Heparin-associated thrombocytopenia: a comparison of three heparin preparations

Heparin-induced platelet aggregation: dose/response relationships for a low molecular weight heparin derivative (PK 10169) and its subfractions

Addition of heparin or heparin derivatives to citrate anticoagulated platelet-rich plasma caused platelet aggregation in a dose-dependent manner. Utilizing heparin, a low molecular weight heparin derivative (PK 10169) and its various subfractions, we determined dose/response relationships for platelet aggregation and found that the ability of these agents to cause platelet aggregation was dependent upon the molecular weight of the individual subfraction used. In comparison to unmodified porcine mucosal heparin, the lower molecular weight derivative (PK 10169) yielded a dose/response curve that was shifted down and to the right, and indicated that this agent was less potent in causing platelet aggregation. In addition, as the molecular weight of PK 10169 subfractions decreased, their dose/response curves were progressively shifted down and to the right. The lowest molecular weight subfraction was essentially without platelet aggregating activity. We also measured the anti IIa and anti Xa activities of these agents and concluded that these activities did not appear to correlate with platelet aggregating activity. Platelet aggregation studies with PK 10169 subfractions of high and low affinity for antithrombin III (AT III) indicated that the platelet aggregating activity of these compounds may not be related to their affinity for AT III, but results were not definitive.

The use of dihydroergotamine and heparin in the prophylaxis of deep venous thrombosis

Three factors leading to the development of postoperative deep venous thrombosis (DVT) are the hypercoagulable state, stasis, and vein wall injury, which occur in patients undergoing surgical procedures. Vein wall injury is thought to occur as a smooth muscle response to surgical trauma in veins distant from the operative site. Heparin and dihydroergotamine (DHE) were combined in an attempt to decrease the hypercoagulable factor and minimize stasis. We believe that by maintaining venous smooth muscle tone, the degree of endothelial damage is also diminished. Low-dose heparin acts through its effect of factor Xa and activation of antithrombin III; DHE selectively increases venous smooth muscle tone to accelerate venous blood flow velocity and minimize venous pooling. The European experience with combination DHE-heparin prophylaxis shows that this combination is more effective than either agent alone, and studies on orthopedic patients have shown that DHE/5,000 is effective in preventing postoperative DVT in this high-risk group. In the US, the Multicenter Trial evaluated postoperative DVT in general surgical patients. The combination of DHE/5,000 was statistically more effective in the prophylaxis of postoperative DVT than placebo (p = 0.0011). The interim results of an ongoing Multicenter Trial on the prophylaxis of postoperative DVT in patients undergoing total hip replacement indicate that DHE/5000 has significant prophylactic efficacy compared to placebo. It is proposed that the mechanism of action of the DHE-heparin combination is synergistic, since all 3 limbs of Virchow's triad are potentially affected.

Treatment of venous thromboembolic disease. A pragmatic approach to anticoagulation and thrombolysis

Heparin (Lipo-Hepin, Liquaemin Sodium) and warfarin sodium (Coumadin, Panwarfin) are the classic anticoagulants in use for venous thromboembolic disease. They work by modifying the coagulation mechanism, heparin having an immediate effect and warfarin having a more delayed effect. The most common adverse effects of anticoagulation therapy are hemorrhagic complications. Thrombolytic therapy should be considered in all patients with massive pulmonary embolism with hypotension and in patients with deep venous thrombosis in the popliteal area or higher. Such therapy has been shown to help preserve the pulmonary microcirculation after pulmonary embolism and to decrease the incidence of the postthrombotic syndrome following deep venous thrombosis. If certain clinical guidelines are followed rigidly, the incidence of significant bleeding complications is low. Although the use of tissue plasminogen activator in venoocclusive disease has been limited to isolated cases, results have been very promising.

Heparin-associated thrombocytopenia: a prospective comparison of bovine lung heparin, manufactured by a new process, and porcine intestinal heparin

Heparin-associated thrombocytopenia has been reported most commonly with bovine lung preparations. We prospectively evaluated the incidence of thrombocytopenia in 43 patients receiving intravenous continuous infusions of either bovine lung heparin, manufactured by a new process, or a standard porcine intestinal mucosa heparin for a minimum of five days in a double-blind, randomized fashion. The decision to continue heparin therapy beyond five days was made by the patient's primary physician. All patients had documented acute thromboembolic disease, pretherapy platelet counts greater than 150 000/mm3, and no evidence of prior coagulation disturbance. No patients had undergone cardiopulmonary bypass or hemodialysis within seven days previous to the initiation of heparin therapy. Thrombocytopenia was defined as a decline in platelet count from the normal range of 150 000-350 000/mm3 to less than 100 000/mm3. Thrombocytopenia occurred in one patient (4.6 percent) receiving bovine lung heparin on day nine of therapy and in no patients (0 percent) receiving porcine intestinal mucosa heparin. Adverse reactions occurred in nine patients (42.9 percent) receiving porcine intestinal heparin and five patients (22.7 percent) receiving bovine lung heparin. This difference was not statistically significant. The results of this study indicate that the incidence of thrombocytopenia is low (less than five percent) with both bovine lung heparin, manufactured by a new process, and porcine intestinal mucosa heparin when therapy is limited to short therapeutic courses (less than 1 week).

Drug-induced thrombocytopenia

A variety of drugs may cause thrombocytopenia. Although it occurs more often than drug-induced anemia it is less well understood because techniques for studying drug-platelet-immune interactions have been unavailable until recently. The mechanisms by which drugs cause thrombocytopenia are varied. Bone marrow suppression or increased peripheral destruction of platelets could be involved. Nonimmunologic as well as immunologic mechanisms may also occur. These different mechanisms of drug-induced thrombocytopenia are reviewed. Diagnostic methods and treatment are also summarized.

Heparin-induced thrombocytopenia. What is its real frequency?

A prospective study of 104 patients was undertaken to determine the frequency of severe heparin-induced thrombocytopenia in patients receiving either bovine lung or porcine mucosal heparin. One of 54 patients randomized to receive bovine heparin and two of 50 patients randomized to receive porcine heparin developed heparin-induced thrombocytopenia (platelet count less than 100,000/microliters). Although three previous studies suggest a remarkably high frequency of bovine heparin-induced thrombocytopenia, or a high frequency compared to porcine heparin, our study supports other evidence that clinically important, severe heparin-induced thrombocytopenia (platelet count less than 100,000/microliters) occurs in 10 percent of patients or less receiving heparin, and that there is no significant difference of occurrence between bovine and porcine heparin.

Trousseau's syndrome. Devastating coagulopathy in the absence of heparin

Two patients with Trousseau's syndrome experienced frequently recurring concomitant arterial and venous thrombotic events that resulted in sequential amputation and loss of the lower extremities. Serial examination of the blood in the patients demonstrated that these devastating thrombotic events were preceded by severe disseminated intravascular coagulopathy that occurred within an interval of a few hours. Warfarin therapy was without effect in preventing the occurrence of these events. Both patients demonstrated the absolute need for intravenous heparin, which effectively prevented the thrombotic events; when it was discontinued, the immediate consequences were disastrous and resulted in death. Techniques for long-term outpatient heparin therapy are discussed.

Heparin-induced thrombocytopenia: a prospective study

Thrombocytopenia is a well-described complication of heparin therapy. Few studies describe the incidence of thrombocytopenia when low-dose heparin (10,000-15,000 units/day) is used for prophylaxis of deep venous thrombosis. In our study, ten of 66 courses (15%) of heparin prophylaxis in coronary care unit patients were accompanied by a mild thrombocytopenia with platelet counts below 150 X 10(3)/mm3. In all cases the platelet count returned to normal despite continued heparin therapy. Patients who became thrombocytopenic had significantly lower initial platelet counts. No cases of severe thrombocytopenia were seen (platelet count below 100 X 10(3)/mm3). No patient developed thrombosis, bleeding or elevated fibrin split products. Mild thrombocytopenia occurring after 2-5 days of low-dose heparin is common, but clinically insignificant.

Thrombocytopenia in a prospective, randomized, double-blind trial of bovine and porcine heparin

A prospective, randomized, double-blind clinical trial of bovine and porcine heparin was conducted. One hundred forty-one patients were randomized, of whom 89 received heparin treatment for six or more days (mean, ten days). Two developed severe thrombocytopenia (platelet count less than 20,000 per microliter); both were randomized to the bovine heparin group, but one inadvertently received two doses of porcine heparin. Laboratory investigation suggested that the thrombocytopenia in these two patients was immunologically mediated, and platelet reactivity to both bovine and porcine heparin was demonstrated. Twenty patients had a decline in platelet count of greater than 50,000 from baseline, although the total count remained above 150,000 per microliter. In seven of these subjects, the platelet count returned to its original level while heparin therapy was continued. Of the 13 patients with a persistent decrease in platelet count, ten had received bovine heparin and their counts decreased by an average of 88,000 per microliter; the reduction in the three porcine-treated patients was 68,000; this difference was not statistically significant. In the remaining patients, the post-treatment platelet counts in both groups were significantly higher than pretreatment values (p less than .005), perhaps indicating a cessation of the platelet consumption that accompanied the original thrombotic event.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterogeneity of heparin lots associated with thrombocytopenia and thromboembolism

Thromboembolic complications may develop in patients with heparin-associated thrombocytopenia, presumably due to the formation of platelet aggregates. An unexpectedly high incidence of pulmonary embolism following coronary artery bypass surgery occurred during a brief period of time at a single institution, and all of these cases were found to be associated with thrombocytopenia. All patients tested during thrombocytopenia (five of five) had an increase in platelet-associated antibody. Serum samples from all five patients tested caused normal platelets to aggregate in vitro in the presence of one specific lot of beef lung heparin, which was in use in the operating room at the time; none of six other lots of beef lung heparin mediated in vitro platelet aggregation. Heparinase digestion of the heparin abolished the aggregating activity. It is concluded that thrombocytopenia and platelet activation caused by heparin may vary greatly even among different lots of heparin prepared from the same source.

Heparin-induced thrombocytopenia--association with a platelet aggregating factor and cross-sensitivity to bovine and porcine heparin

Heparin-induced thrombocytopenia is an infrequently suspected adverse drug reaction since its sequelae often mimic the underlying condition for which the drug is being used. A concomitant decline in platelet count and increase in heparin requirements should alert the clinician to the possible presence of this disorder. A 36-year-old black male developed severe thrombocytopenia with thrombosis while being treated with porcine intestinal mucosal heparin. Platelet counts returned to near-normal levels upon discontinuation of heparin, but quickly dropped again upon resuming treatment with bovine lung heparin. The patient subsequently was treated with warfarin and dipyridamole, with no further complications. Treatment of delayed-onset severe heparin-induced thrombocytopenia consists of stopping the heparin and substituting antiplatelet agents and oral anticoagulants when continued inhibition of coagulation is required.

[Thrombogenic thrombopenia induced by heparin]

Three cases of heparin induced thrombotic thrombocytopenia are reported. Pathogenesis, clinical and biological manifestations as well as treatment are reviewed. Treatment consisted in replacing the heparin by a vitamin K antagonist or a low molecular weight heparin. During heparin treatment, the risk of thrombotic thrombocytopenia should be kept in mind and the platelet count monitored from time to time.

Anticoagulation therapy for venous thromboembolism in patients with gynecologic malignancy

Anticoagulation therapy in 74 patients with gynecologic malignancy and venous thromboembolism was evaluated as to hemorrhagic complications, recurrent thrombosis, and completion of prescribed course. Clinically significant bleeding complications occurred in 25 patients and the course of anticoagulant therapy was not completed in 29 patients because of bleeding complications or death within 3 months. Venous thromboembolism recurred in 11% of patients. Risk factors associated with hemorrhagic complications and unsuccessful completion of anticoagulation therapy include advanced age, advanced stage of malignancy, incomplete surgical resection of tumor, and systemic chemotherapy. Complications of anticoagulant therapy were found to be excessive when compared to those in reports dealing with noncancer patients and may exceed the benefits of therapy in certain patients. Alternative methods of management for this group of high-risk patients are discussed.

Intracavitary thrombi in the right heart associated with multiple pulmonary emboli. Report of two patients

Two-dimensional echocardiography identified intracavitary masses in the right heart in two patients presenting with extensive pulmonary embolism. In one, a right ventricular mass was identified which was confirmed at subsequent autopsy to be an organizing thromboembolus. In the second patient, a right atrial mass was identified; it disappeared with thrombolytic therapy which was accompanied by clinical improvement. We demonstrate that intracardiac thrombi associated with pulmonary embolism may be identified noninvasively by two-dimensional echocardiography. We suggest the presence of thrombi may represent a large intravascular thrombus. This recognition may influence therapeutic decisions.

Heparin-induced thrombocytopenia, thrombosis, and hemorrhage

Sixty-two patients with a heparin-induced thrombocytopenia are reported. Clinical manifestations of this disorder include hemorrhage or, more frequently, thromboembolic events in patients receiving heparin. Laboratory testing has revealed a falling platelet count, increased resistance to heparin, and aggregation of platelets by the patient's plasma when heparin is added. Immunologic testing has demonstrated the presence of a heparin-dependent platelet membrane antibody. The 20 deaths, 52 hemorrhagic and thromboembolic complications, and 21 surgical procedures to manage the complications confirm the seriousness of the disorder. Specific risk factors have not been identified; therefore, all patients receiving heparin should be monitored. If the platelet count falls to less than 100,000/mm3, while the patient is receiving heparin, platelet aggregation testing, using the patient's plasma, is indicated. Management consists of cessation of heparin, platelet anti-aggregating agents, and alternate forms of anticoagulation when indicated.

A randomized study of beef lung and pork mucosal heparin in cardiac surgery

Beef lung heparin had substantially greater anticoagulant activity than pork mucosal heparin during a preoperative heparin tolerance test and also during cardiopulmonary bypass (CPB) in 100 randomized patients. Supplemental heparin was needed during CPB in many more of the patients receiving pork mucosal heparin. Heparin rebound was detected in 16 patients; this low incidence may result from a relatively high protamine:heparin ratio. There was notably less postoperative bleeding in those who received beef lung heparin. Platelet counts were not altered by either type of heparin. It is surprising that the preoperative tolerance curve only predicted heparin sensitivity during CPB in one-half of the patients. Blood activated coagulation time levels were increased markedly by hemodilution and further raised by hypothermia. These data demonstrate that beef lung heparin is better than pork mucosal heparin for CPB.

Heparin-binding platelet proteins demonstrated by crossed affinity immunoelectrophoresis

Platelet proteins that interact with heparin were studied using crossed affinity immunoelectrophoresis. Platelet proteins solubilized in Triton X-100 were applied to crossed immunoelectrophoresis against anti-platelet antibodies, and an intermediate gel containing heparin covalently linked to Sepharose 4B was inserted. Six immunoprecipitates were absent or showed an altered position compared to control immunoplates, indicating that the corresponding antigens were bound to the immobilized heparin. These precipitates represented platelet factor 4, thrombospondin, glycoprotein Ib, and three antigens termed G4, 17 and 25. The subcellular location of the heparin-binding proteins was either in the surface membrane (glycoprotein Ib and the antigens 17 and 25), or in the alpha-granules (platelet factor 4, thrombospondin and G4). both forms of platelet factor 4 appearing after crossed immunoelectrophoresis, i.e. a line-form and a peak-form, bound strongly to the heparin. Glycoprotein Ib showed a weak binding whereas its proteolytic split product glycocalicin did not significantly bind to the heparin in the present system. It is concluded that the platelets contain at least six heparin-binding proteins which are present on the cellular surface or are able to be exposed to the extracellular medium after the release-reaction has occurred.

Fibrinogen binding on human platelets. Influence of different heparins and of pentosane polysulfate

Unfractionated heparin increased the binding of fibrinogen on ADP-treated platelets. The results varied according to both, the platelets of the donor and the kind of heparin preparation used. Beef lung heparin was more active than porcine intestinal mucosa heparin (p less than 0.02). A fraction of low molecular weight low sulfated heparin, did not significantly increase the binding of fibrinogen, except in one case for which the binding of fibrinogen to platelets was largely increased by standard heparin. On the contrary, pentosane polysulfate, a sulfated polysaccharide (of low molecular weight) significantly increased the binding of fibrinogen (p less than 0.01).

Heparin necrosis: an anticoagulant-induced cutaneous infarct

A rare complication of subcutaneous heparin therapy is reported in a 75-year-old man. Large erythematous tender plaque developed in the skin overlying the injection sites. In one area of the abdomen, frank necrosis occurred with subsequent eschar formation. Skin testing with five brands of heparin revealed that the patient had a delayed type of hypersensitivity to heparin. In contrast to coumarin necrosis, heparin necrosis is felt to be a thrombotic phenomenon resulting from immunologically induced platelet aggregation in heparin-sensitive patients. Thrombocytopenia is usually present. The diagnosis can be confirmed by platelet aggregometry and calls for immediate cessation of the heparin injections.

Effect of heparin on platelet monolayer adhesion, aggregation and production of malondialdehyde

Heparin inhibited monolayer adhesion of washed human and rabbit platelets to collagen-coated glass at 2.5 and 20 units/ml concentration, in the absence of red cells. Adhesion of rabbit platelets to de-endothelialized rabbit aorta, under similar conditions, was less strongly inhibited but no inhibition was seen at 40% haematocrit. Addition of plasma reduced, rather than enhanced heparin activity and hirudin 0.5 units/ml had no significant effect. Heparin also inhibited platelet aggregation, release of (14C) 5-HT and production of malondialdehyde in response to collagen and thrombin. Inhibition of thrombin-induced activity was greater in the presence of plasma. However, heparin enhanced aggregation and release evoked by ADP and did not consistently inhibit MDA synthesis produced by arachidonate. The results indicate that in addition to the effects of heparin on platelet function mediated by anti-thrombin activity and the previously described augmentation of responses to ADP, heparin has weak inhibitory activity against platelet-collagen interactions. Binding of heparin to the platelet membrane (and to surfaces to which platelets adhere) could account for these findings by causing non-specific interference with agonist-receptor interactions.

Coagulative interventions during angiography

Incident to his routine diagnostic and interventional activities, the angiographer is becoming increasingly involved in the manipulation of blood clotting factors. Since the field of hemostasis generally extends beyond the sphere of conventional angiographic training, an analysis of selected angiographic aspects was undertaken. This paper reviews and summarizes the fundamentals of coagulation, and appropriate methods for manipulating coagulation during angiography, particularly via heparin and protamine sulfate. Basic aspects of platelet activity, and modifications produced by aspirin and dipyridamole, have been emphasized. Finally, the nature of the fibrinolytic system, and the current role of systemic and selective fibrinolytic therapy have been depicted.

Mural thrombus of the aorta: an important, frequently neglected cause of large peripheral emboli

The association between white thrombus in the aorta and multiple embolic occlusions of peripheral vessels was made 22 years ago. However, mural thrombus has been neglected as a major cause of embolus because the process was attributed to paradoxical effects of heparin. Our recent experience indicates it is a more generalized problem. During the past five years, AP and lateral abdominal aortograms demonstrated the presence of large filling defects within the lumen of the aorta in 20 of 39 patients with sudden occlusion of a distal artery. Thirteen patients were not on heparin. These 3.4 X 1-2 cm defects were present anywhere from T-10 to the aortic bifurcation and were suprarenal in ten patients. The 20 patients had a total of 36 separate embolic events, with five patients experiencing seven occlusions of renal or superior mesenteric arteries. Serious medical problems coexisted, and all patients had at least two of five important "risk factors." These were heart disease, recent thrombophlebitis, heparin therapy, abdominal atherosclerosis and postoperative status. Catheter embolectomy alone was associated with recurrent embolization in four of six patients. Three patients died and two required amputation. Of 12 patients treated by embolectomy combined with open aortotomy, recurrent embolization occurred in none, death in one and amputation in two. All patients with visceral artery occlusions survived with normal function of the previously occluded structure. We urge wider application of abdominal angiography in order to treat more appropriately a sizable proportion of patients whose distal emboli originated from large chunks of white thrombus in the abdominal aorta.