Heparin-induced thrombocytopenia and thrombosis

Use of therapeutic plasma exchange in heparin-induced thrombocytopenia: A population-based study

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is characterized by anti-heparin/platelet factor 4 immune complexes, which are removed by therapeutic plasma exchange (TPE). Our main objective was to study TPE outcomes in HIT using a large administrative claims database.

STUDY DESIGN AND METHODS

We used the National Inpatient Sample (NIS) to identify hospital discharges of adult patients (≥18) with a primary or secondary diagnosis of HIT. Cases were classified into two groups based on TPE use. The primary outcome was in-hospital mortality. Secondary outcomes were thrombotic events, major bleeding, hospital length of stay (LOS), and charges. Multivariable regression analysis, controlling for age and medical comorbidities, was used to examine the association of TPE with study outcomes.

RESULTS

A HIT diagnosis was made in 22 165 discharges, of which 90 (0.4%) received TPE. Corresponding national estimates are 106 435 and 439, respectively. TPE was not associated with decreased in-hospital mortality (OR = 1.72; 95%CI: 0.93-3.17, P = .085). However, TPE was associated with a higher likelihood of major bleeding (OR = 2.35; 95%CI: 1.40-3.68, P = .0009), primarily driven by gastrointestinal bleeding (OR = 2.21; 95%CI: 1.17-4.17, P = .015). TPE was also associated with higher hospital LOS (20.5 vs 10 day, P < .0001) and charges (USD 211181 vs USD 81654, P < .0001).

CONCLUSION

TPE's association with increased bleeding and a prolonged hospital course indicates that it is being used in HIT cases with a severe clinical phenotype. Future studies are needed to better characterize the HIT phenotype that will most benefit from TPE.

Bivalirudin fails to prevent atrial thrombus development in heparin-induced thrombocytopaenia and thrombosis syndrome

An 81-year-old woman presented with acute decompensated heart failure due to new-onset atrial fibrillation and a flail myxomatous mitral valve which necessitated surgical mitral valve repair. No atrial thrombi were noted on transoesophageal echocardiograms performed prior to surgery and intraoperatively. Immediately postoperatively, while treated with unfractionated heparin, the patient developed thrombocytopaenia with positive platelet factor 4 antibodies and an abnormal serotonin functional platelet assay, consistent with heparin-induced thrombocytopaenia. The anticoagulation therapy was changed to the direct thrombin inhibitor bivalirudin with an improvement in the platelet count. Despite bivalirudin therapy, a left atrial layering thrombus was revealed on transoesophageal echocardiogram performed in preparation for cardioversion of the symptomatic atrial fibrillation. Anticoagulation was changed to warfarin, and the patient was discharged without thromboembolic complications neither during her hospital stay nor the 3-year outpatient follow-up.

Recurrent venous thrombosis following free flap surgery: The role of heparin-induced thrombocytopenia

Complications following free tissue transfer have been well established in the literature. Common and rare causes of free flap failure must be addressed by the treating surgeon when microvascular patency is threatened. With the evolution and prevalence of microsurgery, 'rare' causes of free flap failure will become increasingly frequent. A high index of suspicion must be established in patients with multiple failed operative interventions. A case of recurrent free flap failure secondary to heparin-induced thrombocytopenia is presented in a patient with a history of squamous cell carcinoma of the floor of the mouth, and a long-standing history of alcohol and tobacco consumption.

A heparin-bonded vascular graft generates no systemic effect on markers of hemostasis activation or detectable heparin-induced thrombocytopenia-associated antibodies in humans

OBJECTIVES

Almost a third of patients who undergo peripheral bypass procedures do not have suitable veins, making the use of prosthetic materials necessary. Prosthetic materials can cause platelet adhesion and activation of the coagulation cascade on the graft. One potential strategy to reduce this thrombogenicity is to covalently bind heparin to the endoluminal surface of grafts. This human in vivo study examined systemic effects of the endoluminal heparin and addressed whether graft implantation results in (1) a measurable reduction of systemic markers of hemostasis activation compared with control grafts and (2) antibody formation against heparin, potentially responsible for heparin-induced thrombocytopenia (HIT).

METHODS

The study included 20 patients undergoing femoropopliteal bypass grafting, of whom 10 received a standard Gore-Tex Thin Walled Stretch Vascular Graft (W. L. Gore & Associates, Flagstaff, Ariz) and 10 received a heparin-bonded expanded polytetrafluoroethylene (ePTFE) graft (Gore-Tex Propaten Vascular Graft). Blood samples were drawn before and directly after the operation and at days 1, 3, 5, and week 6 after surgery. Established markers of in vivo activation of platelets and blood coagulation (prothrombin fragment 1+2, fibrinopeptide A, soluble glycoprotein V, thrombin-antithrombin complexes, and D-dimers) were measured using standard commercially available techniques. Antiplatelet factor 4/heparin antibody titers were measured using a commercially available enzyme-linked immunosorbent assay, and platelet counts were determined.

RESULTS

No statistical differences were observed in any of the markers of in vivo activation of platelets and blood coagulation between patients receiving Propaten or control ePTFE. Moreover, no antibodies against heparin could be demonstrated up to 6 weeks after implantation.

CONCLUSIONS

No measurable effect of heparin immobilization on systemic markers of hemostasis was found using a heparin-bonded ePTFE graft in vivo. Also, no antibodies against heparin could be detected up to 6 weeks after implantation.

Acute adrenal insufficiency associated with heparin-induced thrombocytopenia

Although the thrombotic risk of heparin-induced thrombocytopaenia (HIT) is well recognized and may affect any vascular bed, the involvement of adrenal veins has been less commonly described. We report the case of a 86-year-old woman who developed bilateral massive adrenal haematoma associated with HIT, resulting in acute adrenal insufficiency. After immediate discontinuation of heparin and starting therapy with danaparoid and hydrocortisone, the clinical evolution was favourable, although adrenal failure was irreversible. When abdominal pain, hypotension and fever occur during heparin therapy, associated with a drop in platelet count, acute adrenal insufficiency secondary to HIT should be considered, as early diagnosis is essential for the treatment of this life-threatening complication.

Acute left main occlusion during percutaneous coronary intervention associated with heparin induced thrombocytopenia with thrombosis syndrome

A 76-year-old male was admitted with Braunwald IIIB unstable angina and treated with intravenous heparin. Coronary angiography 20 days later revealed a severe stenosis in the left circumflex artery. During coronary angioplasty thrombus developed in the circumflex artery, extended in the left main and lead to its occlusion. Normal left coronary artery patency and flow were achieved after intracoronary and intravenous administration of abciximab, and multiple stenting. Platelet-count decrease and an ELISA assay documented the presence of heparin-induced thrombocytopenia with thrombosis syndrome (HITTS). HITTS should be suspected after acute thrombus formation during coronary angioplasty.

Severe enoxaparin-induced thrombocytopenia complicated by pulmonary emboli

Low molecular weight heparins (LMWH) have been widely used in the last decade, especially for prophylaxis of deep venous thrombophlebitis. Enoxaparin-induced thrombocytopenia is rarely encountered, in contrast to its high prevalence among patients treated with unfractionated heparin. We report a case of a patient who was admitted because of a pulmonary embolus due to proximal deep vein thrombophlebitis 2 weeks after surgery, despite prophylaxis with low-dose enoxaparin after prostatectomy. The patient's original normal platelet count (255,000/microl) dropped to 30,000/microl while on enoxaparin therapy. Testing for antibodies against heparin was positive. Warfarin was initiated and an inferior vena caval filter was inserted. Within a few days, platelet count increased to 100,000/microl, pulmonary status improved, and the patient was released in good clinical condition. Heparin-induced thrombocytopenia (HIT) is discussed, as are alternative treatments for unfractionated heparins and LMWH.

Subacute stent thrombosis associated with a heparin-coated stent and heparin-induced thrombocytopenia

Subacute stent thrombosis occurred in a patient 34 days after receiving a heparin-coated (HC) stent. The patient developed heparin-induced thrombocytopenia and diffuse thrombosis after the stent was placed. This raises the concern that patients who develop heparin-associated antibodies in the context of a recently placed HC stent may have an increased risk for subacute stent thrombosis.

Effects of early high-volume continuous venovenous hemofiltration on survival and recovery of renal function in intensive care patients with acute renal failure: a prospective, randomized trial

OBJECTIVE

To study the effects of the initiation time of continuous venovenous hemofiltration and of the ultrafiltrate rate in patients with circulatory and respiratory insufficiency developing early oliguric acute renal failure. The primary end points were mortality at 28 days and recovery of renal function.

DESIGN

A randomized, controlled, two-center study.

SETTING

The closed-format multidisciplinary intensive care units of a university hospital (30 beds) and a teaching hospital (18 beds).

PATIENTS AND INTERVENTIONS

A total of 106 ventilated severely ill patients who were oliguric despite massive fluid resuscitation, inotropic support, and high-dose intravenous diuretics were randomized into three groups. Thirty-five patients were treated with early high-volume hemofiltration (72-96 L per 24 hrs), 35 patients with early low-volume hemofiltration (24-36 L per 24 hrs), and 36 patients with late low-volume hemofiltration (24-36 L per 24 hrs).

RESULTS

Median ultrafiltrate rate was 48.2 (42.3-58.7) mL.kg(-1).hr(-1) in early high-volume hemofiltration, 20.1 (17.5-22.0) mL.kg(-1).hr(-1) in early low-volume hemofiltration, and 19.0 (16.6-21.1) mL.kg(-1).hr(-1) in late low-volume hemofiltration. Survival at day 28 was 74.3% in early high-volume hemofiltration, 68.8% in early low-volume hemofiltration, and 75.0% in late low-volume hemofiltration (p =.80). On average, hemofiltration started 7 hrs after inclusion in the early groups and 42 hrs after inclusion in the late group. All hospital survivors had recovery of renal function at hospital discharge, except for one patient in the early low-volume hemofiltration group. Median duration of renal failure in hospital survivors was 4.3 (1.4-7.8) days in early high-volume hemofiltration, 3.2 (2.4-5.4) days in early low-volume hemofiltration, and 5.6 (3.1-8.5) days in late low-volume hemofiltration (p =.25).

CONCLUSIONS

In the present study of critically ill patients with oliguric acute renal failure, survival at 28 days and recovery of renal function were not improved using high ultrafiltrate volumes or early initiation of hemofiltration.

Use of plasma exchange and heparin during cardiopulmonary bypass for a patient with heparin induced thrombocytopenia: a case report

Patients with documented history of heparin-induced thrombocytopenia (HIT) pose a difficult problem during surgery using cardiopulmonary bypass (CPB). Several alternatives to heparin exist, but these products either are not approved for use in the United States or have more side effects than heparin. We report on a patient with documented heparin-induced antibody and left main coronary artery disease who underwent uneventful coronary artery bypass surgery and recovery by using preoperative plasmaphresis and limited use of porcine intestinal heparin during CPB.

Heparin-induced Thrombocytopenia

Treatment with heparin is associated with two types of thrombocytopenia. The most worrisome of these is the immune-mediated heparin-induced thrombocytopenia (HIT type II). Suspicion of HIT type II mandates immediate cessation of heparin administration and consideration of an alternative anticoagulation therapy. Hirudin and argatroban are approved alternative anticoagulants with no cross-reactivity with the HIT antibody. HIT type II is a clinicopathologic syndrome, and therefore diagnosis requires clinical and laboratory confirmation. The laboratory evaluation for HIT type II should also determine whether or not there is HIT-antibody cross-reactivity with danaparoid and low molecular weight heparin. Patients with HIT type II who require coronary artery bypass graft surgery present a particularly difficult situation, as there is no ideal alternative to heparin anticoagulation.

Acute and Chronic Pulmonary Emboli

Under most circumstances, the goal of treatment of pulmonary embolism is the prevention of recurrent embolic events, achieved through conventional anticoagulant therapy with unfractionated heparin or a low molecular weight heparin, followed by warfarin therapy for a minimum of 6 months. When acute pulmonary embolism is associated with significant right ventricular dysfunction or systemic hypotension, more aggressive intervention may be warranted. Under these circumstances, potential interventions include thrombolytic therapy (either systemic or catheter-directed), placement of an inferior vena caval filter, catheter-based embolectomy, or surgical embolectomy. Chronic thromboembolic pulmonary hypertension may develop in a small minority of patients who survive an acute, massive embolic event or who have suffered recurrent thromboembolic events. Due to the fixed nature of the pulmonary vascular obstruction, vasodilator therapy has proven far less effective in chronic thromboembolic disease than it has in primary pulmonary hypertension and other secondary forms of pulmonary hypertension. Correction of hypoxemia and volume overload and the prevention of recurrent embolic events are essential. Definitive therapy, however, requires surgical intervention to remove the chronic thromboembolic obstruction and to restore patency of the pulmonary vascular bed.

Postoperative neurologic assessment and management of the cardiac surgical patient

The neurologic evaluation of patients in the immediate postoperative period and postanesthetic state is unique and challenging. Neurologic assessment is complicated by the lingering residual effects of anesthetics as well as by the effects of narcotic analgesics, anxiolytics, and muscle relaxants, especially in ventilated patients. In this review we examine the suspected causes, clinical manifestations, diagnostic options, and intervention schemes for the common neurologic syndromes seen after cardiac operations.