Allergy to heparins and anticoagulants with a similar pharmacological profile: an update

Pharmacology of Heparin and Related Drugs

Heparin has been recognized as a valuable anticoagulant and antithrombotic for several decades and is still widely used in clinical practice for a variety of indications. The anticoagulant activity of heparin is mainly attributable to the action of a specific pentasaccharide sequence that acts in concert with antithrombin, a plasma coagulation factor inhibitor. This observation has led to the development of synthetic heparin mimetics for clinical use. However, it is increasingly recognized that heparin has many other pharmacological properties, including but not limited to antiviral, anti-inflammatory, and antimetastatic actions. Many of these activities are independent of its anticoagulant activity, although the mechanisms of these other activities are currently less well defined. Nonetheless, heparin is being exploited for clinical uses beyond anticoagulation and developed for a wide range of clinical disorders. This article provides a "state of the art" review of our current understanding of the pharmacology of heparin and related drugs and an overview of the status of development of such drugs.

Occurrence and extent of bruising according to duration of administration of subcutaneous low-molecular-weight heparin: a quasi-experimental case-crossover study

BACKGROUND

Several authors have documented the role of low-molecular-weight heparin injection techniques in bruising. However, few researchers have measured the influence of injection duration on the occurrence and extent of bruising.

PURPOSE

The aim of this study was to evaluate the influence of different durations of subcutaneous heparin injection on the occurrence and extent of bruising.

METHODS

A quasi-experimental case-crossover study design was adopted in 2010. A consecutive series of patients admitted to 2 orthopedic units in a large (600 beds) teaching hospital located in northern Italy were eligible for enrolment. Injections were administered following a standard procedure. The manipulated variable was the duration of the injection, 10 seconds (treatment A) and 30 seconds (treatment B). The evaluation of bruise occurrence and extension performed after 48 hours and data analysis were conducted in a blinded fashion.

RESULTS

A total of 150 patients receiving their first and second subcutaneous heparin injections (300 injections) were enrolled. Eighty-seven bruises were observed out of 300 injections (29%): 57 of 150 (38%) after injections lasting 10 seconds and 30 of 150 (20%) after injections lasting 30 seconds (relative risk, 1.50; 95% confidence interval, 1.21-1.86; P = .00). Of the 87 bruises that occurred, 69 (79.3%) were small (2-5 mm) and 18 (20.6%) were large (>5 mm), with no difference in size between 10- and 30-second injections (relative risk, 0.91; 95% confidence interval, 0.39-2.12; P = .83).

CONCLUSIONS

Low-molecular-weight heparin injection should be administered over 30 seconds to decrease bruising.

CLINICAL IMPLICATIONS

There is a need to reflect on the feasibility of such a practice because injecting low-molecular-weight heparin at 30 seconds requires accuracy, a steady hand, the absence of tremor, a calm environment, and the ability to administer an infinitesimally small amount of liquid (eg, 0.4 mL) per second.

FcγRIIa proteolysis as a diagnostic biomarker for heparin-induced thrombocytopenia

BACKGROUND

A significant challenge in the management of heparin-induced thrombocytopenia (HIT) patients is making a timely and accurate diagnosis. The readily available enzyme immunoassays (EIAs) have low specificities. In contrast, platelet activation assays have higher specificities, but they are technically demanding and not widely available. In addition, ~ 10% of samples referred for HIT testing are initially classified as indeterminate by the serotonin release assay (SRA), which further delays accurate diagnosis. HIT is characterized by platelet activation, which leads to FcγRIIa proteolysis. This raises the possibility that identification of the proteolytic fragment of FcγRIIa could serve as a surrogate marker for HIT.

OBJECTIVES

To determine the specificity of platelet FcγRIIa proteolysis induced by sera from patients with HIT, and to correlate the results with those of the SRA.

METHODS/PATIENTS

Sera from HIT patients and control patients with other thrombocytopenic/prothrombotic disorders were tested for their ability to proteolyse FcγRIIa. The results were correlated with anti-platelet factor 4 (PF4)/heparin antibodies (EIA), and heparin-dependent platelet activation (SRA).

RESULTS

Only HIT patient samples (20/20) caused heparin-dependent FcγRIIa proteolysis, similar to what was shown by the SRA. None of the samples from the other patient groups or hospital controls caused FcγRIIa proteolysis. Among nine additional samples that tested indeterminate in the SRA, FcγRIIa proteolysis resolved five samples that had a positive anti-PF4/heparin EIA result; three had no FcγRIIa proteolysis, and two were shown to have heparin-dependent FcγRIIa proteolysis

CONCLUSIONS

This study suggests that heparin-dependent FcγRIIa proteolysis is at least as specific as the SRA for the diagnosis of HIT.

Delayed-type heparin allergy: diagnostic procedures and treatment alternatives-a case series including 15 patients

Delayed-type hypersensitivity reactions (DTHRs) after subcutaneous application of unfractionated heparins or low-molecular-weight heparins are not uncommon. Standard allergological testing usually includes intracutaneous skin tests and patch testing of different heparins, heparinoids, and thrombin inhibitors followed by subcutaneous and/or intravenous challenge with skin test-negative drugs. We present data from a single-center case series of 15 patients with DTHR after low-molecular-weight heparin administration. Intracutaneous testing that can be considered as gold standard identified the suspicious elicitor in 11 (73.4%) of 15 of the patients. Patch testing was positive in 5 (33.4%) of 15 of the patients and was only positive in patients who were also reacting in the intradermal testing. Intravenous challenge with heparin sodium was performed in 10 of 15 patients and was well tolerated in all cases, despite prior positive intracutaneous tests with the same substance. Intracutaneous documentation of DTHR was not an adequate predictor of intravenous challenge.

Heparin-induced skin lesions

Heparins are widely used for prophylaxis and treatment of thromboembolic diseases. Besides bleeding complications, heparin-induced skin lesions are the most frequent unwanted adverse effects of subcutaneous heparin treatment. Evidence suggests that these lesions are more common than previously thought. Lesions are most frequently due to either allergic reactions or to possibly life-threatening heparin-induced thrombocytopenia. Early recognition and adequate treatment are highly important, because although both complications initially show a similar clinical picture, their treatment should be fundamentally different. Furthermore, risk factors associated with the patient, drug, and treatment regimen have been identified. We review the clinical range of heparin-induced skin lesions, emphasise evidence and controversies in epidemiology, diagnosis, and differential diagnosis, and discuss the management of patients with these skin lesions.

Definitions and mechanisms of drug hypersensitivity

Adverse drug reactions are a difficult problem faced by clinicians in everyday practice. The mechanisms of drug hypersensitivity are not well understood. This is reflected by difficulties in their classification, which is mainly based upon the current knowledge of immunologic and nonimmunologic mechanisms, onset of symptoms (immediate or nonimmediate) and morphology. For the individual patient, the correct diagnosis and classification is important because strict avoidance of the offending drug might be of vital importance. Considerable experience is required to guide management, to interpret results of investigations and to undertake drug challenges. This article summarizes the current knowledge regarding definitions and mechanisms. However, the field of drug hypersensitivity is rapidly expanding. Modern drugs such as biological agents bare hypersensitivity risks that are potentially mediated by, so far, unknown mechanisms.

Heparin-induced acute adverse reaction--case report of a patient with acute trauma and a genetic predisposition to thrombotic events: a concurrence of events

WHAT IS KNOWN AND OBJECTIVE

The most common complication of heparin therapy is bleeding. Allergic reactions to heparin are rare, and the mechanisms are poorly understood. We report on a case of acute systemic reaction after subcutaneous injections of a low-molecular-weight heparin (LMWH) in a patient with a genetic predisposition to thrombotic events and review the literature on heparin-induced acute adverse reaction.

CASE SUMMARY

A 57-year-old diabetic, hypertriglyceridemic and hypercholesterolemic man was admitted with a fractured right malleolus sustained while driving. He was prescribed parnaparin sodium 4250 IU subcutaneously once a day. During the third injection, the patient developed widespread pain, sickness and facial rash, followed by a state of stupor (Glasgow Coma Scale 8) and was hospitalized in Neurological Unit. He was found to be a carrier of two genetic mutations (i.e. prothrombin G20210A and MTHFR mutation) associated with an increased risk of thrombotic events. Discontinuation of parnaparin and supportive care led to a sufficient recovery of the patient to be discharged 6 days after admission.

WHAT IS NEW AND CONCLUSION

Treatment for heparin-related hypersensitivity reactions is largely supportive and symptomatic. Clinicians should be aware of these rare but potentially serious adverse events. Prothrombin gene mutations are quite common, and guidelines on anticoagulant therapy for affected patients are needed.

Efficacy and safety of low molecular weight heparin prophylaxis for venous thromboembolism following lumbar decompression surgery

OBJECTIVE

To evaluate the efficacy and safety of low molecular weight heparin (LMWH) prophylaxis for venous thromboembolism (VTE) after lumbar decompression surgery.

METHODS

Patients at high or the highest risk of VTE who underwent lumbar spine surgery in Peking Union Medical College Hospital from January 2004 to April 2011 were included in the present study. All the patients received a half dose of LMWH 6 hours after surgery followed by a full dose LMWH once per day until discharge. We recorded incidences of deep venous thrombosis (DVT), pulmonary embolism (PE), bleeding complications, and medication side effects.

RESULTS

Seventy-eight consecutive patients were eligible and enrolled in this study. The mean hospital stat was 8.5±4.5 days. No symptomatic DVT, PE, or major bleeding events were observed. One patient developed wound ecchymosis, another developed wound bleeding, four had mild hepatic aminotransferase level elevation, and one developed a suspicious allergic reaction.

CONCLUSION

LMWH may be applied as an effective and safe prophylaxis for VTE in high-risk patients undergoing lumbar decompression surgery.

Adverse effects of heparin

All the adverse effects of heparins are related to their wide variety of biological activities, with bleeding being the most important safety issue, resulting directly from the potency of heparin as an anticoagulant. However, it is hard to define the bleeding risk, since it depends on numerous parameters including the indication, dosage, method, and duration of heparin application, the clinical study design and definition of bleeding as well as patient characteristics and determinants of bleeding such as type of surgery and co-medication. Nonbleeding complications of heparins are caused by binding of heparin molecules to proteins other than antithrombin and to cells, which is generally more pronounced with unfractionated heparin than with low-molecular-weight heparins. Accordingly, heparin-induced thrombocytopenia, the most severe nonbleeding adverse reaction, occurs about 10 times less with low-molecular-weight heparins than with unfractionated heparin. Frequent and therefore important adverse reactions of heparins are skin lesions resulting from delayed-type hypersensitivity reactions. All the other undesirable effects are discussed as well, but they are mostly clinically irrelevant.

The direct medical costs associated with suspected heparin-induced thrombocytopenia

BACKGROUND

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction associated with heparin exposure. Sunnybrook Health Sciences Centre, a tertiary-care adult academic hospital, has cared for an average of 100 cases of suspected HIT per year. Although the management of suspected HIT is resource intensive, few studies have assessed the cost burden associated with HIT, and none have assessed the costs of suspected HIT.

OBJECTIVE

The objective of this study was to identify and quantify the direct medical costs associated with suspected (confirmed and negative) HIT at a hospital in Canada.

METHODS

A cost-of-illness analysis was conducted in patients with suspected HIT during 2005. Resource utilization variables included (i) laboratory tests to investigate HIT; (ii) HIT-safe anticoagulant use; (iii) diagnostic imaging related to HIT or its treatment; and (iv) additional hospital days attributed to HIT. The average costs per case of confirmed HIT, confirmed HIT with thrombosis (HITT) and negative HIT were calculated in $Can, year 2007 values.

RESULTS

Confirmed HITT cases incurred substantially greater costs ($Can34 155, range 358-202 069; n = 12) than confirmed HIT cases without thrombosis ($Can4575, range 39-16 373; n = 8). The average cost of care for a negative HIT case was $Can119 (range 39-4181; n = 88).

CONCLUSIONS

This is the first study to quantify the costs associated with suspected HIT cases. These cases increase the costs of hospital care and provide further justification for HIT prevention strategies.

Unfractionated heparin for hemodialysis: still the best option

Unfractionated heparin (UFH) is the anticoagulant of choice for most maintenance hemodialysis units in the United States. Low molecular weight heparin (LMWH) is the norm in Western Europe, but is not approved for this indication in the United States. UFH is likely to remain the agent of choice in the United States because of its relative ease of use, safety, and low cost. Coating tubing and dialyzers with heparin is now possible, but systemic anticoagulation with heparin is usually still required. The additional cost of this innovation does not yet justify its use. Side effects of both UFH and LMWH include heparin-induced thrombocytopenia, hypertriglyceridemia, and hyperkalemia. It is uncertain whether osteoporosis is an important side effect, as vitamin D deficiency, secondary hyperparathyroidism, age, and debility are confounding factors. When UFH poses a risk or its use is contraindicated, e.g., after development of heparin-induced thrombocytopenia, the use of direct thrombin inhibitors, regional citrate anticoagulation, citrate dialysate, and heparin-free dialysis may be appropriate.

Analysis of cytokine secretion from lymphocytes of patients with hypersensitivity reactions to contaminated heparins

BACKGROUND

Beginning in 2007, anaphylactoid reactions associated with unfractionated heparin (UFH) occurred and resulted in some fatalities. These reactions were reported to be linked to the complement and contact system activation induced by certain batches of UFH containing the adulterant oversulphated chondroitin sulphate (OSCS).

OBJECTIVES

Drug-specific secretion of selected cytokines from peripheral blood mononuclear cells (PBMC) of patients with hypersensitivity reactions to contaminated heparin was compared with the respective in vitro cytokine pattern of individuals with or without hypersensitivity to heparin, different glycosaminoglycans or other drugs.

METHODS

Study individuals (n = 13) were classified as follows: patients with hypersensitivity reactions to contaminated (OSCS) heparin (n = 3), noncontaminated heparin (n = 1) or other compounds (n = 3) and patients with ongoing heparin therapy without symptoms of intolerance (n = 2). Four healthy individuals served as controls. PBMC were incubated with six different glycosaminoglycan structures. Drug-specific intracellular interleukin (IL)-5, interferon (IFN)-γ and IL-10 production was investigated by flow cytometry, while secretion of IL-5, IL-2 and IFN-γ was analysed by enzyme-linked immunosorbent assay.

RESULTS

PBMC from individuals with hypersensitivity reactions to contaminated heparin secreted considerable amounts of IL-2 in vitro. There was a suggestion that ongoing heparin therapy and the Li-heparin in the vials may have an impact on the lymphocyte reactivity of PBMC.

CONCLUSIONS

The in vitro lymphocyte reactivity pattern of PBMC from individuals with hypersensitivity reactions to contaminated heparins was neither typical for an immune-mediated nor for a nonimmune-mediated reaction. Possible effects of heparins in the test system itself may require consideration.

[Dermal necrosis as cutaneous manifestation of heparin-induced thrombocytopenia II?]

Most of the rare cases of skin necrosis following heparin injections are associated with the immunologically mediated form of heparin-induced thrombocytopenia II (HIT II). We present a 62-year- old woman who developed a necrotic abdominal lesion seven days after starting daily subcutaneous injections of the low molecular heparin enoxaparin. We detected circulating antibodies against the platelet factor 4-complex but no concomitant thrombocytopenia. An isolated, antibody-mediated thrombosis of dermal vessels is the likely underlying cause of the skin necrosis in HIT II.

The complex clinical picture of side effects to anticoagulation

Inflammatory plaques at injection sites are frequent side effects of heparin treatment and a clinical symptom of delayed-type hypersensitivity (DTH) to heparin. In most cases, changing the subcutaneous therapy from unfractionated to low-molecular-weight heparin or treatment with heparinoids does not provide improvement because of extensive cross-reactivity. Because of their completely different chemical structure, hirudins are a safe alternative for anticoagulation. Despite DTH to subcutaneously injected heparins, patients tolerate heparin intravenously. Therefore, in case of therapeutic necessity and DTH to heparins, the simple shift from subcutaneous to intravenous heparin administration is justified. Skin necrosis is a rare complication of anticoagulation. Heparin-induced skin necrosis is 1 of the symptoms of immune-mediated heparin-induced thrombocytopenia and should result in the immediate cessation of heparin therapy to prevent potentially fatal thrombotic events. This is in contrast to coumarin-induced skin necrosis, where therapy may be continued or restarted at a lower dose.

Incidence and causes of heparin-induced skin lesions

BACKGROUND

Little is known about the incidence and causes of heparin-induced skin lesions. The 2 most commonly reported causes of heparin-induced skin lesions are immune-mediated heparin-induced thrombocytopenia and delayed-type hypersensitivity reactions.

METHODS

We prospectively examined consecutive patients who received subcutaneous heparin (most often enoxaparin or nadroparin) for the presence of heparin-induced skin lesions. If such lesions were identified, we performed a skin biopsy, platelet count measurements, and antiplatelet-factor 4 antibody and allergy testing.

RESULTS

We enrolled 320 patients. In total, 24 patients (7.5%, 95% confidence interval [CI] 4.7%-10.6%) had heparin-induced skin lesions. Delayed-type hypersensitivity reactions were identified as the cause in all 24 patients. One patient with histopathologic evidence of delayed-type hypersensitivity tested positive for antiplatelet-factor 4 antibodies. We identified the following risk factors for heparin-induced skin lesions: a body mass index greater than 25 (odds ratio [OR] 4.6, 95% CI 1.7-15.3), duration of heparin therapy longer than 9 days (OR 5.9, 95% CI 1.9-26.3) and female sex (OR 3.0, 95% CI 1.1-8.8).

INTERPRETATION

Heparin-induced skin lesions are relatively common, have identifiable risk factors and are commonly caused by a delayed-type hypersensitivity reaction (type IV allergic response).

[Anesthesia in interventional neuroradiology]

Interventional neuroradiology procedures have become increasingly complex, requiring planning and coordination. Key roles are played by the anesthesiologist and the radiologist, as well as by technicians and nurses. This review aims to analyze the anesthesiologist's part in managing these procedures, from the start of the intervention through the immediate postoperative period. First concerns are to assure patient safety during transfer, maintain the airway, keep the patient immobile and hemodynamically stable, and manage anticoagulant and antiplatelet treatments. Rapid awakening must also be assured so that the patient's neurologic status can be assessed in situ. The anesthesiologist should treat any neurologic complications that develop and that might lead to emergency situations during the procedures.