Heparin-Induced Thrombocytopenia

Understanding Antithrombotic Agents for Rehabilitation Therapy: A Comprehensive Narrative Review

In rehabilitation medicine, attention must be paid to the medication. Among them, antithrombotic drugs are used for the initial treatment and secondary prevention of stroke, so as a basic knowledge, the pharmacological actions, characteristics, indications, and precautions for the use of antithrombotic drugs should be known. Antithrombotic agents are divided into antiplatelet agents and anticoagulants, and the appropriate antithrombotic agent is selected according to the main disease or condition. Antiplatelet agents include aspirin, clopidogrel, ticlopidine, prasugrel, ticagrelor, and cilostazol. Each antiplatelet agent has a different mechanism of action, characteristics, and indications, and should be prescribed with due consideration. Anticoagulants include heparin, synthetic Xa inhibitors, direct oral anticoagulants (DOACs), synthetic antithrombin agents, and warfarin. Knowledge of the mechanism of action, characteristics, and indications of each anticoagulant is necessary, as well as monitoring and dose adjustment. With regard to ischemic cerebrovascular disease (ICD) and antithrombotic agents, the first step is to classify cerebral infarction and to determine whether antiplatelet agents or anticoagulants should be used. Bleeding and recurrence prevention are important considerations in the selection of appropriate antithrombotic agents for the pathophysiology of ICD.

Low-molecular-weight heparin-associated multiple digital necrosis in a patient as a result of heparin-induced thrombocytopenia syndrome

Heparin-induced thrombocytopenia syndrome (HITS) is a rare complication of low-molecular-weight heparin (LMWH). It is an autoimmune-mediated side effect of LMWH which is caused by platelet-activating antibodies that recognize platelet factor-4/ heparin complexes. Although HITS often leads to thrombosis in large veins and arteries, it can be presented as microvascular thrombosis. In this article, we report a case of HITS complicated with multiple digital necrosis after administration of LMWH.

Bleeding and Thrombotic Adverse Events in Hospitalized Patients Under Empiric Treatment for Suspected Heparin-Induced Thrombocytopenia While Awaiting Confirmatory Testing

Empiric management in suspected heparin-induced thrombocytopenia (HIT) is challenging due to imperfect prediction models, latency while awaiting test results and risks of empiric therapies. When there is high clinical suspicion for HIT, cessation of heparin and empiric non-heparin anticoagulation with FDA-approved argatroban is recommended. Alternatively off-label fondaparinux or watchful waiting have been utilized in clinical practice. Outcomes of patients empirically managed for HIT have not been compared directly in clinical trials and patients that ultimately do not have HIT are often overlooked. Clinicians need studies investigating empiric management to guide decision making in suspected HIT. In this study, adverse events (AE) were categorized and compared in patients being evaluated for HIT while undergoing empiric management by non-heparin anticoagulation with argatroban or fondaparinux, both at therapeutic or reduced doses, or watchful waiting with or without heparin. AE were defined as new thrombosis confirmed on imaging or new bleeding event after HIT was first suspected. A retrospective chart review of 312 patients tested for HIT at an academic hospital was conducted. 170 patients met inclusion criteria. Patients were excluded if the 4Ts score was < 4. The 4Ts score is a pretest probability for HIT based on thrombocytopenia degree, timing, alternative causes and presence of thrombosis. Included patients were divided according to management groups and compared with logistic regression analysis. Bleeding risk significantly differed between management groups (p = 0.002). Despite adjustment for bleeding risk, fondaparinux was associated with increased AE, (p = 0.03, OR = 5.81), while argatroban was not. There was no difference in AE based on time to initiation of empiric treatment and no advantage to reduced dosing with either anticoagulant. These findings challenge assumptions surrounding empiric HIT management.

Heparin versus 0.9% saline solution to maintain patency of totally implanted venous access ports in cancer patients: A systematic review and meta-analysis

AIM

The use of heparin and 0.9% saline solution is always controversial for central venous catheters. However, there is no systematic review or guideline about whether saline solution can replace heparin solution in adult cancer patients with totally implantable venous access ports (TIVAPs). The purpose of this review is to evaluate whether saline solution can replace heparin saline to lock TIVAPs.

METHODS

The following databases were searched: PubMed, the Cochrane Library, Web of Science, Embase, CINAHL and Ovid (January 1, 1982, and February 21, 2020). All statistical analyses of the meta-analysis were completed using the Review Manager 5.3.

RESULTS

A total of 201 studies were identified from these databases after initial review, and four studies met inclusion criteria, including 2652 cases. There was little heterogeneity among the included studies (I² < 30%), and all analyses were conducted by the fixed-effects model. The total complications, catheter occlusions, catheter-related bloodstream infections and other complication rates in the heparin solution group were higher than in the saline solution group. In the subgroup analysis of heparin concentration, total complication rates in the saline solution group were higher than with 50 U of heparin and lower than with 100 U of heparin. However, the differences in these complications were small, and no significant difference was observed (all P > 0.05).

CONCLUSIONS

Based on existing clinical studies, we recommend that saline solution can replace 50 or 100 U/ml of heparin as a safe and effective flush solution for TIVAPs.

Heparin induced thrombocytopenia: position paper from the Italian Society on Thrombosis and Haemostasis (SISET)

Heparin induced thrombocytopenia (HIT) is a rare immune mediated adverse drug reaction occurring after exposure to heparin. It is a serious and potentially fatal condition, which may be associated with the development of arterial or venous thrombotic events. Although known for many years, HIT is still often misdiagnosed. Pre- test clinical probability, screening for anti-PF4/heparin antibodies and documentation of their platelet activating capacity are the cornerstones of diagnosis. However, both clinical algorithms and test modalities have limited predictive values and limited diffusion so that the diagnosis and management is challenging in the clinical practice. For this reason, there is an unmet need for novel rational non-anticoagulant therapies based on the pathogenesis of HIT.The present paper reports the position of the Italian Society on Haemostasis and Thrombosis (SISET) in order to increase awareness of HIT among clinicians and other health care professionals and to provide information on the most appropriate management.

Heparin-induced thrombocytopenia (HIT): Identification and treatment pathways

Heparin-induced thrombocytopenia (HIT) is a major health problem, especially in cardiac surgery theaters, cardiac catheterization labs, and intensive care units. Some patients with HIT develop serious thrombotic complications like limb ischemia and gangrene, while others may not develop such complications and have only mild thrombocytopenia. Current laboratory diagnostic tools incur significant time delays before confirming HIT, therefore upon clinical suspicion, treatment of HIT should start immediately while awaiting laboratory results. This is a review of the types, phases, pathophysiology, clinical presentation and diagnosis of HIT, and its current management strategies.

Heparin-Induced Thrombocytopenia: A Comprehensive Clinical Review

Heparin-induced thrombocytopenia is a profoundly dangerous, potentially lethal, immunologically mediated adverse drug reaction to unfractionated heparin or, less commonly, to low-molecular weight heparin. In this comprehensive review, the authors highlight heparin-induced thrombocytopenia's risk factors, clinical presentation, pathophysiology, diagnostic principles, and treatment. The authors place special emphasis on the management of patients requiring procedures using cardiopulmonary bypass or interventions in the catheterization laboratory. Clinical vigilance of this disease process is important to ensure its recognition, diagnosis, and treatment. Misdiagnosis of the syndrome, as well as misunderstanding of the disease process, continues to contribute to its morbidity and mortality.

[Heparin-induced thrombocytopenia type II (HIT II) : A medical-economic view]

BACKGROUND

In the context of inpatient and increasingly ambulatory thrombosis prophylaxis, heparins have been recognised as standard therapy for decades. In addition to the therapeutic benefit, therapy with heparins also entails the risk of undesirable side effects, such as bleeding and thrombocytopenia. Heparin-induced thrombocytopenia (HIT II) is deemed a serious side effect.

AIM

In the following work, HIT II is subjected to a medico-economic consideration (treatment, pharmaceuticals, subsequent costs due to possible complications) and, with regard to a possible HIT II prophylaxis, aspects of increasingly respected patient safety are also considered.

METHODS

In the context of a literature search the active ingredients argatroban and danaparoid, which are approved for HIT II treatment, were evaluated.

RESULTS

HIT II - especially in combination with thromboembolic complications - represents a medical-economic burden for the hospital. Although this is only an orientation guide, it shows that HIT II syndrome is not adequately cost-covered by the G‑DRG system. An early thrombosis prophylaxis with argatroban/danaparoid for HIT II risk patients should therefore be taken into account for medical-related as well as patient safety-relevant aspects. According to experience, the pharmaceutical supply for these medically needed products (anticoagulants) should be ensured for reasons of patient safety.

CONCLUSION

The risk of an immunological response to heparin therapy is known. Within the context of increased patient safety, thrombosis prophylaxis should be issued with a risk-adjusted prophylaxis.

Evidence-Based Criteria for the Choice and the Clinical use of the Most Appropriate Lock Solutions for Central Venous Catheters (Excluding Dialysis Catheters): A GAVeCeLT Consensus

Background

The most appropriate lock solution for central venous access devices is still to be defined. GAVeCeLT – the Italian group for venous access devices – has developed a consensus on the evidence-based criteria for the choice and the clinical use of the most appropriate lock solution for central venous catheters (excluding dialysis catheters).

Method

After the constitution of a panel of experts, a systematic collection and review of the literature has been performed, focusing on clinical studies dealing with lock solutions used for prevention of occlusion (heparin, citrate, urokinase, recombinant tissue plasminogen activator [r-TPA], normal saline) or for prevention of infection (citrate, ethanol, taurolidine, ethylene-diamine-tetra-acetic acid [EDTA], vancomycin, linezolid and other antibiotics), in both adults and in pediatric patients. Studies on central lines used for dialysis or pheresis, on peripheral venous lines and on arterial lines were excluded from this analysis. Studies on lock solutions used for treatment of obstruction or infection were not considered. The consensus has been carried out according to the Delphi method.

Results

The panel has concluded that: (a) there is no evidence supporting the heparin lock; (b) the prevention of occlusion is based on the proper flushing and locking technique with normal saline; (c) the most appropriate lock solution for infection prevention should include citrate and/or taurolidine, which have both anti-bacterial and anti-biofilm activity, with negligible undesired effects if compared to antibiotics; (d) the patient populations most likely to benefit from citrate/taurolidine lock are yet to be defined.

Conclusions

The actual value of heparinization for non-dialysis catheters should be reconsidered. Also, the use of lock with substances with anti-bacterial and anti-biofilm activity (such as citrate or taurolidine) should be taken into consideration in selected populations of patients.

Venous thromboembolism risk assessment, prophylaxis practices and interventions for its improvement (AVAIL-ME Extension Project, Iran)

BACKGROUND

Venous thromboembolism (VTE) is a major health issue worldwide. Data about VTE prophylaxis practices in developing countries are scarce.

OBJECTIVES

The primary objectives of this survey were to define the VTE risk factors in hospitalized patients, to determine the rates of VTE prophylaxis administration and guideline compliance and to assess the effects of an educational program on VTE prophylaxis practices in Iran.

PATIENTS AND METHODS

Data on 1219 patients from twenty hospitals in Iran were extracted from the AVAIL-ME Extension project main databank. VTE risks were categorized according to the Caprini Risk Assessment Model. Logistic regression analysis was carried out to assess factors influencing VTE prophylaxis. We also examined the impact of an educational program which consisted of awareness, risk assessment, internal protocol implementation and re-assessment, on VTE prophylaxis practices.

RESULTS

Of 1219 patients, 789 (65%) and 430 (35%) were surgical and medical, respectively. VTE risks, categorized in low, moderate, high and very high were detected in 14%, 17%, 26% and 43% of patients respectively with a total of 1042(85%) patients being at risk for VTE. Of 882 (85%) eligible patients for VTE prophylaxis, 737 (83.5%) received any drug prophylaxis of whom 265 (62%) were medical and 472 (60%) were surgical. ACCP guidelines compliance was 60% and 33% in surgical and medical patients respectively. Any VTE prevention, drug prophylaxis, mechanical prophylaxis and guideline adherence were, 48% vs. 64%, 45% vs. 60%, 6% vs. 9% and 34% vs. 45% respectively (p<00.1) before and after implementation of the VTE educational program.

CONCLUSIONS

Despite an overall improvement in VTE prevention, areas such as inappropriate use of VTE prophylaxis in a large number of patients, significant under-use of mechanical devices and guideline adherence require closer attention. VTE awareness education is beneficial in improving VTE prophylaxis in Iran.

The frequency of heparin-induced thrombocytopenia in Taiwanese patients undergoing cardiopulmonary bypass surgery

BACKGROUND/PURPOSE

There are few studies on heparin-induced thrombocytopenia (HIT) reported from Taiwan and Asian countries. We conducted a prospective study to investigate the frequency of HIT in patients undergoing cardiopulmonary bypass surgeries.

METHODS

A cohort of 54 patients was enrolled from January 01, 2010 to October 31, 2011. Patients' clinical information was obtained for 4T score classification. Plasma (2-4 mL) was also collected before surgery and on Days 5 and 10 following heparin administration during the bypass procedure. This was tested for anti-heparin/PF4 antibodies and functional assay using flow cytometry (FC).

RESULTS

The mean platelet count for this cohort followed the expected pattern in the postoperative setting. Seven of the 54 (13%) patients had positive antibodies assays before bypass surgery. This increased to 32% on Day 5 and was markedly elevated to 63% on Day 10 after surgery. Only one of the 54 patients (1.8%) was found to have both positive antibody assay and platelet activation, but no clinical HIT/thrombosis developed.

CONCLUSION

Our study is the first report on the rates of HIT in the setting of cardiopulmonary bypass surgery in Taiwan and demonstrated no clinical HIT occurrence, despite the high frequency of HIT antibody in our cohort.

Heparin-induced thrombocytopenia (HIT II) in liver transplant recipients: a retrospective multivariate analysis of prognostic factors

We investigated the prevalence of HIT II in liver transplant recipients and analysed associated factors. In recipients with clinically suspected HIT II in the 4Ts pretest clinical scoring system HIPA-assay was performed. Next, 37 clinical variables were analysed retrospectively for their association with HIT II. Factors significantly correlated to our findings in univariate analysis were included in a multivariate model and binary logistic regression analysis. Among 46 recipients 21 patients were suspicious in the 4Ts pretest and 14 of them (30.4%) were diagnosed HIT-antibody positive. Patient's age (P = 0.001), postoperative dialysis (P = 0.028), and postoperative hospital stay (P = 0.035) were significantly associated with development of HIT-antibodies in univariate analysis. Postoperative dialysis and postoperative hospital stay turned out as epiphenomena of patient's age, the only independent predictor (P = 0.021). Using multiple χ(2) -testing, a cut-off could be calculated, assigning patients younger than 59 years to a low risk group and patients of 59 years and older to a high risk group. High incidence of peri-operative HIT II seroconversion in liver transplant recipients is not associated with factors known to induce thrombocyte activation, like blood products or cell-saver. Only patients' age was identified as independent predictor.

Usefulness of anti-PF4/heparin antibody test for intensive care unit patients with thrombocytopenia

BACKGROUND

It is critical to differentiate heparin-induced thrombocytopenia (HIT) from disseminated intravascular coagulation (DIC) in heparinized intensive care unit (ICU) patients with thrombocytopenia because the therapeutic approach differs based on the cause. We investigated the usefulness of PF4/heparin antibody tests in these patients.

METHODS

A total of 127 heparinized ICU patients whose platelet counts were <150×10(9)/L or reduced by >50% after 5-10 days of heparin therapy were enrolled. PF4/heparin antibodies were measured using 2 immunoassays. We assessed the probability of HIT by using Warkentin's 4T's scoring system for antibody positive patients and compared routinely performed coagulation test results between patients with and without antibodies to evaluate the ability of these tests to discriminate between HIT and DIC.

RESULTS

Positive results were obtained for 14 (11.0%) and 11 (8.7%) patients in the 2 assays. The analysis performed using the 4T's scoring system revealed that 11 of 20 (15.7%) patients with antibodies in at least 1 assay had intermediate or greater probability of HIT. Patients without antibodies had significantly higher levels of D-dimer than those with antibodies. However, there were no intergroup differences in platelet counts, PT, aPTT, fibrinogen, DIC score, and rate of overt DIC.

CONCLUSION

Seropositivity for PF4/heparin antibody was 8.7-11.0% in the patients with thrombocytopenia, and more than a half of them had an increased probability of HIT. Among the routine coagulation tests, only D-dimer was informative for differentiating HIT from DIC. PF4/heparin antibody test is useful to ensure appropriate treatment for thrombocytopenic heparinized ICU patients.

National survey of central venous catheter flushing in the intensive care unit

BACKGROUND

Evidence is needed on the best solution for flushing central venous catheters.

OBJECTIVE

To understand current flushing practices for short-term central venous catheters among critical care nurses before implementation of a randomized, controlled trial comparing physiological saline with heparin solution for flushing to maintain catheter patency.

METHODS

A 6-item survey including demographic data was mailed to 2000 practicing critical care nurses in the United States. An additional 316 surveys were completed at the annual conference of the American Association of Critical-Care Nurses.

RESULTS

Most (71.5%) of the 632 respondents who completed the survey were staff nurses. Most respondents (64.6%; 95% CI, 60.86%-68.34%) reported using physiological saline exclusively to flush central venous catheters and maintain patency. For heparin-containing solutions, the concentration and volume used varied. The most commonly reported volumes for flushing were 10 mL for saline (63%; 95% CI, 59.18%-66.82%) and 3 mL for heparin (50.2%; 95% CI, 43.5%-56.9%).

CONCLUSION

Flushing practices for central venous catheters vary widely. A randomized controlled trial is needed to determine the optimal flushing solution to maintain short-term patency.

Dabigatran Use in a Postoperative Coronary Artery Bypass Surgery Patient with Nonvalvular Atrial Fibrillation and Heparin-PF4 Antibodies

OBJECTIVE:

To present a case of dabigatran use for nonvalvular atrial fibrillation in a patient from a population for whom it has not been studied. Postoperative coronary artery bypass patients have significant bleeding risk and potential to develop heparin-induced thrombocytopenia (HIT).

CASE SUMMARY:

A 70-year-old male with a history of paroxysmal atrial fibrillation in sinus rhythm prior to surgery developed atrial fibrillation on postoperative day 2 after coronary artery bypass surgery. Because of thrombocytopenia, anticoagulation to decrease stroke risk with atrial fibrillation was initiated with dabigatran 150 mg orally twice daily beginning on postoperative day 4. Later on postoperative day 4, after dabigatran was administered, the patient's HIT screening test was positive for heparin/PF4 antibodies; however, he was not clinically diagnosed with HIT. Heparin was not used postoperatively and transition dosing from dabigatran to warfarin was started on postoperative day 8, the day of discharge. At the time of the outpatient follow-up appointment, the patient had no signs of thrombosis or bleeding complications.

DISCUSSION:

Dabigatran is a direct thrombin inhibitor approved for nonvalvular atrial fibrillation. In this case, the physician ordered dabigatran for an approved use, according to manufacturer labeling. However, patients with this diagnosis would have been excluded from the RE-LY (Randomized Evaluation of Long-term Anticoagulant Therapy) trial, on which Food and Drug Administration approval was based. Our patient had thrombocytopenia with a low pretest probability for HIT but was positive for heparin/PF4 antibodies, based on enzyme immunoassay testing. Dabigatran was continued for atrial fibrillation and not switched to any other direct thrombin inhibitor, such as argatroban, lepirudin, or bivalirudin, which are listed in the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines, 8th edition, for the Treatment and Prevention of Heparin Induced Thrombocytopenia.

CONCLUSIONS:

Further research on the use of dabigatran in patients with recent coronary bypass surgery and heparin/PF4 antibodies is needed before any recommendations can be made.

Heparin-induced thrombocytopenia: in vitro studies on the interaction of dabigatran, rivaroxaban, and low-sulfated heparin, with platelet factor 4 and anti-PF4/heparin antibodies

Heparin is a widely used anticoagulant. Because of its negative charge, it forms complexes with positively charged platelet factor 4 (PF4). This can induce anti-PF4/heparin IgG Abs. Resulting immune complexes activate platelets, leading to the prothrombotic adverse drug reaction heparin-induced thrombocytopenia (HIT). HIT requires treatment with alternative anticoagulants. Approved for HIT are 2 direct thrombin inhibitors (DTI; lepirudin, argatroban) and danaparoid. They are niche products with limitations. We assessed the effects of the DTI dabigatran, the direct factor Xa-inhibitor rivaroxaban, and of 2-O, 3-O desulfated heparin (ODSH; a partially desulfated heparin with minimal anticoagulant effects) on PF4/heparin complexes and the interaction of anti-PF4/heparin Abs with platelets. Neither dabigatran nor rivaroxaban had any effect on the interaction of PF4 or anti-PF4/heparin Abs with platelets. In contrast, ODSH inhibited PF4 binding to gel-filtered platelets, displaced PF4 from a PF4-transfected cell line, displaced PF4/heparin complexes from platelet surfaces, and inhibited anti-PF4/heparin Ab binding to PF4/heparin complexes and subsequent platelet activation. Dabigatran and rivaroxaban seem to be options for alternative anticoagulation in patients with a history of HIT. ODSH prevents formation of immunogenic PF4/heparin complexes, and, when given together with heparin, may have the potential to reduce the risk for HIT during treatment with heparin.

Heparin-associated thrombocytopenia in 24,401 patients with venous thromboembolism: findings from the RIETE Registry

BACKGROUND

Whether the treatment of venous thromboembolism (VTE) with unfractionated heparin (UFH) confers a higher risk of thrombocytopenia than does treatment with low molecular weight heparin (LMWH) remains controversial, and very few data are available from routine clinical practice.

OBJECTIVES

We assessed the incidence, risk factors and prognosis of heparin-associated thrombocytopenia (HAT) according to the type of heparin therapy, UFH or LMWH.

PATIENTS/METHODS

Data were obtained from the international prospective Registro Informatizado de la Enfermedad TromboEmbolica venosa (RIETE), which included 25,369 patients with confirmed VTE until February 2009. Among them, 24,401 patients were treated either with UFH or with LMWH, and had available information about the 6-month occurrence of confirmed thrombocytopenia, defined as a platelet count ≤ 150,000 mm(-3) .

RESULTS

One hundred and forty-one patients receiving UFH and/or LMWH developed thrombocytopenia within a 6-month period. The incidence of HAT was significantly higher in the UFH group (1.36%, 95% confidence interval [CI] 0.79-2.17) than in the LMWH group (0.54%, 95% CI 0.44-0.64). As compared with LMWH, UFH significantly increased the risk of HAT in female patients (adjusted hazard ratio [HR] 4.90%, 95% CI 2.58-9.31, P = 0.001) but not in male patients (adjusted HR 1.60%, 95% CI 0.64-3.97, P = 0.31); P = 0.027 for comparison. In each gender, the UFH-associated excess risk was confined to patients with VTE unrelated to cancer. The poor prognosis of patients with thrombocytopenia was not influenced by the type of heparin therapy.

CONCLUSIONS

In routine clinical practice, treatment of VTE with UFH seems to confer a higher risk of thrombocytopenia than does treatment with LMWH, especially in women and non-cancerous patients.

The AVAIL ME Extension: a multinational Middle Eastern survey of venous thromboembolism risk and prophylaxis

BACKGROUND

Venous thromboembolism (VTE) is a major worldwide problem.

OBJECTIVES

The primary objectives of this survey were to identify patients at risk for VTE, to define the rate of patients receiving appropriate VTE prophylaxis and to examine the frequency of the presence of guidelines and their application.

PATIENTS AND METHODS

Ten countries, 101 hospitals and a total of 4983 patients were included in this multinational cross-sectional survey. Standardized case report forms were filled out by trained individuals on one predefined day. Risks were categorized according to the Caprini Risk Assessment Model. Logistic regressions were carried out to assess factors that determined VTE prophylaxis.

RESULTS

Of 4983 patients, 3368 (68%) and 1615 (32%) were surgical and medical, respectively. Seven hundred and seventy-two (15.5%) were considered to be at low risk, 1001 (20%) at moderate risk, 1289 (26%) at high risk and 1921 (38.5%) at very high risk for VTE. Of 3575 (72%) patients who were eligible to receive VTE prophylaxis, 2747 (77%) received any drug prophylaxis. Among these patients 720/1056 (68%) and 2027/2519 (80%) were medical and surgical patients, respectively. The overall compliance with ACCP guidelines was 38%, being 24% for medical patients and 44% for surgical patients.

CONCLUSIONS

The results of this large multinational survey, although indicating overall improvement in VTE prophylaxis, identify a considerable number of patients who either did not receive any VTE prophylaxis or received it inappropriately. Although more medical patients were at risk for VTE, they were given prophylaxis less frequently than surgical patients. Concordance with VTE prophylaxis guidelines was higher in surgical patients, but overall application of these tools was unacceptably low.

HIT heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is a significant complication of heparin therapy. The NP is in a pivotal position to identify patients at greater risk for HIT and promptly diagnose and intervene to prevent serious thrombotic complications.

Piperacillin and vancomycin induced severe thrombocytopenia in a hospitalized patient

In hospitalized patients with complex medical problems on numerous drugs, thrombocytopenia may have a multiple confounding etiology. Keeping this in mind, it is of utmost importance to monitor the platelet count regularly during hospitalization and on subsequent follow-up visits, even after the most probable etiology has been identified/most likely causative drug has been withdrawn. Isolated thrombocytopenia with no evidence of microangiopathic hemolysis on the peripheral blood smear in an acutely ill hospitalized patient implicated sepsis, disseminated intravascular coagulation and drugs as the most probable causes. Our patient represents an uncommon case of antibiotic-induced severe immune thrombocytopenia, as he developed both vancomycin-dependent and piperacillin-dependent antibodies, while being treated for cellulitis (vancomycin-specific antibodies of the IgG isotype, and both IgG and IgM antibodies specific for piperacillin were identified in laboratory testing). Vancomycin was stopped before the reports were available. Following this, the patient's platelet count showed a transient upward trend, but then the thrombocytopenia worsened drastically reaching a nadir of 10,000/µL. The platelet count returned to normal only after piperacillin/tazobactam was stopped after a week, thus establishing it as the cause of the more severe thrombocytopenia, which occurred later on; this was subsequently confirmed by the laboratory results. Vancomycin is an established cause of drug-induced immune thrombocytopenias, especially in acutely ill, hospitalized or elderly patients, whereas incidents of piperacillin/tazobactam-induced immune thrombocytopenia are uncommon. In case clinical suspicion is high, workup should include immunoprecipitation and flow cytometry studies to confirm antiplatelet antibodies.

Review: Contaminants in Heparin: Review of the Literature, Molecular Profiling, and Clinical Implications

Background: The contaminant isolated from contaminated heparin was oversulfated chondroitin sulfate (OSCS). Other possible contaminants should be evaluated. Methods: Contaminants were isolated from recalled contaminated heparin and were compared to OSCS from animal sources and to heparin by-products synthetically persulfated. Results: A great variability in molecular weight was observed in the isolated contaminants. Dermatan sulfate with high-molecular-weight in addition to OSCS was detected. Oversulfated chondroitin sulfate from different sources as well as heparin by-products produced activation of prekallikrein to kallikrein at variable rates as measured by the generation of kallikrein. All agents produced activation of the complement system. All compounds formed complexes with platelet factor 4 (PF4) and all produced 14C serotonin release in the heparin-induced thrombocytopenia (HIT) analysis. The agents also exhibited variable anticoagulant responses that were mostly mediated via heparin cofactor II. Conclusion: These results suggest that heparin contaminants represent a heterogeneous group of oversulfated glycosaminoglycans (OSGAGs) which may mediate multiple pathophysiologic responses.

Heparin flushing and other interventions to maintain patency of central venous catheters: a systematic review

AIM

This paper is a report of a review to assess clinical studies comparing the effectiveness of different means of maintaining central venous catheter patency.

BACKGROUND

Flushing with heparin is a routine part of central venous catheter maintenance, but it presents risks, including heparin-induced thrombocytopenia. Other techniques used to prevent occlusion of catheters include saline flushes, heparin-bonded catheters and pressure caps.

DATA SOURCES

A search was conducted using the MEDLINE, CINAHL, EMBASE, Cochrane, National Guideline Clearinghouse and University Healthsystem Consortium databases.

METHODS

A systematic review of effectiveness was conducted, using GRADE criteria to assess the strength of evidence for each intervention. The review period covered 1982 or earlier to January 2008.

RESULTS

There is weak evidence that heparin flushing reduces occlusion of catheters, but no evidence that it reduces bloodstream infections. Results from clinical trials of pressure caps are inconsistent regarding their ability to maintain catheter patency, but provide moderate evidence that at least some varieties of caps are associated with increased bloodstream infections.

CONCLUSION

The evidence base on heparin flushing and other interventions to prevent catheter occlusion is small, and published studies are of low quality. There is insufficient evidence on which to conclude that flushing catheters with heparin is more effective than flushing with saline solution.

Management of acquired bleeding problems in cancer patients

Cancer patients can have acquired bleeding problems for many reasons. In this review, an approach to the evaluation and management of the bleeding patient is discussed. Specific issues including coagulation defects, thrombocytopenia, platelet dysfunction, and bleeding complications of specific hematological malignancies due to anticoagulation, are discussed.

Drug-induced thrombocytopenia in critically ill patients

Thrombocytopenia occurs in 15% to 58% of intensive care unit patients. The incidence varies based upon patient population, timing and frequency of platelet monitoring, and definition of thrombocytopenia. Up to 25% of acutely ill patients develop drug-induced thrombocytopenia. When drug-induced thrombocytopenia is suspected, nondrug related causes must be evaluated and excluded. Establishing the diagnosis of drug-induced thrombocytopenia is challenging, as hundreds of medications have been implicated. Medications commonly associated with drug-induced thrombocytopenia include glycoprotein IIb/IIIa inhibitors, cinchona alkaloids, antibiotics, anticonvulsants, and heparin. Once the diagnosis is suspected, clinicians should identify the start date of medications to assess the timeline of development. The likelihood of each medication causing thrombocytopenia must be evaluated. The risk vs. benefit of discontinuing the suspected medication and availability of alternative medications must be assessed. The role of corticosteroids, immune globulin, and plasmapheresis is uncertain. Once the offending agent has been discontinued, the overall prognosis is excellent. In the case of suspected or confirmed heparin-induced thrombocytopenia, an alternative anticoagulant should be initiated. Drug-induced thrombocytopenia should be documented in the medical record and reported according to institutional and national standards. This review focuses on immune-mediated drug-induced thrombocytopenia from medications commonly utilized in the critically ill patient.

The prothrombotic potential of platelet factor 4

Heparin-induced thrombocytopenia (HIT) is a prothrombotic disorder initiated by heparin administration. It is caused by the formation of pathogenic antibodies to complexes of platelet factor-4 (PF4) and heparin on platelet surfaces that cause platelet activation, aggregation and thrombosis. There has been intense research on this intriguing, drug-related thrombocytopenia explaining several characteristic aspects of this condition. However, prothrombotic potential of the key player, PF4 has not been investigated in many studies although it has been shown to be critical in monocyte chemotaxis, monocyte-platelet interaction, and megakaryocyte suppression, all of which can contribute to the pathophysiology of HIT. This article explains the important role of PF4 released during platelet activation with the administration of heparin in the pathogenesis of thrombocytopenia and thrombosis in HIT.

Hematological issues in critically ill patients with cancer

Patients with solid and hematologic malignancies presenting with major bleeding or thrombotic complications, potentially life-ending events in a cancer patient's clinical course, usually require admission to an intensive care unit (ICU), making their diagnosis and management even more important for the intensivist. Given the significant advances in the diagnosis and treatment of almost all types of cancers in recent years, the intensivist is likely to encounter an ever-increasing number of cancer patients in the ICU setting with these complications. Abnormal hemostasis can occur as a consequence of both the pathology and treatment of cancer. Because cancer can have multiple effects on hemostatic equilibrium, treatment of these complications can be more complex than in the general population. This article reviews the physiology of coagulation and fibrinolysis, with special attention to those aspects that are most frequently altered in the setting of malignancy. The pathophysiology of bleeding and thrombotic complications specific to critically ill cancer patients are then detailed, and the diagnostic and therapeutic strategies are discussed. Special emphasis is placed on new cancer medications that have an effect on hemostasis, and on novel clotting and anticoagulant agents that are available to the intensivist for the management of these patients.

Adverse drug reactions affecting blood cells

Numerous medications and other xenobiotics are capable of producing adverse reactions (ADRs) affecting red cells, platelets or neutrophils. Occasionally, more than one blood element is affected simultaneously. As with all drug reactions, some side effects are a direct consequence of a known pharmacologic action of the drug and are dose-dependent; others occur sporadically and relatively independent of dose. The latter ("idiosyncratic") reactions are unpredictable and, in general, have no known underlying genetic basis. Many are antibody-mediated, as would be expected since cellular immune effector cells have little direct access to circulating blood cells. In this chapter, we will discuss idiosyncratic drug reactions affecting blood and blood forming tissues with an emphasis on those thought to be immune-mediated.

Thrombocytopenia and other hot topics

A frequent issue in the management of cancer patients with thrombosis is thrombocytopenia, whether related to chemotherapy, heparin, or other drugs. The oncologist will have multiple new anticoagulants to choose from in the future, but for now, the effect of these experimental agents on cancer thrombosis is unknown. Despite the effectiveness of anticoagulation in cancer patients, survival benefit remains controversial. Given the ongoing clinical questions and new drugs, anticoagulant therapy in patients with cancer promises to have an exciting future.

Topical thrombins: benefits and risks

Whether from surgical misadventure, inherent patient factors, or iatrogenic causes, postoperative bleeding can be a consequence of any surgical procedure. There are many methods and products available to assist in managing or preventing bleeding. For each method, there may be specific benefits and indications, but they may also carry some degree of risk. Topical thrombin is used extensively in many surgical specialties, especially in the cardiovascular and neurosurgical arenas where other hemostatic modalities may not be appropriate choices. As a class, topical thrombins are generally a safe and effective method for achieving intraoperative hemostasis; however, some members of the class carry associated risks with their use. For example, the United States Food and Drug Administration required the addition of a black-box warning to the prescribing information of bovine-derived thrombin, the oldest member of the class, due to concerns of immune-mediated coagulopathies developing after use. In addition, human thrombin derived from pooled plasma has its own, if theoretical, risk of transmitting infections due to viral or prion agents. We address the topical thrombin class and review each product in the context of the current literature.

Management of acquired bleeding problems in cancer patients

Cancer patients can have acquired bleeding problems for many reasons. In this review, an approach to the bleeding patient in the Emergency Department is discussed. Specific issue including coagulation defects, thrombocytopenia, platelet dysfunction, bleeding complications of specific hematological malignancies and due to anticoagulation, are discussed.

Hematologic complications of critical illness: anemia, neutropenia, thrombocytopenia, and more

All critically ill patients are at risk for hematological complications during their hospitalization. It is essential that critical care nurses understand the hematological system and common complications. The purpose of this article is to briefly review some basic hematologic concepts involving each of the 3 cell lines: the white blood cell, the red blood cell, and platelets. The content focuses on how to assess these cell lines when there is dysfunction. Examples of disease processes involving the increased and decreased production of each cell line as well as destruction processes are discussed from a critical care perspective. The critical care nurse needs to continually incorporate this information into practice as research continues to formulate critical care practice.

Drug-induced hematologic syndromes

Objective. Drugs can induce almost the entire spectrum of hematologic disorders, affecting white cells, red cells, platelets, and the coagulation system. This paper aims to emphasize the broad range of drug-induced hematological syndromes and to highlight some of the newer drugs and syndromes. Methods. Medline literature on drug-induced hematologic syndromes was reviewed. Most reports and reviews focus on individual drugs or cytopenias. Results. Drug-induced syndromes include hemolytic anemias, methemoglobinemia, red cell aplasia, sideroblastic anemia, megaloblastic anemia, polycythemia, aplastic anemia, leukocytosis, neutropenia, eosinophilia, immune thrombocytopenia, microangiopathic syndromes, hypercoagulability, hypoprothrombinemia, circulating anticoagulants, myelodysplasia, and acute leukemia. Some of the classic drugs known to cause hematologic abnormalities have been replaced by newer drugs, including biologics, accompanied by their own syndromes and unintended side effects. Conclusions. Drugs can induce toxicities spanning many hematologic syndromes, mediated by a variety of mechanisms. Physicians need to be alert to the potential for iatrogenic drug-induced hematologic complications.

Drug-induced immune thrombocytopenia: pathogenesis, diagnosis, and management

Drug-induced immune thrombocytopenia (DITP) can be triggered by a wide range of medications. Although many cases of DITP are mild, some are characterized by life-threatening bleeding symptoms. The pathogenesis of DITP is complex, in that at least six different mechanisms have been proposed by which drug-induced antibodies can promote platelet destruction. It is possible in many cases to identify antibodies that react with platelets in the presence of the sensitizing drug, but the required testing is technically demanding and not widely available. Therefore, a decision on whether to discontinue an implicated medication in a patient suspected of having DITP must be made on clinical grounds. An algorithm is available that can be helpful in assessing the likelihood that a particular drug caused thrombocytopenia, but the most important aspects of patient management are a high index of suspicion and a careful history of drug exposure in an individual who presents with acute, often severe thrombocytopenia of unknown etiology. How drugs induce platelet-reactive antibodies and how, once formed, the antibodies cause platelet destruction following exposure to the drug is poorly understood. Further studies to address these issues and characterize more completely the range of drugs and drug metabolites that can cause DITP are needed.

Incidence of deep venous thrombosis after subarachnoid hemorrhage

Object

The aim of this study was to determine the efficacy of venous ultrasonography in screening for deep venous thrombosis (DVT) after subarachnoid hemorrhage (SAH). A large cohort of patients who had suffered SAH was evaluated with the primary end points of ascertaining the incidence of asymptomatic DVT with venous Doppler ultrasonography screening and of identifying risk factors for the development of DVT and subsequent pulmonary embolism.

Methods

Data from patients with aneurysmal SAH who had been admitted to the neurosurgical intensive care unit (ICU) between December 2002 and October 2006 were retrospectively evaluated. Patients who had undergone surgical or endovascular treatment of an aneurysm following SAH and survived ≥ 15 days were included in the study.

Results

The overall incidence of DVT among the entire study cohort was 18%. A subgroup analysis identified all patients, with or without symptoms for DVT, who had undergone venous Doppler ultrasonography screening. The incidence of asymptomatic DVT was 24%. Univariate analysis of all patients revealed a significant correlation between the risk of DVT and Hunt and Hess grade (r = 0.38, p < 0.0001), Fisher grade (r = 0.31, p < 0.0001), total hospital stay (r = 0.49, p < 0.0001), and number of days in the ICU (r = 0.48, p < 0.0001). Multivariate analysis demonstrated that the total hospital stay and number of days in the ICU were significant predictors of DVT in all patients (p < 0.0001 and p < 0.0002, respectively). In the subgroup of screened patients, Hunt and Hess grade, total hospital stay, and number of days in the ICU were significant predictors of DVT. Although screened patients were more likely to have DVT (χ2 = 6.0976, p < 0.02), there was no significant difference in the incidence of DVT or pulmonary embolism between patients who did and those who did not undergo routine lower-extremity Doppler ultrasonography screening.

Conclusions

Routine compressive venous Doppler ultrasonography is an efficient, noninvasive means of identifying DVT as a screening modality in both symptomatic and asymptomatic patients following aneurysmal SAH. The ability to confirm or deny the presence of DVT in this patient population allows one to better identify the indications for chemoprophylaxis. Prophylaxis for venous thromboembolism in neurosurgical patients is common. Emerging literature and anecdotal experience have exposed risks of complications with prophylactic anticoagulation protocols. The identification of patients at high risk—for example, those with asymptomatic DVT—will allow physicians to better assess the role of prophylactic anticoagulation.