Interpretation of the international normalised ratio in patients with liver disease

A mini review on the regulation of coagulation homeostasis through interfering with vitamin K-dependent coagulation/anticoagulation factors

Coagulation disorders, such as excessive bleeding or thrombosis, present significant health challenges. Vitamin K-dependent proteins (VKDPs), including coagulation and anticoagulation factors, are essential for maintaining the coagulation homeostasis due to their key roles in the coagulation cascade. Therefore, VKDPs have become significant targets for regulating coagulation homeostasis, and various strategies have been developed, primarily including small molecule drugs and nanomaterials. This review presents the summary of these strategies, focusing on the mechanisms, effectiveness and limitations. It first discusses the pivotal role of VKDPs in the coagulation cascade, followed by an in-depth analysis of how small molecule drugs and nanomaterials to regulate hemostasis through interfering with VKDPs. Furthermore, this review addresses the challenges faced in the current approaches and potential future research directions. We hope this review will contribute to advancing the development of novel methods for modulating coagulation homeostasis through VKDP interference.

The historical origins of modern international normalized ratio targets

Prothrombin time (PT) and its derivative international normalized ratio (INR) are frequently ordered to assess the coagulation system. Plasma transfusion to treat incidentally abnormal PT/INR is a common practice with low biological plausibility and without credible evidence, yet INR targets appear in major clinical guidelines and account for the majority of plasma use at many institutions. In this article, we review the historical origins of INR targets. We recount historical milestones in the development of the PT, discovery of vitamin K antagonists (VKAs), motivation for INR standardization, and justification for INR targets in patients receiving VKA therapy. Next, we summarize evidence for INR testing to assess bleeding risk in patients not on VKA therapy and plasma transfusion for treating mildly abnormal INR to prevent bleeding in these patients. We conclude with a discussion of the parallels in misunderstanding of historic PT and present-day INR testing with lessons from the past that might help rationalize plasma transfusion in the future.

Coagulopathy and hemostasis management in patients undergoing liver transplantation: Defining a dynamic spectrum across phases of care

Patients with acute and chronic liver disease present with a wide range of disease states and severity that may require liver transplantation (LT). Physiologic alterations occur that are dynamic throughout all phases of perioperative care, creating complex management scenarios that necessitate multidisciplinary clinical care. Specifically, alterations in hemostasis in liver disease can be pronounced and evolve with disease progression over time. Recent studies and society guidance address this emerging paradigm and offer recommendations to assist with hemostatic management in patients with liver disease. However, patients undergoing LT are unique and diverse, often with unstable disease that requires specialized approaches. Our aim is to provide a focused review of hemostatic management of the LT patient, distinguish unique aspects of the three main phases of care (before LT, perioperative, and after LT), and identify knowledge gaps and critical areas of future research.

Different risks of hemorrhage in patients with elevated international normalized ratio from chronic liver disease versus warfarin therapy, a population-based retrospective cohort study

BACKGROUND

Patients with chronic liver disease (CLD) often present with an elevated international normalized ratio (INR). Although elevated INR reflects a higher risk of hemorrhage among warfarin users, its clinical significance in CLD patients is less clear.

OBJECTIVES

We used Veterans Health Administration data to quantify the association between INR and (non-variceal) hemorrhage in patients with CLD compared to warfarin users.

METHODS

We performed a multivariate competing risk analysis to study the association between INR and hemorrhage in the two cohorts. We used an interaction term between INR and cohort (CLD/warfarin users) to test if INR had different effects on hemorrhage in the two cohorts.

RESULTS

Data from 80 134 patients (14, 412 with CLD and 65, 722 taking warfarin) were analyzed. The effect of INR on the risk of hemorrhage differed between CLD patients and warfarin users (interaction P < .001). As INR increased above 1.5, the adjusted hazard ratio (aHR) for hemorrhage in CLD patients increased to 2.25 but remained fairly constant with further elevation of INR values. In contrast, the risk of hemorrhage in patients taking warfarin remained low with INR in the subtherapeutic (INR <2.0) and therapeutic ranges (INR 2.0-3.0), and increased exponentially with INR in the supratherapeutic range (aHR 1.64 with INR >3.0-3.5, and 4.70 with INR >3.5).

CONCLUSIONS

The relationship between INR and risk of hemorrhage in CLD patients is different from that in warfarin users. Caution should be exercised extrapolating data from warfarin users to make clinical decisions in CLD patients.

Association Between Plasma Apolipoprotein M With Alzheimer’s Disease: A Cross-Sectional Pilot Study From China

Background

Recent evidence of genetics and metabonomics indicated a potential role of apolipoprotein M (ApoM) in the pathogenesis of Alzheimer’s disease (AD). Here, we aimed to investigate the association between plasma ApoM with AD.

Methods

A multicenter, cross-sectional study recruited patients with AD (n = 67), age- and sex-matched cognitively normal (CN) controls (n = 73). After the data collection of demographic characteristics, lifestyle risk factors, and medical history, we examined and compared the plasma levels of ApoM, tau phosphorylated at threonine 217 (p-tau217) and neurofilament light (NfL). Multivariate logistic regression analysis was applied to determine the association of plasma ApoM with the presence of AD. The correlation analysis was used to explore the correlations between plasma ApoM with cognitive function [Mini–Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA)], activities of daily living (ADL), and the representative blood-based biomarkers (plasma p-tau217 and NfL). Receiver operating characteristic (ROC) analysis and Delong’s test were used to determine the diagnostic power of plasma ApoM.

Results

Plasma ApoM and its derived indicators (ratios of ApoM/TC, ApoM/TG, ApoM/HDL-C, and ApoM/LDL-C) were significantly higher in AD group than those in CN group (each p &lt; 0.0001). After adjusted for the risk factors of AD, the plasma ApoM and its derived indicators were significantly associated with the presence of AD, respectively. ApoM (OR = 1.058, 95% CI: 1.027–1.090, p &lt; 0.0001), ApoM/TC ratio (OR = 1.239, 95% CI: 1.120–1.372, p &lt; 0.0001), ApoM/TG ratio (OR = 1.064, 95% CI: 1.035–1.095, p &lt; 0.0001), ApoM/HDL-C ratio (OR = 1.069, 95% CI: 1.037–1.102, p &lt; 0.0001), and ApoM/LDL-C ratio (OR = 1.064, 95% CI:1.023–1.106, p = 0.002). In total participants, plasma ApoM was significantly positively correlated with plasma p-tau217, plasma NfL, and ADL (each p &lt; 0.0001) and significantly negatively correlated with MMSE and MoCA (each p &lt; 0.0001), respectively. In further subgroup analyses, these associations remained in different APOEϵ 4 status participants and sex subgroups. ApoM/TC ratio (ΔAUC = 0.056, p = 0.044) and ApoM/TG ratio (ΔAUC = 0.097, p = 0.011) had a statistically remarkably larger AUC than ApoM, respectively. The independent addition of ApoM and its derived indicators to the basic model [combining age, sex, APOEϵ 4, and body mass index (BMI)] led to the significant improvement in diagnostic power, respectively (each p &lt; 0.05).

Conclusion

All the findings preliminarily uncovered the association between plasma ApoM and AD and provided more evidence of the potential of ApoM as a candidate biomarker of AD.

Association Between Serum C1q Tumor Necrosis Factor-Related Protein 9 and the Clinical Characteristics and Prognosis of Ischemic Stroke

Introduction

C1q tumor necrosis factor (TNF)-related protein 9 (CTRP9) is a novel member of the C1q/TNF superfamily. According to our previous review, CTRP9 plays a vital role in the process of cardiovascular diseases, including regulating energy metabolism, modulating vasomotion, protecting endothelial cells, inhibiting platelet activation, inhibiting pathological vascular remodeling, stabilizing atherosclerotic plaques, and protecting the heart. We proposed that CTRP9 could play multiple positive and beneficial roles in vascular lesions in ischemic stroke (IS). Here, we aimed to study the relationship between serum CTRP9 and the etiology, severity, and prognosis of IS patients.

Methods

A total of 302 patients with IS and 173 non-stroke controls were selected from the same hospital, and all patients with IS were followed up 12 months after stroke onset. Stroke etiology was classified according to the Trial of ORG 10172 in Acute Stroke Treatment classification. Symptomatic severity was determined using the National Institutes of Health Stroke Scale score. The lesion volume of acute cerebral ischemia was measured using magnetic resonance imaging (MRI). The unfavorable functional outcome was a combination of death or major disability 12 months after stroke onset. Receiver operating characteristic (ROC) curves and integrated discrimination improvement (IDI) and net reclassification improvement (NRI) statistics were applied in the statistical analysis.

Results

We found that serum CTRP9 levels and the ratios of CTRP9/total cholesterol (TC), CTRP9/triglyceride (TG), CTRP9/low-density lipoprotein cholesterol (LDL-C), and CTRP9/high-density lipoprotein cholesterol (HDL-C) were associated with the presence of IS. Moreover, the serum CTRP9 concentration was positively associated with the severity of IS. Incorporation of CTRP9/LDL-C levels into a fully adjusted model for IS-cardioembolic (CE) improved discrimination and calibration, and significantly improved reclassification. In addition, CTRP9 was a predictor of unfavorable functional outcomes.

Conclusions

All the findings indicated that serum CTRP9 could be a promising blood-derived biomarker for the early evaluation and prognosis assessment of IS.

Trial Registration

Chinese Clinical Trial Registry, ChiCTR1800020330.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40120-021-00296-7.

Evaluation of STA-NeoPTimal, an extraction thromboplastin reagent with ISI close to 1

INTRODUCTION

The prothrombin time (PT) is the most requested test to investigate patients with congenital or acquired coagulopathies or to monitor oral anticoagulant therapy. However, thromboplastins can show markedly different responsiveness to the defects induced by vitamin K antagonist (VKA) therapy and are thus characterized by their ISI (International Sensitivity Index). INR results are optimal for patients under VKA but for patients screened for other reasons expressing PT results as ratio can be more appropriate. As it is very difficult to define the PT results reporting unit from the PT testing request, it would be ideal to use a thromboplastin with ISI = 1. The study aims to compare our reference PT reagent with two candidate thromboplastins with ISI close to 1.

METHODS

We compared 3 different thromplastins: two rabbit brain extracted based reagents (STA-Neoplastine CI Plus, with ISI = 1.26, routinely used in our laboratory and STA-NeoPTimal with ISI = 1.01) and a recombinant thromboplastin (STA-Neoplastine R with ISI = 0.97). The comparison was done on 175 samples: 75 from individuals without coagulation defects and 100 from patients under VKA.

RESULTS

STA-NeoPTimal and STA-Neoplastine R well correlate to our reference, STA-Neoplastine CI Plus: regression equations are y = 1.186x-0.1351, r²  = .9454 and y = 1.1432x-0.1554, r²  = .9951, respectively. The lowest bias on INR results was obtained with STA-NeoPTimal reagent (interval: -0.7/+0.4).

CONCLUSION

We conclude that STA-NeoPTimal can be used in the laboratory as it gives results comparable to those obtained with STA-Neoplastine CI Plus. Besides, thanks to its ISI = 1, it guarantees reporting a PT ratio equal to INR which avoids errors.

Coagulation status of critically ill patients with and without liver disease assessed using a novel thrombin generation analyzer

The liver synthesizes the majority of pro- and anti-coagulant and fibrinolytic proteins, and during liver dysfunction synthesis of these proteins is reduced. The end point of conventional hemostatic tests, such as the prothrombin time (PT), occurs when only 5% of thrombin generation (TG) has taken place and is not sensitive to the effects of natural anti-coagulants. The aim of this study was to determine whether TG in the presence of thrombomodulin (TM) provides more useful information about coagulation potential, in comparison to the PT. Analysis was performed on ST Genesia, a novel TG analyzer from Diagnostica Stago. TG was measured using STG-Thromboscreen, a reagent containing an intermediate concentration of human tissue factor (TF) ± rabbit TM to account for anti-coagulant protein C (PC) activity. Platelet-poor plasma (PPP) samples were from the Intensive Care Study of Coagulopathy-2 (ISOC-2), which recruited patients admitted to critical care with a prolonged PT (3 seconds above the reference range). Despite a prolonged PT, 48.0% and 60.7% of patients in the liver and non-liver groups had TG parameters within the normal range. Addition of TM reduced TG by 34.5% and 41.8% in the liver and non-liver groups, respectively. Interestingly, fresh frozen plasma (FFP) transfusion had no impact on TG. Measurement of TG with addition of TM provides a more informative assessment of coagulation capacity and indicates that hemostasis is balanced in patients with liver disease during critical illness, despite conventional tests suggesting that bleeding risk is increased.

Overview of Plasma and Platelet Transfusions in Critically Ill Children

Critically ill children are a unique population who frequently receive plasma and platelet transfusions for both active bleeding and mitigation of bleeding risk. While these products are frequently administered, transfusion indications in this population remain unclear, and practice varies across institutions and providers. In this manuscript, we will outline the current evidence regarding plasma and platelet transfusions for hemostasis in the pediatric intensive care setting. For both products, we will describe the product composition, epidemiology, and product indications and discuss the potential risks and benefits involved with the transfusion. We will also discuss knowledge gaps and future areas of research.

Prophylactic plasma transfusion for patients without inherited bleeding disorders or anticoagulant use undergoing non-cardiac surgery or invasive procedures

BACKGROUND

In the absence of bleeding, plasma is commonly transfused to people prophylactically to prevent bleeding. In this context, it is transfused before operative or invasive procedures (such as liver biopsy or chest drainage tube insertion) in those considered at increased risk of bleeding, typically defined by abnormalities of laboratory tests of coagulation. As plasma contains procoagulant factors, plasma transfusion may reduce perioperative bleeding risk. This outcome has clinical importance given that perioperative bleeding and blood transfusion have been associated with increased morbidity and mortality. Plasma is expensive, and some countries have experienced issues with blood product shortages, donor pool reliability, and incomplete screening for transmissible infections. Thus, although the benefit of prophylactic plasma transfusion has not been well established, plasma transfusion does carry potentially life-threatening risks.

OBJECTIVES

To determine the clinical effectiveness and safety of prophylactic plasma transfusion for people with coagulation test abnormalities (in the absence of inherited bleeding disorders or use of anticoagulant medication) requiring non-cardiac surgery or invasive procedures.

SEARCH METHODS

We searched for randomised controlled trials (RCTs), without language or publication status restrictions in: Cochrane Central Register of Controlled Trials (CENTRAL; 2017 Issue 7); Ovid MEDLINE (from 1946); Ovid Embase (from 1974); Cumulative Index to Nursing and Allied Health Literature (CINAHL; EBSCOHost) (from 1937); PubMed (e-publications and in-process citations ahead of print only); Transfusion Evidence Library (from 1950); Latin American Caribbean Health Sciences Literature (LILACS) (from 1982); Web of Science: Conference Proceedings Citation Index-Science (CPCI-S) (Thomson Reuters, from 1990); ClinicalTrials.gov; and World Health Organization (WHO) International Clinical Trials Registry Search Platform (ICTRP) to 28 January 2019.

SELECTION CRITERIA

We included RCTs comparing: prophylactic plasma transfusion to placebo, intravenous fluid, or no intervention; prophylactic plasma transfusion to alternative pro-haemostatic agents; or different haemostatic thresholds for prophylactic plasma transfusion. We included participants of any age, and we excluded trials incorporating individuals with previous active bleeding, with inherited bleeding disorders, or taking anticoagulant medication before enrolment.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane.

MAIN RESULTS

We included five trials in this review, all were conducted in high-income countries. Three additional trials are ongoing. One trial compared fresh frozen plasma (FFP) transfusion with no transfusion given. One trial compared FFP or platelet transfusion or both with neither FFP nor platelet transfusion given. One trial compared FFP transfusion with administration of alternative pro-haemostatic agents (factors II, IX, and X followed by VII). One trial compared the use of different transfusion triggers using the international normalised ratio measurement. One trial compared the use of a thromboelastographic-guided transfusion trigger using standard laboratory measurements of coagulation. Four trials enrolled only adults, whereas the fifth trial did not specify participant age. Four trials included only minor procedures that could be performed by the bedside. Only one trial included some participants undergoing major surgical operations. Two trials included only participants in intensive care. Two trials included only participants with liver disease. Three trials did not recruit sufficient participants to meet their pre-calculated sample size. Overall, the quality of evidence was low to very low across different outcomes according to GRADE methodology, due to risk of bias, indirectness, and imprecision. One trial was stopped after recruiting two participants, therefore this review's findings are based on the remaining four trials (234 participants). When plasma transfusion was compared with no transfusion given, we are very uncertain whether there was a difference in 30-day mortality (1 trial comparing FFP or platelet transfusion or both with neither FFP nor platelet transfusion, 72 participants; risk ratio (RR) 0.38, 95% confidence interval (CI) 0.13 to 1.10; very low-quality evidence). We are very uncertain whether there was a difference in major bleeding within 24 hours (1 trial comparing FFP transfusion vs no transfusion, 76 participants; RR 0.33, 95% CI 0.01 to 7.93; very low-quality evidence; 1 trial comparing FFP or platelet transfusion or both with neither FFP nor platelet transfusion, 72 participants; RR 1.59, 95% CI 0.28 to 8.93; very low-quality evidence). We are very uncertain whether there was a difference in the number of blood product transfusions per person (1 trial, 76 participants; study authors reported no difference; very low-quality evidence) or in the number of people requiring transfusion (1 trial comparing FFP or platelet transfusion or both with neither FFP nor platelet transfusion, 72 participants; study authors reported no blood transfusion given; very low-quality evidence) or in the risk of transfusion-related adverse events (acute lung injury) (1 trial, 76 participants; study authors reported no difference; very low-quality evidence). When plasma transfusion was compared with other pro-haemostatic agents, we are very uncertain whether there was a difference in major bleeding (1 trial; 21 participants; no events; very low-quality evidence) or in transfusion-related adverse events (febrile or allergic reactions) (1 trial, 21 participants; RR 9.82, 95% CI 0.59 to 162.24; very low-quality evidence). When different triggers for FFP transfusion were compared, the number of people requiring transfusion may have been reduced (for overall blood products) when a thromboelastographic-guided transfusion trigger was compared with standard laboratory tests (1 trial, 60 participants; RR 0.18, 95% CI 0.08 to 0.39; low-quality evidence). We are very uncertain whether there was a difference in major bleeding (1 trial, 60 participants; RR 0.33, 95% CI 0.01 to 7.87; very low-quality evidence) or in transfusion-related adverse events (allergic reactions) (1 trial; 60 participants; RR 0.33, 95% CI 0.01 to 7.87; very low-quality evidence). Only one trial reported 30-day mortality. No trials reported procedure-related harmful events (excluding bleeding) or quality of life.

AUTHORS' CONCLUSIONS

Review findings show uncertainty for the utility and safety of prophylactic FFP use. This is due to predominantly very low-quality evidence that is available for its use over a range of clinically important outcomes, together with lack of confidence in the wider applicability of study findings, given the paucity or absence of study data in settings such as major body cavity surgery, extensive soft tissue surgery, orthopaedic surgery, or neurosurgery. Therefore, from the limited RCT evidence, we can neither support nor oppose the use of prophylactic FFP in clinical practice.

The Misunderstood Coagulopathy of Liver Disease: A Review for the Acute Setting

The international normalized ratio (INR) represents a clinical tool to assess the effectiveness of vitamin-K antagonist therapy. However, it is often used in the acute setting to assess the degree of coagulopathy in patients with hepatic cirrhosis or acute liver failure. This often influences therapeutic decisions about invasive procedures or the need for potentially harmful and unnecessary transfusions of blood product. This may not represent a best-practice or evidence-based approach to patient care. The author performed a review of the literature related to the utility of INR in cirrhotic patients using several scientific search engines. Despite the commonly accepted dogma that an elevated INR in a cirrhotic patient corresponds with an increased hemorrhagic risk during the performance of invasive procedures, the literature does not support this belief. Furthermore, the need for blood-product transfusion prior to an invasive intervention is not supported by the literature, as this practice increases the risk of complications associated with a patient's hospital course. Many publications ranging from case studies to meta-analyses refute this evidence and provide examples of thrombotic events despite elevated INR values. Alternative methods, such as thromboelastogram, represent alternate means of assessing in vivo risk of hemorrhage in patients with acute or chronic liver disease in real-time in the acute setting.

Use of fresh-frozen plasma in 2012 at the Fondazione Ca' Granda Hospital of Milan: assessment of appropriateness using record linkage techniques applied to data routinely recorded in various hospital information systems

BACKGROUND

The Quality Unit of a research and teaching hospital in Milan assessed the increased clinical use of fresh-frozen plasma in patients treated during 2012 in order to evaluate the appropriateness of this use.

MATERIALS AND METHODS

For each patient in the study, a pathology profile was generated by means of record linkage techniques involving data collected through different information systems. Patients' information was combined using the patient identifier key generating pathology profiles exported to an Excel file. The profiles were reviewed by two haematologists who identified 101 potentially inappropriate treatments for which the medical records had to be reviewed manually.

RESULTS

In 2012, 490 patients were transfused and for 473 cases the automatic record linkage provided a complete profile. The information relating to the remaining patients did not match, mainly because the patients underwent outpatient procedures for which clinical information is not automatically recorded. In the overall audit only 13 treatments were judged inappropriate.

DISCUSSION

Our study supports the view that record linkage techniques applied to data routinely recorded in different hospital information systems could be potentially extended to support clinical audits, enabling the generation of automated patient profiles that can be easily evaluated, relegating manual checks on medical records to doubtful cases only. Moreover, the method applied in this study allows the analysis of a full set of cases instead of sample surveys, increasing the robustness of the audit results.

Clinical bleeding and thrombin generation in admissions to critical care with prolonged prothrombin time: an exploratory study

BACKGROUND

Prolongation of prothrombin time (PT) is often recorded in critical illness, but has limited ability to predict risk of bleeding. This exploratory study was aimed at assessing a role for thrombin generation (TG) to predict bleeding.

STUDY DESIGN AND METHODS

TG was measured by calibrated automated thrombography in admissions to intensive care with prolonged PT. Bleeding events were recorded up to Day 5 after enrollment and correlated with results of PT ratio (PTR) and variables of TG.

RESULTS

A total of 306 patients were recruited. A total of 101 bleeding events developed in 46 patients during the period of observation. Many patients with prolonged PT had endogenous thrombin potential (ETP), which was within the normal range (120/251 patients, 47.8%) or even elevated (8%). Although some patients had a reduction in ETP or peak thrombin, these were present over a wide range of PTR. There was no suggestion by receiver operating characteristic analysis that variables of conventional TG were sensitive at predicting bleeding. No bleeding events were documented in patients defined as ETP high, despite elevated PTR.

CONCLUSION

Future studies need to explore a role for alternatives tests of coagulation in critical illness. Development of TG assays is required to positively identify more patients at increased bleeding risk or to exclude a larger number at low risk and how this relates to subgroups, such as patients with liver disease, and the need for prophylactic plasma transfusion.

Fondaparinux is effective for acute portal vein thrombosis in decompensated cirrhotic patients

Portal vein thrombosis (PVT) is a rare but serious complication in the decompensated stage of cirrhosis, and recurrent upper gastrointestinal bleeding and refractory ascites can occur in such patients. In decompensated cirrhotic patients, the application of conventional anticoagulant therapy is limited due to severe coagulation disorders, thrombocytopenia, and history of gastrointestinal bleeding.In this study, we sought to investigate the effect of fondaparinux on acute PVT in decompensated cirrhotic patients.Patients were treated with fondaparinux (2.5 mg, q 24 h, subcutaneously) in the region of the umbilicus for conventional liver protection, after a clear diagnosis was made and contraindications such as active bleeding were ruled out. Other anticoagulants and circulation-improving drugs were not administered. Platelet count, prothrombin time, international normalized ratio, D dimer (DD), and liver function were measured. Furthermore, portal vein color Doppler ultrasound was performed every 7 days while patients were treated with fondaparinux and after portal vein recanalization.The portal vein was recanalized in all patients after treatment (P = .018). The decline in DD had a predictive value for portal vein recanalization (P = .018). No side effects such as bleeding or thrombocytopenia occurred in any of the patients (P > .05).Selective factor Xa inhibitor fondaparinux is effective and safe for acute PVT in decompensated cirrhotic patients.

Consensus Report by the Pediatric Acute Lung Injury and Sepsis Investigators and Pediatric Blood and Marrow Transplant Consortium Joint Working Committees on Supportive Care Guidelines for Management of Veno-Occlusive Disease in Children and Adolescents: Part 2-Focus on Ascites, Fluid and Electrolytes, Renal, and Transfusion Issues

Even though hepatic veno-occlusive disease (VOD) is a potentially fatal complication of hematopoietic cell transplantation (HCT), there is paucity of research on the management of associated multiorgan dysfunction. To help provide standardized care for the management of these patients, the HCT Subgroup of the Pediatric Acute Lung Injury and Sepsis Investigators and the Supportive Care Committee of the Pediatric Blood and Marrow Transplant Consortium, collaborated to develop evidence-based consensus guidelines. After conducting an extensive literature search, in part 2 of this series we discuss the management of fluids and electrolytes, renal dysfunction; ascites, pleural effusion, and transfusion and coagulopathy issues in patients with VOD. We consider the available evidence using the GRADE criteria.

Prophylactic plasma transfusion for patients undergoing non-cardiac surgery

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: To determine the clinical effectiveness and safety of prophylactic plasma transfusion for people with confirmed or presumed coagulopathy requiring non-cardiac surgery.

Recognition and Management of Hemostatic Disorders in Critically Ill Patients Needing to Undergo an Invasive Procedure

Abnormal laboratory coagulation test results are frequently documented in critically ill patients, and these patients often also need to undergo invasive procedures. Clinicians have an understandable desire to minimize any perceived heightened risk of bleeding complications in those patients who require invasive procedures. In this setting, prophylactic administration of platelets or plasma is commonplace. This review explores the nature of these sequential statements and the degree to which these statements are supported by evidence. We discuss the complexity of managing the low risk of procedure-related bleeding in a setting where coagulation tests fail to reliably predict this risk. The role of prophylactic transfusion of platelets and plasma and correction of medication-induced coagulopathy is also reviewed. New strategies are required to improve the evidence base, including novel methodological approaches or the use of a clinical scoring system.

Thromboelastometry versus standard coagulation tests versus restrictive protocol to guide blood transfusion prior to central venous catheterization in cirrhosis: study protocol for a randomized controlled trial

Background

Liver failure patients have traditionally been empirically transfused prior to invasive procedures. Blood transfusion is associated with immunologic and nonimmunologic reactions, increased risk of adverse outcomes and high costs. Scientific evidence supporting empirical transfusion is lacking, and the best approach for blood transfusion prior to invasive procedures in cirrhotic patients has not been established so far.

The aim of this study is to compare three transfusion strategies (routine coagulation test-guided – ordinary or restrictive, or thromboelastometry-guided) prior to central venous catheterization in critically ill patients with cirrhosis.

Methods/design

Design and setting: a double-blinded, parallel-group, single-center, randomized controlled clinical trial in a tertiary private hospital in São Paulo, Brazil. Inclusion criteria: adults (aged 18 years or older) admitted to the intensive care unit with cirrhosis and an indication for central venous line insertion. Patients will be randomly assigned to three groups for blood transfusion strategy prior to central venous catheterization: standard coagulation tests-based, thromboelastometry-based, or restrictive. The primary efficacy endpoint will be the proportion of patients transfused with any blood product prior to central venous catheterization. The primary safety endpoint will be the incidence of major bleeding. Secondary endpoints will be the proportion of transfusion of fresh frozen plasma, platelets and cryoprecipitate; infused volume of blood products; hemoglobin and hematocrit before and after the procedure; intensive care unit and hospital length of stay; 28-day and hospital mortality; incidence of minor bleeding; transfusion-related adverse reactions; and cost analysis.

Discussion

This study will evaluate three strategies to guide blood transfusion prior to central venous line placement in severely ill patients with cirrhosis. We hypothesized that thromboelastometry-based and/or restrictive protocols are safe and would significantly reduce transfusion of blood products in this population, leading to a reduction in costs and transfusion-related adverse reactions. In this manner, this trial will add evidence in favor of reducing empirical transfusion in severely ill patients with coagulopathy.

Trial registration

ClinicalTrials.gov, identifier: NCT02311985. Retrospectively registered on 3 December 2014.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-1835-5) contains supplementary material, which is available to authorized users.

The Utility of Viscoelastic Testing in Patients Undergoing IR Procedures

Whole-blood viscoelastic testing can identify patient-specific coagulation disturbances, allowing for targeted repletion of necessary coagulation factors and differentiation between coagulopathy and surgical bleeding that requires intervention. Viscoelastic testing complements standard coagulation tests and has been shown to decrease transfusion requirements and improve survival in bleeding patients. Viscoelastic testing also can be used to predict bleeding and improve the care of patients undergoing interventional radiology (IR) procedures.

Four-Factor Prothrombin Complex Concentrate for Coagulopathy Reversal in Patients With Liver Disease

A 4-factor prothrombin complex concentrate (4F-PCC, Kcentra®) was recently approved in the United States for the reversal of vitamin K antagonist-associated major bleeding, but it is often used to reverse coagulopathy in patients with liver disease (LD). This single-center, retrospective study analyzed the efficacy and safety of 4F-PCC administered in patients with and without LD. Prothrombin time/International Normalized Ratio (PT/INR) reversal with 4F-PCC was attempted in 85 patients; LD was documented in 31 patients. Coagulopathy reversal and hemostasis with 4F-PCC were inferior in patients with LD compared to patients without LD. Coagulopathy reversal, defined as INR = 1.5 after 4F-PCC administration, was achieved in 6 (19.4%) LD patients, compared to 44 (81.5%) non-LD patients ( p < 0.01). Hemostasis was achieved in 6 LD patients (19.4%) compared to 23 non-LD patients (42.6%) ( p = 0.03). Thromboembolic events occurred in 1 LD patient (3.2%) and 8 non-LD patients (14.8%) ( p = 0.15). Mortality was 51.6% in LD patients and 18.5% in non-LD patients ( p < 0.01). These observations suggest that the efficacy of 4F-PCC is suboptimal to correct coagulopathy and hemostasis in patients with LD, who have high rates of in-hospital mortality due to sequelae of LD. The incidence of thromboembolic events appeared comparable, suggesting that 4F-PCC does not cause undue thromboembolism in LD patients. In conclusion, 4F-PCC appears to be safe in LD patients when administered judiciously; however, further studies are necessary to optimize its use and elucidate its hemostatic potential in this patient population.

Plasma from chronic liver disease subjects exhibit differential ability to generate thrombin

Liver fibrosis in chronic liver disease (CLD) results in complex alterations in procoagulant and anticoagulant proteins. Although an elevated international normalized ratio (INR) is a prominent feature of progressive fibrosis, the utility of the INR to accurately reflect the net effect of these changes on the coagulation system is uncertain. In subjects with CLD, elevated INRs have been observed in both bleeding and thrombotic complications, suggesting limitations of the INR in characterizing the coagulation status. Unlike the INR, which is preferentially sensitive to the extrinsic pathway, the direct measurement of thrombin generation better captures the global coagulation cascade. We conducted a pilot study measuring the INR, chromogenic factor X and thrombin generation in CLD subjects and compared them with control subjects and subjects on warfarin anticoagulation. We observed a large interquartile range in thrombin generation among compensated CLD subjects across a narrow INR range, suggesting that the INR is a suboptimal surrogate measure of thrombin generation in CLD subjects.

Effect of diseases on response to vitamin K antagonists

INTRODUCTION

The purpose of this review article is to summarize the literature on diseases that are documented to have an effect on response to warfarin and other VKAs.

METHODS

We searched the English literature from 1946 to September 2015 via PubMed, EMBASE, and Scopus for the effect of diseases on response vitamin K antagonists including warfarin, acenocoumarol, phenprocoumon, and fluindione.

DISCUSSION

Among many factors modifying response to VKAs, several disease states are clinically relevant. Liver disease, hyperthyroidism, and CKD are well documented to increase response to VKAs. Decompensated heart failure, fever, and diarrhea may also elevate response to VKAs, but more study is needed. Hypothyroidism is associated with decreased effect of VKAs, and obese patients will likely require higher initial doses of VKAs.

CONCLUSION

In order to minimize risks with VKAs while ensuring efficacy, clinicians must be aware of the effect of disease states when prescribing these oral anticoagulants.

Blood Products

Perioperative hemorrhage, anemia, thrombocytopenia, and coagulopathy are common in the surgical intensive care unit. As a result, blood product transfusion occurs frequently. While red blood cell, plasma, and platelet transfusions have a lifesaving role in the resuscitation of patients with trauma and hemorrhagic shock, their application in other settings is under scrutiny. Current data would suggest a conservative approach be taken, thus avoiding unnecessary transfusion and associated potential adverse events. New and developmental products such as prothrombin complex concentrates offer appealing alternatives to traditional transfusion practice—potentially with fewer risks—however, further investigation into their safety and efficacy is required before practice change can take place.

How I treat poisoning with vitamin K antagonists

Severe deficiency of vitamin K-dependent proteins in patients not maintained on vitamin K antagonists is most commonly associated with poisoning by or surreptitious ingestion of warfarin, warfarin-like anticoagulants, or potent rodenticides ("superwarfarins"), such as brodifacoum. Serious bleeding manifestations are common. Superwarfarins are 2 orders of magnitude more potent than warfarin and have a half-life measured in weeks. These rodenticides are readily available household environmental hazards and are sometimes consumed accidentally or as manifestations of psychiatric disease. Immediate diagnosis and proper therapy is critically important to minimize morbidity and mortality because this condition, affecting thousands of patients annually, is reversible. Treatment with large doses of oral vitamin K1, often over months to years, to maintain a near-normal prothrombin time can reverse the coagulopathy associated with superwarfarins. Although these patients initially present to various medical specialties, the hematologist is often consulted to offer the definitive diagnosis and proper therapy.

Biomarkers in Hepatic Disease: A Review Focused on Critically Ill Patients

The ability to make a diagnosis early and appropriately is paramount for the survival of the critically ill ICU patient. Along with the myriad physical examination and imaging modalities available, biomarkers provide a window on the disease process. Herein we review hepatic biomarkers in the context of the critical care patient.

Impact of sustained virus elimination on natural anticoagulant activity in patients with chronic viral hepatitis C

Previous studies have reported reduced synthesis of various hemostatic factors in patients with chronic liver disease. Whether changes in plasma levels of these proteins reflect recovered liver synthetic function following virological eradication therapy has not been approved yet. The aim of the study was to determine the impact of sustained viral suppression achieved with pegylated interferon alpha and ribavirin on hemostatic parameters including natural anticoagulants in patients with chronic hepatitis C. The following coagulation screening tests were obtained in thirty patients with chronic viral hepatitis C before and after completion of antiviral treatment: activated partial thromboplastin time, prothrombin time, plasma fibrinogen and natural anticoagulant proteins antithrombin III, protein C (PC) and total protein S (PS) activity. Only patients who achieved durable virus suppression were included. The mean PC and PS levels were significantly lower in patients with chronic viral hepatitis C before antiviral therapy than in healthy controls (79.04 ± 16.19 % vs. 109.92 ± 21.33% and 54.04 ± 16.11% vs. 87.60 ± 8.15%, respectively; (p<0.001). Mean levels of PC exhibited a significant increase by 14.69 % after the completion of antiviral treatment (93.73 ± 14.18%, p<0.001) as well as PS levels, which significantly increased by 21.46% (75.50 ± 15.43, p<0.001) when compared with pre-treatment values. No remarkable fluctuations in other hemostatic parameters were noted. Protein C and protein S are sensitive markers of hepatocyte synthetic impairment and are valuable markers in monitoring the efficacy of antiviral treatment in chronic hepatitis C patients. Larger studies are needed to confirm our results.

Portal vein thrombosis and liver transplantation: implications for waiting list period, surgical approach, early and late follow-up

Portal vein thrombosis (PVT) is a well-known and relatively common complication of liver cirrhosis. In the past, PVT was considered as a contraindication for liver transplantation (LT). To characterize prevalence, risk factors, perioperative management and outcome of PVT in the setting of LT, the English literature published between 1991 and 2011 was reviewed. Of 6807 articles, 280 were selected, and 39 experiences were analyzed in detail (methodology, type and duration of treatments, peri-operative management, strategy to avoid recurrence, strengths and weaknesses, Oxford evidence level, citations). 3/39 studies were prospective; 9/39 were based on prospectively recorded databases; no studies of 1, 2a, 3a level of evidence were present; 5/39 were recognized as level 2b, 23/39 as level 3b, and 8/39 as level 4. High complication rate has been reported with consequent effect on graft and patient survival. Overall, PVT presents today good results similar to those obtained in patients without PVT undergoing LT even if they require a higher transfusion number and a longer ICU/hospital stay. Reported cases were retrospectively stratified according to Yerdel classification. Grade 1-2 patients (76%) do well with eversion thromboendovenectomy, resection of damaged vein and porto-portal anastomosis. Results of patients with grade 3-4 (24%) are inferior, however data on outcome in this subsets are fragmented and do not allow a reliable analysis. Moreover, results obtained in grade 3-4 cases are better in transplant centers with large specific experience. The small number of reports suggests caution. The role of anticoagulant treatment is still debated. Although in cirrhotics with PVT LT remains a demanding procedure, PVT should not be considered a contraindication anymore.

The International Normalized Ratio overestimates coagulopathy in stable trauma and surgical patients

BACKGROUND

The international normalized ratio (INR) was developed to assess adequacy of Coumadin dosing. Its use has been generalized to guide fresh frozen plasma (FFP) therapy in stable patients. Thrombelastography (TEG) is a whole-blood assay measuring the viscoelastic properties of the clot in near real time. This study hypothesized that INR does not reflect coagulopathy and should not be used to guide FFP therapy in stable trauma and surgical patients.

METHODS

Prospective observational data were collected from stable trauma and surgical patients (n = 106) who received FFP transfusions. Pretransfusion and posttransfusion blood samples were obtained to assess complete blood count, standard coagulation parameters (INR, partial thromboplastin time, fibrinogen and D-dimer), soluble clotting factors (II, V, VII, VIII, IX, X, XI, XII, proteins C and S) and TEG. Data were analyzed using a Mann-Whitney U-test. Significance was defined as p < 0.05.

RESULTS

A total of 262 U of FFP were transfused, with 78% of 106 patients receiving two or more units. Despite a reduction in INR, median TEG values remained within normal limits, while clotting factor levels retained adequate function to produce normal clotting before and following FFP transfusion.

CONCLUSION

The use of FFP in this population did not affect coagulation status in a clinically relevant manner based on TEG values and coagulation factor function. INR is not a predictor of coagulopathy and should not be used to guide coagulation factor replacement in stable trauma and surgical patients.

LEVEL OF EVIDENCE

Diagnostic study, level III.

Transfusion guidelines: when to transfuse

Transfusion of blood and blood components has been a routine practice for more than half a century. The rationale supporting this practice is that replacement of blood loss should be beneficial for the patient. This assumption has constituted the underpinning of transfusion medicine for many decades. Only over the past 20 years, we have seen a more concerted effort to answer very basic questions regarding the value of transfusion therapy. An assessment of the value of transfusion based on well-designed and appropriately powered randomized, controlled trials is the first step in optimizing transfusion practices. Systematic reviews provide the second step by building the knowledge base necessary to assess the impact of transfusion practice on patient outcomes. The third step is the development of clinical practice guidelines, and this occurs when systematic reviews are interpreted by individuals with expertise in transfusion medicine. Such guidelines are typically supported by professional organizations and/or health authorities. Implementation of clinical practice guidelines can be challenging, especially in an area as heterogeneous as transfusion medicine. However, clinical practice guidelines are necessary for the practice of evidence-based medicine, which optimizes patient care and improves patient outcomes. This review focuses on clinical practice guidelines for transfusion of three blood components: RBCs, platelets and plasma. In addition, we provide the approach used to implement clinical practice guidelines at our own institution.

Evidence review: periprocedural use of blood products

Blood product transfusion has not been subject to rigorous clinical study, and great practice variations exist. Of particular concern to hospitalists is the use of red blood cells, plasma, and platelets prior to invasive procedures to correct anemia or perceived bleeding risk. We summarize the known risks associated with periprocedural anemia, prolonged international normalized ratio (INR), and thrombocytopenia, as well as the effects of blood product administration on clinical outcomes. Clinical trial evidence argues for a restrictive red blood cell transfusion threshold (a hemoglobin level of 7-8 g/dL or symptomatic anemia) for most perioperative patients. There are no high-quality data to guide plasma and platelet transfusions around the time of procedures. Available data do not support the use of prothrombin time/INR to guide prophylactic administration of plasma, and there are scarce data to guide platelet use around the time of an invasive procedure. Therefore, we rely on current consensus expert opinion, which recommends administration of plasma in moderate- to high-risk procedures when INR is >1.5. We recommend platelet transfusion in low-risk procedures when platelet count is <20,000/μL, for average-risk procedures when platelet count is <50,000/μL, and for procedures involving the central nervous system when the platelet count is <100,000/μL.

Portal vein thrombosis: a clinician-oriented and practical review

With advances in modern imaging techniques, portal vein thrombosis (PVT) is being increasingly diagnosed. It has a wide ranging clinical spectrum from being an asymptomatic state to a potentially life-threatening situation. It is not unusual to find it as an incidental finding in the abdominal imagings done for other reasons. It is commonly associated with cirrhosis and abdominal malignancies and also has a strong association with prothrombotic disorders. It is often difficult for the clinicians to decide whether PVT is acute or chronic. This poses great challenges to its management strategies that include anticoagulants, thrombolysis, and surgical options. Timely diagnosis and appropriate management have great bearings on its outcomes of morbidity and mortality. In this clinician-oriented review, we have provided a concise review of clinical aspects of PVT and discussed various management strategies while addressing the common questions that come to a physician's mind dealing with such a patient.

Venous thromboembolism in cirrhosis

The cirrhosis population represents a unique subset of patients who are at risk for both bleeding and developing venous thromboembolic events (VTEs). It has been commonly misunderstood that these patients are naturally protected from thrombosis by deficiencies in coagulation factors. As a result, the cirrhosis population is often falsely perceived to be "autoanticoagulated." However, the concept of "autoanticoagulation" conferring protection from thrombosis is a misnomer. While patients with cirrhosis may have a bleeding predisposition, not uncommonly they also experience thrombotic events. The concern for this increased bleeding risk often makes anticoagulation a difficult choice. Prophylactic and therapeutic management of VTE in patients with cirrhosis is a difficult clinical problem with the lack of clear established guidelines. The elucidation of laboratory and/or clinical predictors of VTE will be useful in this setting. This review serves to examine VTE and the use of anticoagulation in the cirrhosis population.

Oral anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

The objective of this article is to summarize the published literature concerning the pharmacokinetics and pharmacodynamics of oral anticoagulant drugs that are currently available for clinical use and other aspects related to their management.

METHODS

We carried out a standard review of published articles focusing on the laboratory and clinical characteristics of the vitamin K antagonists; the direct thrombin inhibitor, dabigatran etexilate; and the direct factor Xa inhibitor, rivaroxaban

RESULTS

The antithrombotic effect of each oral anticoagulant drug, the interactions, and the monitoring of anticoagulation intensity are described in detail and discussed without providing specific recommendations. Moreover, we describe and discuss the clinical applications and optimal dosages of oral anticoagulant therapies, practical issues related to their initiation and monitoring, adverse events such as bleeding and other potential side effects, and available strategies for reversal.

CONCLUSIONS

There is a large amount of evidence on laboratory and clinical characteristics of vitamin K antagonists. A growing body of evidence is becoming available on the first new oral anticoagulant drugs available for clinical use, dabigatran and rivaroxaban.

Proteomic analyses of human plasma: Venus versus Mars

BACKGROUND

Plasma is vital for the resuscitation of injured patients and to restore necessary procoagulants, especially Factors (F)II, FV, FVII, FX, and FXIII; however, female plasma has been implicated in the majority of transfusion-related acute lung injury (TRALI) cases and male-only plasma transfusion regimens have significantly decreased the incidence of TRALI. Little is known about the human plasma proteome, and no comparisons have been made between male and female plasma; therefore, we hypothesize that there are significant differences between plasma from male and female donors.

STUDY DESIGN AND METHODS

Five units of fresh-frozen plasma each were collected from nulliparous female donors and male donors, and the proteome was analyzed by depleting the 14 most common proteins by immunoaffinity columns followed by protein separation by one dimension gel electrophoresis, tryptic digestion of the proteins, analysis of the peptides by liquid chromatography-tandem mass spectrometry, and identification employing human protein sequence databases.

RESULTS

Female plasma versus male plasma contained pregnancy zone protein (419- to 580-fold), FV (twofold), α(1)-antitrypsin (twofold), β(2) -microglobulin (twofold), and Complement Factors H and C4B (1.5- to 2-fold) at significantly higher concentrations than males and males contained significant increases in Fc-binding protein (twofold), protein Z-dependent protease inhibitor (twofold), phosphatidylinositol glycan-specific phospholipase (fourfold), protein S-100 (threefold), and transgelin-2 (14-fold) versus females (p < 0.005). The increases in FV, α(1)-antitrypsin, and β(2)-microglobulin were confirmed by an activity assay or immunoblots.

CONCLUSION

We conclude that there are proteomic differences between male and female plasma, which could be exploited to improve clinical outcomes in transfused patients.

A national study of plasma use in critical care: clinical indications, dose and effect on prothrombin time

INTRODUCTION

Fresh frozen plasma (FFP) is widely used, but few studies have described patterns of plasma use in critical care. We carried out a multicentre study of coagulopathy in intensive care units (ICUs) and here describe overall FFP utilisation in adult critical care, the indications for transfusions, factors indicating the doses used and the effects of FFP use on coagulation.

METHODS

We conducted a prospective, multicentre, observational study of all patients sequentially admitted to 29 adult UK general ICUs over 8 weeks. Daily data throughout ICU admission were collected concerning coagulation, relevant clinical outcomes (including bleeding), coagulopathy (defined as international normalised ratio (INR) >1.5, or equivalent prothrombin time (PT)), FFP and cryoprecipitate use and indications for transfusion.

RESULTS

Of 1,923 admissions, 12.7% received FFP in the ICU during 404 FFP treatment episodes (1,212 FFP units). Overall, 0.63 FFP units/ICU admission were transfused (0.11 units/ICU day). Reasons for FFP transfusion were bleeding (48%), preprocedural prophylaxis (15%) and prophylaxis without planned procedure (36%). Overall, the median FFP dose was 10.8 ml kg⁻¹, but doses varied widely (first to third quartile, 7.2 to 14.4 ml kg⁻¹). Thirty-one percent of FFP treatments were to patients without PT prolongation, and 41% were to patients without recorded bleeding and only mildly deranged INR (<2.5). Higher volumes of FFP were administered when the indication was bleeding (median doses: bleeding 11.1 ml kg⁻¹, preprocedural prophylaxis 9.8 ml kg⁻¹, prophylaxis without procedure 8.9 ml kg⁻¹; P = 0.009 across groups) and when the pretransfusion INR was higher (ranging from median dose 8.9 ml kg⁻¹ at INR ≤ 1.5 to 15.7 ml kg⁻¹ at INR >3; P < 0.001 across ranges). Regression analyses suggested bleeding was the strongest predictor of higher FFP dose. Pretransfusion INR was more frequently normal when the transfusion indication was bleeding. Overall, posttransfusion corrections of INR were consistently small unless the pretransfusion INR was >2.5, but administration during bleeding was associated with greater INR corrections.

CONCLUSIONS

There is wide variation in FFP use by ICU clinicians, and a high proportion of current FFP transfusions are of unproven clinical benefit. Better evidence from clinical trials could significantly alter patterns of use and modify current treatment costs.

Venous thrombosis in patients with chronic liver disease

Patients with chronic liver disease are susceptible to bleeding and thrombotic complications of their disease, but the incidence of thrombosis and what predisposes them to thrombotic disease is largely unknown. One hundred and eight patients with chronic liver disease admitted with a first episode of venous thromboembolism, matched with patients of similar age, sex, and cause of liver disease without thrombosis were compared in a retrospective, case-control study over a 4-year period at two academic hospitals in Rhode Island. Incidence was determined from all admissions of patients with chronic liver disease during the specified time. Minimum and maximum values of complete blood counts, liver and kidney function tests, and coagulation tests during admission were compared between cases and controls. Incidence of new venous thrombosis in patients admitted with chronic liver disease was 0.73%. Patients with thromboses were more likely to have a lower albumin (2.77 vs. 3.49; P < 0.01) and hematocrit (37.7 vs. 40.2; P < 0.01) and higher platelet counts (143 vs. 109; P = 0.03), bilirubin (1.71 vs. 1.11; P < 0.01) and activated partial thromboplastin time (87 vs. 60.3; P < 0.01) as compared with controls. Although the incidence of thrombosis in patients with chronic liver disease is lower than the general medical population, hypoalbuminemia, anemia, and hyperbilirubinemia may confer increased risk of thrombosis whereas thrombocytopenia may be protective. Elevation of traditional markers of coagulation such as the prothrombin time and partial thromboplastin time does not safeguard against thrombotic events.