Management of Coagulation and Anticoagulation in Liver Transplantation Candidates

A narrative review: predicting liver transplant graft survival using artificial intelligence modeling

Liver transplantation is the only treatment for patients with liver failure. As demand for liver transplantation grows, it remains a challenge to predict the short- and long-term survival of the liver graft. Recently, artificial intelligence models have been used to evaluate the short- and long-term survival of the liver transplant. To make the models more accurate, suitable liver transplantation characteristics must be used as input to train them. In this narrative review, we reviewed studies concerning liver transplantations published in the PubMed, Web of Science, and Cochrane databases between 2017 and 2022. We picked out 17 studies using our selection criteria and analyzed them, evaluating which medical characteristics were used as input for creation of artificial intelligence models. In eight studies, models estimating only short-term liver graft survival were created, while in five of the studies, models for the prediction of only long-term liver graft survival were built. In four of the studies, artificial intelligence algorithms evaluating both the short- and long-term liver graft survival were created. Medical characteristics that were used as input in reviewed studies and had the biggest impact on the accuracy of the model were the recipient's age, recipient's body mass index, creatinine levels in the recipient's serum, recipient's international normalized ratio, diabetes mellitus, and recipient's model of end-stage liver disease score. To conclude, in order to define important liver transplantation characteristics that could be used as an input for artificial intelligence algorithms when predicting liver graft survival, more models need to be created and analyzed, in order to fully support the results of this review.

Guidelines for the management of coagulation disorders in patients with cirrhosis

Coagulation management in the patient with cirrhosis has undergone a significant transformation since the beginning of this century, with the concept of a rebalancing between procoagulant and anticoagulant factors. The paradigm that patients with cirrhosis have a greater bleeding tendency has changed, as a result of this rebalancing. In addition, it has brought to light the presence of complications related to thrombotic events in this group of patients. These guidelines detail aspects related to pathophysiologic mechanisms that intervene in the maintenance of hemostasis in the patient with cirrhosis, the relevance of portal hypertension, mechanical factors for the development of bleeding, modifications in the hepatic synthesis of coagulation factors, and the changes in the reticuloendothelial system in acute hepatic decompensation and acute-on-chronic liver failure. They address new aspects related to the hemorrhagic complications in patients with cirrhosis, considering the risk for bleeding during diagnostic or therapeutic procedures, as well as the usefulness of different tools for diagnosing coagulation and recommendations on the pharmacologic treatment and blood-product transfusion in the context of hemorrhage. These guidelines also update the knowledge regarding hypercoagulability in the patient with cirrhosis, as well as the efficacy and safety of treatment with the different anticoagulation regimens. Lastly, they provide recommendations on coagulation management in the context of acute-on-chronic liver failure, acute liver decompensation, and specific aspects related to the patient undergoing liver transplantation.

Direct Oral Anticoagulants versus Vitamin K Antagonists in Cirrhotic Patients with Atrial Fibrillation: Update of Systematic Review and Meta-Analysis

BACKGROUND

Prevention of ischemic stroke is an essential part of managing atrial fibrillation (AF). In recent years, direct oral anticoagulants (DOACs) have emerged as an alternative to vitamin K antagonists (VKAs). Little is understood regarding the efficacy and safety of DOACs in AF patients with liver cirrhosis (LC).

OBJECTIVE

This meta-analysis is designed to evaluate the benefits and risks of DOACs compared to VKAs in AF patients with concomitant LC.

METHODS

A thorough search was conducted in PubMed, Cochrane Library, Web of Science, Embase, Scopus, and CNKI databases up to February 2023. A total of seven clinical studies including 7551 patients were analyzed in this meta-analysis. All data analyses were performed using Review Manager software version 5.3.

RESULTS

Regarding efficacy outcomes, DOACs had comparable clinical benefit in reducing ischemic stroke/systemic thromboembolism (HR=0.79, 95% CI [0.59, 1.06], p = 0.12) to VKAs. The incidence of all-cause death was similar between the DOACs and VKAs group (HR 0.94, 95% CI [0.69, 1.28], p = 0.69). Regarding safety outcomes, DOACs were associated with a significantly lower risk of major bleeding (HR 0.61, 95% CI [0.50, 0.75], p < 0.00001), intracranial hemorrhage (HR 0.55, 95% CI [0.31, 0.98], p = 0.04) and major gastrointestinal bleeding (HR 0.66, 95% CI [0.51, 0.85], p = 0.001) than VKAs. Additional subgroup analysis of advanced cirrhosis revealed that DOACs were associated with a significantly lower risk of major bleeding (HR 0.59, 95% CI [0.39, 0.89], p = 0.01) than VKAs. There were no significant differences between the DOACs and VKAs group concerning the incidence of ischemic stroke/systemic thromboembolism (HR 1.38, 95% CI [0.75, 2.55], p = 0.31) and major gastrointestinal bleeding (HR 0.65, 95% CI [0.41, 1.04], p = 0.08).

CONCLUSION

DOACs are associated with more favorable safety outcomes and may be a feasible option of oral anticoagulant for individuals with atrial fibrillation and cirrhosis. Pending validation by randomized prospective studies, the findings of this study should be interpreted with caution.

Individualized Management of Coagulopathy in Patients with End-Stage Liver Disease

Over the last decades, individualized approaches and a better understanding of coagulopathy complexity in end-stage liver disease (ESLD) patients has evolved. The risk of both thrombosis and bleeding during minimally invasive interventions or surgery is associated with a worse outcome in this patient population. Despite deranged quantitative and qualitative coagulation laboratory parameters, prophylactic coagulation management is unnecessary for patients who do not bleed. Transfusion of red blood cells (RBCs) and blood products carries independent risks for morbidity and mortality, including modulation of the immune system with increased risk for nosocomial infections. Optimal coagulation management in these complex patients should be based on the analysis of standard coagulation tests (SCTs) and viscoelastic tests (VETs). VETs represent an individualized approach to patients and can provide information about coagulation dynamics in a concise period of time. This narrative review will deliver the pathophysiology of deranged hemostasis in ESLD, explore the difficulties of evaluating the coagulopathies in liver disease patients, and examine the use of VET assays and management of coagulopathy using coagulation factors. Methods: A selective literature search with PubMed as the central database was performed with the following.

Blood loss during liver transplantation is a predictor of postoperative thrombosis

Liver transplantation (LT) is an effective way to cure end-stage liver diseases (ESLDs), which have generally been regarded as examples of acquired bleeding disorders. However, postoperative thrombosis after LT is recognised and remains a life-threatening complication. This study aimed to show that blood loss during LT is a predictor of postoperative thrombosis and to establish a predictive model. We analysed the medical records of all patients who underwent LT at the First Affiliated Hospital of Xi'an Jiaotong University from January 2017 to April 2019 to identify the risk factors for post-transplant thrombosis. The predictive nomogram was established based on independent predictors identified by logistic regression analysis. Blood loss during LT of ≥31.25 mL/kg can predict postoperative thrombosis, and the nomogram achieved an accurate prediction.

Safety of direct oral anticoagulants in patients with liver disease: a systematic review and meta-analysis

BACKGROUND

Direct oral anticoagulants (DOACs), such as apixaban, edoxaban, rivaroxaban, or dabigatran, are an effective treatment for atrial fibrillation (AF) and deep venous thromboembolism. We hope to evaluate the safety of DOACs versus warfarin/low molecular weight heparin (LMWH) in improving bleeding events in patients with different severity of the liver disease.

METHODS

We systematically searched the Cochrane Library, PubMed, and Embase databases for studies reporting the effects of DOACs in patients with liver cirrhosis. A random-effects model or fixed-effects model was selected to pool risk ratios (RR) and 95% confidence intervals (CI).

RESULTS

A total of 18 studies involving 41,447 participants was included in this meta-analysis. Compare with warfarin/ LMWH, the use of DOACs significantly reduced the incidence of all bleeding (RR: 0.76; 95%CI: 0.66 to 0.87), major bleeding (RR: 0.51; 95%CI: 0.28 to 0.91), intracranial hemorrhage (RR: 0.50; 95%CI: 0.31 to 0.81), and gastrointestinal bleeding (RR: 0.76, 95% CI: 0.60 to 0.97), and all-cause death in patients with liver disease (RR: 0.77; 95%CI: 0.62 to 0.95). Similar results were observed in atrial fibrillation patients with liver disease and cirrhosis subgroups. Furthermore, the pooled estimates of the Child-Turcotte-Pugh (CTP) class indicated that DOACs reduced the incidence of all bleeding (RR: 0.61; 95%CI: 0.45 to 0.82), gastrointestinal bleeding (RR 0.55; 95%CI: 0.37 to 0.83), and all-cause death (RR: 0.62; 95%CI: 0.49 to 0.79) in patients with mild to moderate cirrhosis.

CONCLUSIONS

Our study demonstrates that DOACs significantly reduce the risk of bleeding in patients with liver disease compared with warfarin/LMWH.

Validation of 5 models predicting transfusion, bleeding, and mortality in liver transplantation: an observational cohort study

BACKGROUND

Historically, orthotopic liver transplantation (OLT) has been associated with massive blood loss, blood transfusion and morbidity. In order to predict such outcomes five nomograms have been published relating to transfusions and morbidity associated with OLTs. These nomograms, developed on the basis of three cohorts of patients consisting of 406, 750, and 800 having undergone OLTs, aimed to predict a transfusion of ≥1 red blood cell unit (RBC), a transfusion of >2 RBC units, a blood loss of >900 ml, as well as one-month and one-year survival rates. The aim of this study was to validate these five nomograms in a contemporary, independent cohort of patients.

METHODS

Five nomograms were previously developed based on 406, 750, and 800 OLTs. In this study we performed a temporal validation of these nomograms on contemporary patients that consisted of three cohorts of 800, 250, and 200 OLTs. Logistic regression coefficients from the historic development cohorts were applied to the three contemporary temporal validation cohorts.

RESULTS

The most accurate nomogram was able to predict transfusion of ≥1 RBC units with an area under the curve (AUC) was 0.91. The second-best nomogram was able to predict bleeding of >900 ml with an AUC of 0.70. T he AUC of the third nomogram (transfusion of >2 RBC units) was 0.70. However, is temporal validation was suboptimal, due to a low prevalence of OLTs transfused with >2 RBC units. The last 2 nomograms exhibited clearly suboptimal AUC values of 0.54 and 0.61.

CONCLUSION

Two of the five nomograms predict blood transfusion and blood loss with excellent accuracy. Transfusion of ≥1 RBC unit and blood loss of >900 ml can be predicted on the basis of these nomograms. However, these nomograms are not accurate to predict one-month and one-year survival rates. These results should be further cross-validated, ideally prospectively, in additional external independent cohorts.

Development of Machine Learning Models Predicting Estimated Blood Loss during Liver Transplant Surgery

The incidence of major hemorrhage and transfusion during liver transplantation has decreased significantly over the past decade, but major bleeding remains a common expectation. Massive intraoperative hemorrhage during liver transplantation can lead to mortality or reoperation. This study aimed to develop machine learning models for the prediction of massive hemorrhage and a scoring system which is applicable to new patients. Data were retrospectively collected from patients aged >18 years who had undergone liver transplantation. These data included emergency information, donor information, demographic data, preoperative laboratory data, the etiology of hepatic failure, the Model for End-stage Liver Disease (MELD) score, surgical history, antiplatelet therapy, continuous renal replacement therapy (CRRT), the preoperative dose of vasopressor, and the estimated blood loss (EBL) during surgery. The logistic regression model was one of the best-performing machine learning models. The most important factors for the prediction of massive hemorrhage were the disease etiology, activated partial thromboplastin time (aPTT), operation duration, body temperature, MELD score, mean arterial pressure, serum creatinine, and pulse pressure. The risk-scoring system was developed using the odds ratios of these factors from the logistic model. The risk-scoring system showed good prediction performance and calibration (AUROC: 0.775, AUPR: 0.753).

A Review of Direct-acting Oral Anticoagulants and Their Use in Solid Organ Transplantation

Direct-acting oral anticoagulant (DOAC) use has increased dramatically since their introduction because of the growing evidence of proven efficacy and enhanced safety compared with warfarin and the low-molecular-weight heparins in the general population. Unfortunately, there is a dearth of quality data regarding the safety and efficacy of the DOACs in patients awaiting organ transplant and those who received a solid organ transplant. This review aims to evaluate the available literature and considerations regarding anticoagulation use in transplant recipients, focusing on preoperative, perioperative, and postoperative DOAC use.

Primary Nonfunction of the Liver Allograft

Severe allograft dysfunction, as opposed to the expected immediate function, following liver transplantation is a major complication, and the clinical manifestations of such that lead to either immediate retransplant or death are the catastrophic end of the spectrum. Primary nonfunction (PNF) has declined in incidence over the years, yet the impact on patient and healthcare teams, and the burden on the organ pool in case of the need for retransplant should not be underestimated. There is no universal test to define the diagnosis of PNF, and current criteria are based on various biochemical parameters surrogate of liver function; moreover, a disparity remains within different healthcare systems on selecting candidates eligible for urgent retransplantation. The impact on PNF from traditionally accepted risk factors has changed somewhat, mainly driven by the rising demand for organs, combined with the concerted approach by clinicians on the in-depth understanding of PNF, optimal graft recipient selection, mitigation of the clinical environment in which a marginal graft is reperfused, and postoperative management. Regardless of the mode, available data suggest machine perfusion strategies help reduce the incidence further but do not completely avert the risk of PNF. The mainstay of management relies on identifying severe allograft dysfunction at a very early stage and aggressive management, while excluding other identifiable causes that mimic severe organ dysfunction. This approach may help salvage some grafts by preventing total graft failure and also maintaining a patient in an optimal physiological state if retransplantation is considered the ultimate patient salvage strategy.

Transcatheter interventions for valvular heart diseases in liver cirrhosis patients

There is an increasing prevalence of patients who have both liver cirrhosis (LC) and severe valvular heart disease. This combination typically poses prohibitive risk for liver transplantation. LC related malnourishment, hypoalbuminemia and hyperdynamic circulation places patients with severe LC at higher rates for significant bleeding and/or thrombosis, as well as infectious and renal complications, after either surgical or transcatheter valvular interventions. Although there remains scarce comparative evidence, the preponderance of data suggest that percutaneous strategies are preferred over surgical ones. A multidisciplinary team is ideal for identifying those patients with LC who would benefit from transcatheter valvular heart interventions.

The utility and complications of plasma administration in cirrhotic patients undergoing minimally invasive procedures

Patients with cirrhosis have coagulopathy often necessitating correction with blood products, such as plasma products (fresh frozen plasma and plasma frozen within 24 h) prior to certain invasive procedures. However, plasma administration has the potential for substantial negative adverse effects such as volume overload, transfusion-related lung injury and allergic/anaphylactic reactions. In addition, its effectiveness in preventing bleeding is similarly unclear. The purpose of this study was to determine the safety and efficacy of plasma administration in cirrhotic patients undergoing minimally invasive procedures, specifically vascular access placement, transjugular liver biopsies, renal biopsies and thoracenteses. In this retrospective cohort study, we identified patients receiving plasma products in preparation for an invasive procedure, with the primary outcomes of volume overload and bleeding. Of the 145 transfusion events that met the criteria from 2015 to 2018, the median INR decreased from 2.7 to 2.2 pre and post plasma administration and 13.8% of recipients had complications of volume overload. The cost of acquisition of plasma administered below clinically impactful doses accumulates to an estimated 19 000 dollars over this time period, not including nursing preparation or production costs. Plasma products minimally, if at all, improved laboratory values of coagulation and in some patients led to adverse effects.

Dabigatran Reversal With Idarucizumab in 2 Patients With Portal Vein Thrombosis Undergoing Orthotopic Liver Transplantation

There are limited data to guide the use of anticoagulation in cirrhotic patients prior to liver transplantation especially when using direct oral anticoagulants. In this article, we present 2 cases. The first is a 42-year-old male with cirrhosis complicated by portal vein thrombosis (PVT) treated with dabigatran who underwent orthotopic liver transplantation without complication. The second case is a 65-year-old man with alcoholic cirrhosis complicated by PVT treated with dabigatran who underwent orthotopic liver transplantation and required reoperation for surgical bleeding. Both patients were treated with dabigatran's reversal agent idarucizumab prior to incision. In this case series, we discuss the treatment of cirrhotic patients with various anticoagulants, considerations for anticoagulant selection and reversal prior to liver transplant, and questions for future investigation.

Effects of Bivalirudin and Unfractionated Heparin on Liver and Renal Function in Chinese Patients with Coronary Artery Disease Undergoing Coronary Angiography with/without Percutaneous Coronary Intervention

BACKGROUND AND AIMS

Unfractionated heparin (UFH) and bivalirudin are widely used as anticoagulants in cardiovascular medicine, including for thrombosis prevention during coronary angiography (CAG) and percutaneous coronary intervention (PCI). Little is known of the effects of UFH and bivalirudin on liver and kidney function in patients subjected to these procedures. This study compared the effects of bivalirudin and UFH on liver/renal function in patients with coronary artery disease who underwent CAG, with or without PCI.

METHODS

The study comprised 134 consecutive patients (40-89 years-old), who underwent CAG (or CAG and PCI); among them, 66 and 68 patients were subject to, respectively, bivalirudin or UFH. The following indicators of liver/renal function were measured before and after the procedures: plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen, estimated glomerular filtration rate (eGFR), creatinine clearance, and serum creatinine. Patients were further stratified by severity of chronic kidney disease (CKD), based on original eGFR.

RESULTS

Relative to baseline, in the bivalirudin group, ALT and AST were higher after CAG (p=0.005, 0.025), while blood urea nitrogen and serum creatinine were lower (p=0.049, <0.001). In the UFH group, ALT, AST, eGFR, and creatinine clearance were lower after CAG (p≤0.001, all). Patients given bivalirudin with moderate or severe CKD, but not those with mild CKD, gained significant improvement in kidney function.

CONCLUSIONS

Relative to UFH, bivalirudin may better safeguard the renal function of patients with coronary artery disease who undergo CAG, especially patients with moderate-to-severe renal insufficiency. UFH may cause less liver damage than bivalirudin.

Perioperative Transfusion is Related to the Length of Hospital Stays in Primary Liver Cancer Patients

Purpose

Blood loss may be corrected with red blood cell transfusion, but may ultimately contribute to negative impacts. This study was a retrospective analysis to assess the impact of perioperative blood transfusion on hospital stay days in liver cancer patients.

Methods

We retrospectively examined data from patients with primary liver cancer who underwent curative resection. Patients were divided into perioperative blood transfusion (PBT) and non-PBT groups. Data were given as means and SDs for continuous variables and as counts and percentage for categorical variables. The correlation between blood transfusion and hospital stay days was analyzed by Fisher's exact test. Multivariable logistic regression analyses were used to identify independent predictors of length of hospital stays.

Results

Totally 206/1031 patients (20.3%) were given perioperative transfusion. The mean length of hospital stay was 17.8 days in PBT and 13.9 days in non-PBT groups. Our multivariable logistic regression showed transfusion, total bilirubin, indirect bilirubin, and the ratio of albumin to bilirubin were all indicators of the length of hospital stay days. Perioperative transfusion was also associated with prolonged length of hospital stays (95% CI: 0.395-0.811, p = 0.002). Transfusion also affected intrinsic coagulation factors (activated partial thromboplastin time, fibrinogen, platelet), inflammatory index (neutrocyte to lymphocyte ratio, monocyte), albumin and bilirubin levels.

Conclusion

Perioperative transfusion of blood was associated with a significantly increased length of hospital stays probably via changing intrinsic coagulation and inflammatory factors and bilirubin levels in plasma.

Safety and Efficacy of Anticoagulation in Patients with Cirrhosis: A Meta-Analysis

BACKGROUND AND AIMS

Portal vein thrombosis is a serious adverse event that occurs during liver cirrhosis. We performed a meta-analysis to evaluate the safety and efficacy of anticoagulant therapy and prophylactic anticoagulant therapy in cirrhosis patients with (/without) portal vein thrombosis.

METHODS

Eligible comparative studies were identified by searching the following electronic databases: PubMed, Embase, Cochrane Library, Web of Science, and CNKI. A meta-analysis was performed to calculate odds ratios and 95% confidence intervals using fixed-effects models. Recanalization and thrombus progression were defined as the primary outcomes. Secondary outcomes included adverse events and death mortality.

RESULTS

A total of 3479 patients were included in this analysis. Compared with the control group, the recanalization rate in the anticoagulant therapy group was increased (P < 0.00001) in patients with cirrhosis and portal vein thrombosis without increasing adverse events. Multiple use of enoxaparin in small doses is safer than single large doses (P=0.004). Direct oral anticoagulants are more effective (P < 0.00001) and safer than traditional anticoagulants. Prophylactic anticoagulant therapy can effectively prevent portal vein thrombosis formation (P < 0.00001).

CONCLUSIONS

Anticoagulation therapy can treat or prevent portal vein thrombosis in patients with liver cirrhosis and is a relatively safe treatment.

Portal vein thrombosis: an overview of current treatment options

Portal vein thrombosis (PVT) is a splanchnic vascular disorder characterised by a recent or chronic thrombotic occlusion of the portal venous system. Its aetiology is miscellaneous, and its management is demanding since PVT can play a critical role as far as morbidity and mortality are concerned. Indeed, PVT can develop as a complication of portal hypertension (PH), in association or not with advanced chronic liver disease, and aggravate its clinical consequences such as variceal bleeding and ascites. Furthermore, a diagnosis of PVT in a non-cirrhotic context can potentially reveal a previously unknown hypercoagulable condition, requiring further diagnostic steps and specific treatment in addition to anticoagulation. In addition to established therapeutic approaches, new strategies, including newer pharmacological treatments and interdisciplinary invasive procedures, gain more attention and have been increasingly introduced into clinical practice. This review aims at discussing the current knowledge in terms of treatment options for PVT.

Mortality and Hepatic Decompensation in Patients With Cirrhosis and Atrial Fibrillation Treated With Anticoagulation

BACKGROUND AND AIMS

Outcomes with anticoagulation (AC) are understudied in advanced liver disease. We investigated effects of AC with warfarin and direct oral anticoagulants (DOACs) on all-cause mortality and hepatic decompensation as well as ischemic stroke, major adverse cardiovascular events, splanchnic vein thrombosis, and bleeding in a cohort with cirrhosis and atrial fibrillation (AF).

APPROACH AND RESULTS

This was a retrospective, longitudinal study using national data of U.S. veterans with cirrhosis at 128 medical centers, including patients with cirrhosis with incident AF, from January 1, 2012 to December 31, 2017 followed through December 31, 2018. To assess the effects of AC on outcomes, we applied propensity score (PS) matching and marginal structural models (MSMs) to account for confounding by indication and time-dependent confounding. The final cohort included 2,694 veterans with cirrhosis with AF (n = 1,694 and n = 704 in the warfarin and DOAC cohorts after PS matching, respectively) with a median of 4.6 years of follow-up. All-cause mortality was lower with warfarin versus no AC (PS matched: hazard ratio [HR], 0.65; 95% confidence interval [CI], 0.55-0.76; MSM models: HR, 0.54; 95% CI, 0.40-0.73) and DOACs versus no AC (PS matched: HR, 0.68; 95% CI, 0.50-0.93; MSM models: HR, 0.50; 95% CI, 0.31-0.81). In MSM models, warfarin (HR, 0.29; 95% CI, 0.09-0.90) and DOACs (HR, 0.23; 95% CI, 0.07-0.79) were associated with reduced ischemic stroke. In secondary analyses, bleeding was lower with DOACs compared to warfarin (HR, 0.49; 95% CI, 0.26-0.94).

CONCLUSIONS

Warfarin and DOACs were associated with reduced all-cause mortality. Warfarin was associated with more bleeding compared to no AC. DOACs had a lower incidence of bleeding compared to warfarin in exploratory analyses. Future studies should prospectively investigate these observed associations.

Prothrombin Complex Concentrate in Liver Transplant Surgery: Correction of Therapeutic Anticoagulation and the Coagulopathy of End-Stage Liver Disease: Case Series

Suggested treatment for active bleeding or invasive procedure prophylaxis has been described in the setting of end-stage liver disease (ESLD) in patients not receiving anticoagulation, and has included fresh frozen plasma (FFP), prothrombin complex concentrates (PCC), platelets, and cryoprecipitate. Today, the therapy for pharmacologically anticoagulated patients with ESLD presenting for liver transplant surgery remains controversial, poorly studied, and physician-dependent. We observed a variety of treatments administered at initiation of liver transplantation to correct acquired coagulopathy at our leading transplant center and present these cases. Three patients receiving preoperative therapeutic anticoagulation with warfarin for acute deep venous thrombosis and/or atrial fibrillation were transfused PCC, FFP, and/or cryoprecipitate for liver or liver-kidney transplant surgery. No thrombotic complications occurred, and one patient required reoperation for hemorrhage. We report data from these cases including estimated blood loss, presence of complications, duration of ICU stay, and length of hospitalization. Perioperative orthotopic liver transplant hematologic management and a review of relevant literature is presented.

Thrombopoietin Receptor Agonists in Patients with Chronic Liver Disease

Thrombocytopenia is one of the most common hematologic complications in cirrhosis. Despite limited data linking platelet count and bleeding risk in patients with cirrhosis, the use of platelets transfusions for invasive procedures has been a common practice. Recently, thrombopoietin (TPO) receptor agonists have been approved for use in patients with chronic liver disease (CLD) undergoing invasive procedures. The aim of this study was to review current literature on bleeding risk in patients with cirrhosis and the use of platelet transfusions and TPO receptor agonists in the context of invasive procedures. PubMed search was conducted to find articles relating to cirrhosis, thrombocytopenia, and new novel treatments for this condition. Search terms included CLD, cirrhosis, thrombocytopenia, bleeding, thrombosis, coagulopathy, hemostasis, and TPO receptor agonists. Romiplostim, eltrombopag, avatrombopag, and lusutrombopag are approved TPO receptor agonists, with avatrombopag and lusutrombopag specifically approved for use in patients with CLD undergoing invasive procedures. In patients with platelet counts < 50,000/mm³, avatrombopag and lusutrombopag increased the platelet counts above this threshold in the majority of treated patients and reduced the frequency of platelet transfusions. At the approved doses, incidence of thrombosis was not increased and therapies were well tolerated. Studies were not powered to assess whether risk of bleeding complications was reduced and the fundamental question of whether correction of thrombocytopenia is warranted in patients undergoing invasive procedures remains unanswered. The use of TPO receptor agonists has resulted in less requirement for platelet transfusions. In patients with cirrhosis undergoing invasive procedures for whom platelet transfusion is planned, TPO receptor agonists are an alternative and avoid the risks associated with transfusions. However, there is need for a thoughtful approach to manage bleeding risk in patients with cirrhosis undergoing procedures, with the consideration of a comprehensive hemostatic profile, the severity of portal hypertension, and the complexity of the invasive procedure to guide decisions regarding transfusions or use of TPO receptor agonists.

How Much Is the Inevitable Loss of Different Coagulation Factors During Blood Product-Free Liver Transplantations?

BACKGROUND

Bloodless liver transplantations (LT) have already been reported, but special characteristics of hemostatic changes remain less defined. The aim of this study was to evaluate the "inevitable" loss of coagulation factors (CF) in blood product-free LT.

METHODS

Blood product and CF concentrate-free LT patient data were analyzed in terms of the first 2 days of perioperative hemostasis kinetics (N = 59). CF levels (FI, II, V, VII, X, and XIII), platelet (PLT) levels, and hemoglobin levels were measured before LT (T1), on arrival at the intensive care unit (T2), and 12, 24, and 48 hours after LT (T3, T4, and T5, respectively). Thromboelastographic (TEG) parameters were determined before and at the end of LT (T1-T2).

RESULTS

Fibrinogen levels decreased by 1.2 ± 0.6 g/L, prothrombin levels by 26% ± 14%, factor V levels by 40% ± 23%, VII levels by 29% ± 19%, and X levels by 39% ± 22% (P < .001). From T2 to T4 fibrinogen increased by 0.9 ± 0.6g/L for 24 hours (P < .001). Factor II, V, and VII levels increased by 20% ± 16%, 31% ± 32%, and 12% ± 27%, respectively, between T3 and T5 (P < .001). However, factor X reached only half of the T1 level (T3-T5, P < .001). Platelet count increased in 34 (58%) patients at T2 (P < .001). The TEG parameters remained in the normal range during LT (T1-T2).

CONCLUSION

The major findings of this study advocate that "inevitable" levels of CF decrease during LT by an average of 1.2 g/L in terms of fibrinogen and 23% to 40% regarding factors II, V, VII, and X. The authors suggest that knowing the "magic numbers" and comparing them against baseline laboratory results might predict the possibility of blood product-free transplant, providing confidence and safety to the surgeon and the anesthetist.

Aortic valve-sparing procedure-a durable choice in liver transplantation recipient

A 44-year old man with aortic regurgitation and aneurysm of the ascending aorta underwent an aortic valve-sparing procedure as a durable treatment before liver transplantation. Since patients with chronic liver failure are at high risk of hemorrhagic complications at time of major surgery, while management of warfarin administration may still represent a concern, the choice of a cardiac procedure which avoids any anticoagulant treatment appeared justified.

In Vitro Evaluation of Pro- and Anticoagulant Drugs in Children with End-Stage Liver Disease Undergoing Liver Transplantation

Background Pro- and anticoagulant drugs are commonly used in pediatric liver transplantation to prevent and treat thrombotic and bleeding complications. However, the combination of baseline hemostatic changes in children with liver disease and additional changes induced by transplantation makes this very challenging. This study aimed to analyze the efficacy of clinically available pro- and anticoagulant drugs in plasma from children undergoing liver transplantation.

Methods In vitro effects of pro- and anticoagulant drugs on thrombin generation capacity were tested in plasma samples of 20 children (≤ 16 years) with end-stage liver disease undergoing liver transplantation, and compared with 30 age-matched healthy controls.

Results Addition of pooled normal plasma had no effect in patients or controls, while 4-factor prothrombin complex concentrate increased thrombin generation in both patients and controls, with enhanced activity in patients. At start of transplantation, dabigatran and unfractionated heparin had a higher anticoagulant potency in patients, whereas 30 days after transplantation low molecular weight heparin was slightly less effective in patients. Effects of rivaroxaban were comparable between patients and controls.

Conclusion This study revealed important differences in efficacy of commonly used pro- and anticoagulant drugs in children with end-stage liver disease undergoing liver transplantation. Therefore, dose adjustments of these drugs may be required. The results of this study may be helpful in the development of urgently needed protocols for strategies to prevent and treat bleeding and thrombotic complications in pediatric liver transplantation.

Assessment and management of coagulopathy in critically-ill patients with liver failure

PURPOSE OF REVIEW

This review provides insight into our current understanding of the pathophysiology and treatment of coagulopathy associated with liver failure, and bleeding risk assessment.

RECENT FINDINGS

Patients with end-stage liver disease (ESLD) have a rebalanced coagulation profile and are at risk for both excessive clotting and bleeding. Hypercoagulability is associated with profound endothelial dysfunction and an increased concentration of liver-independent coagulation factors. Because of this rebalanced coagulation profile, standard laboratory tests have been demonstrated to be ineffective in either predicting and/or guiding the management of coagulopathy. Viscoelastic testing, however, is able to provide a dynamic assessment of clot formation in whole blood and has been demonstrated to be invaluable in both monitoring and management of coagulation problems associated with liver failure. More recently, there is increasing interest in thrombin generation tests to monitor coagulation in patients with ESLD.Multiple institutional protocols for prophylaxis and treatment of ESLD-related thromboses have been developed. High-quality studies evaluating these approaches are lacking.

SUMMARY

Patients with ESLD are at risk for excessive bleeding and clotting. Treatment of any significant coagulopathy should not be based solely on standard laboratory tests. Thrombosis prophylaxis has to be considered in susceptible populations.

Hemostatic Balance in Pediatric Acute Liver Failure: Epidemiology of Bleeding and Thrombosis, Physiology, and Current Strategies

Pediatric Acute Liver Failure (PALF) is a rapidly progressive clinical syndrome encountered in the pediatric ICU which may rapidly progress to multi-organ dysfunction, and on occasion to life threatening cerebral edema and hemorrhage. Pediatric Acute Liver Failure is defined as severe acute hepatic dysfunction accompanied by encephalopathy and liver-based coagulopathy defined as prolongation of International Normalized Ratio (INR) >1.5. However, coagulopathy in PALF is complex and warrants a deeper understanding of the hemostatic balance in acute liver failure. Although an INR value of >1.5 is accepted as the evidence of coagulopathy and has historically been viewed as a prognostic factor of PALF, it may not accurately reflect the bleeding risk in PALF since it only measures procoagulant factors. Paradoxically, despite the prolongation of INR, bleeding risk is lower than expected (around 5%). This is due to "rebalanced hemostasis" due to concurrent changes in procoagulant, anticoagulant and fibrinolytic systems. Since the liver is involved in both procoagulant (Factors II, V, IX, XI, and fibrinogen) and anticoagulant (Protein C, Protein S, and antithrombin) protein synthesis, PALF results in "rebalanced hemostasis" or even may shift toward a hypercoagulable state. In addition to rebalanced coagulation there is altered platelet production due to decreased thrombopoietin production by liver, increased von Willebrand factor from low grade endothelial cell activation, and hyperfibrinolysis and dysfibrinogenemia from altered synthetic liver dysfunction. All these alterations contribute to the multifactorial nature of coagulopathy in PALF. Over exuberant use of prophylactic blood products in patients with PALF may contribute to morbidities such as fluid overload, transfusion-associated lung injury, and increased thrombosis risk. It is essential to use caution when using INR values for plasma and factor administration. In this review we will summarize the complexity of coagulation in PALF, explore "rebalanced hemostasis," and discuss the limitations of current coagulation tests. We will also review strategies to accurately diagnose the coagulopathy of PALF and targeted therapies.