Low-dose aspirin therapy is associated with few side effects but does not prevent hepatic artery thrombosis in liver transplant recipients

What is the optimal management of thromboprophylaxis after liver transplantation regarding prevention of bleeding, hepatic artery, or portal vein thrombosis? A systematic review of the literature and expert panel recommendations

BACKGROUND

A key tenet of clinical management of patients post liver transplantation (LT) is the prevention of thrombotic and bleeding complications. This systematic review investigated the optimal management of thromboprophylaxis after LT regarding portal vein thrombosis (PVT) or hepatic artery thrombosis (HAT) and prevention of bleeding.

METHODS

Systematic review following PRISMA guidelines and recommendations using the GRADE approach derived from an international expert panel. Seven databases were used to conduct extensive literature searches focusing on the use of anticoagulation in LT and its impact on the following outcomes: PVT, HAT, and bleeding (CRD42021244288).

RESULTS

Of the 2478 articles/abstracts screened, 16 studies were included in the final review. All articles were critically appraised by a panel of independent reviewers. There was wide variation regarding the anticoagulation protocols used. Thromboprophylaxis with therapeutic doses of heparin/Vitamin K antagonist combination did not decrease the risk of de novo or the recurrence of PVT but was associated with an increased risk of bleeding in some studies. Only the use of aspirin resulted in a small but significant decrease in the incidence of HAT post-LT, yet it did not increase the risk of bleeding.

CONCLUSIONS

Based on existing data and expert opinion, thromboprophylaxis at therapeutic or prophylactic dose is not recommended for prevention of de novo PVT following LT in patients not at high risk. Aspirin should be considered as the standard of care following LT to prevent HAT. Thromboprophylaxis should be strongly considered in recipients at risk of HAT and PVT following LT.

Risk factors and management of hepatic artery stenosis post liver transplantation

BACKGROUND

Hepatic Artery Stenosis (HAS) after liver transplantation (LT), if untreated, can lead to hepatic artery thrombosis (HAT) that carries significant morbidity.

AIMS

To identify risk factors associated with HAS and determine if endovascular therapy (EVT) reduces the occurrence of HAT.

METHODS

This is a retrospective cohort study of adult LT patients between 2013 and 2018. The primary outcome was development of HAT, and secondary outcomes included graft failure and mortality. Logistic regression was used to ascertain the odds ratio of developing HAS. Outcomes between intervention types were compared with Fisher's-exact test.

RESULTS

The odds of HAS doubled in DCD-donor recipients (OR=2.27; P = 0.04) and transplants requiring vascular reconstruction for donor arterial variation (OR=2.19, P = 0.046). Of the 63 identified HAS patients, 44 underwent EVT, 7 with angioplasty alone, 37 combined with stenting. HAT was not significantly different in those who underwent angioplasty with or without stenting than conservative treatment (P = 0.71). However, compared to patients without HAS, patients with HAS had higher odds of biliary stricture and decreased graft and overall patient survival (log-rank P < 0.001 & P = 0.019, respectively).

CONCLUSION

HAS is significantly higher in DCD-graft recipients. EVT was not associated with reduction in HAT progression. HAS has poor graft and overall survival.

How to Handle Arterial Conduits in Liver Transplantation? Evidence From the First Multicenter Risk Analysis

OBJECTIVE

The aims of the present study were to identify independent risk factors for conduit occlusion, compare outcomes of different AC placement sites, and investigate whether postoperative platelet antiaggregation is protective.

BACKGROUND

Arterial conduits (AC) in liver transplantation (LT) offer an effective rescue option when regular arterial graft revascularization is not feasible. However, the role of the conduit placement site and postoperative antiaggregation is insufficiently answered in the literature.

STUDY DESIGN

This is an international, multicenter cohort study of adult deceased donor LT requiring AC. The study included 14 LT centers and covered the period from January 2007 to December 2016. Primary endpoint was arterial occlusion/patency. Secondary endpoints included intra- and perioperative outcomes and graft and patient survival.

RESULTS

The cohort was composed of 565 LT. Infrarenal aortic placement was performed in 77% of ACs whereas supraceliac placement in 20%. Early occlusion (≤30 days) occurred in 8% of cases. Primary patency was equivalent for supraceliac, infrarenal, and iliac conduits. Multivariate analysis identified donor age >40 years, coronary artery bypass, and no aspirin after LT as independent risk factors for early occlusion. Postoperative antiaggregation regimen differed among centers and was given in 49% of cases. Graft survival was significantly superior for patients receiving aggregation inhibitors after LT.

CONCLUSION

When AC is required for rescue graft revascularization, the conduit placement site seems to be negligible and should follow the surgeon's preference. In this high-risk group, the study supports the concept of postoperative antiaggregation in LT requiring AC.

Perioperative management of antithrombotic treatment

End-stage liver disease is characterized by multiple and complex alterations of hemostasis that are associated with an increased risk of both bleeding and thrombosis. Liver transplantation further challenges the feeble hemostatic balance of patients with decompensated cirrhosis, and the management of antithrombotic treatment during and after transplant surgery, which is particularly difficult. Bleeding was traditionally considered the major concern during and early after surgery, but it is increasingly recognized that transplant recipients may also develop thrombotic complications. Pathophysiology of hemostatic complications during and after transplantation is multifactorial and includes pre-, intra-, and postoperative risk factors. Risk stratification is important, as it helps the identification of high-risk recipients in whom antithrombotic prophylaxis should be considered. In recipients who develop thrombosis during or after surgery, prompt treatment is indicated to prevent graft failure, retransplantation, and death.

Perioperative hemostatic management in the cirrhotic patient: a position paper on behalf of the Liver Intensive Care Group of Europe (LICAGE)

Recent data demonstrated that amongst patients undergoing elective surgery the prevalence of cirrhosis is 0.8% equating to approximately 25 million cirrhotic patients undergoing surgery each year worldwide. Overall, the presence of cirrhosis is independently associated with 47% increased risk of postoperative complications and over two and a half-increased risk of in-hospital mortality in patients undergoing elective surgery. In particular, perioperative patients with chronic liver disease have long been assumed to have a major bleeding risk on the basis of abnormal results for standard tests of hemostasis. However, recent evidence outlined significant changes to traditional knowledge and beliefs and, nowadays, with more sophisticated laboratory tests, it has been shown that patients with chronic liver disease may be in hemostatic balance as a result of concomitant changes in both pro- and antihemostatic pathways. The aim of this paper endorsed by the Liver Intensive Care Group of Europe was to provide an up-to-date overview of coagulation management in perioperative patients with chronic liver disease focusing on patient blood management, monitoring of hemostasis, and current role of hemostatic agents.

Hypercoagulability in End-stage Liver Disease: Review of Epidemiology, Etiology, and Management

In this review, we analyze the epidemiology of thromboses related to end-stage liver disease (ESLD), discuss causes of hypercoagulability, describe susceptible populations, and critically evaluate proposed prophylaxis and treatment of thromboses. Classically, ESLD has been regarded as a model for coagulopathy, and patients were deemed to be at high risk for bleeding complications. Patients with ESLD are not auto-anticoagulated, and they do not have a lower risk of portal vein thrombosis, intracardiac thrombus formation, pulmonary embolism or hepatic artery thrombosis. Though the cause of hypercoagulability is multifactorial, endothelial dysfunction likely plays a central role for all patients with ESLD. Some subpopulations, such as patients with nonalcoholic steatohepatitis and autoimmune conditions, are at increased risk of thrombotic events as are patients of Hispanic ethnicity. The science behind prophylaxis of different types of clotting and treatment of thromboses is developing rapidly. A number of medications, including low molecular weight heparin, unfractionated heparin, aspirin, vitamin K antagonists, and direct oral anticoagulants can be used, but clear guidelines are lacking. Acute intraoperative clotting can be associated with high mortality. Routine use of transesophageal echocardiography can be helpful in early recognition and treatment of intraoperative thrombosis. Heparin should be reserved for cases of intracardiac thrombus/pulmonary embolism without hemodynamic instability. In unstable patients, low dose of recombinant tissue plasminogen activator can be used. In this new era of heightened awareness of thrombotic events in ESLD patients, prospective randomized trials are urgently needed to best guide clinical practice.

Coagulopathy Before and After Liver Transplantation: From the Hepatic to the Systemic Circulatory Systems

The hemostatic environment in patients with cirrhosis is a delicate balance between prohemostatic and antihemostatic factors. There is a lack of effective laboratory measures of the hemostatic system in patients with cirrhosis. Many are predisposed to pulmonary embolus, deep vein thrombosis, and portal vein thrombosis in the pretransplantation setting. This pretransplantation hypercoagulable milieu seems to extend for at least several months post-transplantation. Patients with nonalcoholic fatty liver disease, inherited thrombophilia, portal hypertension in the absence of cirrhosis, and hepatocellular carcinoma often require individualized approach to anticoagulation. Early reports suggest a potential role for low-molecular-weight heparins and direct-acting anticoagulants.

Liver transplant recipients with portal vein thrombosis receiving an organ from a high-risk donor are at an increased risk for graft loss due to hepatic artery thrombosis

We hypothesize that recipients with pretransplant portal vein thrombosis (PVT) receiving organs from high-risk donors (HRD) are at an increased risk of HAT. Data on all liver transplants in the United States from February 2002 to March 2015 were analyzed. Recipients were sorted into two groups: those with PVT and those without. HRDs were defined by donor risk index (DRI) >1.7. Multivariable logistic regression models were constructed to assess the independent risk factors for HAT with the resultant graft loss ≤90 days from transplantation. A total of 60 404 candidates underwent liver transplantation; of those recipients, 623 (1.0%) had HAT, of which 66.0% (n = 411) received organs from HRDs compared with 49.3% (n = 29 473) in recipients without HAT (P < 0.001); 2250 (3.7%) recipients had pretransplantation PVT and received organs from HRDs. On adjusted multivariable analysis, PVT with a HRD organ was the most significant independent risk factor (OR 3.56, 95% CI 2.52-5.02, P < 0.001) for the development of HAT. Candidates with pretransplant PVT who receive an organ from a HRD are at the highest risk for postoperative HAT independent of other measurable factors. Recipients with pretransplant PVT would benefit from careful donor selection and possibly anticoagulation perioperatively.

Pediatric transplantation: preventing thrombosis

Due to progressive advances in surgical techniques, immunosuppressive therapies, and supportive care, outcomes from both solid organ transplantation and hematopoietic stem cell transplantation continue to improve. Thrombosis remains a challenging management issue in this context, with implications for both graft survival and long-term quality of life. Unfortunately, there remains a general paucity of pediatric-specific data regarding thrombosis incidence, risk stratification, and the safety or efficacy of preventative strategies with which to guide treatment algorithms. This review summarizes the available evidence and rationale underlying the spectrum of current practices aimed at preventing thrombosis in the transplant recipient, with a particular focus on risk factors, pathophysiology, and described antithrombotic regimens.

Hepatic artery stenosis after liver transplantation: is endovascular treatment always necessary?

Hepatic artery stenosis (HAS) is thought to predispose patients to biliary complications secondary to ischemic injury. Despite this, the clinical significance of HAS remains poorly defined. The aims of this study were to determine the prevalence and outcomes of HAS and to define which patients might benefit from endovascular treatment. From a prospective database of 662 adult patients undergoing liver transplantation between 2000 and 2011, we identified 54 patients who developed HAS. HAS was defined as any stenosis > 70% that was seen during multidetector computed tomographic angiography (MDCTA) or digital subtraction angiography. The benefit of endovascular therapy was evaluated with propensity score matching. New biliary complications occurred in 17 patients (31.4%), and 23 of the 54 study patients with HAS received endovascular treatment. Among the propensity score-matched patients, the biliary stricture-free survival time was significantly longer for those who received endovascular therapy (P = 0.03). An incidental diagnosis (P = 0.07) and a time from transplantation > 6 months (P = 0.021) were associated with a reduced risk of developing biliary stricture. Patients with symptomatic HAS who received treatment had better biliary stricture-free survival than patients who were treated conservatively, although no significant difference was recorded (P = 0.11). No patient with asymptomatic HAS and normal liver function tests developed biliary strictures. In conclusion, HAS intervention was associated with improved biliary stricture-free survival. In patients with late-onset HAS (≥6 months) and asymptomatic patients, endovascular treatment is not warranted.

Late hepatic artery thrombosis after pediatric liver transplantation: a cross-sectional study of 34 patients

Hepatic artery thrombosis (HAT) after liver transplantation (LT) increases patient morbidity and mortality. Early HAT is considered to occur within the first month after LT, whereas late HAT occurs after the first month. Few studies have addressed late HAT after LT, especially in pediatric patients. Between 1987 and 2007, 99 patients (age < 18 years) underwent deceased donor LT. Thirty-four of 66 eligible patients (52%) underwent magnetic resonance imaging (MRI) according to protocol. On the basis of MRI findings, the patients were grouped as those who experienced late HAT and those who did not. Additionally, potential risk factors for late HAT were analyzed retrospectively. P values were adjusted for multiplicity. The median age at LT was 1.7 years [interquartile range (IQR) = 1.0-9.6 years], and the median follow-up time at MRI was 9.5 years (IQR = 4.0-16.4 years). Late HAT was diagnosed in 15 of the 34 patients [44%, 95% confidence interval (CI) = 29%-61%] undergoing MRI and in 3 of these patients with angiography preceding MRI. Ultrasonography revealed late HAT in 6 of these 15 patients with a sensitivity of 40% (95% CI = 20%-64%). The donor/recipient weight ratio remained significantly higher for the patients with late HAT versus the patients without late HAT after P values were adjusted (5.4 versus 1.9, P = 0.03). No marked differences were observed in laboratory or liver histology parameters between the groups. In conclusion, late HAT is common after pediatric LT. The donor/recipient weight ratio was higher for patients with late HAT, and this was attributable to the lower weight of the recipients. No salient features of late HAT were observed with respect to laboratory or histological parameters, at least in terms of our study's cross-sectional period.

Early aspirin therapy may reduce hepatic artery thrombosis in liver transplantation

BACKGROUND

Hepatic artery thrombosis (HAT) remains among the leading causes of early graft loss after liver transplantation. Our transplant center began using universal aspirin prophylactic therapy immediately posttransplantation in 2007. The aim of this study was to determine the safety and efficacy of early aspirin therapy on clinical outcomes.

METHODS

This large-scale, cross-sectional analysis included all adult liver transplantations performed between 2000 and 2009. Pediatric and multiorgan transplants were excluded. Patients were grouped and compared based on whether they received early initiation of aspirin 325 mg PO daily posttransplantation.

RESULTS

A total of 541 adult liver transplantations occurred during the study period; 439 had complete documentation and were analyzed. Clinical outcomes show aspirin patients had similar rates of early and late HAT, but had significantly lower early HAT, defined as HAT occurring within the first 30 days posttransplant, leading to graft loss. Other clinical outcomes were similar between groups including bleeding events and wound complications.

CONCLUSIONS

Immediate initiation of aspirin therapy after liver transplantation may reduce the rate of HAT leading to early graft loss, without increasing bleeding or other complication rates.

Early hepatic artery thrombosis after liver transplantation: a systematic review of the incidence, outcome and risk factors

To clarify inconsistencies in the literature we performed a systematic review to identify the incidence, risk factors and outcome of early hepatic artery thrombosis (eHAT) after liver transplantation. We searched studies identified from databases (MEDLINE, EMBASE, Science Citation Index) and references of identified studies. Seventy-one studies out of 999 screened abstracts were eligible for this systematic review. The incidence of eHAT was 4.4% (843/21, 822); in children 8.3% and 2.9% in adults (p < 0.001). Doppler ultrasound screening (DUS) protocols varied from 'no routine' to 'three times a day.' The median time to detection was at day seven. The overall retransplantation rate was 53.1% and was higher in children (61.9%) than in adults (50%, p < 0.03). The overall mortality rate of patients with eHAT was 33.3% (range: 0-80%). Mortality in adults (34.3%) was higher than in children (25%, p < 0.03). The reported risk factors for eHAT were, cytomegalovirus mismatch (seropositive donor liver in seronegative recipient), retransplantation, arterial conduits, prolonged operation time, low recipient weight, variant arterial anatomy, and low volume transplantation centers. eHAT is associated with significant graft loss and mortality. Uniform definitions of eHAT and uniform treatment modalities are obligatory to confirm these results and to obtain a better understanding of this disastrous complication.

Platelets in liver transplantation: friend or foe?

Apart from the well-known role of blood platelets in hemostasis, there is emerging evidence that platelets have various nonhemostatic properties that play a critical role in inflammation, angiogenesis, tissue repair and regeneration, and ischemia/reperfusion (I/R) injury. All these processes may be involved in the (patho)physiological alterations occurring in patients undergoing liver transplantation. Experimental and clinical research points toward a dualistic role of platelets in patients undergoing liver transplantation, resulting in both beneficial and detrimental effects. Although a low platelet count is generally considered a risk factor for perioperative bleeding, recent studies have indicated that platelet function in patients with cirrhosis may not be as abnormal as previously assumed. Platelet transfusions are frequently considered in liver transplant recipients to correct low platelet counts and to prevent bleeding; however, evidence-based transfusion thresholds are lacking, and the other detrimental and nonhemostatic properties of platelets are generally not weighed in this respect. First, platelets have been shown to contribute to I/R injury of the liver graft via induction of sinusoidal endothelial cell apoptosis. Second, platelet transfusion has been identified as an independent risk factor for reduced survival via mechanisms that are not completely understood yet. On the other hand, recent studies indicate that platelets are critically involved in restoration after liver injury and in liver regeneration via serotonin-mediated mechanisms. These findings make platelets both friend and foe in liver transplantation. The scientific challenge will be to further dissect the mechanisms and clinical relevance of these contrasting roles of platelets in liver transplantation.

Can antiplatelet prophylaxis reduce the incidence of hepatic artery thrombosis after liver transplantation?

To ascertain whether postoperative antiplatelet therapy could reduce the incidence of hepatic artery thrombosis (HAT) after liver transplantation (LT), 838 consecutive adult whole-graft LTs performed from April 1986 to August 2005 that survived beyond the first postoperative month were reviewed. Antiplatelet prophylaxis with aspirin (100 mg per day) was given following 236 LTs; the median starting time was 8 postoperative days (range, 1 to 29 days). Early HAT was observed in 29 cases. The median time of presentation was 5 postoperative days (range, 1-28 days), and the effect of aspirin on this type of complication was therefore not assessable. A total of 14 cases of late HAT were observed (1.67 %). The median time of presentation was 500.5 days (range, 50-2,405 days). Late HAT occurred in 1 out of 236 (0.4 %) patients who were maintained under antiplatelet prophylaxis and in 13 out of 592 (2.2 %) who did not receive prophylaxis (P = 0.049). Risk factors for late HAT (grafts retrieved from donors who died of cerebrovascular accident and/or use of iliac conduit at transplantation) were present in 498 LTs: in this group the incidence of late HAT was significantly higher among cases who did not receive prophylaxis (12/338 vs 1/160; p = 0.037). There were no hemorrhagic complications associated with the use of aspirin. In conclusion,antiplatelet prophylaxis can effectively reduce the incidence of late HAT after LT, particularly in those patients at risk for this complication.

Infected bilomas in liver transplant recipients, incidence, risk factors and implications for prevention

Bilomas, infected hepatic fluid collections, are a frequent complication of liver transplantation. We report a case-control cohort study to determine the incidence and microbiologic profile of bilomas and risk factors for biloma formation in 492 patients undergoing liver transplantation from 1994 to 2001. Fifty-seven patients (11.5%) developed one or more bilomas; 95% in the first year post-transplantation. The most common initial infecting pathogens were enterococci (37%), one-half resistant to vancomycin (VRE); coagulase-negative staphylococci (26%); and Candida species (26%). Infection by coagulase-negative staphylococci was strongly associated with the presence of a T-tube (OR 9.60, p=0.02). In stepwise logistic regression multivariable analyses, hepatic artery thrombosis (OR 90.9, p<0.0001), hepatic artery stenosis (OR 13.2, p<0.0001) and Roux-en-Y choledochojejunostomy (OR 5.8, p=0.03) were independent risk factors for biloma formation; ursodeoxycholic acid use was highly protective (OR 0.1, p=0.002). Strategies to prevent biloma formation must focus on measures to prevent hepatic artery thrombosis and colonization of liver transplant patients by multiresistant nosocomial pathogens. T-tube drainage post-transplantation bears reassessment. The protective effect of ursodeoxycholic acid found in this study warrants confirmation in a prospective multicenter, randomized trial.

Increased late hepatic artery thrombosis rate and decreased graft survival after liver transplants with zero cross-reactive group mismatches

The use of broad-specificity cross-reactive groups (CREGs) at the A and B HLA loci has been proposed as a means to improve both access and outcome for renal transplantation but has not yet been studied for liver transplantation. We retrospectively analyzed our results for all adult liver transplantations performed at our center between 1989 and 1996 for which HLA typing and complete 3-year follow-up data were available. Two hundred eight transplantations were studied, with a mean follow-up of 66 +/- 2 months (range, 36 to 110 months); A and B loci were converted to CREGs by the method of Rodey. Thirteen percent of the patients with 0 CREG mismatches had hepatic artery thrombosis versus 2% for those with 1 or more mismatches (odds ratio, 6.7; 95% confidence interval, 2.6 to 17.3 by univariate analysis; odds ratio, 3.5; 95% confidence interval, 1.1 to 11.7 by logistic regression analysis). These events occurred significantly later in the 0-CREG mismatch group (21 +/- 7 v 4 +/- 2 months posttransplantation; P =.04 by Student's t-test). Graft survival rates were significantly lower for patients with 0 CREG mismatches (56% v 68% at end of study; P =.05 by Cox-Mantel test). The number of CREG mismatches had no effect on the frequency of rejection, steroid-resistant rejection, or infectious complications, including cytomegalovirus. Neither total nor individual A, B, or DR HLA matching had an effect on outcome. There appears to be little evidence that intentional CREG matching would improve outcomes for liver transplantation and, under some circumstances, could be deleterious.