Haemostasis and thrombosis in liver disease

Effects of PCSK9 on thrombosis and haemostasis in a variety of metabolic states: Lipids and beyond (Review)

Proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitors are widely recognised as being able to induce a potent reduction in low‑density lipoprotein‑cholesterol. An increasing number of studies have suggested that PCSK9 also influences the haemostatic system by altering platelet function and the coagulation cascade. These findings have significant implications for anti‑PCSK9 therapy in patients with specific coagulation conditions, including expanded indications, dose adjustments and drug interactions. The present review summarises the changes in PCSK9 levels in individuals with liver diseases, chronic kidney diseases, diabetes mellitus, cancer and other disease states, and discusses their impact on thrombosis and haemostasis. Furthermore, the structure, effects and regulatory mechanisms of PCSK9 on platelets, coagulation factors, inflammatory cells and endothelial cells during coagulation and haemostasis are described.

Perilla oil and α-linolenic acid ameliorated thrombosis in rats induced by collagen and epinephrine

Perilla frutescens is an annual herbaceous plant widely cultivated for oil production in China, Japan, and Korea. In this study, we investigated the effect of perilla oil (PO) on thrombosis induced by collagen and epinephrine (CE) in rats. The oral administration of PO significantly increased prothrombin time (PT) and activated partial thromboplastin time (aPTT) in the blood plasma and inhibited the expression of cells adhesion markers (CAMs) such as intercellular CAM-1 (ICAM-1), vascular CAM (VCAM-1), E-selectin and P-selectin in the aorta tissue. Furthermore, pulmonary occlusion induced by CE in rats was suppressed by PO. α-Linolenic acid (ALA) was quantified at 60.14 ± 2.50 g/100 g of PO, and its oral administration at the same concentration with that in PO exerted the similar effect on PT, aPTT, ICAM-1, VCAM-1, E-selectin and P-selectin in CE-induced thrombosis rats. Taken together, PO and ALA significantly ameliorated thrombosis by regulating CAMs.

Potential Effects of Coronaviruses on the Liver: An Update

The coronaviruses that cause notable diseases, namely, severe acute respiratory syndrome (SARS), middle east respiratory syndrome (MERS) and coronavirus disease 2019 (COVID-19), exhibit remarkable similarities in genomic components and pathogenetic mechanisms. Although coronaviruses have widely been studied as respiratory tract pathogens, their effects on the hepatobiliary system have seldom been reported. Overall, the manifestations of liver injury caused by coronaviruses typically involve decreased albumin and elevated aminotransferase and bilirubin levels. Several pathophysiological hypotheses have been proposed, including direct damage, immune-mediated injury, ischemia and hypoxia, thrombosis and drug hepatotoxicity. The interaction between pre-existing liver disease and coronavirus infection has been illustrated, whereby coronaviruses influence the occurrence, severity, prognosis and treatment of liver diseases. Drugs and vaccines used for treating and preventing coronavirus infection also have hepatotoxicity. Currently, the establishment of optimized therapy for coronavirus infection and liver disease comorbidity is of significance, warranting further safety tests, animal trials and clinical trials.

The hemostatic and thrombotic complications of liver disease

Hepatic cirrhosis leads to numerous hematologic derangements resulting in a complex and tenuously rebalanced hemostatic milieu. The utility of common hematologic tests including the INR and aPTT in assessing hemostatic and thrombotic risk in patients with cirrhosis is limited, and consensus on transfusion thresholds and proper management of thrombotic complications continues to evolve. This review summarizes the pathophysiology of key derangements of hemostasis including those of platelets, von Willebrand factor, pro- and anticoagulation factors, and fibrin. Additionally, the pathogenesis, consequences, optimal management, and prevention of major thrombotic and bleeding complications in cirrhosis arte discussed.

Bleeding Disorders in Primary Fibrinolysis

Fibrinolysis is a complex enzymatic process aimed at dissolving blood clots to prevent vascular occlusions. The fibrinolytic system is composed of a number of cofactors that, by regulating fibrin degradation, maintain the hemostatic balance. A dysregulation of fibrinolysis is associated with various pathological processes that result, depending on the type of abnormality, in prothrombotic or hemorrhagic states. This narrative review is focused on the congenital and acquired disorders of primary fibrinolysis in both adults and children characterized by a hyperfibrinolytic state with a bleeding phenotype.

Transfusion with Cryoprecipitate for Very Low Fibrinogen Levels Does Not Affect Bleeding or Survival in Critically Ill Cirrhosis Patients

BACKGROUND

 Fibrinogen (FIB) levels less than 150 mg/dL have been associated with increased rates of bleeding and lower survival in critically ill cirrhosis patients.

OBJECTIVE

 We aimed to determine if treatment with cryoprecipitate (CRYO) for low FIB levels is associated with bleeding outcomes or survival.

METHODS

 A total of 237 cirrhosis patients admitted to an intensive care unit at a tertiary care liver transplant center with initial FIB levels less than 150 mg/dL were retrospectively assessed for CRYO transfusion, bleeding events, and survival outcomes.

RESULTS

 The mean MELD score was 27.2 (95% confidence interval [CI]: 26.0-28.3) and CLIF-C acute on chronic liver failure score was 53.4 (51.9-54.8). Ninety-nine (41.8%) were admitted for acute bleeding and the remainder were admitted for nonbleeding illnesses. FIB level on admission correlated strongly with disease severity. After adjusting for disease severity, FIB on admission was not an independent predictor of 30-day survival (hazard ratio [HR]: 0.99, 95% CI: 0.99-1.01, p = 0.68). CRYO transfusion increased FIB levels but had no independent effect on mortality or bleeding complications (HR: 1.10, 95% CI: 0.72-1.70, p = 0.65).

CONCLUSION

 In cirrhosis patients with critical illness, low FIB levels on presentation reflect severity of illness but are not independently associated with 30-day mortality. Treatment of low FIB with CRYO also does not affect survival or bleeding complications, suggesting FIB is an additional marker of severity of illness but is not itself a direct factor in the pathophysiology of bleeding in critically ill cirrhosis patients.

Platelet function testing in patients with post-operative tonsillectomy bleeding may be a useful early identifier of inherited platelet function disorders

BACKGROUND

Post-tonsillectomy bleeding is the most frequent complication of tonsillectomy. Inherited platelet function disorders have an estimated prevalence of 1 per cent. Any association between post-tonsillectomy bleeds and undiagnosed inherited platelet function disorders has not been investigated before.

OBJECTIVES

To assess the prevalence of inherited platelet function disorders in a cohort of post-tonsillectomy bleed patients.

METHODS

An observational cohort study was conducted using hospital digital records. Platelet function analyser 100 ('PFA-100') closure time was tested on post-tonsillectomy bleed patients who presented to hospital.

RESULTS

Between 2013 and 2017, 9 of 91 post-tonsillectomy bleed patients who underwent platelet function analyser 100 testing (9.89 per cent) had positive results. Five patients (5.49 per cent) had undiagnosed inherited platelet function disorders. Four patients had false positive results secondary to a non-steroidal anti-inflammatory drug effect (specificity of 95.3 per cent) proven by repeat testing six weeks later, off medication. The false negative rate was 0 per cent.

CONCLUSION

The prevalence of inherited platelet function disorders in our post-tonsillectomy bleed cohort is five-fold higher than in the general population. Platelet function analyser 100 testing when patients present with a post-tonsillectomy bleed allows management of their inherited platelet function disorder.

Hypercoagulability (thrombin generation) in patients with cirrhosis is detected with ST-Genesia

BACKGROUND

Thrombin generation assays (TGAs) performed with calibrated automated thrombography (CAT) in the presence of thrombomodulin (TM) indicate plasma hypercoagulability in cirrhosis.

OBJECTIVE

To evaluate, in the presence of TM, the new ST-Genesia automated device developed for improving TGA vs the previously used CAT method, with plasma samples of patients with cirrhosis.

PATIENTS/METHODS

Platelet-poor plasma samples were prepared from citrated blood samples of 52 healthy controls and 85 patients with cirrhosis (severity evaluated using the Child-Pugh score [CP]). TGAs were performed using CAT with PPP-Reagent and ST-Genesia with the STG-ThromboScreen reagent, in the presence of TM. Endogenous thrombin potential (ETP) was chosen as the main parameter.

RESULTS

Whatever the method, ETP values were higher in patients than in healthy controls. All patients identified as hypercoagulable with ST-Genesia and STG-ThromboScreen were found hypercoagulable with CAT and PPP-Reagent. Conversely, eight and ten patients in the CP-A and CP-B classes respectively were identified as hypercoagulable only with CAT. The use of ST-Genesia with the STG-ThromboScreen reagent with TM led to a bias, with higher ETP values for healthy controls and lower for patients compared with CAT. Crossover analysis (CAT with the STG-ThromboScreen reagent) evidenced a substantial effect of the STG-ThromboScreen reagent; the analyzer (including calibration and data analysis) plays a lesser role.

CONCLUSION

ST-Genesia evidences hypercoagulability in patients with cirrhosis when TG is studied in the presence of TM, but the results are not interchangeable with those obtained with CAT.

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.

Magnesium Therapy Improves Rotational Thromboelastometry Findings Prior to Liver Transplantation: A Randomized Clinical Trial

An important challenge during orthotopic liver transplantation (OLT) is optimal coagulation management. There are diverse studies regarding effect of Mg sulfate on coagulation system. This study evaluates the impact of Mg sulfate on the coagulation parameters of the rotational thromboelastometry (ROTEM) in patients about to undergo OLT. In this randomized clinical trial, 60 patients who were going to undergo OLT were randomly allocated into two groups. In the Mg group, the patients received a 1.5 g infusion of Mg 5 min before the surgical incision. In the control group, patients received a physiological saline instead of Mg. Plasma Mg levels before and after the infusions were measured in both groups. Also, three ROTEM tests: EXTEM, INTEM and FIBTEM were performed before and after the infusions. Baseline mean plasma magnesium levels were within normal range in the control and Mg groups: 2.06 and 2.18 mg/dl, respectively. After magnesium therapy, the mean plasma Mg level in the Mg group increased to 2.78 mg/dl in compared to the control group that was 2.01 mg/dl (P < 0.000). Mean value of the clotting time (CT) in the magnesium group were significantly decreased from 129.50 ± 7.76, 381.86 ± 8.51 and 114.26 ± 6.80 to 86.13 ± 3.4, 209.33 ± 6.68 and 81.56 ± 5.01 in the EXTEM, INTEM, and FIBTEM respectively after intervention in the Mg group (P = 0.001). Among patients with end-stage liver diseases who have ROTEM evidence of hypocoagulability, magnesium could correct CT parameter of the ROTEM tests.

Plasma D-dimer as a novel biomarker for predicting poor outcomes in HBV-related decompensated cirrhosis

This study aim was to evaluate whether plasma D-dimer levels could serve as a novel prognostic biomarker for 1-month mortality in patients with HBV-related decompensated cirrhosis (HBV-DeCi).This was a retrospective study that enrolled 132 HBV-DeCi patients. Univariate and multivariate regression models were used to identify risk factors for mortality. The area under the receiver operating characteristic curve was calculated to estimate and compare the predictive values of different prognostic markers.In the present study, the plasma D-dimer levels were higher in the nonsurviving group than in the surviving group. Additionally, the D-dimer level was positively correlated with the model for end-stage liver disease (MELD) score. The results of multivariate analysis showed that both the MELD score and D-dimer level are independent predictors of 1-month mortality in HBV-DeCi patients (both P < .01).Plasma D-dimer can be considered a new additional prognostic marker for 1-month mortality in HBV-DeCi patients.

The Utility of Thromboelastography to Guide Blood Product Transfusion

OBJECTIVES

To provide an overview of the clot viscoelastic testing technology and to describe its utility in guiding blood product transfusions.

METHODS

A case scenario will be discussed as well as interpretation of thromboelastography (TEG) tracings. In addition, literature examining the utility of viscoelastic testing in guiding patient management and blood product transfusions will be reviewed.

RESULTS

TEG/rotational thromboelastometry (ROTEM) is useful in evaluating clot kinetics in trauma and acutely bleeding patients. TEG/ROTEM parameters are reflective of values measured using standard coagulation assays; however, TEG/ROTEM parameters are more rapidly available and more costly. TEG and ROTEM are used in three main settings: cardiac surgery, liver transplantation, and trauma to assess global hemostasis and administration of blood products.

CONCLUSIONS

TEG/ROTEM can be helpful in guiding resuscitation and blood product transfusion. Several studies have demonstrated a reduction in transfusion of blood components with TEG/ROTEM; however, other studies have suggested that TEG/ROTEM is not clinically effective in guiding transfusion.

The Effects of Liver Disease on Surgical Outcomes Following Adult Spinal Deformity Surgery

BACKGROUND

As the prevalence of chronic liver disease continues to rise in the United States, understanding the effects of liver dysfunction on surgical outcomes has become increasingly important. The objective of this study was to assess the effects of chronic liver disease on 30-day complications following adult spinal deformity (ASD) surgery.

METHODS

We performed a retrospective cohort study of 2337 patients in the 2008-2015 American College of Surgeons National Surgical Quality Improvement Program database who underwent corrective ASD surgery. Patients with liver disease were identified based on a Model for End-Stage Liver Disease-Na score ≥10. A univariate analysis was performed to compare 30-day postoperative complications between patients with and without liver disease. A multivariate regression analysis adjusting for differences in baseline patient characteristics was performed to identify complications that were associated with liver disease.

RESULTS

Patients with liver disease had a significantly greater incidence of postoperative pulmonary complications (6.3% vs. 2.9%; P < 0.001), blood transfusion (34.6% vs. 24.0%; P < 0.001), sepsis (2.2% vs. 0.9%; P = 0.011), prolonged hospitalization (19.0% vs. 8.0%; P < 0.001), as well as any 30-day complication (45.4% vs. 29.4%; P < 0.001). The multivariate regression analysis identified liver disease as a risk factor for prolonged hospitalization (odds ratio [OR] 2.16; 95% confidence interval [CI] 1.64-2.84; P < 0.001), pulmonary complications (OR 1.78; 95% CI 1.16-2.74; P = 0.009), blood transfusion (OR 1.67; 95% CI 1.36-2.05; P < 0.001), and any 30-day complication (OR 1.43; 95% CI 1.15-1.77; P = 0.001).

CONCLUSIONS

The multisystem pathophysiology of liver dysfunction predisposes patients to postoperative complications following ASD surgery. A multidisciplinary approach in surgical planning and preoperative optimization is needed to minimize liver disease-related complications and improve patient outcomes.

Novel insights into the assessment of risk of upper gastrointestinal bleeding in decompensated cirrhotic children

OBJECTIVES

Cirrhotic children wait-listed for liver transplant are prone to bleeding from gastrointestinal varices. Grade 2-3 esophageal varices, red signs, and gastric varices are well-known risk factors. However, the involvement of hemostatic factors remains controversial because of the rebalanced state of coagulation during cirrhosis.

METHODS

Children suffering from decompensated cirrhosis were prospectively included while being on waitlist. Portal hypertension was assessed by ultrasound and endoscopy. Coagulopathy was evaluated through conventional tests, thromboelastometry, and platelet function testing. The included children were followed up until liver transplantation, and all bleeding episodes were recorded. Children with or without bleeding were compared according to clinical, radiological, endoscopic, and biological parameters. In addition, validation of a predictive model for risk of variceal bleeding comprising of grade 2-3 esophageal varices, red spots, and fibrinogen level <150 mg/dL was applied on this cohort.

RESULTS

Of 20 enrolled children, 6 had upper gastrointestinal bleeding. Significant differences were observed in fibrinogen level, adenosine diphosphate, and thrombin-dependent platelet aggregation. The model used to compute the upper gastrointestinal bleeding risk had an estimated predictive performance of 81.0%. Platelet aggregation analysis addition improved the estimated predictive performance up to 89.0%.

CONCLUSIONS

We demonstrated an association between hemostatic factors and the upper gastrointestinal bleeding risk. A low fibrinogen level and platelet aggregation dysfunction may predict the risk of bleeding in children with decompensated cirrhosis. A predictive model is available to assess the upper gastrointestinal bleeding risk but needs further investigations. Clinicaltrials.gov number: NCT03244332.

The risk factors of portal vein thrombosis in patients with liver cirrhosis

This study was designed to identify and assess risk factors for portal vein thrombosis (PVT) in patients with cirrhosis. A total of 98 cirrhosis patients with PVT were identified and 101 cirrhosis patients without PVT were chosen as the control group in this retrospective study. Several variables were measured and the two groups PVT and non-PVT were compared statistically. PVT was identified in 98 patients (10%). Significant differences in hematocrit, international normalized ratio, albumin, bilirubin and glucose were determined between the groups (P<0.05). Out of the thrombophilic risk factors in the patients with PVT factor V Leiden was identified in 8.8%, prothrombin gene 6.6% and methylenetetrahydrofolate reductase 2.2%. There was no difference in survival time between groups (P>0.05).

Pathogenesis and diagnosis of disseminated intravascular coagulation

Several clinical conditions, in particular those associated with a systemic inflammatory response, can cause some degree of activation of coagulation but when the procoagulant stimulus is sufficiently severe and overcomes the natural anticoagulant mechanisms of coagulation, disseminated intravascular coagulation (DIC) may occur. The clinical manifestations of DIC encompass multiorgan dysfunction caused by fibrin-platelet clots in the microcirculation, and bleeding caused by consumption of platelets and coagulation factors. Molecular mechanisms that play a role in inflammation-induced effects on coagulation have been recognized in much detail. Exposure of blood to tissue factor is the most common trigger, whereas the intravascular coagulation is propagated due to loss of function of physiological anticoagulants and impaired fibrinolysis. In patients with DIC, various abnormalities in routine coagulation parameters may be observed, including thrombocytopenia, prolonged global coagulation assays, or high levels of fibrin split products. In addition, more sophisticated tests for activation of individual factors or pathways of coagulation may point to specific involvement of these components in the pathogenesis of the disorder. A combination of readily available tests is usually sufficient in establishing the diagnosis of DIC, and for this purpose, several scoring algorithms have been developed. Some specific clinical situations may elicit coagulation responses that can be distinguished from DIC or may occur in combination with DIC, including dilutional coagulopathy, liver failure-related coagulation derangement, and thrombotic microangiopathies.

Increased factor VIII plays a significant role in plasma hypercoagulability phenotype of patients with cirrhosis

Essentials The role of increased factor VIII in cirrhosis-induced hypercoagulability has never been demonstrated. Factor VIII and protein C effects were characterized by thrombin generation with thrombomodulin. Factor VIII elevation plays a significant role in cirrhosis-induced plasma hypercoagulability. Only protein C and factor VIII normalization led to thrombin generation similar to controls.

SUMMARY

Background In cirrhosis, thrombin generation (TG) studied in the presence of thrombomodulin (TM) indicates plasma hypercoagulability. Although the role of protein C (PC) deficiency has been investigated, the influence of an increase in the factor VIII level has never been addressed. Objectives We investigated the roles of high FVIII and low PC levels in increased TG in the presence of TM. Methods Blood samples were prospectively collected from 35 healthy controls and 93 patients with cirrhosis (Child-Turcotte-Pugh [CTP]-A, n = 61; CTP-B, n = 19; and CTP-C, n = 13) and FVIII levels > 150% (n = 48) and/or PC levels < 70% (n = 88). TG was performed with tissue factor (5 pm), phospholipids, and TM (4 nm). FVIII and PC levels were normalized by adding an inhibitory anti-FVIII antibody and exogenous PC, respectively. Results The endogenous thrombin potential (ETP) in the presence of TM was higher in patients than in controls. After FVIII normalization, the ETP (median) decreased from 929 nm min to 621 nm min (CTP-A), 1122 nm min to 1082 nm min (CTP-B), and 1221 nm min to 1143 nm min (CTP-C); after PC normalization, it decreased from 776 nm min to 566 nm min (CTP-A), 1120 nm min to 790 nm min (CTP-B), and 995 nm min to 790 nm min (CTP-C). The ETP was reduced by 17% and 30%, respectively, but normal TG was not restored. When both FVIII and PC levels were normalized, the ETP decreased from 929 nm min to 340 nm min (CTP-A), 1122 nm min to 506 nm min (CTP-B), and 1226 nm min to 586 nm min (CTP-C), becoming similar to control levels. Conclusion Cirrhosis-induced plasma hypercoagulability, as demonstrated in these experimental conditions, can be partly explained by opposite changes in two factors: PC level (decrease) and FVIII level (increase).

Primary hyperfibrinolysis: Facts and fancies

Fibrinolysis is a complex process that controls both hemostasis and thrombosis. The regulation of the fibrinolytic system is mediated through a wide array of cofactors and inhibitors that maintain the hemostatic balance in a delicate equilibrium. As a consequence, disturbances in the fibrinolysis pathway are associated with various disease states, ranging from thrombotic to hemorrhagic clinical phenotypes. In particular, a number of inherited and acquired disorders are associated with an enhanced fibrinolysis leading to a bleeding tendency that in some cases may be life-threatening. Hyperfibrinolysis has been classified into primary and secondary forms but such differentiation, which may have important treatment implications, is still controversial. This narrative review will be focused on inherited and acquired conditions associated with primary hyperfibrinolysis.

How I treat disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is a condition characterized by systemic activation of coagulation, potentially leading to thrombotic obstruction of small and midsize vessels, thereby contributing to organ dysfunction. At the same time, ongoing consumption of platelets and coagulation proteins results in thrombocytopenia and low concentrations of clotting factors, which may cause profuse hemorrhagic complications. DIC is always secondary to an underlying condition, such as severe infections, solid or hematologic malignancies, trauma, or obstetric calamities. A reliable diagnosis of DIC can be made through simple scoring algorithms based on readily available routine hemostatic parameters. The cornerstone of supportive treatment of this coagulopathy is management of the underlying condition. Additionally, administration of heparin may be useful, and restoration of physiological anticoagulants has been suggested, but has not been proven successful in improving clinically relevant outcomes so far. In patients with major bleeding or at risk for hemorrhagic complications, administration of platelet concentrates, plasma, or coagulation factor concentrates should be considered.

The Coagulation Profile of End-Stage Liver Disease and Considerations for Intraoperative Management

The coagulopathy of end-stage liver disease results from a complex derangement in both anticoagulant and procoagulant processes. With even minor insults, cirrhotic patients experience either inappropriate bleeding or clotting, or even both simultaneously. The various phases of liver transplantation along with fluid and blood product administration may contribute to additional disturbances in coagulation. Thus, anesthetic management of patients undergoing liver transplantation to improve hemostasis and avoid inappropriate thrombosis in the perioperative environment can be challenging. To add to this challenge, traditional laboratory tests of coagulation are difficult to interpret in patients with end-stage liver disease. Viscoelastic coagulation tests such as thromboelastography (Haemonetics Corporation, Braintree, MA) and rotational thromboelastometry (TEM International, Munich, Germany) have helped to reduce transfusion of allogeneic blood products, especially fresh frozen plasma, but have also lead to the increased use of fibrinogen-containing products. In general, advancements in surgical techniques and anesthetic management have led to significant reduction in blood transfusion requirements during liver transplantation. Targeted transfusion protocols and pharmacologic prevention of fibrinolysis may further aid in the management of the complex coagulopathy of end-stage liver disease.

Preoperative Thromboelastography as a Sensitive Tool Predicting Those at Risk of Developing Early Hepatic Artery Thrombosis After Adult Liver Transplantation

BACKGROUND

Whilst causes of hepatic artery thrombosis (HAT) after liver transplantation (LT) are multifactorial, early HAT (E-HAT) remains pertinent complication impacting on graft and patient survival. Currently there is no screening tool that would identify patients with increased risk of developing E-HAT.

METHODS

We analyzed the native procoagulant state of LT recipients, identified through pretransplant thromboelastographic (TEG) data among other known risk factors, to identify risk factors for E-HAT.

RESULTS

The outcomes of 828 adult patients undergoing LT between 2008 and 2013 were analyzed. Overall, 79 (9.5%) patients experienced HAT, E-HAT was diagnosed in 23, and in the remainder this was "late" HAT. The maximum amplitude (MA) on preoperative TEG was significantly higher in patients diagnosed with E-HAT compared with those who did not (71.2 mm vs 57.9 mm; P < 0.0001). Receiver operating characteristic analysis with the cutoff value for MA of 65 mm or greater returned area under the curve of 0.750 (P < 0.001) predicting E-HAT with a sensitivity of 70%. A total of 7% of patients with an MA of 65 mm or greater went on to develop E-HAT (hazard ratio, 5.28; 95% confidence interval, 2.10-12.29; P < 0.001), whereas only 1.2% patients with an MA less than 65 mm experienced E-HAT.

CONCLUSIONS

Preoperative TEG may reliably identify group of recipients at greater risk of developing E-HAT, and intense surveillance and anticoagulation prophylaxis may avoid this serious complication after LT.

Efficacy and safety of pharmacological venous thromboembolism prophylaxis following liver resection: a systematic review and meta-analysis

BACKGROUND

Current guidelines recommend pharmacological prophylaxis for patients undergoing abdominal surgery for malignancy. Liver resection exposes patients to risk factors for venous thromboembolism, but there is a risk of bleeding. The aim of this study is to evaluate the evidence base supporting the use of pharmacological thromboprophylaxis in liver surgery.

METHODS

An electronic search was carried out for studies reporting the incidence of VTE following liver resection comparing patients receiving pharmacological prophylaxis with those who did not. The search resulted in 990 unique citations. Following the application of strict eligibility criteria 5 studies comprise the final study population.

RESULTS

Included studies report on 3675 patients undergoing liver resection between 1999 and 2013. 2256 patients received chemical thromboprophylaxis, 1412 had mechanical prophylaxis only and 7 received no prophylaxis. Meta-analysis revealed lower VTE rates in patients receiving chemical thromboprophylaxis (2.6%) compared to without prophylaxis (4.6%) (Dichotomous correlation test, odds ratio: 0.631 [95% Cl: 0.416-0.959], Fixed model, p = 0.030). Data regarding bleeding could not be pooled for meta-analysis, but chemical thromboprophylaxis was reported as safe in four studies.

CONCLUSION

This systematic review and meta-analysis of retrospective studies indicates that the use of perioperative chemical thromboprophylaxis reduces VTE incidence following liver surgery without an apparent increased risk of bleeding.

Bleeding related to disturbed fibrinolysis

The components and reactions of the fibrinolysis system are well understood. The pathway has fewer reactants and interactions than coagulation, but the generation of a complete quantitative model is complicated by the need to work at the solid‐liquid interface of fibrin. Diagnostic tools to detect disease states due to malfunctions in the fibrinolysis pathway are also not so well developed as is the case with coagulation. However, there are clearly a number of inherited or acquired pathologies where hyperfibrinolysis is a serious, potentially life‐threatening problem and a number of antifibrinolytc drugs are available to treat hyperfibrinolysis. These topics will be covered in the following review.

Blood: tests used to assess the physiological and immunological properties of blood

The properties of blood and the relative ease of access to which it can be retrieved make it an ideal source to gauge different aspects of homeostasis within an individual, form an accurate diagnosis, and formulate an appropriate treatment regime. Tests used to determine blood parameters such as the erythrocyte sedimentation rate, hemoglobin concentration, hematocrit, bleeding and clotting times, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, mean cell volume, and determination of blood groups are routinely used clinically, and deviations outside the normal range can indicate a range of conditions such as anemia, pregnancy, dehydration, overhydration, infectious disease, cancer, thyroid disease, and autoimmune conditions, to mention a few. As these tests can be performed relatively inexpensively and do not require high levels of technical expertise, they are ideally suited for use in the teaching laboratory, enabling undergraduate students to link theory to practice. The practicals described here permit students to examine their own blood and that of their peers and compare these with clinically accepted normal ranges. At the end of the practicals, students are required to answer a number of questions about their findings and to link abnormal values to possible pathological conditions by answering a series of questions based on their findings.

Bleeding complications in critically ill patients with liver cirrhosis

BACKGROUND/AIMS

Patients with liver cirrhosis (LC) are at risk for critical events leading to Intensive Care Unit (ICU) admission. Coagulopathy in cirrhotic patients is complex and can lead to bleeding as well as thrombosis. The aim of this study was to investigate bleeding complications in critically ill patients with LC admitted to a medical ICU (MICU).

METHODS

All adult patients admitted to our MICU with a diagnosis of LC from January 2006 to December 2012 were retrospectively assessed. Patients with major bleeding at the time of MICU admission were excluded from the analysis.

RESULTS

A total of 205 patients were included in the analysis. The median patient age was 62 years, and 69.3% of the patients were male. The most common reason for MICU admission was acute respiratory failure (45.4%), followed by sepsis (27.3%). Major bleeding occurred in 25 patients (12.2%). The gastrointestinal tract was the most common site of bleeding (64%), followed by the respiratory tract (20%). In a multivariate analysis, a low platelet count at MICU admission (odds ratio [OR], 0.98; 95% confidence interval [CI], 0.97 to 0.99) and sepsis (OR, 8.35; 95% CI, 1.04 to 67.05) were independent risk factors for major bleeding. The ICU fatality rate was significantly greater among patients with major bleeding (84.0% vs. 58.9%, respectively; p = 0.015).

CONCLUSIONS

Major bleeding occurred in 12.2% of critically ill cirrhotic patients admitted to the MICU. A low platelet count at MICU admission and sepsis were associated with an increased risk of major bleeding during the MICU stay. Further study is needed to better understand hemostasis in critically ill patients with LC.

Venous Thromboembolism Prophylaxis in Liver Surgery

BACKGROUND

At a recently concluded Americas Hepato-Pancreato-Biliary Association Annual Meeting, a Clinical Practice Guidelines Conference Series was convened with the topic focusing on Venous Thromboembolism (VTE) Prophylaxis in Liver Surgery. The symposium brought together hepatobiliary surgeons from three continents as well as medical experts in hematology and coagulation.

METHODS

The content of the discussion included literature reviews, evaluation of multi-institutional VTE outcome data, and examination of practice patterns at multiple high-volume centers.

RESULTS

Literature review demonstrated that, within gastrointestinal surgery, liver resection patients are at particularly high-risk for VTE. Recent evidence clearly indicates a direct relationship between the magnitude of hepatectomy and postoperative VTE rates, however, the PT/INR does not accurately reflect the coagulation status of the post-hepatectomy patient. Evaluation of available data and practice patterns regarding the utilization and timing of anticoagulant VTE prophylaxis led to recommendations regarding preoperative and postoperative thromboprophylaxis for liver surgery patients.

CONCLUSIONS

This conference was effective in consolidating our knowledge of coagulation abnormalities after liver resection. Based on the expert review of the available data and practice patterns, a number of recommendations were developed.

Oral anticoagulant therapy in atrial fibrillation patients at high stroke and bleeding risk

Atrial fibrillation (AF) is associated with a 5-fold greater risk of ischemic stroke or systemic embolism compared with normal sinus rhythm. Cardioembolic AF-related strokes are often more severe, fatal or associated with greater permanent disability and higher recurrence rates than strokes of other aetiologies. These strokes may be effectively prevented with oral anticoagulant (OAC) therapy, using either vitamin K antagonists (VKAs) or non-vitamin K antagonist OACs (NOACs) such as the direct thrombin inhibitor dabigatran or direct factor Xa inhibitors rivaroxaban, apixaban or edoxaban. Most AF patients have a positive net clinical benefit from OAC, excluding those with AF and no conventional stroke risk factors. Balancing the risks of stroke and bleeding is necessary for optimal use of OAC in clinical practice, and modifiable bleeding risk factors must be addressed. Concerns remain over 'non-changeable' bleeding risk factors such as older age, significant renal or hepatic impairment, prior stroke(s) or prior bleeding event(s) and active malignancies. Such AF patients are often termed 'special' AF populations, due to their 'special' risk profile that includes increased risks of both thromboembolic and bleeding events, and due to fear of bleeding complications these AF patients are often denied OAC. Evidence shows, however, that the absolute benefits of OAC are the greatest in patients at the highest risk, and NOACs may offer even a greater net clinical benefit compared to warfarin particularly in these high risk patients. In this review article, we summarize available data on stroke prevention in AF patients at increased risk of both stroke and bleeding and discuss the use of NOACs for thromboprophylaxis in these 'special' AF populations.

Gastrointestinal endoscopy in the cirrhotic patient

As advances in liver disease continue, including the increasing use of liver transplantation, the endoscopist needs to be familiar with the standards of care and potential complications in the management of the cirrhotic population. This includes both elective endoscopic procedures, such as screening colonoscopies and variceal banding, as well as the acutely bleeding cirrhotic patient. Peri-procedural management and standards of care for acute gastrointestinal hemorrhaging of cirrhotic patients will be emphasized. This article will focus on the plethora of data available to highlight the benefits of endoscopic intervention in the care of patients with liver disease and outline the areas of future emphasis.

Antifibrinolytic amino acids for upper gastrointestinal bleeding in people with acute or chronic liver disease

BACKGROUND

Upper gastrointestinal bleeding is one of the most frequent causes of morbidity and mortality in the course of liver cirrhosis. People with liver disease frequently have haemostatic abnormalities such as hyperfibrinolysis. Therefore, antifibrinolytic amino acids have been proposed to be used as supplementary interventions alongside any of the primary treatments for upper gastrointestinal bleeding in people with liver diseases. This is an update of this Cochrane review.

OBJECTIVES

To assess the beneficial and harmful effects of antifibrinolytic amino acids for upper gastrointestinal bleeding in people with acute or chronic liver disease.

SEARCH METHODS

We searched The Cochrane Hepato-Biliary Controlled Trials Register (February 2015), Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 2 of 12, 2015), MEDLINE (Ovid SP) (1946 to February 2015), EMBASE (Ovid SP) (1974 to February 2015), Science Citation Index EXPANDED (1900 to February 2015), LILACS (1982 to February 2015), World Health Organization Clinical Trials Search Portal (accessed 26 February 2015), and the metaRegister of Controlled Trials (accessed 26 February 2015). We scrutinised the reference lists of the retrieved publications.

SELECTION CRITERIA

Randomised clinical trials irrespective of blinding, language, or publication status for assessment of benefits and harms. Observational studies for assessment of harms.

DATA COLLECTION AND ANALYSIS

We planned to summarise data from randomised clinical trials using standard Cochrane methodologies and assessed according to the GRADE approach.

MAIN RESULTS

We found no randomised clinical trials assessing antifibrinolytic amino acids for treating upper gastrointestinal bleeding in people with acute or chronic liver disease. We did not identify quasi-randomised, historically controlled, or observational studies in which we could assess harms.

AUTHORS' CONCLUSIONS

This updated Cochrane review identified no randomised clinical trials assessing the benefits and harms of antifibrinolytic amino acids for upper gastrointestinal bleeding in people with acute or chronic liver disease. The benefits and harms of antifibrinolytic amino acids need to be tested in randomised clinical trials. Unless randomised clinical trials are conducted to assess the trade-off between benefits and harms, we cannot recommend or refute antifibrinolytic amino acids for upper gastrointestinal bleeding in people with acute or chronic liver diseases.

Prominent protein Z-induced thrombin inhibition in cirrhosis: a new functional assay for hypercoagulability assessment

BACKGROUND AND AIMS

Protein Z (PZ) is an anticoagulant that accelerates the inhibitory effect of PZ-dependent protease inhibitor (ZPI) on coagulation factor Xa. We assessed functional status of PZ system in 158 patients with liver cirrhosis and 59 healthy controls.

METHODS

Plasma PZ and ZPI levels were measured by enzyme immunoassay. Thrombin generation assays (TGA) were performed with and without thrombomodulin (TM) or PZ, and the ratios were calculated by dividing TGA values with TM or PZ by values without TM or PZ.

RESULTS

PZ and ZPI levels were reduced and elevated in advanced cirrhosis, respectively. The lag time ratio-PZ was significantly higher in cirrhosis patients than controls and correlated with the model for end-stage liver disease score. The peak thrombin ratio-PZ and endogenous thrombin potential (ETP) ratio-PZ were significantly lower in cirrhosis patients than controls and correlated with the severity of liver cirrhosis. The peak thrombin ratio-PZ was dramatically reduced in advanced cirrhosis. Cirrhosis patients had a significantly higher ETP ratio-TM than the controls, although the ratio was not correlated with cirrhosis severity. The lag time ratio-PZ and peak time ratio-PZ were significantly correlated with the levels of all coagulation and anticoagulation factors. Interestingly, the lag time ratio-PZ and peak thrombin ratio-PZ were significantly associated with thrombotic events.

CONCLUSION

The anticoagulant role of PZ is insufficient in advanced stages of cirrhosis. Our newly developed functional assay for measuring the PZ system is expected to reflect the ongoing hypercoagulability of cirrhosis.

Coagulopathy in liver disease: a balancing act

Liver disease results in complex alterations of all 3 phases of hemostasis. It is now recognized that hemostasis is rebalanced in chronic liver disease. The fall in clotting factor levels is accompanied by a parallel fall in anticoagulant proteins. High von Willebrand factor levels counteract defects in primary hemostasis. Conventional coagulation tests do not fully reflect the derangement in hemostasis and do not accurately predict the risk of bleeding. Global coagulation assays (thrombin generation, thromboelastography) reflect the interaction between procoagulant factors, anticoagulant factors, platelets, and the fibrinolytic system and show promise for assessing bleeding risk and guiding therapy. These assays are not yet commercially approved or validated. Prevention of bleeding should not be aimed at correcting conventional coagulation tests. Thrombopoietin receptor agonists were shown to increase the platelet count in cirrhotic patients undergoing invasive procedures but may increase the risk of thrombosis. Rebalanced hemostasis in liver disease is precarious and may be tipped toward hemorrhage or thrombosis depending on coexisting circumstantial risk factors. Bacterial infection may impair hemostasis in cirrhosis by triggering the release of endogenous heparinoids. There are no evidence-based guidelines for hemostatic therapy of acute hemorrhage in liver disease. There is currently inadequate evidence to support the use of recombinant FVIIa, prothrombin complex concentrates, or tranexamic acid in acute variceal or other hemorrhage.

Tranexamic acid--an old drug still going strong and making a revival

Experience with tranexamic acid, an indirect fibrinolytic inhibitor, started as soon as it was released from Shosuke Okamoto's lab in the early 1960s. It was first prescribed to females with heavy menstrual blood loss and to patients with hereditary bleeding disorders. Soon the indications were widened to elective surgery because of its blood saving effects. Contraindications are few, most important is ongoing venous or arterial thrombosis and allergy to tranexamic acid, and the doses has to be reduced in renal insufficiency. In randomized controlled trials, however, patients with other risk factors are excluded as well (patients with history of cardiovascular disease, thromboembolism, bleeding diathesis, renal failure with creatinine >250μmol/L, pregnancy, and patients on treatment with anticoagulants). Recent meta-analyses of several randomized controlled trials in orthopedic arthroplasty have shown that tranexamic acid reduces peri- and postoperative blood loss, blood transfusion requirements and reoperations caused by bleedings. In general, the preoperative dose was 10-15mg/kg i.v. (or 1g), followed or not, by one or two doses, some as continuous infusion i.v. To validate relationship between dose and effect more data are needed. No evidence was found of increased thromboembolic accidents or other adverse events in the patients on tranexamic acid compared to the control groups. In major cardiac surgery tranexamic acid has been used in a large number of controlled trials with various dosing schemes in which the highest dosages seem to be associated with neurotoxicity; therefore a maximum total dose of 100mg/kg especially in patients over 50years of age is recommended by ISMICS (International Society for Minimally Invasive Cardiothoracic Surgery). Other indications for tranexamic acid are reviewed here as well. In recent years the extensive trial in severe trauma with massive bleedings using tranexamic acid was presented, CRASH-2 (Clinical Randomisation of an Antifibrinolytic in Significant Haemorrhage) comprising more than 20,000 patients. It showed that the survival was increased when tranexamic acid was given early after the accident compared to placebo; further studies are taking place is this field to get more information. Of utmost importance is the ongoing WOMAN (World Maternal Antifibrinolytic) a randomized, double-blind, placebo controlled trial among 15,000 with clinical diagnosis of postpartum haemorrhage bearing in mind that each year a large number of women in low and middle income countries, die from causes related to childbirth. In summary, we consider tranexamic acid is a drug of great value to reduce almost any kind of bleeding, it is cheap and convenient to use and has principally few contraindications. It may be added, that tranexamic acid is included in the WHOs list of essential medicines.

Deep vein thrombosis and pulmonary embolism in cirrhotic patients: Systematic review

Patients with liver cirrhosis were traditionally believed to be protected against development of blood clots. Lately, studies have shown that these patients may probably be at an increased risk of venous thrombotic complications. Although the hemostatic changes in the chronic liver disease patients and the factors that may predict bleeding vs thrombotic complications remains an area of active research, it is believed that the coagulation cascade is delicately balanced in these patients because of parallel reduced hepatic synthesis of pro and anticoagulant factors. Thrombotic state in cirrhotic patients is responsible for not only portal or non-portal thrombosis [deep vein thrombosis (DVT) and pulmonary embolism (PE)]; it has also been associated with progression of liver fibrosis. The use of anticoagulants in cirrhosis patients is a challenging, and often a scary situation. This review summarizes the current literature on the prevalence of venous thrombosis (DVT and PE), risk factors and safety of prophylactic and therapeutic anticoagulation in patients with chronic liver disease.

Point of care perioperative coagulation management in liver transplantation and complete portal vein thrombosis

Liver transplantation (LT) is a serious hemostatic challenge in patients with portal vein thrombosis (PVT). Advances in monitoring systems have improved surgery in this setting. We report the successful application of a point-of-care (POC) rotational viscoelastic thromboelastometry-guided (TEM) testing system (ROTEM) which allowed management of coagulation during LT in a 64-year-old cirrhotic patient with a model for end-stage liver disease (MELD) score of 16. Perioperatively, the patient showed complete PVT, hepatomegaly, splenomegaly, recanalization of the umbilical vein, and portosystemic shunt. Macroscopic liver and spleen adherences with collateral circulation were evident. Coagulation factors and fibrinolysis were assessed preoperatively and at graft reperfusion to evaluate the need of hemostatic therapy. Based on ROTEM findings, the patient received 16 g of human fibrinogen concentrate, half preoperatively (with prothrombin complex concentrate 2000 IU, tranexamic acid 1 g, and platelets 2 IU), and two doses of 4 g before and after graft reperfusion; we achieved normalization of all monitored parameters. No ischemia-reperfusion syndrome was present. Postoperatively portal vein flux at Color-Doppler ultrasonography was normal. After a 3-day ICU stay, the patient was moved to the Department of Surgery and discharged on day 14. The postoperative course was uneventful and did not require any further haemostatic therapy.

Hematologic manifestations of liver disease

The liver plays a key role in both protein biosynthesis and lipid metabolism. As a result, hepatic synthetic dysfunction can have adverse effects on both cellular and soluble components of blood. Anemia may occur due to the hemolysis of acanthocytes (spur cells), which is ultimately due to abnormal lipid composition of the red blood cell membrane. Thrombocytopenia may result from several different mechanisms. Cytopenias also may be a consequence of hypersplenism. The liver is the primary site for synthesis of most procoagulant and anticoagulant proteins. The coagulopathy of liver disease is therefore complex. Early in the course of liver disease, thrombocytopenia and a coagulopathy associated with a prothrombotic state are not uncommon, whereas with more advanced disease pancytopenia and coagulopathy associated with hemorrhage become manifest. Fresh frozen plasma and adjuncts to hemostasis may be used as temporizing measures in bleeding patients. However, definitive management of many of the defects due to fulminant hepatic failure requires liver transplantation.

Higher prognostic value of soluble fibrin complexes than D-dimer and fibrin degradation product for disseminated intravascular coagulation in patients with liver cirrhosis

Fibrin-related markers may help differentiate disseminated intravascular coagulation (DIC) from liver cirrhosis-associated dysfunctional coagulation. We investigated the significance of three fibrin-related markers [D-dimer, fibrin degradation product (FDP), and soluble fibrin complexes (sFC)] for the assessment of DIC status and prognosis. We classified 235 patients with suspected DIC into two groups according to their condition: the liver cirrhosis group (n = 47) and the no liver cirrhosis group (n = 188). Prothrombin time (PT), and fibrinogen, sFC, D-dimer, antithrombin, and protein C concentrations were measured and DIC scores were calculated using four parameters: platelet count, D-dimer, fibrinogen, and PT. In the liver cirrhosis group, the sFC concentration increased significantly in accordance with DIC score compared with the no liver cirrhosis group, and this increase was more prominent than D-dimer and FDP concentration increases. For the diagnosis of overt DIC in patients with liver cirrhosis, the area under the concentration curve (AUC) was larger for sFC (0.746) than for D-dimer (0.733) and FDP (0.687). Cox analysis also indicated that an elevated sFC concentration is a more significant prognostic factor of DIC than D-dimer or FDP (hazard ratio: 10.78; P = 0.036) in liver cirrhosis group; however, it was not a prognostic factor in the no liver cirrhosis group. sFC is a powerful diagnostic and prognostic marker of DIC in patient with liver cirrhosis. The use of sFC is expected to enhance the diagnosis and prognosis of DIC, particularly in patients with liver cirrhosis.

Preoperative variables associated with transfusion requirements in orthotopic liver transplantation

BACKGROUND

Patients with end-stage chronic liver disease (CLD) and submitted to orthotopic liver transplantation (OLT) usually require blood transfusion during the procedure or in the post-operative period due to hemorrhage. Risk factors for transfusion need are not fully known. This study aimed to identify the factors associated with blood components requirements.

METHODS

In this retrospective study a total of 166 consecutive patients submitted to OLT with the piggyback technique, between 2001 and 2011, were evaluated for number of blood components transfused during surgical procedure and the four subsequent days (total of 5 days). We evaluated the association between the number of units transfused and clinical variables, such as: Child-Turcotte-Pugh (CTP) and MELD scores, hemoglobin concentration (Hb), INR, serum creatinine, bilirubin and albumin concentrations, and total, hypothermic and normothermic time of graft ischemia.

RESULTS

152 (91.6%) Patients were transfused (median of 24 units of blood components). Risk factors for higher blood transfusion requirements were CTP, INR, Hb and total time of graft ischemia. The group with CTP-A score received less blood components than CTP-B/C (11.5 vs 27; P=0.002). The group with Hb<10 required a higher number of blood units (34.5 vs 23; P=0.003). The group with INR<1.5 received less blood units (20.5 vs 31; P=0.012). The group transplanted with a graft exposed to less than the median of 555 min of ischemia received less transfusion (21 vs 27; P=0.03). MELD score and the other factors were not associated with blood requirements.

CONCLUSION

These results demonstrate that CTP, but not MELD score, hemoglobin concentration, INR, and total time of graft ischemia are preoperative variables associated with blood requirements during OLT and in the subsequent days.

Coagulopathies in the PICU: DIC and liver disease

Bleeding in patients in pediatric intensive care units is associated with an increased risk of mortality. Fortunately, most patients with an abnormal coagulation profile do not bleed because this is generally secondary to liver disease or dietary-induced vitamin K deficiency. When the laboratory markers of coagulopathy are the result of disseminated intravascular coagulation, bleeding is common and the risk of mortality extreme. Although interventions directed toward correcting the abnormal coagulation test results are generally initiated, they are also generally either not warranted or not fully successful.

Anticoagulant therapy with the oral direct factor Xa inhibitors rivaroxaban, apixaban and edoxaban and the thrombin inhibitor dabigatran etexilate in patients with hepatic impairment

The direct factor Xa (FXa) inhibitors rivaroxaban, apixaban and edoxaban, and the thrombin inhibitor dabigatran etexilate (dabigatran) have gained approval for use in several indications, most notably for the prevention and treatment of venous thromboembolism (VTE) and for the prevention of stroke in patients with atrial fibrillation. Hepatic impairment can affect the disposition of these anticoagulants considerably not only because of the hepatic metabolism of the direct FXa inhibitors but also because moderate to severely impaired hepatic function will affect coagulation. This review describes the key pharmacological properties of novel oral anticoagulants with special attention to patients with impaired hepatic function. In subjects with moderately impaired liver function (i.e. Child-Pugh classification B), the area under the plasma concentration-time curve (AUC) of rivaroxaban (10 mg single dose) is increased by 2.27-fold, which is paralleled by an increase in FXa inhibition. The AUC of apixaban (5 mg single dose) is increased by 1.09-fold, whereas the AUC of edoxaban (15 mg single dose) is decreased by 4.8 % and the AUC of dabigatran (150 mg single dose) is decreased by 5.6 %. Specific labelling restrictions for rivaroxaban, apixaban and dabigatran regarding impaired hepatic function are based on both the Child-Pugh classification and liver-related exclusion criteria applied in pivotal clinical trials. Rivaroxaban is contraindicated in patients with hepatic disease associated with coagulopathy and clinically relevant bleeding risk, including cirrhotic patients classified as Child-Pugh B and C. Apixaban can be used with caution in patients with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment or in patients with alanine aminotransferase and aspartate aminotransferase levels >2× upper limit of normal (ULN). Apixaban is not recommended in patients with severe hepatic impairment and is contraindicated in those with hepatic disease associated with coagulopathy and clinically relevant bleeding risk. Dabigatran is not recommended in patients with elevated liver enzymes (>2× ULN). Dabigatran is contraindicated in patients with hepatic impairment or liver disease expected to have any impact on survival. Currently, edoxaban is not available in the US or European markets. However, the Japanese label did not restrict use in hepatic dysfunction but advises care in patients with severe hepatic impairment.

Potential usefulness of thrombopoietin receptor agonists in haemophiliacs with thrombocytopaenia due to chronic liver disease

New thrombopoietin receptor agonists (TPO-RA) eltrombopag and romiplostin were initially used for refractory immune thrombocytopaenic purpura, but more recently reported experience shows that they may also be applied to patients with thrombocytopaenia secondary to hepatitis C virus (HCV)-related chronic liver disease (CLD) in certain clinical situations; in haemophilic patients these drugs are always part of a therapeutic approach involving other haemostatic resources required to cover the joint congenital and acquired bleeding diathesis found in these patients. Platelet count elevation before invasive procedures or surgery or prior to and during antiviral therapy involving interferon are the main clinical applications of these drugs; they might also be useful in cases with advanced CLD and severe thrombocytopaenia in order to prevent recurrent bleeding episodes (namely articular and muscular in haemophilic individuals) or reduce bleeding risk in patients with multiple haemorrhagic risk factors. Long-term prophylactic treatment with factor concentrates in such cases is mandatory. There have been some reports of portal or splanchnic thromboses in patients on TPO-RA with CLD, especially in cases undergoing invasive procedures who reach platelet counts at least 200×10/l and often with additional risk factors for thrombosis. For this reason, and although haemophilic patients have an important protection against thrombosis, platelet counts should ideally be maintained between 50 and 100×10/l with dose adjustments carried out as required and initial doses of eltrombopag in patients with moderate or severe CLD, especially in prolonged treatments, should be reduced to 25 g once daily. These new drugs can be a useful adjuvant tool in patients with thrombocytopaenia secondary to CLD.

Intraoperative hypercoagulability during liver transplantation as demonstrated by thromboelastography

Thrombotic complications are more common in liver disease than might be expected because of the coagulopathy described by conventional coagulation tests. Some of these complications may be life-threatening. The phenomenon of hypercoagulation is associated with complications in many populations, but the incidence in liver transplant recipients is unclear. We performed a retrospective database review of intraoperative thromboelastography (TEG) for 124 liver transplant recipients. We assessed the prevalence of hypercoagulation in this group and investigated the relative frequency of both shortened TEG reaction times (R times) and increased net clot strength (G) values. These findings were correlated with thrombotic complications. At the baseline, the prevalence of high G values was 15.53% on native TEG, and the prevalence of shortened R times was 6.80% on native-heparinase TEG. Patients with cholestatic pathologies had particularly high rates of hypercoagulation (42.9% with primary biliary cirrhosis and 85.7% with primary sclerosing cholangitis), but hypercoagulation was also common in patients with fulminant hepatic failure (50%) and nonalcoholic steatohepatitis (37.5%). There was a poor correlation between the TEG R time and the international normalized (INR), with 37.7% of TEG analyses demonstrating a short R time with an INR > 2. Six of the patients developed early hepatic artery thrombosis (5%); 3 of these patients had TEG evidence of high G values (P = 0.25), and 4 had short R times (not significant). In conclusion, intraoperative TEG evidence of high G values and short R times is relatively common in liver transplantation. It is unclear what bearing this condition has on thrombotic complications. Conventional coagulation tests have no ability to diagnose this condition. It is conceivable that such patients may come to harm if hypercoagulability is unrecognized and, therefore, inappropriately managed.

Hypercoagulability as a contributor to thrombotic complications in the liver transplant recipient

Traditionally, perioperative bleeding complications were a major concern during orthotopic liver transplantation, but a tremendous decline in transfusion requirements has been reported over the last decade. In recent years, there has been an increasing awareness towards perioperative thrombotic complications, including liver vessel thrombosis, and systemic venous and arterial thromboembolic events. Whereas a number of these thrombotic complications were previously categorized as surgical complications, increasing clinical and laboratory evidence suggest a role for the haemostatic system in thrombotic complications occurring during and after transplantation. High levels of the platelet adhesive protein von Willebrand factor with low levels of its regulator ADAMTS13, an increased potential to generate thrombin, and temporary hypofibrinolysis are all indicative of increased haemostatic potential after transplantation. Clinical evidence for a role of the haemostatic system in post-operative thromboses includes a higher thrombotic risk in patients with various acquired thrombotic risk factors. Although data on efficacy of anticoagulant therapy after liver transplantation are scarce, one study has shown a significant decrease in the risk for late hepatic artery thrombosis by antithrombotic therapy with aspirin. These findings suggest that antihaemostatic therapy in prevention or treatment of thromboembolic complications after liver transplantation may be relevant. Studies on efficacy and safety of these interventions are required as many of the thrombotic complications have a pronounced negative impact on graft and patient survival.

Prothrombin complex concentrate in the reduction of blood loss during orthotopic liver transplantation: PROTON-trial

BACKGROUND

In patients with cirrhosis, the synthesis of coagulation factors can fall short, reflected by a prolonged prothrombin time. Although anticoagulants factors are decreased as well, blood loss during orthotopic liver transplantation can still be excessive. Blood loss during orthotopic liver transplantation is currently managed by transfusion of red blood cell concentrates, platelet concentrates, fresh frozen plasma, and fibrinogen concentrate. Transfusion of these products may paradoxically result in an increased bleeding tendency due to aggravated portal hypertension. The hemostatic effect of these products may therefore be overshadowed by bleeding complications due to volume overload.In contrast to these transfusion products, prothrombin complex concentrate is a low-volume highly purified concentrate, containing the four vitamin K dependent coagulation factors. Previous studies have suggested that administration of prothrombin complex concentrate is an effective method to normalize a prolonged prothrombin time in patients with liver cirrhosis. We aim to investigate whether the pre-operative administration of prothrombin complex concentrate in patients undergoing liver transplantation for end-stage liver cirrhosis, is a safe and effective method to reduce perioperative blood loss and transfusion requirements.

METHODS/DESIGN

This is a double blind, multicenter, placebo-controlled randomized trial.Cirrhotic patients with a prolonged INR (≥1.5) undergoing liver transplantation will be randomized between placebo or prothrombin complex concentrate administration prior to surgery. Demographic, surgical and transfusion data will be recorded. The primary outcome of this study is RBC transfusion requirements.

DISCUSSION

Patients with advanced cirrhosis have reduced plasma levels of both pro- and anticoagulant coagulation proteins. Prothrombin complex concentrate is a low-volume plasma product that contains both procoagulant and anticoagulant proteins and transfusion will not affect the volume status prior to the surgical procedure. We hypothesize that administration of prothrombin complex concentrate will result in a reduction of perioperative blood loss and transfusion requirements. Theoretically, the administration of prothrombin complex concentrate may be associated with a higher risk of thromboembolic complications. Therefore, thromboembolic complications are an important secondary endpoint and the occurrence of this type of complication will be closely monitored during the study.

TRIAL REGISTRATION

The trial is registered at http://www.trialregister.nl with number NTR3174. This registry is accepted by the ICMJE.

Risk factors for bleeding and clinical implications in patients undergoing liver transplantation

INTRODUCTION

Advanced liver disease is characterized by prolonged global coagulation tests such as prothrombin time (PT). Using Model of End-stage Liver Disease (MELD) score-based allocation, many current transplant recipients show advanced end-stage liver disease with an elevated international normalized ratio (INR). The relationship between abnormalities in coagulation tests and the risk of bleeding has been recently challenged among liver disease patients. In this study we reassessed risk factors for bleeding and the clinical implications for patients who underwent orthotopic liver transplantation (OLT).

METHODS

We studied OLT patients between 2005 and 2011 excluding combined transplantations, retransplantations, or cases due to acute liver failure. We collected prospectively pre-OLT, during OLT, and post-OLT clinical and biochemical data to assess the risk for bleeding using linear regression models.

RESULTS

The strongest predictor of overall survival among 286 patients with a mean follow-up of 32 months was the number of blood transfusions (P = .005). The risk factor for bleeding during surgery investigated by multivariate analysis only showed the INR (P < .001) and the presence of ascites (P = .003) to independently correlate with the amount of blood transfusion. Receiver operation characteristics (ROC) analysis performed to determine the risk for massive blood transfusion (more than 6 units) revealed a cut-off value for INR ≥ 1.6. Appreciation of the operative field by the surgeon during the intervention as "wet" versus "dry", amounts of blood transfusion and fresh frozen plasma, and stay in the intensive care unit (ICU) and in the hospital were all significantly different (P < .001) for patients with INR <1.6 versus INR ≥ 1.6.

CONCLUSIONS

Bleeding during OLT affects the outcome. The risk is independently influenced by the presence of ascites (probably reflecting the degree portal hypertension) and an INR ≥ 1.6. To improve survival after OLT therapeutic interventions should be further explored to reduce the need for blood transfusions.