Journal of

Clinical Medicine

Review
Thrombocytopenia and Hemostatic Changes in Acute
and Chronic Liver Disease: Pathophysiology, Clinical
and Laboratory Features, and Management
Rüdiger E. Scharf 1,2

1 Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Harvard Medical School,
Boston, MA 02115, USA
2 Division of Experimental and Clinical Hemostasis, Hemotherapy, and Transfusion Medicine, Blood and
Hemophilia Comprehensive Care Center, Institute of Transplantation Diagnostics and Cell Therapy,
Heinrich Heine University Medical Center, D-40225 Düsseldorf, Germany; rscharf@uni-duesseldorf.de

Abstract: Thrombocytopenia, defined as a platelet count <150,000/µL, is the most common compli-
cation of advanced liver disease or cirrhosis with an incidence of up to 75%. A decrease in platelet
count can be the first presenting sign and tends to be proportionally related to the severity of hepatic
failure. The pathophysiology of thrombocytopenia in liver disease is multifactorial, including (i)
splenomegaly and subsequently increased splenic sequestration of circulating platelets, (ii) reduced
hepatic synthesis of thrombopoietin with missing stimulation both of megakaryocytopoiesis and
thrombocytopoiesis, resulting in diminished platelet production and release from the bone marrow,
and (iii) increased platelet destruction or consumption. Among these pathologies, the decrease in



thrombopoietin synthesis has been identified as a central mechanism. Two newly licensed oral throm-


bopoietin mimetics/receptor agonists, avatrombopag and lusutrombopag, are now available for
Citation: Scharf, R.E.
targeted treatment of thrombocytopenia in patients with advanced liver disease, who are undergoing
Thrombocytopenia and Hemostatic
invasive procedures. This review summarizes recent advances in the understanding of defective
Changes in Acute and Chronic Liver
but at low level rebalanced hemostasis in stable cirrhosis, discusses clinical consequences and per-
Disease: Pathophysiology, Clinical
sistent controversial issues related to the inherent bleeding risk, and is focused on a risk-adapted
and Laboratory Features, and
Management. J. Clin. Med. 2021, 10,
management of thrombocytopenia in patients with chronic liver disease, including a restrictive
1530. https://doi.org/10.3390/ transfusion regimen.
jcm10071530
Keywords: advanced liver disease; bleeding risk; cirrhosis; hemostasis; thrombocytopenia; throm-
Academic Editor: Hugo ten Cate bopoietin receptor agonists/mimetics

Received: 1 February 2021

Accepted: 24 March 2021
Published: 6 April 2021 1. Introduction
Complex disorders of the hemostatic apparatus are present in acute and chronic
Publisher’s Note: MDPI stays neutral
liver disease, involving combined abnormalities of the megakaryocyte-platelet system,
with regard to jurisdictional claims in
coagulation, and fibrinolysis. Apart from coagulation defects (international normalized
published maps and institutional affil-
ratio, INR > 1.5) due to reduced hepatocellular synthetic capacity, thrombocytopenia of
iations.
variable extent is a frequent feature both in acute and chronic liver disease. Importantly, a
decrease in platelet count tends to occur prior to clinical manifestations associated with
progressive liver failure and decompensation. Thus, thrombocytopenia can be a sensitive
noninvasive biomarker of liver disease and be used as a clinical diagnostic tool.
Copyright: © 2021 by the author.
This review covers several aspects of platelet pathology in the context of a defective
Licensee MDPI, Basel, Switzerland.
but at low level rebalanced hemostasis in stable cirrhosis, addresses clinical features and
This article is an open access article
controversial issues, and discusses progress in the management of patients with chronic
distributed under the terms and
liver disease and associated risks.
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).

J. Clin. Med. 2021, 10, 1530. https://doi.org/10.3390/jcm10071530 https://www.mdpi.com/journal/jcm

J. Clin. Med. 2021, 10, 1530 2 of 17

2. Incidence of Thrombocytopenia
An analysis by the Acute Liver Failure Study Group, enrolling 1600 patients, docu-
mented that the median platelet count on admission was approximately 130,000/µL; 60%
of patients had platelets counts <150,000/µL, 35% <100,000/µL, and 10% <50,000/µL [1].
Despite a perceived hemorrhagic diathesis, clinically significant bleeding is rather uncom-
mon in acute liver disease. This observation is confirmed by a recent analysis on adult
1770 patients with acute liver failure by a Dutch Study Group [2]. Despite a median INR
of 2.7 and platelet count of 96,000/µL on admission, hemorrhagic complications occurred
in only 187 patients (11%), including 173 spontaneous and 22 postprocedural bleeding
events. However, 20 subjects among this patient cohort experienced an intracranial hem-
orrhage [2]. Progressive thrombocytopenia in acute liver disease can be an indicator of
impending multi-organ failure, as documented in a retrospective study [3]. Specifically,
an early decrease in platelets (during days 1 to 7 after admission) was proportional to the
grade of hepatic encephalopathy, requirement for treatment with vasopressor agents, and
kidney replacement therapy [3].
In patients with advanced fibrosis or liver cirrhosis, the prevalence of thrombocy-
topenia ranges between 15 and 75% [4–6]. A progressive decrease in platelet count is
considered as a noninvasive indicator for the development of portal hypertension due to
severe liver fibrosis or cirrhosis [7]. Overall, the degree of thrombocytopenia appears to be
proportionally related to the severity of liver disease but is not associated with spontaneous
bleeding, unless platelets counts decrease to <50,000–60,000/µL [8–13].

3. Is Thrombocytopenia a Predictive Parameter of the Bleeding Risk in Chronic

Liver Disease?
Several investigators have suggested that thrombocytopenia may be of predictive
validity regarding hemorrhagic events in patients with cirrhosis. However, data on the
overall significance of lowered platelet counts among this patient population are equivocal.
Thus, a number of studies indicate severe thrombocytopenia (<50,000/µL) to be a predictor
of major bleeding and re-bleeding in the peri-interventional setting [14], while others
cannot confirm an explicit correlation between low platelet counts and the incidence of
periprocedural hemorrhage [6,15]. The conflicting conclusions result, at least in part, from
differences in study populations and procedures.

4. Pathophysiology
Thrombocytopenia in liver disease results from increased splenic sequestration due to
portal hypertension and subsequent hypersplenism [7,8,13,16], decreased thrombopoietin
(TPO) production [6,17–19], and/or from toxic or virus-induced suppression of megakary-
ocytopoiesis [6,19–21]. In the past, low platelet counts in liver disease were mainly at-
tributed to splenic pooling and/or consumption. By contrast, autoantibody-mediated
platelet destruction is of minor importance in most cases with chronic liver disease, but
may be relevant in hepatitis C-induced cirrhosis [6]. In these patients, antiplatelet anti-
bodies are detectable, often at high levels [22]. More recently, the impact of abnormal
rheological conditions, resulting from enhanced portal pressure, is also discussed as an
additional mechanism of increased platelet destruction in chronic liver disease [19]. It is
hypothesized that platelets, upon exposure to high shear stress and subsequent activation,
are rapidly eliminated from the circulation, thereby potentiating thrombocytopenia. How-
ever, this contention is distinct from established high-shear conditions resulting in bleeding
complications due to loss of high-molecular-weight von Willebrand factor [23].
During the past decades, detailed exploration of the association between hepatic
synthesis of TPO and residual hepatic function allowed a more specific insight into the
pathophysiology of thrombocytopenia in liver disease. In fact, TPO levels are near-normal
or even increased in acute hepatic disease [18]. This is in contrast to patients with chronic
liver disease, in whom TPO serum levels are significantly decreased and therefore thought
to be a central pathomechanism to thrombocytopenia in cirrhosis [6,24]. TPO is pre-
J. Clin. Med. 2021, 10, 1530 3 of 17

dominantly synthesized in hepatocytes and, consequently, reduced upon damage to or

destruction of liver cell mass. Importantly, among other cytokines involved, TPO is the
only one, driving both megakaryocytopoiesis and thrombocytopoiesis at all stages of
differentiation and maturation (i.e., from stem cell to multipotent progenitor committed
megakaryocyte progenitor cell, immature and mature megakaryocyte to the formation and
release of platelets) [25]. The availability of TPO receptor agonists in patients with chronic
liver disease and severe thrombocytopenia has therefore been highly anticipated [26,27].
Details on the use of the agents are discussed in the Management Section 9.

5. “Low-Level” Hemostasis—A Defective but Rebalanced System in Liver Disease

Despite the multifaceted hemostatic defects, bleeding episodes due to compromised
hemostasis are relatively infrequent in patients with liver disease. Based on clinical and
systematic laboratory findings, we hypothesized as early as the mid-1980s that a balanced
low-level hemostatic equilibrium due to a concordant reduction in pro- and anti-hemostatic
components is present in stable liver cirrhosis [8,16]. However, this balance is extremely
labile and thus can be easily destabilized by various triggers (e.g., infection, variceal bleed-
ing, decompensated liver cirrhosis, invasive procedures, or inadequate hemotherapy with
prothrombotic components such fresh-frozen plasma, activated prothrombin complex con-
centrates, or recombinant factor VIIa). More recent studies have confirmed our contention
of a rebalanced hemostasis (Figure 1), resulting from a commensurate decline in pro- and
anti-hemostatic factors both in patients with acute and chronic liver disease [28–30].

Figure 1. The concept of rebalanced hemostasis in patients with liver disease. In healthy subjects (A), hemostasis is in stable
equilibrium. In patients with liver disease (B), concomitant changes in pro- and antihemostatic components and pathways
result in rebalance of the hemostatic apparatus despite the quantitative and qualitative disease-related defects, affecting
platelets (primary hemostasis), coagulation (secondary hemostasis), and fibrinolysis. Thus, hemostasis is rebalanced at low
level, but the equilibrium now is extremely labile. In patients with decompensated liver disease (C) and comorbidities,
various stimuli can lead to destabilization and tip the balance toward either bleeding or thrombosis [29]. Modification
of a scheme, taken from Eby and Caldwell [31]. Abbreviations: α2 -AP, α2 -antiplasmin; Antithromb, antithrombin; DIC,
disseminated intravascular coagulation; DVT, deep vein thrombosis; F, factor; PAI-1, plasminogen activator inhibitor-1;
PE, pulmonary embolism; Plt’let, platelet; TAFI, thrombin activatable fibrinolysis inhibitor; t-PA, tissue-type plasminogen
activator; VWF, von Willebrand factor.
J. Clin. Med. 2021, 10, 1530 4 of 17

Moreover, despite decreased procoagulant coagulation factors, thrombocytopenia and

suspected platelet dysfunction, patients with acute or chronic liver disease can display hyperco-
agulable features, which may explain, at least in part, that thrombotic complications are more
common than spontaneous bleeding complications [28–30]. For example, apart from normal
or even enhanced thrombin generation in liver cirrhosis [12,32,33], Stravitz et al., have shown
increased levels of highly procoagulant platelet-derived microparticles [34].
In addition, elevated plasma levels of von Willebrand factor (VWF), typically observed
in chronic liver disease, can compensate for the low numbers of circulating platelets [35] and
may restore primary hemostasis [28,30,32]. Concomitantly, concentrations of ADAMTS13,
a plasma metalloprotease that cleaves high-molecular-weight VWF species into smaller
and less prohemostatic VWF multimers, are decreased in patients with cirrhosis and
thus support VWF-mediated platelet adhesion to the subendothelium at sites of vascular
lesions [32,36]. However, these compensatory mechanisms fail to operate in patients with
end-stage liver disease (Figure 1), in whom prominent bleeding complications remain a
serious concern [32].

6. Platelet Dysfunction in Liver Cirrhosis

Concomitant platelet function defects, as suggested in chronic liver disease, are less
well defined [23]. Generally, it has been assumed that platelet function deteriorates with the
severity of liver disease. Older studies have described in vitro aggregation abnormalities
in response to several agonists [37,38]. Some of the platelet aggregation defects were at-
tributed to elevated levels of fibrinogen/fibrin degradation products or dysfibrinogenemia,
both of which are rather common in chronic hepatitis and cirrhosis. Combined α- and
δ-granule storage pool deficiency, as reported in a small series of patients [39], can impair
platelet function and favor a hemorrhagic diathesis in chronic liver disease. However,
platelets from patients with severe but stable cirrhosis display a normal content of α- and
δ-granule constituents [8,16]. Thus, if at all, storage pool deficiency does not appear to play
a significant role in the pathogenesis of platelet defects in cirrhotic patients. Importantly,
toxic effects of ethanol may also contribute to platelet dysfunction [20]. Other possible
mechanisms include defects in the glycoprotein (GP) Ib of the GPIb-IX-V complex [40],
decreased availability of arachidonic acid and consequently reduced biosynthesis of throm-
boxane A2 [41], increased cholesterol content of the platelet plasma membrane, impaired
transmembrane signaling [41], elevated sialic acid concentration of circulating platelets,
and hypersialylated fibrinogen [8].
Platelet defects resulting from various mechanisms, as outlined above, may remain
compensated and clinically inapparent as long as platelet function (and/or coagulation)
is not inhibited pharmacologically [42]. Therefore, drug-induced platelet dysfunction is a
major concern, specifically in thrombocytopenic patients with liver cirrhosis.
By contrast, antiplatelet antibodies, rather infrequently found in patients with acute
or chronic viral liver disease, appear to be of minor relevance in this setting with regard to
qualitative or quantitative platelet disorders [4]. The diagnosis of impending disseminated
intravascular coagulation (DIC) in patients with liver disease is often difficult to ascertain
because of the multiple hemostatic alterations.

7. Clinical Features of Bleeding in Liver Disease

Bleeding is common among patients with liver disease but less frequent than generally
assumed and also emphasized in traditional textbooks. Hemorrhagic diathesis includes
spontaneous hematomas, oozing from oropharyngeal mucosa, and bleeding upon dental
extraction, skin puncture, or from biopsy sites. Compared with age-matched individuals,
the incidence of non-variceal upper gastrointestinal hemorrhage in patients with liver
disease is estimated to be twice as high as in the general population (50–100 per 100,000
person per year) [43]. By contrast, intracranial bleeding is rare.
Given the fact that about 50% of cirrhotic patients develop gastroesophageal varices
(and that one-third will experience variceal hemorrhage), patients with chronic liver disease
J. Clin. Med. 2021, 10, 1530 5 of 17

are at risk for bleeding complications. This is illustrated by a high in-hospital mortality rate
of approximately 15% for each episode of acute gastrointestinal hemorrhage, and variceal
bleeding is the cause of death for approximately 6% of patients with liver cirrhosis [31].
Predictors of a first upper gastrointestinal bleeding in cirrhotic patients include presence of
varices, elevated variceal pressure, and laboratory evidence of decreased hepatocellular
synthesis (with or without manifest coagulopathy), and thrombocytopenia.
Moderate or severe bleeding complications reported after percutaneous liver biopsy
are consistently low with rates of 0.5 to 0.7% in large contemporary series [31,44]. However,
these findings should be considered with caution since most of the data from these studies
are derived from patients in relatively stable or compensated condition of advanced liver
disease. This is also true for attempts to correlate hemostasis test results with clinical
outcome or prediction of bleeding in the setting of invasive procedures.
Drugs represent the most common cause of acquired platelet dysfunction in our
overmedicated society. Apart from typical antiplatelet agents such as aspirin, adenosine
diphosphate receptor antagonists, and integrin αIIbβ3 (GPIIb-IIIa) receptor blockers, other
widely used agents, including non-steroidal anti-inflammatory drugs, antibiotics, cardio-
vascular and lipid-lowering drugs, selective serotonin reuptake inhibitors, and a plethora
of miscellaneous agents, diets, and food additives or spices can affect platelet function and
cause or aggravate a hemorrhagic diathesis [42].

8. Laboratory Assessment of Bleeding Risk in Liver Disease

8.1. Hemostasis Screening Tests—Often Inconclusive
Analysis of hemostasis in patients with advanced liver disease remains crucial for
correct diagnosis, management decisions, assessment of bleeding risk, and monitoring
of treatment, specifically of hemotherapy. However, most routine laboratory hemostasis
tests are not really suitable to predict bleeding. For example, prolongation of bleeding
time is found in about 40% of cirrhotic patients but a poor predictor of hemorrhage after
percutaneous liver biopsy [31]. Moreover, screening coagulation tests are imprecise and
display potentially misleading results in advanced liver disease. In particular, prothrombin
time (INR) is of limited predictive value with regard neither to the bleeding nor to the
thrombotic risk in a given patient. Thus, an elevated INR only reflects a reduction in
procoagulant coagulation factors due to decreased hepatocellular synthesis but not the con-
comitant decline in anticoagulant activity of the protein C pathway. Alternative methods
such as thrombin generation assays might not be routinely available and have not been
sufficiently validated to be recommended as replacements for INR. This is in contrast to
thromboelastography (TEG), a viscoelastic assay that more closely reflects global hemosta-
sis in vivo. Importantly, TEG may overcome some of the limitations or shortcomings of
standard coagulation tests in patients with acute and chronic liver disease [45].

8.1.1. Thromboelastography
TEG allows to dissect the kinetic conversion of fibrinogen into fibrin, the dynamics
of fibrin- and platelet-driven clot formation, and the assessment of clot strength and clot
stability. TEG can also be helpful for detecting abnormal fibrinolysis.
TEG is now widely used in patients with acute and chronic liver disease, specifically
in subjects undergoing liver transplantation to guide replacement therapy with hemo-
static factor concentrates (during the pre-anhepatic and anhepatic phases) and to monitor
treatment of hyperfibrinolysis. However, neither the TEG method nor the hemotherapeu-
tic consequences for correction of TEG parameters are consistently standardized across
transplantation centers [45].
Interestingly, patients with cirrhosis secondary to cholestatic liver disease such as
primary biliary cirrhosis (PBC) or primary sclerosing cholangitis (PSC) have been found to
be hypercoagulable by TEG when compared to patients with noncholestatic entities [46,47].
This difference may be due to higher levels of fibrinogen and a still intact platelet function
in the cholestatic stetting despite similar degrees of portal hypertension in the different
J. Clin. Med. 2021, 10, 1530 6 of 17

patient populations [48]. Taken together, these observations may explain the lower rates of
bleeding complications and fewer transfusion needs during liver transplantation in patients
with PBC or PSC than in those with end-stage liver disease of other etiology. Moreover,
several studies have demonstrated that TEG parameters indicative of hypocoagulation
and/or thrombocytopenia are associated with liver disease severity and outcomes [49–51].

8.1.2. Standardization and Validation of Whole Blood Viscoelastic Assays

Most investigations suggest that analysis of patients with acute and chronic liver
disease by TEG provides a more reliable assessment of the hemorrhagic risk than standard
coagulation assays and determination of the bleeding time. However, only a few studies
have directly compared the results of standard coagulation and viscoelastic assays. Overall,
a poor correlation between test parameters of both approaches was reported [52].
During the past years, attempts have been made to implement standardization of
viscoelastic testing in a variety of clinical conditions including acute and chronic liver
disease [53]. Two commercially devices are currently used: the TEGTM (TEG500 and
TEG6s) and ROTEM (with a number of different modules including ROTEM platelet). The
clinical utility and reliability of thromboelastography have recently been assessed in a
prospective validation study [54]. Moreover, thromboelastographic reference ranges within
a population of cirrhotic patients undergoing liver transplantation are now proposed [55].

8.2. MELD Score

The model for end-stage liver disease (MELD), initially created in 2000 by investigators
from the Mayo Clinic to predict survival in patients with portal hypertension undergoing
placement of transjugular intrahepatic portosystemic shunts (TIPS) [56], and subsequent
refinement modifications of the MELD score are being broadly used to predict survival and
bleeding complications in a variety of patient cohorts with liver disease of different etiology
and distinct interventions [57,58]. MELD incorporates three widely available variables
(INR, serum creatinine, and serum bilirubin). Thus, the score is affected by variability and
interlaboratory variation of INR determinations [31], which in turn specifically limits its
application to predict bleeding complications along with invasive procedures [59]. Conse-
quently, most physicians are left in the difficult position of relying on clinical assessment
of the individual bleeding risk when deciding whether or not to administer potentially
harmful hemotherapy or hemostatic treatment.

8.3. Platelet Thresholds—Not Based on High-Quality Data

By contrast to screening coagulation tests, thrombocytopenia can be an indicator of
increased hemorrhagic risk in patients with liver disease. As documented by a number
of retrospective case series [31,60,61], bleeding complication rates after percutaneous liver
biopsies are higher at platelet counts <50,000/µL. Based on these data, most recognized
centers in Europe require preprocedural platelet counts >80,000/µL, whereas a survey
of US centers showed a preference for a platelet threshold of >50,000/µL [60]. Thus, the
evidence for a valid “cutoff” value remains scanty.
A very recent re-evaluation of published studies has revealed the paucity of data to
recommend a “safe” minimum platelet number for invasive procedures in patients with
chronic liver disease [61]. Importantly, in a large retrospective study of patients having
percutaneous liver biopsy, implementation of less stringent preprocedural hemostasis
parameters (INR < 2.0, platelet counts >25,000/µL) was associated with fewer hemorrhagic
complication rates and a decrease in preprocedural administration of fresh-frozen plasma
and platelet concentrates in comparison with using “historical” cut-off levels (INR < 1.5,
platelet counts > 50,000/µL) [62]. A possible explanation for this apparent contradiction is
that INR and platelet counts are surrogate markers of liver fibrosis and/or portal hyper-
tension, which per se may be risk factors for bleeding. Such a contention would provide a
plausible reason that attempts to correct hemostatic changes can increase the hemorrhagic
risk since defective hemostasis is not necessarily the underlying cause of bleeding, and
J. Clin. Med. 2021, 10, 1530 7 of 17

increasing the intravascular volume is likely to be counterproductive [61]. As discussed

below, transfusion-associated circulatory overload is a major concern in the management
of patients with chronic liver disease.

9. Management of Thrombocytopenia in Patients with Liver Disease

Generally, the approach to bleeding in patients with acute or chronic hepatic dis-
ease can be divided into supportive measures, prophylactic treatment prior to invasive
procedures, and in rescue therapy for active bleeding. In particular, management of throm-
bocytopenia in cirrhotic patients is a challenging task for physicians both in the in- and
out-patient setting.

9.1. Hemotherapy with Platelet Concentrates

Until recently, transfusion of platelets has been a gold standard for the management
of thrombocytopenia in liver disease patients. Generally, two types of platelet concentrates
are available for hemotherapy: single-donor apheresis platelet concentrates (SDAPC) and
pooled whole blood-derived platelet concentrates (PPC) that are obtained from 4 to 6
donors and prepared either using the platelet rich plasma (PRP-PC) or the buffy coat
(BC-PC) method [63–65]. There is ongoing debate on whether or not SDAPC are superior
to PPC, specifically with regard to individuals, who frequently require multiple platelet
transfusions such as cirrhotic patients [66–70]. Of note, SDAPC are preferentially used in
France, Germany, and the UK, whereas in the USA more than 90% of platelet transfusions
are performed using pooled PRP-PC.

9.2. Limitations of Platelet Transfusions

Despite advances in pathogen safety, platelet collection, preparation technologies,
and storage modalities, potential risks associated with hemotherapy persist, including
infection, alloimmunization, febrile non-hemolytic effects, hemolysis, and transfusion-
related acute lung injury (TRALI). Refractoriness to platelet transfusions resulting from
HLA alloimmunization is a serious complication in up to 50% of patients, who permanently
require hemotherapy with platelets. Another concern in cirrhotic patients results from
the fact that transfused platelets are rapidly sequestered in the spleen leading to low
increments. Consequently, transfusion therapy is only effective in the short term.

9.3. Prophylactic or “On-Demand” Platelet Transfusions

Facing with low platelet counts and the hemorrhagic risk, most physicians are inclined
to reach “near-normal” platelet levels in patients with acute or chronic liver disease. Thus,
prophylactic platelet transfusions are common practice “to warrant safety and optimal
care”. However, as outlined above (Section 8 Laboratory Assessment), no evidence-based
“trigger” for platelet transfusions exists. Consequently, guidelines from various societies
provided only weak recommendations with regard to platelet count threshold levels at
which “platelet transfusions should be considered” prior to scheduled invasive procedures.
Very recent guidelines from the British Society of Gastroenterology, the Royal College of
Radiologists, and the Royal College of Pathology and from the American Gastroenterol-
ogy Association now define a uniform but still empirical “cut-off” with a platelet count
of >50,000/µL as threshold needed prior to high-risk procedures/interventions [61,71].
Outside the interventional setting, no prophylactic platelet transfusions should be initi-
ated to prevent patients from being subjected to unnecessary transfusions that provide no
additional benefit [72].
By contrast, treatment with SDAPC or PPC remains a cornerstone of rescue therapy
for active bleeding in patients with hepatic failure. As discussed below, additional plasma-
derived or recombinant products such as fibrinogen concentrate or activated factor VIIa
(rFVIIa) may be required to control severe hemorrhagic complications in the majority of
patients.
J. Clin. Med. 2021, 10, 1530 8 of 17

9.4. Thrombopoietin (TPO) Receptor Agonists

The use of TPO receptor agonists/mimetics has provided substantial progress in the treat-
ment of acquired thrombocytopenia in various conditions, including liver disease [25,73–79].
Among the four available agents, two of them, avatrombopag and lusutrombopag, received
approval in 2018 by the Food and Drug Administration for treating thrombocytopenia in
patients with chronic liver disease needing a scheduled invasive procedure [80,81]. Both second-
generation TPO receptor agonists are orally administered drugs.

9.4.1. Avatrombopag
In two seminal, identically designed, double-blind, randomized, placebo-controlled
phase-3 trials, ADAPT-1 and ADAPT-2, avatrombopag was demonstrated to be superior to
placebo in reducing the need for platelet transfusions or any rescue therapy for bleeding
in 435 patients with thrombocytopenia and chronic liver disease undergoing a scheduled
invasive procedure [82]. In both studies, patients were stratified into two groups based on
lower (<40,000/µL) or higher (>40,000/µL to <50,000/µL) baseline platelet count levels.
The efficacy of avatrombopag was documented in both cohorts with a significantly greater
proportion in drug-treated than in corresponding placebo groups (Table 1). Upon ad-
ministration of the TPO receptor agonist (40 or 60 mg daily for 5 days), platelet counts
increased with a peak effect between days 10 and 13 and returned to baseline levels by day
35 [82]. The overall safety profile was similar for avatrombopag and placebo, except for
hyponatremia reported as the most serious adverse effect.

Table 1. Efficacy of second-generation TPO receptor agonists for the treatment of thrombocytopenia in patients with chronic
liver disease scheduled for invasive procedures. Synopsis of results from four multicentric, randomized, double-blind,
placebo-controlled phase-3 trials [82–84].

N of Patients Baseline Outcome

Agent Trial Dosing
(Drug/Placebo) Platelet Count Percentage of Responders *
Avatrombopag Drug Placebo
60 mg/d for 5 d <40,000/L 65.6% 22.9%
ADAPT-1 n = 231 (149/82)
=40,000/µL to
40 mg/d for 5 d 88.1% 38.2%
<50,000/µL
60 mg/d for 5 d <40,000/L 68.6% 34.9%
ADAPT-2 n = 204 (128/76)
=40,000/µL to
40 mg/d for 5 d 87.9% 33.3%
<50,000/µL
Lusutrombopag Drug Placebo
L-PLUS-1 n = 96 (48/48) 3 mg/d for 7 d <50,000/µL 79% 12.5%
n = 215
L-PLUS-2 3 mg/d for 7 d <50,000/µL 64.8% 29.0%
(108/107)
* Responders were defined as patients not requiring platelet transfusion or rescue therapy for bleeding through 7 days after the invasive procedure.

9.4.2. Lusutrombopag
Efficacy and safety of lusutrombopag were assessed in two randomized, double-
blind, placebo-controlled trails, L-PLUS-1 and L-PLUS-2, enrolling 96 and 215 cirrhotic
patients undergoing invasive interventions, respectively [83,84]. Key endpoints of the
studies were avoidance of preprocedure platelet transfusions (L-PLUS-1 and -2), avoidance
of rescue therapy for bleeding (L-PLUS-2), and number of days with platelet counts
>50,000/µL (L-PLUS-2). Both trials showed that lusutrombopag (3 mg once daily for up to
7 days) was effective in achieving and maintaining the target platelet count in patients with
thrombocytopenia (<50,000/µL) and chronic liver disease (Table 1). The median time to
reach peak levels in platelet counts was 12 days, and the median duration of platelet levels
over the threshold lasted 19 days [84]. No significant safety concerns were raised in both
J. Clin. Med. 2021, 10, 1530 9 of 17

trials. The most common adverse effect of lusutrombopag was headache, while the most
common serious adverse event was portal-vein thrombosis [84]. However, the number of
thrombotic complications did not differ between drug- and placebo-treated patients (two
in each group).

9.4.3. Treatment Algorithm for the Management of Thrombocytopenia in Liver Disease

In the light of new options given by the availability of safe and efficacious agents,
Saab and Brown recently proposed a treatment algorithm [25] based on the original version
by Gangireddy et al. [85]. Core elements of the updated modification (Figure 2) include (i)
stratification of patients according to their degree of thrombocytopenia (with a “wait and
re-examine” strategy for those with mild decrease in platelet count), (ii) administration
of a TPO receptor agonist as first-line, and (iii) transfusion of platelet concentrates as
second-line treatment or “back-up” option for high-risk patients, major surgery, or rescue
therapy for patients with active hemorrhage.

Figure 2. Proposed management of mild, moderate, and severe thrombocytopenia in patients with chronic liver disease.
Displayed is the compilation of a treatment algorithm, originally designed by Gangireddy et al. [85] and subsequently
adapted by Saab and Brown [25]. In this modification, administration of plasma products (e.g., fibrinogen concentrate,
activated factor VII, prothrombin complex concentrate) as rescue therapy for active bleeding is omitted for clarity. To confirm
no need for treatment, patients with mild thrombocytopenia should have periodic re-examination including complete blood
screening. Of note, for moderate and severe thrombocytopenia, the use of TPO receptor agonists is now considered as
first-choice treatment option, whereas platelet transfusions are restricted to major surgery and control of active hemorrhage.
The star indicates that, upon platelet transfusion, a target platelet count >100,000/µL is aimed at. Abbreviations: CBC,
complete blood cell count; DIC, disseminated intravascular coagulation; LFT, liver function testing; PSE, partial splenic
embolization; TCP, thrombocytopenia; TPO, thrombopoietin.

It must be stressed, however, that the proposed treatment algorithm displayed in

Figure 2 should be considered as a provisional recommendation, which requires careful
evaluation and validation before becoming clinical practice. Specifically, caution is ad-
vised at this time regarding the use of TPO receptor agonists in patients with moderate
thrombocytopenia when in critical conditions such as intracranial bleeding.
J. Clin. Med. 2021, 10, 1530 10 of 17

9.4.4. Thrombotic Risk in Chronic Liver Disease Patients upon Treatment with TPO
Receptor Agonists
Thrombotic events are a key safety concern with the use of either platelet transfusions
or the administration of TPO receptor agonist to raise platelet counts in cirrhotic patients
with severe thrombocytopenia. For example, a phase-3 trial using eltrombopag in this
condition prior to invasive procedures was prematurely terminated because of an increased
rate of thrombotic complications [27]. However, by contrast to subsequent trials evaluat-
ing second-generation TPO receptor agonists in chronic liver disease, eltrombopag was
assessed by the ELEVATE (Eltrombopag Evaluated for its Ability to Overcome Thrombocy-
topenia and Enable Procedures) study group without abdominal imaging for splanchnic
thrombosis at baseline. Thus, it is possible that some of the patients had a subclinical
portal-vein thrombosis at study entry [27].
Several recent reviews and meta-analyses of studies (including more than 2200 pa-
tients in total) that compared the effect of three TPO receptor agonists (eltrombopag,
avatrombopag, and lusutrombopag) and placebo in patients with chronic liver disease and
thrombocytopenia reported on a trend toward increased risk of portal-vein thrombosis
upon preprocedural treatment with the TPO receptor agonist (1.6% overall for the drugs
vs. 0.6% for placebo) [25,86–88]. However, this difference was not statistically significant.
Interestingly, a significant association between portal-vein thrombosis and TPO receptor
agonist was shown for eltrombopag alone but not with avatrombopag or lusutrombopag
treatments. In accord with these results, Michelson et al., reported that avatrombopag
leads to an approximately two-fold increase in platelet counts but not in platelet activation
among thrombocytopenic patients with liver disease [89].
Another analysis reviewed the number of arterial and venous thromboembolic events
in more than 1700 patients treated with either eltrombopag or placebo in the preprocedural
setting and identified a significantly higher rate of thromboembolic events in patients
treated with eltrombopag (3.6%) than in those with placebo (1.1%) [25]. Overall, there are
differences among oral TPO receptor agonists regarding their thrombotic potential, with
eltrombopag carrying a significant thrombotic risk. However, this conclusion is questioned
by others due to the fact that eltrombopag, as discussed above, was studied in the ELEVATE
trial without appropriate pre-screening for portal-vein thrombosis [90].

9.4.5. Medico-Economic Evaluation of Treatment with TPO Receptor Agonists vs.

Platelet Transfusion
Several studies have assessed the clinical effectiveness in relation to the estimated cost-
effectiveness of avatrombopag, lusutrombopag, and platelet transfusions. Some results of
these analyses are equivocal or conflicting [91–94]. For example, Mladsi et al., reported that
avatrombopag reduced the need for platelet transfusions and thus produced cost-savings
compared with platelet transfusion (80% fewer prophylactic platelet transfusions, USD
4250 lower costs) or lusutrombopag (42% fewer platelet transfusions, USD 5820 lower
costs) [91,92]. Others concluded from their cost-effectiveness analysis that avatrombopag
and lusutrombopag are more expensive than no TPO receptor agonist over lifetime, as
savings from avoiding platelet transfusions are exceeded by the drug cost and appear to be
without long-term health benefits [93]. However, such a contention disregards that platelet
transfusions are inappropriate as a sustained management option in patients with chronic
liver disease.

10. Management of Hemostasis in Patients with Liver Disease

10.1. General Supportive Measures
Several general measures should be considered to stabilize or improve hemostasis
in patients with liver disease, specifically in those with decompensated cirrhosis. Among
others, these measures include: (i) control of the viral load (hepatitis B, C, or E virus),
(ii) prevention and appropriate treatment of bacterial infection(s), (iii) therapy of renal
dysfunction, and, importantly, (iv) avoidance of volume extension to reduce any side-effects
J. Clin. Med. 2021, 10, 1530 11 of 17

on portal pressure and collateral vessels, in particular, varices. Indeed, understanding

that volume extension increases portal pressure and promotes or exacerbates manifest
bleeding in cirrhotic patients has had a significant impact on their management. Overall,
this contention has promoted the concept of a “low-volume” approach to patients with
chronic liver disease [31].

10.2. Additional Options for Supportive Hemotherapy to Bleeding Patients with Liver Disease
In accord with the “low-volume” concept but by contrast to common practice, a restric-
tive transfusion regimen is required in patients with liver disease to avoid prohemostatic
hemotherapy and treatment-induced thrombotic complications or alloimmunization with
resulting platelet refractoriness. Consequently, recent UK and US guidelines strongly
recommend that blood products should be used sparingly in patients with acute or chronic
liver disease [61,71].
Apart from the hemotherapy-induced increase of portal pressure, the risk of transfusion-
associated circulatory overload, transfusion-related acute lung injury (TRALI), transmission
of pathogens, alloimmunization, and/or transfusion reactions are major concerns. For man-
agement of active bleeding or high-risk invasive procedures the following transfusion
thresholds are currently recommended to improve hemostasis in advanced liver disease:
hematocrit >25%, platelet count >50,000/µL, and fibrinogen >120 mg/dL [61]. Of note,
previously used thresholds for correction of the INR are no longer recommended since
target reductions of INR are not supported by evidence.

10.2.1. Fresh-Frozen Plasma (FFP)

Upon administration at common dosing (10 mL/kg), FFP has minimal effect on defec-
tive coagulation; only 10% of cirrhosis patients reach a reduction in INR [31]. The large vol-
ume of FFP required to reach an arbitrary INR target and to improve thrombin generation
causes circulatory overload, thus limiting the indication and usefulness of FFP considerably.

10.2.2. Prothrombin Complex Concentrates (PCCs) and/or Fibrinogen Concentrates

Replacement therapy with 4-factor (F) PCCs containing FII, FIX, FVII, and FX along
with variable amounts of proteins C, S, and Z offers an attractive option to restore vitamin
K-dependent coagulation factors with minimal volume.
In addition, whenever indicated (e.g., FI levels < 80 mg/dL), targeted substitution of
fibrinogen using fibrinogen concentrates (e.g., HaemocomplettanTM , initial dosing 2 g or
30 mg/kg) should be considered and monitored by appropriate monitoring of coagulation
and platelet function testing (e.g., by aggregometry). Two recent retrospective single-
center studies confirm that hemotherapy with PCCs (and co-administration of fibrinogen
concentrate) is safe and effective in patients with acute or chronic liver disease and liver
transplantation [95,96]. Importantly, the rate of thromboembolic events in association with
coagulation factor replacement therapy was less than 3% [95]. However, these treatment
options must not be generalized.
By contrast, special caution and careful decision making are required. As discussed
above (see Section 8 “Low Level” Hemostasis and Figure 1), patients with stable liver
cirrhosis display a labile low-level equilibrium of pro- and anti-hemostatic components
that is highly susceptible to pathogenic triggers such as inappropriate hemotherapy [8,16].
Specifically, decompensated liver disease can lead to increased consumption of coagulation
factors, including progressive hypofibrinogenemia and progressive thrombocytopenia,
often associated with hyperfibrinolysis [16,28]. Elevated levels of platelet, coagulation
and fibrinolysis activation markers may be indicative of their defective clearance [29],
mainly due to the reduced hepatocyte mass and a compromised monocyte-macrophage
system, and/or reflect, in part, ongoing low-grade disseminated intravascular coagulation
(DIC) [16,97]. Such a condition is prone to be boosted by inappropriate replacement therapy
and eventually resulting in manifest DIC [11,97].
J. Clin. Med. 2021, 10, 1530 12 of 17

10.2.3. Recombinant Activated Factor VII (rFVIIa)

rFVIIa is successfully used in a variety of conditions, including chronic liver disease,
to control active hemorrhage [98–100]. Main settings related to end-stage liver disease are
upper gastrointestinal bleeding (mainly from esophageal varices) and major surgery such
as hepatectomy and liver transplantation. According to Consensus European Guidelines
on the use of rFVIIa, this agent should not be administered to patients with Child-Pugh A
cirrhosis; moreover, treatment with rFVIIa of acute hemorrhage in advanced liver disease
(Child-Pugh B or C cirrhosis) is uncertain [101]. In addition, a number of thrombotic com-
plications (stroke, myocardial ischemia, and portal-vein thrombosis) have been reported
in patients with advanced liver disease following administration of rFVIIa, thus raising
concerns on its safety in this setting (for which no license of rFVIIa exists) [99].

10.2.4. Red Blood Cells (RBC)

Transfusion of packed RBC should also be managed restrictively due to adverse side
effects on portal pressure, analogously to volume expansion upon administration of FFP, as
outlined above. Current recommendations indicate a target hemoglobin of 7 to 8 g/dL [31].
Prior to scheduled invasive interventions, slightly higher hemoglobin levels (8.5 to 9.5
g/dL) should be achieved to improve hemostasis and thus reduce the risk of periprocedural
complications [61].

10.3. Other Specific Agents

10.3.1. Vitamin K
Replacement therapy can be considered in liver disease patients with an increased
INR, which may in part reflect vitamin K deficiency (causing abrogated γ-carboxylation of
coagulation factors II, VII, IX, and X and of proteins C and S). However, vitamin K deficiency
is rather uncommon in this setting, unless there is coexisting cholestasis, antibiotic therapy,
recent malnutrition, or long-term intensive care. If used, vitamin K should be administered
parenterally due to impaired oral or intestinal adsorption in patients with liver failure.
Caution is required, as intravenous application of vitamin K carries the risk of anaphylaxis.

10.3.2. Desmopressin (1-Deamino-8-Arginine Vasopressin, DDAVP)

DDAVP is frequently used to improve hemostasis empirically. The agent can decrease
prolonged bleeding time due to drug-induced acute release of von Willebrand factor from
its endothelial storage organelles. The benefit of DDAVP administration in patients with
liver disease is debated controversially. In fact, several randomized trials comparing
DDAVP and placebo prior to invasive procedures (e.g., percutaneous liver biopsy; partial
hepatectomy in patients with hepatocellular cancer) showed no difference in blood loss
or transfusion requirements [31]. Overall, while side effects (e.g., headache, nausea, flush,
diarrhea, or hyponatremia) from DDAVP are infrequent, and the agent is commonly used
preprocedurally, its clinical efficacy has not been established in this setting.

10.3.3. Antifibrinolytics
Antifibrinolytics may be useful when cirrhosis-associated hyperfibrinolysis is sus-
pected or proven. Two agents are available, ε-aminocaproic acid (EACA) and tranexamic
acid (TA), both of which abrogate binding of plasminogen or plasmin to fibrin, thus in-
hibiting fibrinolysis. There are only small series of patients and a number of case reports,
demonstrating the efficacy and safety of EACA or TA in liver failure and advanced cirrho-
sis [102,103]. A systematic review and meta-analysis of more than 20 randomized controlled
trials (with a total of 1400 patients) documented a reduction in RBC transfusions during
liver transplantation when comparing TA to placebo, while the efficacy of EACA remained
unproven in this setting (due an unpowered study) [104]. Importantly, this meta-analysis
did not provide evidence for an increased risk of thromboembolic events associated with
antifibrinolytic treatment in liver transplantation [104]. Overall, antifibrinolytic agents
appear to be safe and well tolerated in cirrhotic patients [31].
J. Clin. Med. 2021, 10, 1530 13 of 17

11. Conclusions
Hemostatic dysfunction in acute and chronic liver disease and novel therapeutic
options to control thrombocytopenia are a prime example for the significant progress
that has been made in recent years. According to traditional paradigms, liver cirrhosis
was considered as the epitome of an acquired coagulopathy that in combination with
thrombocytopenia and/or thrombopathy causes hemorrhagic complications. Based on
recent findings, this contention has been revised fundamentally in several aspects.
Firstly, patients with liver failure are also prone to thrombotic events, which may
be even more common than bleeding complications, except for end-stage liver disease.
Secondly, the commensurate decrease in pro- and antihemostatic components can lead
to a rebalanced low-level hemostatic equilibrium. The rebalanced hemostatic system is,
however, labile and can be destabilized by various triggers, which in turn may explain
the occurrence of both bleeding and thrombotic complications. Thirdly, thrombocytopenia
in liver cirrhosis results from multifaceted causes; apart from splenic pooling, decreased
production of TPO plays a major role, as documented by the correlation between TPO
levels and residual hepatic function. Fourthly, defective platelet function as a concomitant
cause of bleeding events in hepatic failure has been overestimated in the past. However,
drug-induced platelet inhibition remains an ongoing concern in this setting. Fifthly, high
levels of plasma von Willebrand factor can restore platelet-vessel wall interaction and
thus rebalance primary hemostasis that may be compromised otherwise in chronic hepatic
disease. Sixthly, rebalanced hemostasis and, all the more, hypercoagulable features in
liver disease have a major impact on the prevention and management of both bleeding
and thrombosis.
This, however, is a challenging demand, which remains difficult to accompl in clinical
practice. Most of routinely available hemostasis screening tests are inconclusive and
without predictive validity in patients with liver disease, and comprehensive hemostasis
profiles have to be restricted in this population to those undergoing high-risk invasive
procedures such as major surgery.
Currently, the platelet threshold required for thrombocytopenic patients, who are
scheduled for higher-risk interventions, is rather “defined” empirically but not based
on study data of appropriate quality. However, recent advances are likely to solve this
issue: the two newly licensed TPO receptor agonists, avatrombopag and lusutrombopag,
were shown to be safe and efficacious at increasing platelet levels and avoiding platelet
transfusions for invasive procedures in patients with thrombocytopenia and chronic liver
disease. It can be expected that both agents will evolve to be the new standard of care for
managing thrombocytopenia in patients with chronic liver disease.

Funding: Work from the author’s laboratory that is cited here was supported by grants from the
Deutsche Forschungsgemeinschaft (Scha 358/3-1; Collaborative Research Center, SFB612). Funding
of the author’s research at Boston Children’s Hospital by a grant from the Society of Thrombosis and
Hemostasis Research (GTH) is also acknowledged.
Acknowledgments: The author is grateful to Dieter Häussinger, Düsseldorf, for stimulating discus-
sion and careful review of the manuscript.
Conflicts of Interest: The author declares no conflict of interest.

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