Heparin-induced thrombocytopenia: a possible complication of heparin-coated pulmonary artery catheters

Cephalad misplacement of a pulmonary artery catheter in a patient with a preexisting Hickman catheter

Background

Pulmonary artery catheter insertion is a routine practice in high-risk patients undergoing cardiac surgery. However, pulmonary artery catheter insertion is associated with numerous complications that can be devastating to the patient. Incorrect placement is an overlooked complication with few case reports to date.

Case presentation

An 18-year-old male patient underwent elective mitral valve replacement due to severe mitral valve regurgitation. The patient had a history of synovial sarcoma, and Hickman catheter had been inserted in the right internal jugular vein for systemic chemotherapy. We made multiple attempts to position the pulmonary artery catheter in the correct position but failed. A chest radiography revealed that the pulmonary artery catheter was bent and pointed in the cephalad direction. Removal of the pulmonary artery catheter was successful, and the patient was discharged 10 days after the surgery without complications.

Conclusions

To prevent misplacement of the PAC, clinicians should be aware of multiple risk factors in difficult PAC placement, and be prepared to utilize adjunctive methods, such as TEE and fluoroscopy.

The Routine Use of the Pulmonary Artery Catheter Should Be Abandoned

The pulmonary artery catheter (PAC) is the most common method of measuring cardiac output in cardiac surgery. However, its use has always been questioned in terms of survival benefit, specifically with regard to the accuracy of its measurements and its invasive nature, with the potential for serious complications. In this review we aimed to develop a clear understanding of the pitfalls of the use of PAC, and discuss its risks and available alternatives. We conclude that there is no indication for the routine use of PAC such that clinicians should carefully consider the clinical risks and benefits on a patient by patient basis.

Heparin-induced thrombocytopenia: a renal perspective

Heparin-induced thrombocytopenia (HIT) is a clinicopathologic syndrome in which one or more clinical events, usually thrombocytopenia or thrombosis, are temporally related to heparin administration and caused by HIT antibodies. Rapid and accurate diagnosis is essential given the high incidence of thrombosis at around the time of initial disease recognition. Discontinuation of heparin and initiation of alternative anticoagulants reduces HIT-associated morbidity and mortality. The clinical consequences of HIT in hemodialysis patients remain unclear, with several studies reporting no clinical sequelae and others describing complications such as thrombocytopenia or clotting of the extracorporeal circuit. Frequent clotting of the extracorporeal circuit has also been reported in HIT-antibody-positive patients on continuous veno-venous hemofiltration. Several recent findings are of particular interest to nephrologists. An acute systemic reaction has been described as a presentation of HIT in hemodialysis patients shortly after administration of an unfractionated heparin bolus. This syndrome is important to recognize as it might mimic a dialyzer reaction. More recently, the presence of a positive HIT-antibody test or increasing titers of HIT antibody were associated with increased mortality in hemodialysis patients, raising the question of whether these antibodies have a role in the increased cardiovascular mortality seen in these patients. HIT-antibody production is often transient and small numbers of hemodialysis patients with undetectable antibody levels have been rechallenged with heparin without adverse clinical consequences.

Heparin-induced thrombocytopenia complicating hemodialysis

Hemodialysis complicated by heparin-induced thrombocytopenia (HIT) is a rare event requiring anticoagulation with direct-thrombin inhibitors. Contaminant calcific uremic arteriolopathy (calciphylaxis) further complicates this situation due to the possibility that warfarin anticoagulation may exacerbate skin necrosis. The authors report a patient with renal failure and calciphylaxis who developed HIT after starting hemodialysis. She was successfully treated with Argatroban.

Unfractionated Heparin, Low Molecular Weight Heparins, and Pentasaccharide: Basic Mechanism of Actions, Pharmacology, and Clinical Use

During the past decade, a large number of new anticoagulant and antithrombotic drugs have been developed. These agents represent a wide variety of substances that are derived using natural sources, biotechnology-based methods, and synthetic approaches. Because of the structural and molecular characteristics, these agents exhibit physicochemical and functional diversities. Thus, each of these classes of drugs controls thrombogenesis by way of distinct mechanisms. The main classes of these new drugs include peptides, peptidomimetics, heparinomimetics, and recombinant proteins. Despite these significant developments, heparin and heparin-derived drugs have continued to play a major role in the management of thrombotic and cardiovascular disorders.

Clinical aspects of heparin-induced thrombocytopenia and thrombosis and other side effects of heparin therapy

Heparin, first used to prevent the clotting of blood in vitro, has been clinically used to treat thrombosis for more than 50 years. Although several new anticoagulant drugs are in development, heparin remains the anticoagulant of choice to treat acute thrombotic episodes. The clinical effects of heparin are meritorious, but side effects do exist. Bleeding is the primary untoward effect of heparin. Major bleeding is of primary concern in patients receiving heparin therapy. However, additional important untoward effects of heparin therapy include heparin-induced thrombocytopenia, heparin-associated osteoporosis, eosinophilia, skin reactions, allergic reactions other than thrombocytopenia, alopecia, transaminasemia, hyperkalemia, hypoaldosteronism, and priapism. These side effects are relatively rare in a given individual, but given the extremely widespread use of heparin, some are quite common, particularly HITT and osteoporosis. Although reasonable incidences of many of these side effects can be "softly" deduced from current reports dealing with unfractionated heparin, at present the incidences of these side effects with newer low molecular weight heparins appear to be much less common. However, only longer experience will more clearly define the incidence of each side effect with low molecular weight preparations.

Functional heterogeneity of antiheparin-platelet factor 4 antibodies: implications in the pathogenesis of the HIT syndrome

Heparin-induced thrombocytopenia represents one of the most severe drug-induced disorders of platelets. This syndrome is believed to be mediated through antibodies generated against a heparin-platelet factor 4 complex. Complexation of a sulfated mucopolysaccharide chain of heparin with a platelet granular protein (platelet factor 4) produces an allosteric modification of platelet factor 4 resulting in neoepitope formation and the generation of antiheparin-platelet factor 4 antibodies. These antibodies are capable of activating platelets by binding to heparin, platelet factor 4 and the Fc receptor on platelets, resulting in a complex pathophysiology involving ischemic, thrombotic, and inflammatory processes. To characterize this antibody, IgG fractions were obtained from the serum of patients with heparin-induced thrombocytopenia using ammonium sulphate precipitation and heparin-platelet factor 4-sepharose 4B affinity chromatography methods. With the affinity purification, two major components, peaks I and II, with high antiheparin-platelet factor 4 antibody titers were eluted. The purity of all the fractionated immunoglobulins was established by sodium dodecylsulphate-polyacrylamide gel electrophoretic analyses. While peak I did not induce 14C-serotonin release from platelets in the heparin-dependent assay for heparin-induced thrombocytopenia antibodies (14C-serotonin release assay), peak II and the IgGs obtained with the ammonium sulphate precipitation method exhibited a strong and concentration-dependent activation in the presence and absence of heparin and low molecular weight heparin. These immunoglobulins were treated with heparinase, a cationic ion-exchange resin (Heparsorb), or dialyzed to remove traces of heparin, and when tested in the 14C-serotonin release assay, showed the same high degree of activity. These data are suggestive of the generation of heparin-induced thrombocytopenia antibodies capable of activating platelets directly in a nonheparin-dependent manner. These observations underscore the complex pathophysiology of heparin-induced thrombocytopenia syndrome and suggest that the severity of this syndrome in some patients may be due to the generation of "super-active" heparin-induced thrombocytopenia antibodies capable of activating platelets without the requirement of heparin. This could explain why the cessation of heparin in patients does not necessarily correct the symptoms of heparin-induced thrombocytopenia or associated thrombosis.

Heparin-induced thrombocytopenia, paradoxical thromboembolism, and other side effects of heparin therapy

Although several new anticoagulant drugs are in development, heparin remains the drug of choice for most anticoagulation needs. The clinical effects of heparin are meritorious, but side effects do exist. Important untoward effects of heparin therapy including heparin-induced thrombocytopenia, heparin-associated osteoporosis, eosinophilia, skin reactions, allergic reactions other than thrombocytopenia and alopecia will be discussed in this article.

Conservation of blood during cardiovascular surgery

Conservative use of allogeneic red blood cell (RBC) transfusion is a growing trend in cardiovascular surgery. Recent advances in blood conservation measures have reduced, and in some cases eliminated, the need for allogeneic RBC transfusions in some of these patients. Reduced reliance on allogeneic RBC transfusion requires close collaboration among the clinical pathology, anesthesia, and surgery services managing the patient. Preoperative conservation measures include donation of autologous blood and treatment with recombinant human erythropoietin (Epoetin alfa). Meticulous surgical technique, moderate hemodilution, aprotinin, hemostatic techniques, blood salvage, and autotransfusion are intraoperative measures that can reduce blood loss. Postoperatively, even severe blood deficits can often be restored with adequate diet and rest and the use of actinics.