗中管路和透析器凝血情况比较差别不大,两组差异无统计学意义(P＞0.05);阿加曲班组与肝素组治疗后穿刺点压迫止血平均时间比较差异有统计学意义(P＜0.01);阿加曲班组治疗后组织器官出血较肝素组明显减少,两组比较差异有统计学意义(P＜0.05).结论 阿加曲班在HD抗凝治疗中抗凝效果确切,出血风险较普通肝素少,安全性高,尤其适用于有出血倾向的HD患者.     

Usefulness of Thrombelastography for Dosage Monitoring of Low Molecular Weight Heparin and Unfractionated Heparin During Hemodialysis

Low molecular weight heparin (LMH) acts as an anticoagulation agent mainly through its anti-activated coagulation factor X (Xa) activity. Thrombelastography (TEG) is expected to be useful to monitor the dosage of LMH during hemodialysis because reaction time on TEG (TEG-r) is considered to reflect blood thromboplastin formation time, which depends on the formation of Xa. To test this possibility, we compared the usefulness of TEG, activated coagulation time (ACT), activated partial thromboplastin time (APTT), and anti-Xa activity in 28 hemodialysis patients using both conventional unfractionated heparin (UFH) and LMH on separate dialysis procedures. Anti-Xa activity of LMH was comparable to that of UFH when it was measured using both LMH and UFH as standards. Anti-Xa activity, which theoretically depended on the heparin concentration in blood samples, did not correlate with the degree of dialyzer clotting. The APTT correlated well with anti-Xa activity in patients using LMH (r = 0.686, p less than 0.01) and UFH (r = 0.906, p less than 0.01), but not with the degree of dialyzer clotting. The TEG-r correlated well with the degree of dialyzer clotting both in patients using LMH and those using UFH (measurements of samples obtained from the venous side of the extracorporeal circuit) and weakly correlated with anti-Xa activity in patients using LMH (r = 0.402, p less than 0.05). The ACT did not correlate with the degree of dialyzer clotting or anti-Xa activity. These results suggest that TEG-r reflects the efficacy of heparin in the extra-corporeal blood circuit, whereas APTT mainly reflects heparin concentration of the blood samples.(ABSTRACT TRUNCATED AT 250 WORDS)     

Monitoring heparin therapy with thromboelastography and activated partial thromboplastin time

Blood coagulability in patients undergoing anticoagulant therapy has been studied using the Thromboelastograph® and activated partial thromboplastin time. Currently used tests, such as activated partial thromboplastin time (APTT) and whole blood clotting time, lack sensitivity and do not correlate well with clinically significant bleeding and clotting events. The Thromboelastograph® is an instrument that allows continuous measurement of overall coagulation and fibrinolysis. Sixty patients on heparin therapy were monitored with thromboelastography and activated partial thromboplastin time. Continuous heparin infusion or intermittent administration was used. The Thromboelastograph® was found to be a more sensitive device for detection of response to heparin than APTT. Early response to heparin was reflected in the reaction time, k time, and maximum amplitude of the thromboelastogram. A more precise administration of heparin was made possible, resulting in use of less heparin and a more stable patient response. A more individualized approach to the patient's therapy was achieved by monitoring with the Thromboelastograph, and the best results were obtained with continuous infusion rather than intermittent administration of heparin.     

Can extra protamine eliminate heparin rebound following cardiopulmonary bypass surgery?

OBJECTIVES: Heparin rebound, the reappearance of anticoagulant activity after adequate neutralization with protamine, is thought to contribute to excessive postoperative bleeding after cardiac surgery. We have previously demonstrated that a significant amount of heparin is bound nonspecifically to plasma proteins and is incompletely neutralized by protamine. The aim of this study was to investigate whether clinically important bleeding attributable to heparin rebound can be eliminated by infusion of small amounts of additional protamine for 6 hours postoperatively and whether this treatment can reduce mediastinal blood loss. METHODS: Three hundred patients undergoing elective cardiac surgery were randomized to receive either a continuous infusion of protamine sulphate (25 mg/h for 6 hours) postoperatively or saline placebo. Serial blood samples were obtained to measure thrombin clotting time and anti-factor Xa activity. Heparin bound nonspecifically to plasma proteins was measured after displacement with a chemically altered heparin with low affinity to antithrombin. Mediastinal blood loss and transfusion requirements were recorded. RESULTS: Heparin rebound was demonstrated in every patient in the placebo group as reflected by increased thrombin clotting time, anti-factor Xa activity, and protein-bound heparin between 1 and 6 hours after surgery. In contrast, heparin rebound was eliminated in the protamine infusion group. The thrombin clotting time was normalized and both heparin concentration and protein-bound heparin were almost undetectable (P <.001). There was a modest 13% reduction in postoperative bleeding but this did not reduce blood transfusions. No adverse events were attributable to the extra protamine. CONCLUSIONS: Postoperative protamine infusion was able to almost totally abolish heparin rebound. In the context of this study, protamine infusion resulted in reduced postoperative bleeding but the magnitude was insufficient to alter transfusion requirements.     

Antithrombin replacement during extracorporeal membrane oxygenation

Heparin remains the predominant anticoagulant during extracorporeal membrane oxygenation (ECMO). Heparin acts by potentiating the anticoagulant effect of antithrombin (ATIII). Acquired ATIII deficiency, common in pediatric patients requiring ECMO, may result in ineffective anticoagulation with heparin. ATIII replacement may result in increased bleeding. Our objective is to determine ATIII's effect on anticoagulation and blood loss during ECMO. A retrospective chart review was performed of all patients at Children's Hospital of Wisconsin who received ATIII while supported on ECMO in 2009. ATIII activity levels, heparin drip rate, and activated clotting times (ACT) were compared before, 4, 8, and 24 h after ATIII administration. Chest tube output and packed red blood cell (pRBC) transfusion volume were compared from 24 h before ATIII administration to 24 h after. Twenty-eight patients received ATIII as a bolus dose during the course of 31 separate times on ECMO support. The median age of these patients was 0.3 years (range 1 day-19.5 years). ATIII activity increased significantly at 8 and 24 h after administration. No significant difference was noted in heparin drip rate, ACT levels, chest tube output, or pRBC transfusion volume. ATIII administration resulted in higher ATIII activity levels for 24 h without a significant effect on heparin dose, ACT, or measures of bleeding.     

Small soft left ventricular assist device powered by intraaortic balloon pump console for infants: a less expensive option

We have developed a pneumatically driven 20 cc soft ventricle for temporary right, left, or biventricular assist. The ventricle consists of a vacuum-formed soft housing, diaphragm, tricuspid outflow valve, and biflap inflow valve. All components including inflow and outflow valves were made with Pellethane. The advantages of this blood pump are as follows: it eliminates use of the quick connect system and therefore is less thrombogenic; the biflap inflow valve provides low inflow resistance; the soft ventricle is easy to implant; the polyurethane valves eliminate blood damage and thromboembolism and are low in cost compared with mechanical valves; and the vacuum-forming technique is reliable, fast, capable of mass production, and therefore inexpensive. We have already demonstrated in both in vitro and in vivo experiments that this ventricle has excellent hemodynamic performance with less blood damage and thrombogenesis. In this study, we evaluated the possible application of a well-defined and widely distributed intraaortic balloon pump (IABP) console to the 20 cc left ventricular assist device (LVAD) driver. The pump was tested in 6 mongrel dogs (6 to 10 kg) using an IABP console. The pump was connected between the left atrium and the ascending aorta, placed paracorporeally on the chest wall, and driven at a synchronous or fixed rate mode without using vacuum. The 20 cc ventricle could maintain the same output as the control output of the natural heart at filling pressures of 5 to 10 mm Hg during the entire observation time of 5 h. Thus, this 20 cc soft ventricle has the potential to be widely used for the treatment of severe heart failure in infants because of its excellent hemodynamic performance, simplicity, and low cost.     

Effect of heparin and prostacyclin-heparin infusion on blood coagulation in haemodialysed patients

In 10 patients (8 men and 2 women) aged 28 to 58 years (mean 44.4 years) treated by repeated haemodialysis due to end-stage renal failure, the bleeding time, whole-blood coagulation time, one-stage prothrombin time, thrombin time of plasma, activated partial thromboplastin time (APTT), fibrinogen level and euglobulin lysis time have been determined (1) during a 4-hour haemodialysis using heparin as an antithrombotic agent, and (2) one week later in the course of another haemodialysis using prostacyclin-heparin. The values for any of the above parameters with both anticoagulant treatment types did not differ. Plasma fibrinogen level after haemodialysis was significantly lower after administration of heparin alone as compared with the group treated by prostacyclin-heparin infusion. During haemodialysis performed with prostacyclin-heparin infusion, activation of the blood fibrinolytic system was manifested by a significant shortening of euglobulin lysis time, observed after 1.5 hours and after the end of haemodialysis. The above phenomenon did not occur when haemodialysis was performed with heparin alone.     

Heparin inhibits fibrin, but not leukocytes, in a model of deep-vein thrombosis

Previous studies with models of deep-vein thrombosis (DVT) have demonstrated that leukocyte (PMN)-mediated vein injury may be an initiating event in DVT (14, 17). Since heparin (H) can prevent DVT, we studied its effect on vascular injury and thrombosis in our model. Three groups of rabbits were treated with H either sc (73 and 147 U/kg) or iv (662 U/kg). Scanning electron microscopy revealed that the 73 U/kg sc dose was ineffective. All veins had PMN accumulation, fibrin deposition and complex thrombus formation. There was no increase in anti-Xa activity; activated partial thromboplastin times (APTT) and whole blood clotting times were normal. The 147 U/kg sc and the intravenous dose did not inhibit PMN-mediated vein injury. The endothelium was sloughed by migrating PMNs, basement membrane was exposed, and platelets adhered to it. Thrombosis was completely absent in the iv dose group. This correlated with increased anti-Xa activity and prolonged APTT and whole blood clotting times. Our results indicate that heparin does not inhibit the PMN adhesion and migration which produces vascular injury. However, the anticoagulant activity of heparin effectively reduces fibrin deposition and complex thrombus formation.     

A low molecular heparin fraction as an anticoagulant during hemodialysis

During 18 hemodialyses of patients with chronic uremia a low molecular weight heparin fraction (mean MW 5000 d) was used as an anticoagulant without complications. For comparison conventional heparin was used during 18 dialyses in the same patients. Equipotent doses, with regard to Xa inhibition of heparin and the 5000d fraction, suppressed FPA generation (fibrin formation) equally. The APT-times were less prolonged by the 5000d fraction. When the 5000d fraction was doubled in relation to conventional heparin with regard to Xa inhibition, the suppression of FPA generation was more effective than with conventional heparin, without more pronounced APTT prolongations. In conclusion this heparin fraction was found to be useful as an anticoagulant during hemodialysis and to give less pronounced APTT prolongation than conventional heparin.     

Laboratory heparin resistance in burn injury complicated by venous thrombosis

Anticoagulation with heparin is required in the management of the burn patient if their clinical course is complicated by venous thrombosis. Heparin therapy is commonly monitored by the activated partial thromboplastin time (APTT) but this assay can be unreliable in patients with acute inflammation because of an increase in plasma factor VIII levels that result in an underestimation of the heparin concentration. We report an example of heparin resistance that occurred in a patient who developed venous thrombosis following extensive second-degree burns. Heparin doses in excess of 60,000 units per day were required to produce a significant elevation in the APTT. The plasma factor VIII level was found to be markedly elevated to 455% and the plasma heparin concentration as determined by the anti-factor Xa assay was disproportionately elevated in relation to the APTT. Physicians treating patients with burn injury complicated by venous thrombosis should be aware of the potential development of factor VIII-related heparin resistance when large amounts of heparin are required to obtain a satisfactory elevation in the APTT. Measurement of the plasma heparin concentration will avoid excessive heparin administration and the serious bleeding which can result.     

N-脱硫酸肝素对ICR雌性小鼠骨形态计量学的影响

目的探讨肝素诱发骨质疏松症的发病机理。方法ICR雌性小鼠共30只分成3个实验组，普通肝素组和N-脱硫酸肝素组各10只，分别按1IU／g．day给予药物；生理盐水组10只，给予同体积的生理盐水。自12w月龄开始每日皮下注射，28d后心脏采血，检测PT及APTY；取双侧胫骨，制成组织切片，AIJP和TRAP染色计数成骨细胞和破骨细胞；使用图形处理软件测量兴趣区域（AOI）的骨小梁长度和面积等，结果进行t检验。结果普通肝素组与N-脱硫酸肝素组在骨小梁面积、成骨细胞计数、破骨细胞计数方面两组之间比较无显著性差异，而与生理盐水组之间存在显著性差异（P〈0．05）；N-脱硫酸肝素组与普通肝素组在PT、APTT方面均存在显著性差异（P〈0．05）。结论N-硫酸基团在普通肝素的体内抗凝血作用中起重要作用，但是该基团与诱导骨质疏松的形成之间缺乏明显的相关性。     

Heparin kinetics in vascular surgery

Currently there is little information available about the efficacy of heparin during vascular surgery or of the effects of surgical trauma on heparin kinetics. This study was undertaken to evaluate the kinetics of heparin therapy during vascular surgery. Nine patients undergoing major vascular surgery (one carotid, one common iliac and seven aortic operations) were studied both preoperatively and intra-operatively, each patient acting as his own control. Following determination of control activated partial thromboplastin time (APTT) and plasma heparin levels, heparin (100 u/kg body weight) was administered intravenously. Heparin dosage ranged form 4500 units to 8600 units with a mean dose of 6500 units. Plasma heparin and APTT levels were then measured at 10 minute intervals for 1 hour and 20 minute intervals for a second hour. The mean pre-operative and intra-operative APTT levels at ten minutes attained maximal values of 6.6 +/- 3.7 and 8.8 +/- 1.7 times the control respectively. At the end of 2 hours the mean APTT remained greater than 2.5 times the control in both groups. Mean plasma heparin level was 0.83 +/- 0.04 units at 10 minutes and was almost identical in both groups. Heparin level was not a reliable indicator of anticoagulant effect as most patients achieved the same levels but had markedly differing APTT results. The results of this study suggest that excessive doses of heparin may be used in vascular surgery and that surgical trauma does not significantly alter sensitivity to heparin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Gastrointestinal blood loss in haemodialysis patients during use of a low-molecular-weight heparinoid anticoagulant

In a randomised cross-over study we assessed total blood loss in 14 dialysis patients using 59Fe as a marker for measurement in a whole-body counting system. In one period the patients received standard heparin, in the other ORG 10172, a new low-molecular-weight-heparinoid. Our results show no significant difference between the two study periods with regard to blood loss and dialyser blood retention. In some patients a delayed bleeding ('oozing') from the puncture site was noticed as a side-effect of treatment with the low-molecular-weight-heparinoid. We conclude that this heparinoid is effective as an anticoagulant in regular dialysis treatment, but it seems to have no advantage over standard heparinisation with regard to occult bleeding. This may be related to the prolonged plasma anti-Xa activity (30.8 h) of this compound compared to standard heparin in dialysis patients.     

ACCURACY OF COAGULATION STUDIES PERFORMED ON BLOOD SAMPLES OBTAINED FROM ARTERIAL CANNULAE

We have assessed the accuracy of coagulation studies in bloodobtained from intra-arterial cannulae. Paired samples were studiedin blood from 39 patients receiving intensive care; one samplewas obtained by venepuncture and the other from an intra-arterialcannula after the apparatus deadspace plus 5 ml of blood hadbeen discarded. Activated partial thromboplastin time (APTT)(with throm-boplastin routinely used in our laboratory), pro-thrombintime (PT), thrombin time (TT), fibrinogen and heparin assayswere measured on each sample. In 37 sample pairs, APTT was measuredalso using a different thromboplastin. The median differencebetween the sample pairs was 5.5 s for APTT (P = 0.032) and1.0 s (P = 0.048) for TT, the times for arterial cannula samplesbeing longer. There was no significant difference between arterialcannula and venepuncture samples for PT or fibrinogen concentration.Heparin assays revealed heparin contamination in samples obtainedfrom arterial can-nulae in 15 of 30 patients not receiving heparin.It is concluded that, when coagulation studies are performedusing the techniques used routinely in our laboratory, a bloodsample from an arterial cannula may give clinically misleadinginformation because of contamination with small amounts of heparin,and that separate venepuncture is recommended.     

Successful treatment of right ventricular thrombus with heparin and sodium warfarin therapy: a case report

A 75-year-old woman came to our emergency clinic complaining of abdominal pain. Acute cholecystitis was diagnosed, and parenteral antibiotic therapy was initiated. Because of palpitation, she had a consultation with the cardiology clinic. Echocardiography showed a 2.7 x 2.2 cm mobile thrombus attached to the apex of the right ventricle. Since no thromboembolic complications were present, we decided to begin administering heparin and oral anticoagulant. After the administration of unfractionated heparin for 48 hours, the patient was shifted to low-molecular weight heparin because it is easier to use and requires no follow-up. The patient received low-molecular weight heparin in addition to sodium warfarin for 5 days. Administration of heparin was then stopped and treatment was continued with sodium warfarin. In the series of weekly echocardiography evaluations, a gradual reduction was noted in the apical mass, which was initially considered to be a thrombus, and 3 weeks later evaluation revealed that the thrombus in the right ventricle had disappeared completely. No thromboembolic complications were observed during the follow-up period.     

微创经皮肾镜治疗口服抗凝/抗血小板药物结石患者的安全性及疗效分析

目的探讨微创经皮肾镜碎石取石术(MPCNL)治疗口服抗凝药物/抗血小板的上尿路结石患者的疗效及安全性。方法2015年6月至2017年10月,47例接受口服抗凝/抗血小板药物治疗的上尿路结石患者在中山大学附属第三医院岭南医院行MPCNL治疗,围手术期采用低分子肝素替代治疗,术后采用气囊尿管作为肾造瘘管。选取同期行MPCNL治疗的未接受抗凝/抗血小板治疗的、无凝血功能障碍的上尿路结石患者50例进入对照组。比较两组患者间年龄、性别、体质量指数、结石大小等一般情况及手术时间、结石清除率、血红蛋白下降值、住院时间、并发症发生率等的差异。结果两组患者在手术时间、结石清除率、血红蛋白下降值、并发症发生率方面比较差异无统计学意义,抗凝组患者住院时间较非抗凝组时间长,差异具有统计学意义,但是两组患者术后住院天数比较差异无统计学意义。结论围手术期予低分子肝素替代治疗,术后予气囊尿管作为肾造瘘管牵拉压迫止血,口服抗凝/抗血小板药物的上尿路结石患者行MPCNL治疗是安全有效的。     

Effectiveness of FUT-175, protease inhibitor, as an anticoagulant to hemodialysis

(6-Amidino-2-naphthyl 4-guanidino benzoate) dimethanesulfonate (FUT-175), a protease inhibitor, has been reported to be an effective anticoagulant during hemodialysis without heparin. The anticoagulant activity of FUT-175 is also reported to be short. We applied FUT-175 to 33 patients who were undergoing hemodialysis and susceptible to bleeding, to avoid the use of heparin. The concentration and anticoagulant activity of FUT-175 were relatively stable during hemodialysis. A 20-40 mg/h dose of FUT-175 prolonged coagulation time sufficiently in the instrumental blood of the extracorporeal circuit but not in the systemic blood. Its anticoagulant activity decreased immediately after hemodialysis. Therefore, we could manage all patients without any bleeding trouble during hemodialysis with FUT-175 as an anticoagulant. Although there were side effects of FUT-175, such as nausea, vomiting, itching and eruption, they were not serious, and FUT-175 could be administered without interruption. FUT-175 seems to be useful as an anticoagulant during hemodialysis for patients susceptible to bleeding.     

Off-pump coronary artery bypass for a heparin-allergic patient

A 46-year-old man with no history of drug allergy developed acute myocardial infarction. Coronary angiographic findings revealed triple vessel disease. Serum hepatic enzymes were elevated due to heparin administered to control infarction, and an allergic reaction developed exclusively due to heparin. To avoid heparin use, we adopted heparin-free off-pump coronary artery bypass grafting through median sternotomy. The systemic anticoagulant agent argatroban was administered to maintain active clotting time over 200 seconds. The left internal thoracic artery was anastomosed to the left anterior descending artery, the radial artery to the diagonal branch, and the right gastroepiploic artery to the right coronary artery. Patency was confirmed by postoperative coronary angiography. No complications were noted. For patients with heparin allergy, off-pump coronary artery bypass grafting is a useful maneuver, because it can be conducted using anticoagulant agents other than heparin.