IU Heparin Research Articles

Heparin neutralization by an extract of the human placenta: measurements and the concept of placental barrier to heparin.

A soluble extract from human placenta was found to neutralize heparin in a factor Xa-dependent heparin assay system. In comparison with serum the antiheparin activity of placenta tissue is 10 times higher (extract from 1 g of placenta neutralizes 8.94 +/- 3.31 IU of heparin; 1 ml of serum approximately 1 IU). The substance neutralizing heparin has not been identified, but it has been found that it is nondialyzable, is not adsorbed on heparin-Sepharose, and does not act progressively. It was suggested that the substance(s) responsible for the antiheparin effect in vitro might contribute to the failure of heparin to penetrate the placenta in vivo (placental barrier to heparin).

The influence of preoperative anticoagulation on heparin response during cardiopulmonary bypass

The effect of preoperative anticoagulant therapy on intraoperative heparin response in patients undergoing cardiac operations was examined in a prospective study. The study included 45 patients with different preoperative anticoagulant treatments: 10 patients received treatment with phenprocoumon (a warfarin analogue) (group M), 12 patients received treatment with intravenous heparin (group Hiv), and 13 patients received treatment with subcutaneous heparin (group Hsc). The control group consisted of 10 patients who did not receive anticoagulant therapy before operation (group C). Preoperative antithrombin III activity was highest in group M (85% +/- 6%) and lowest in group Hiv (70% +/- 15%, p less than 0.05). The activated clotting time, determined 10 minutes after bolus injection of 250 IU (group M) or 375 IU heparin (all other groups), was 529 +/- 109 seconds in group C, greater than 1000 seconds in group M, 483 +/- 99 seconds in group Hsc, and 406 +/- 63 seconds in group Hiv (p less than 0.05). Heparin consumption during cardiopulmonary bypass varied between 4.6 +/- 1.4 IU/kg.min (group Hiv) and 2.6 +/- 0.9 IU/kg.min (group M) (p less than 0.05). Despite this increased heparin consumption, the patients who had received heparin before operation demonstrated increased activation of coagulation at the end of cardiopulmonary bypass (thrombin-antithrombin III complex, 19 +/- 4.1 ng/ml in group M and 61 +/- 7 ng/ml in group Hsc, p less than 0.05; cross-linked fibrin fragments, 257 +/- 92 ng/ml in group M and 875 +/- 152 ng/ml in group Hiv, p less than 0.05). Increased platelet activation was also found in patients with preoperative heparin therapy (beta-thromboglobulin at the end of cardiopulmonary bypass was 585 +/- 88 ng/ml in group M versus 1341 +/- 190 ng/ml in group Hsc, p less than 0.05). Drainage from the chest tube 24 hours after operation was 815 +/- 305 ml in group C, 644 +/- 238 ml in group M, 1133 +/- 503 ml in group Hsc, and 950 +/- 505 ml in group Hiv (p less than 0.05 for group M versus group Hsc). This study suggests that patients who receive heparin therapy before operation face a high risk of insufficient anticoagulation during cardiopulmonary bypass if standard heparin doses are used. Therefore, for patients who receive preoperative heparin therapy, a larger (500 IU/kg) initial bolus of heparin is recommended before cardiopulmonary bypass. On the other hand, patients who undergo preoperative treatment with phenprocoumon receive sufficient anticoagulative effect with a heparin bolus of 250 IU/kg.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of subcutaneously administered dermatan sulfate (MF 701) on the coagulation and fibrinolytic parameters of healthy volunteers

Eight healthy volunteers were given single subcutaneous doses of dermatan sulfate (DS, 100, 200 and 400 mg), heparin (5,000 IU) and placebo in random order. Wash-out between treatments was > 10 days. Serial blood samples were taken before and up to 24 hours after treatment to measure coagulation and fibrinolytic parameters. Thrombin generation was significantly inhibited by DS and heparin as compared to placebo. The effect of DS was dose-dependent. Peak inhibition after 200 mg DS was comparable to that of 5,000 IU heparin, but lasted longer. A small, bordeline significant prolongation of APTT was observed after 400 mg DS and heparin. The changes in PAI and fibrinolytic activities were those of the circadian variation. No changes were seen in the other parameters tested. In conclusion, single s.c. doses of DS (200, or 400 mg) inhibit ex vivo thrombin generation equally or more than 5,000 IU heparin and for a longer time. The effect of both treatments on fibrinolysis is negligible.

Swine as a Model for Cardiovascular Research: Improved Cardiopulmonary Bypass Techniques

A large-animal model is essential for the assessment of functional parameters in cardiovascular surgical research. To date the canine model has been used successfully because of its availability and tolerance to cardiopulmonary bypass. However, because of decreased availability and increased cost, an alternative animal model is now needed. The swine model has been used in experimental cardiac procedures, but complications during cardiopulmonary bypass have presented a formidable challenge. These complications include enormous fluid shifts from the vascular bed, increased metabolic acidosis, and marked hemoglobinuria. To eliminate these deleterious complications within the swine model, a number of technical alterations were achieved. The priming solution used for the extracorporeal circuit was altered to consist of 1000 mL lactated Ringer's solution. 500 mL 20% mannitol, 500 mL 6% dextran in 5% detrose solution. 50 mEq sodium bicarbonate, and 10,000 IU heparin. The extracorporeal circuit employed the use of membrane oxygenation. Three different blood flow rates (150, 175, and 200 mL/kg min-1) were studied. We conclude that the optimum blood flow rate for cardiopulmonary bypass in swine is in the range of 175-200 mL/kg min-1. Membrane oxygenation results in less damage to blood during cardiopulmonary bypass. The asanguinous hyperosmolar priming solution is beneficial for cardiopulmonary bypass in swine to greatly reduce fluid shifts, prevent metabolic acidosis, and eliminate hemoglobinuria.

Increased serum levels of fibrinogen degradation products due to treatment with recombinant tissue-type plasminogen activator for acute myocardial infarction are related to bleeding complications, but not to coronary patency

The association of increasing serum levels of fibrinogen degradation products after recombinant tissue-type plasminogen activator (rt-PA) therapy with bleeding and early coronary patency was assessed in 242 patients with acute myocardial infarction. After administration of 5,000 IU heparin, a median of 40 mg (range 35 to 60) of double chain rt-PA was given intravenously in 90 min. Bleeding occurred in 62 patients; in 73% of patients it was observed within the 1st 24 h and 84% of events consisted of hematoma or prolonged bleeding, or both, at puncture sites. Bleeding events occurred 2.12 times as often in patients with serum levels of fibrinogen degradation products >85 mg/liter as in patients with serum levels <22 mg/liter (95% confidence interval 1.01 to 4.43).The infarct-related coronary vessel was patent in 65% of patients at 90 min after the start of rt-PA infusion. In patients with high serum levels of fibrin(ogen) degradation products, coronary patency at 90 min after the start of rt-PA infusion was not better (13% less, 95% confidence interval −33%, 13%) than in patients with low serum levels. This uncoupling of thrombolytic effect in terms of coronary patency and systemic fibrinogenolysis confirms the experimentally demonstrated fibrin specificity of double chain rt-PA in human subjects. Because fibrin specificity of single chain rt-PA is at least similar to that of double chain rt-PA, the observations in this analysis most likely hold also for single chain rt-PA.These findings suggest that a dose of rt-PA just below the threshold that causes systemic fibrinogenolysis might be optimal in terms of bleeding and coronary patency. Measurements of fibrinogen degradation products during rt-PA infusion might help to titrate rt-PA dosing in individual patients.

Urethane as a sole general anaesthetic in cats used for electroretinogram studies

Cats are very sensitive to induction of anaesthesia by urethane. To anaesthetize cats with urethane, 1.0–1.3 g/kg, of freshly prepared urethane is administered intravenously at a rate of 1.92 g/h, while anaesthesia is maintained with 0.5% halothane in a 66% 33% nitrous oxide/carbogen gas mixture. Cats can then be maintained for up to 3 days by intravenous infusion at a rate of 4 ml/h of a 100 ml solution containing 50 IU heparin, 2.4 mg atropine, 4.7 g anhydrous d-glucose, and 240 mg urethane/kg. Using this anaesthetic, excellent electroretinograms can be recorded with no interfering eye movements.

FEMORAL ARTERY RECANALISATION WITH PERCUTANEOUS ANGIOPLASTY AND SEGMENTALLY ENCLOSED PLASMINOGEN ACTIVATOR

To establish whether re-occlusion of the femoral artery could be prevented, in 6 consecutive patients undergoing percutaneous transluminal angioplasty (PTA) for superficial femoral artery occlusion the recanalised segment was isolated, with a 7-French double-balloon catheter. 5 mg recombined human tissue-type plasminogen activator (rt-PA) and 1000 IU heparin were then infused into the enclosed space for 30 minutes, followed by intravenous heparin for 24 hours. At 10 and 30 days all 6 patients had evidence of recanalisation and remission of symptoms. Mean ankle-arm pressure index improved by 72% at 24 hours, by 118% at 10 days, and by 103% at 30 days after the procedure. No patients had major complications. Treatment of superficial femoral artery occlusions by PTA with rt-PA and intravenous heparin seems to prevent rethrombosis.

Postheparin Plasma Diamine Oxidase in Patients With Small Bowel Crohn's Disease

Diamine oxidase (DAO) is an enzyme located almost exclusively in villus tip enterocytes of mammals. Its plasma activity, normally very low, is enhanced by intravenous heparin, which releases the enyzme from small bowel enterocytes into the blood. Plasma postheparin DAO (PHD) values have been shown to be significantly reduced in patients with malabsorption and villous atrophy and inversely correlated with 24-h fecal fat, thus suggesting that PHD reflects the mature enterocytic mass. We have assayed PHD in 51 patients with small bowel Crohn's disease by measuring the area under the plasma DAO curve over a 120-min period after an intravenous bolus of 15,000 IU of heparin. Postheparin plasma DAO was significantly lower (p less than 0.001) in patients (328 +/- 175 U/ml.min) than in 20 normal subjects (508 +/- 101 U/ml.min; range, 391-749). Postheparin diamine oxidase values were inversely correlated with Crohn's disease activity index (CDAI), but no correlation was found with extent of disease assessed radiologically by either double-contrast small bowel enema or barium meal follow-through. In 6 patients with active disease (CDAI, 297 +/- 99) and low PHD values (188 +/- 100 U/ml.min), the assay was repeated after a clinically effective course of antiinflammatory drugs. A significant increase in PHD values (388 +/- 112 U/ml.min) was observed (p less than 0.005). These data indicate that mucosal involvement is common in small bowel Crohn's disease and that PHD may be useful in assessing and monitoring mucosal damage in these patients.

Adjusted subcutaneous heparin versus heparin plus dihydroergotamine in prevention of deep vein thrombosis after total hip arthroplasty

In a prospective randomized study, two different antithrombotic regimens were compared with regard to their effects on the incidence of deep vein thrombosis (DVT) in 102 patients undergoing elective total hip arthroplasty. Fifty patients (group 1) received heparin subcutaneously three times daily in doses adjusted as a function of activated partial thromboplastin time (APTT), and 52 patients (group 2) received a fixed dose of 5,000 IU heparin plus 0.5 mg dihydroergotamine twice daily. Both treatments were started 2 days before operation and continued for 7–9 days after operation, when venography of the operated leg was performed in all patients. The overall incidence of DVT was 22% in group 1 and 19.6% in group 2. Eight patients (16%) in group 1 and four (7.6%) in group 2 developed proximal DVT. These differences were not statistically significant. Hemorrhagic complications occurred more frequently in group 1. Heparin plus dihydroergotamine is a simple and effective method of preventing DVT in patients undergoing total hip arthroplasty. Daily APTT-adjusted subcutaneous heparin remains the best method of prevention of DVT in patients with contraindications to the use of dihydroergotamine and those with two or more DVT risk factors.

Acute coronary thrombolysis with recombinant human tissue-type plasminogen activator: Initial patency and influence of maintained infusion on reocclusion rate

An intravenous infusion of 40 mg of recombinant tissue-type plasminogen activator (rt-PA) was given intravenously over 90 minutes to 123 patients with acute myocardial infarction (AMI) of less than 4 hours' duration. A coronary angiogram was recorded at the end of the infusion in 119 patients. Central assessment of the angiograms revealed a patent infarct-related artery in 78 patients (patency rate 66%, 95% confidence limits 57 to 74%). Patients with a patent infarct-related artery at the first angiogram were randomized in a double-blind manner to receive a subsequent 6-hour infusion of either 30 mg of rt-PA or placebo. All patients had received an initial bolus of 5,000 IU of heparin and then 1,000 IU/hour until a second angiogram was recorded 6 to 24 hours after the start of the second perfusion. At central assessment of the second coronary angiogram the reocclusion rate was 2 of 36 patients who received rt-PA at the second infusion and 3 of 37 patients not receiving this drug (or the 2 groups combined 7%, 95% confidence limits 2 to 15%). Three of 60 patients (5%, 95% confidence limits 1 to 14%) with patent arteries on both previous angiograms had a later occlusion as judged on the angiogram recorded at hospital discharge. No difference in late reocclusion rates between the 2 treatment groups was observed.

Plasma clearance of fat emulsion during continuous heparin infusion.

Intravenous fat tolerance was tested in two groups of patients given a continuous i.v. infusion of heparin for several days. One group of 11 patients with deep vein thrombosis (DVT) of the leg was given 25,000-35,000 IU heparin daily for 4-5 days. The other group comprised 10 patients who had central venous catheters (CVC) for total parenteral nutrition. These patients were given 20,000 IU heparin daily for 6 days as prophylaxis against CVC-related thrombosis. In the DVT group heparinization was associated with a 44% decrease in plasma fat removal capacity (P less than 0.05). This reduction persisted for 2 days after the discontinuation of heparin therapy. In the CVC group the plasma fat removal capacity decreased by 29% during heparinization (P greater than 0.05, NS). During heparinization activated partial thromboplastin time was more than three times the basal value in the DVT group but less than twice those in the CVC group. One week after the heparin therapy the serum triglyceride levels were higher in both groups compared with initial values (DVT group: 1.2 +/- 0.2 s.e. mean vs. 1.7 +/- 0.3 mmol/l; P less than 0.05. CVC group: 1.0 +/- 0.1 vs. 1.4 +/- 0.2 mmol/l; NS). The possibility that full-dose heparinization reduces plasma fat removal capacity and that this may be due to a partial depletion of lipoprotein lipase stores is discussed.

Prophylaxis of Postoperative Thromboembolism with Heparin-Dihydroergotamine Combination

The effect and safety of a fixed combination — 5000 iu of heparin + 0.5 mg of dihydroergotamine every 12 h subcutaneously (HDHE) versus 5000 iu of heparin every 8 h subcutaneously (LDH) for prophylaxis of postoperative venous thromboembolism was evaluated in a prospective randomized clinical trial involving 142 patients undergoing major abdominal surgery. Using the radiofibrinogen uptake test postoperative deep venous thrombosis was detected in 10% of 70 patients in the HDHE group and in 14% of 72 patients of the LDH group. Seven patients died. Neither fatal, nor contributory pulmonary emboli were found at autopsy. Pulmonary microembolism diagnosed with lung perfusion scintigraphy and chest radiography developed in three patients treated with LDH and in one patient treated with HDHE. Significantly more wound haematomas and injection site bruises were observed in the LDH group. The conclusion drawn was that the 12-hourly regimen of heparin with DHE was as effective in preventing venous thromboembosis as the 8-hourly heparin regimen. The lowering of the heparin dose significantly reduced both the number of wound haematomas and injection site bruising.

Prevention of superficial phlebitis during peripheral parenteral nutrition

Fifty-four patients receiving peripheral parenteral nutrition consisting of 3.5 percent amino acids in a 5 percent dextrose solution were randomly assigned in a double-blind fashion to receive this solution with or without an antiphlebitic mixture (1000 IU heparin, 5 mg hydrocortisone, and 1.8 mEq sodium hydroxide as a buffer). The addition of antiphlebitic mixture resulted in a marked and highly significant reduction in the incidence of phlebitis and a prolongation of the number of phlebitis-free hours during infusion of peripheral parenteral nutrition (p < 0.005).

Anticoagulant effects of a low molecular weight heparinoid (ORG 10172) in human volunteers and haemodialysis patients

Org 10172, a low MW heparinoid derived from animal intestinal mucosal tissue, has a mean molecular weight of 6500 D and a specific activity of 8.0 anti-Xa U/mg. Its elimination half-life after i.v. administration is 18 hours. Six human volunteers received repeated single i.v. injections of 800 and 3200 anti-Xa units of Org 10172, 5000 IU heparin or placebo. Bleeding time, platelet count and plasma betathromboglobulin were not affected by Org 10172 or heparin. Heparin stimulated ADP-induced platelet aggregation (0.2 uM; p< 0.05) and inhibited thrombin induced aggregation (0.3 U/ml; p< 0.05), while the heparinoid lacked these effects. Heparin increased plasma platelet factor 4, whereas Org 10172 had no effect. In contrast to heparin Org 10172 had only a minor effect on the activated partial thromboplastin time and thrombin time, while both compounds induced anti-Xa activity in plasma. In a crossover study in six haemodialysis patients, both heparin and Org 10172 (34.4 and 22.4 anti-Xa units/kg/body weight) succesfully prevented clotting of the extracorporeal circuit. Microscopical analysis of the artificial kidney membranes showed that the 34.4 unit Org 10172 dosage was as effective as heparin in preventing fibrin deposition. The haemostatic and coagulation effects were as expected from those observed in the volunteers except that there was a slower elimination of the plasma anti-Xa response. In addition heparin and Org 10172 (34.4 anti-Xa units/kg) inhibited the Xa-induced platelet aggregation (0.5 U/ml; p< 0.01 and p< 0.001 respectively)

Dihydroergotamine-Heparin Prophylaxis of Postoperative Deep Vein Thrombosis

To the Editor.— The recent multicenter report on prophylaxis of postoperative thrombosis 1 and the editorial by Dr Hirsh 2 were excellent. Postoperative deep vein thrombosis (DVT), with the pulmonary embolism that so frequently follows it, continues to be one of the commonest causes of in-hospital deaths in this country. Considering its frequent occurrence, it is rather shocking how seldom appropriate prophylactic measures are being used in routine surgical practice. This study demonstrated quite clearly that dihydroergotamine with heparin, 5,000 IU, was more effective than the same dose of dihydroergotamine with 2,500 IU of heparin and, likewise, more effective than dihydroergotamine alone or 5,000 IU of heparin alone. This raises the question again as to whether the appropriate dose of heparin should not be chosen on the basis of the patient's probable sensitivity. As pointed out by Dr Hirsh, 2 the recent study of Leyvraz et al 3 demonstrates that

The Heparin-Mobilisable Pool of Platelet Factor 4: A Comparison of Intravenous and Subcutaneous Heparin and Kabi Heparin Fragment 2165

Some clinical advantages are claimed for low molecular weight heparin so the mobilisation of platelet factor 4 (PF 4) from the endothelial pool by the heparins may be relevant. Unfractionated (UF) heparin has been compared with Kabi heparin fragment 2165. A single intravenous (i.v.) injection of 60 iu/kg heparin was compared with 5000 anti-Xa units of Kabi-2165. Less PF 4 was mobilised by Kabi-2165 and some apparently remained in the pool and was released when the pool was subsequently challenged by giving i.v. heparin. Subcutaneous (s.c.) injections of 5000 iu heparin twice daily were compared with 5000 anti-Xa units of Kabi-2165 once daily, each given for a week. The plasma PF 4 was never raised yet when finally challenged with i.v. heparin the pool was "empty" or refractory after the s.c. heparin but some PF 4 remained after the s.c. Kabi-2165. The two glycosaminoglycans (GAGs) had widely differing half-lives but the t/2 of the PF 4 mobilised by the two GAGs was similar even though the PF 4 is apparently bound to the GAG.

Prevention of postvenographic thrombosis by heparin flush: fibrinogen uptake measurements.

The incidence of postphlebographic venous thrombosis was investigated by 125I-labeled fibrinogen uptake tests in 60 patients whose veins were flushed with saline solution containing 10,000 IU of heparin after leg phlebography. Ionic methylglucamine iodamide was used as the contrast medium. In six patients superficial thrombophlebitis extending from the contrast-medium injection site was observed after phlebography. The incidence of deep venous thrombosis was 3.3%, significantly less than that reported for studies using triiodinated ionic contrast media without flushing the veins with a heparin solution. It is comparable to the incidence of venous thrombosis reported after using nonionic contrast media. The authors conclude that flushing the veins with heparinized saline solution can improve the safety of phlebography considerably.

Prophylactic efficacy of low-dose dihydroergotamine and heparin in postoperative deep venous thrombosis following intra-abdominal operations

Postoperative pulmonary embolism continues to be a problem in patient care, especially in high-risk patients. This study was designed to evaluate a combined pharmacologic approach to the prophylaxis of postoperative deep venous thrombosis (DVT) by mediating at least two and probably three of Virchow's predisposing factors. Patients 40 years of age and older undergoing operations greater than 45 minutes under general anesthesia were placed in one of five treatment groups and studied by a prospective randomized, double-blind protocol. Study drugs were the following: (1) 0.5 mg of dihydroergotamine plus 5000 IU of sodium heparin (DHE 5000), (2) 0.5 mg DHE plus 2500 IU heparin (DHE 2500), (3) 5000 IU of HEP (HEP 5000), (4) 0.5 mg of DHE (DHE 0.5), and (5) a placebo. Study medications were administered 2 hours preoperatively and continuously thereafter every 12 hours postoperatively subcutaneously in the anterior abdominal wall for 5 to 7 days or until a positive radiofibrinogen uptake test (RFUT). The RFUT was performed according to standardized technique and was used to establish the presence or absence of DVT. This report is an analysis of the major subgroup of patients undergoing intra-abdominal operations. Results showed a highly statistically significant prophylactic benefit from DHE 5000 compared with the placebo (p < 0.003) and all other treatment groups (p < 0.05). There was no significant benefit from DHE 2500, HEP 5000 (p > 0.13), and DHE 0.5 (p > 0.3). All patients who entered the study had two or more risk factors for postoperative DVT, and high-risk patients were distributed equally throughout all treatment groups. DHE 5000 maintained its prophylactic benefit in high-risk patients. Evaluation of operative blood loss, postoperative blood loss, hematomas (wound or injection site), hematuria, postoperative hemoglobin difference, and adverse reactions revealed no significant difference between the study medications and the placebo. It is proposed that DHE 5000 has a synergistic prophylactic effect by mediating all three limbs of Virchow's triad: hypercoagulability (heparin), stasis (DHE), and vein wall injury secondary to venodilatation (DHE). DHE 5000 is recommended for patients at high risk of developing postoperative DVT and pulmonary embolism; however, it should be avoided in patients with acute myocardial infarction, sepsis, and sustained hypotension.

Toxicity of plasma from hemodialysis patients treated with heparin or prostacyclin.

Hemodialysis was performed in 6 uremic patients with either a bolus dose of 5 000 IU heparin or prostacyclin at a constant infusion rate of 5 ng/kg/min. Clinical data, plasma triglycerides (TG), free fatty acids (FFA), platelet aggregation, white blood cell count and plasma toxicity were measured prior to and during both procedures. No serious side-effects were recorded. Heparin induced a fall in plasma TG, a rise in FFA and increased plasma toxicity. Prostacyclin infusion had no effect on these parameters. During both tests a marked drop in white blood cell count was found 15 min after the start of hemodialysis. During heparin dialysis no clotting was observed in the extracorporeal circuit. During prostacyclin dialysis clotting was observed at the venous line in three cases.

Histidine-Rich Glycoprotein Modulates the Anticoagulant Activity of Heparin in Human Plasma

Addition of 0.05 IU of heparin per ml normal plasma prolongs its thrombin time from 20 to 27s , but that of plasma specifically depleted in histidine-rich glycoprotein (by immunoadsorption) from 20 to 180s . Reconstitution of the depleted plasma with normal plasma or with purified histidine-rich glycoprotein normalizes its thrombin time. In 54 plasma samples from hospitalized patients a significant negative correlation was found between the anticoagulant activity of heparin measured by thrombin inhibition and the plasma level of histidine-rich glycoprotein (r = 0.69). It is concluded that the level of histidine-rich glycoprotein modulates the anticoagulant activity of heparin in human plasma to an extent which appears to be pharmacologically and possibly clinically relevant.