Renal transplant recipients are at high risk for both symptomatic and asymptomatic deep vein thrombosis

Prophylactic Anticoagulation Reduces the Risk of Kidney Graft Venous Thrombosis in Recipients From Uncontrolled Donation After Circulatory Death Donors With High Renal Resistive Index

Background

Uncontrolled donation after circulatory death (uDCD) increases organ availability for kidney transplantation (KT) at the expense of a higher risk of primary graft nonfunction (PNF). At least half of the cases of PNF are secondary to graft venous thrombosis. The potential benefit from prophylactic anticoagulation in this scenario remains unclear.

Methods

In this single-center retrospective study we compared 2 consecutive cohorts of KT from uDCD with increased (≥0.8) renal resistive index (RRI) in the Doppler ultrasound examination performed within the first 24-72 h after transplantation: 36 patients did not receive anticoagulation ("nonanticoagulation group") and 71 patients underwent prophylactic anticoagulation until normalization of RRI in follow-up Doppler examinations ("anticoagulation group").

Results

Anticoagulation was initiated at a median of 2 d (interquartile range, 2-3) after transplantation and maintained for a median of 12 d (interquartile range, 7-18). In 4 patients (5.6%), anticoagulation had to be prematurely stopped because of the development of a hemorrhagic complication. In comparison with the nonanticoagulation group, recipients in the anticoagulation group had a lower 2-wk cumulative incidence of graft venous thrombosis (19.4% versus 0.0%; P < 0.001) and PNF (19.4% versus 2.8%; P = 0.006). The competing risk analysis with nonthrombotic causes of PNF as the competitive event confirmed the higher risk of graft thrombosis in the nonanticoagulation group (P = 0.0001). The anticoagulation group had a higher incidence of macroscopic hematuria (21.1% versus 5.6%; P = 0.049) and blood transfusion requirements (39.4% versus 19.4%; P = 0.050) compared with the nonanticoagulation group. No graft losses or deaths were attributable to complications potentially associated with anticoagulation.

Conclusions

Early initiation of prophylactic anticoagulation in selected KT recipients from uDCD with an early Doppler ultrasound RRI of ≥0.8 within the first 24-72 h may reduce the incidence of graft venous thrombosis as a cause of PNF.

Incidence and risk factors of venous thromboembolism in kidney transplantation patients: a prospective cohort study

To investigate the incidence and explore the risk factors of venous thromboembolism (VTE) within 6 months after kidney transplantation. Total of 331 kidney transplant recipients were assessed by venous ultrasonography for VTE at 14 days, 1 month, 3 months, and 6 months post-transplantation. Cox forward regression were used to identify the independent risk factors of VTE. This study registration number is ChiCTR1900020567 and the date of registration was 2019/01/08. The cumulative incidence of VTE was 2.72% (9/331) within 6 months after transplant. 77.8% (7/9) of VTEs occurred in the first 3 months post-transplantation. 88.9% (1/9) of VTEs were asymptomatic, 66.7% (6/9) of VTEs were mural thromboses and in the right lower extremity. Central vena catheterization (HR = 6.94) and severe pulmonary disease (including pneumonia) (HR = 57.35) were the risk factors for VTE in kidney transplantation recipients. KT patients are the high risk population of VTE. Future interventions should be strengthen for KT patients to receive a minimum of 3-month of precautionary measures for VTE, including infection prevention, and strengthening thromboprophylaxis on the CVC or transplanted side of lower extremity.

Prevalence, risk, and outcomes of venous thromboembolic events in kidney transplant recipients: a nested case-control study

INTRODUCTION

Thromboembolism is more common in kidney transplant recipients (KTRs) than in the general population. Studies evaluating arterial and venous thromboembolism (VTE) in KTRs are scarce and the magnitude and risk factors are mostly undefined.

METHODS

A nested control study was conducted from January 1, 2007, to December 31, 2019. Adult KTRs who were detected to have VTE events during this period were included. The primary outcome was to assess the prevalence of VTE in this population. Secondary outcomes were the assessment of the time to occurrence of the thromboembolic events after transplantation and assessing the risk factors and patient survival. For each subject studied, 4 controls were matched from the data set.

RESULTS

Amongst 2158 patients, 97 (4.5%) were found to have VTE. The median follow-up time was 3.9 years (6-156 months). A total of 101 VTE events were recorded. The most common site of VTE was the lower limb deep vein thrombosis in 79 patients (0.03%)).In multivariate Cox regression analysis, serum creatinine of more than 3 mg/dl [HR 1.30, 95% CI (1.03-1.38)] was independently associated with increased VTE risk. Patients who developed a VTE had higher mortality as compared to patients who did not develop VTE. No increased risk of graft failure was found in VTE patients.

CONCLUSION

This study suggests that kidney transplantation surgery is a moderate risk factor for VTE, and VTE is associated with higher morbidity and mortality. However, prospective studies are needed to establish a definite role of VTE in outcomes in KTRs.

Venous Thromboembolism Risk Assessment in Hospitalized Cancer Patients: A Single Center Study

This study aimed to identify predictors of venous thromboembolism (VTE) in hospitalized cancer patients and develop a predictive model using demographic, clinical, and laboratory data. Our analysis showed that patient groups categorized under a very high risk, and high risk, patients with low hemoglobin levels and renal disease were at a significantly increased risk of developing VTE. We developed a VTE risk-assessment model (RAM) with moderate discriminatory performance, high specificity, and negative predictive value, indicating its potential utility in identifying patients without VTE risk. However, the model's positive predictive value and sensitivity were low due to the low prevalence of VTE within the analyzed population. Future studies are needed to analyze additional predictive factors, and to validate the effectiveness of our VTE RAM to safely rule out VTE, compare it with other VTE RAMs in hospitalized cancer patients, and address any limitations of our study.

The association of venous thromboembolism with blood transfusion in kidney transplant patients

BACKGROUND

Red blood cell transfusion (RBCT) is common after kidney transplantation and could have pro-thrombotic effects predisposing to venous thromboembolism (VTE). The risks for developing of VTE after RBCT in kidney transplant patients are unknown.

STUDY DESIGN AND METHODS

This was a retrospective cohort study of adult kidney transplant recipients from 2002 to 2018. The exposure of interest was receipt of RBCT after transplant. Cox proportional hazards models were used to calculate hazard ratios (HR) for the outcomes of venous thromboembolism [VTE] (deep venous thrombosis [DVT] or pulmonary embolism [PE]) using RBCT as a time-varying, cumulative exposure.

RESULTS

Out of 1258 kidney transplants recipients, 468 (37%) were transfused during the study period. Seventy-nine study participants (6.3%) developed VTE, 72 DVT (5.7%), and 22 PE (1.8%). For the receipt of 1, 2, 3-5, and >5 RBCT, compared to individuals never transfused, the number of events and adjusted HR (95%CI) for VTE were 6 (6.2%) HR 1.57 (0.69-3.58), 9 (7.6%) HR 2.54 (1.30-4.96), 15 (11.9%) HR 2.73 (1.38-5.41), and 23 (18.1%) HR 5.77 (2.99-11.14) respectively; for DVT, it was 6 (6.2%) HR 1.94 (0.84-4.48), 9 (7.6%) HR 2.92 (1.44-5.94), 14 (11.1%) HR 3.29 (1.63-6.65), and 21 (16.5%) HR 6.97 (3.53-13.76), respectively. For PE, among transfused individuals, there were 14 events (3.0%) and the HR was 2.40 (1.02-5.61).

CONCLUSION

The risks for developing VTE, DVT, and PE were significantly increased in kidney transplant patients receiving RBCT after transplant. Receipt of RBCT should prompt considerations for judicious monitoring and assessment for thrombosis.

A Patient with Sickle Cell Disease and Recurrent Venous Thromboembolism after Renal Transplantation

Venous thromboembolism (VTE) is a life-threatening complication, especially in case of recurrence. The appropriate duration of anticoagulant treatment following the first event is crucial. Risk factors that increase the risk of recurrence of VTE are many, and include medications, kidney disease, renal transplantation (RT), and a diagnosis of sickle cell disease (SCD). There are currently no guidelines that define the duration of anticoagulant therapy after the first event in a patient with RT. We report a case of recurring episodes of VTE after RT in a SCD patient. Our case suggests that the use of a long-term anticoagulant treatment may be recommended in patients with SCD and RT after the first event of VTE.

Comparative efficacy and safety of oral anticoagulants for the treatment of venous thromboembolism in the patients with different renal functions: a systematic review, pairwise and network meta-analysis

OBJECTIVES

To compare the efficacy and safety of direct oral anticoagulants (DOACs) in patients with venous thromboembolism (VTE) and different renal functions.

DESIGN

Systematic review containing pairwise and Bayesian network meta-analysis of randomised controlled trials (RCTs).

DATA SOURCES

MEDLINE, EMBASE and Cochrane Library.

ELIGIBILITY CRITERIA

RCTs reporting the efficacy and safety outcomes of DOACs in different creatinine clearance (CrCl) subgroups.

DATA EXTRACTION AND SYNTHESIS

Data extraction and quality assessment were undertaken by two independent reviewers. Data were pooled using the DerSimonian-Laird method in pairwise meta-analysis. Network meta-analysis within a Bayesian framework was conducted.

RESULTS

Data from 10 RCTs were included. In the treatment of acute VTE, DOACs did not significantly reduce recurrent VTE or VTE-related death (OR, 0.96; 95% CI, 0.82 to 1.11) but significantly reduced bleeding events (0.76, 0.68 to 0.90) compared with warfarin. In the extended treatment of VTE, DOACs produced significant benefits in recurrent VTE or VTE-related death (0.23, 0.16 to 0.29), but significantly increased bleeding events (1.86, 1.04 to 3.33) compared with placebo/aspirin. There were no significant differences in efficacy and safety of DOACs among the three CrCl stratified subgroups in acute and extended treatment of VTE (p for subgroup heterogeneity >0.1). Bayesian network meta-analysis suggested that apixaban 2.5 mg and 5 mg two times per day were associated with a lower risk of bleeding than dabigatran, rivaroxaban, warfarin and aspirin in the subgroup with CrCl >80 mL/min.

CONCLUSIONS

For the treatment of acute VTE, DOACs are similar to warfarin in reducing recurrent VTE and VTE-related death but are significantly superior to warfarin in reducing the risk of bleeding. For the efficacy and safety of DOACs across different CrCl stratifications (30-50, 50-80 and more than 80 mL/min), no significant difference was found. In light of minimal evidence, apixaban might be associated with a lower risk of bleeding in patients with VTE and CrCl >80 mL/min.

PROSPERO REGISTRATION NUMBER

CRD42018090896.

Statin Therapy and the Incidence of Thromboembolism and Vascular Events Following Liver Transplantation

Statin therapy may reduce the risk of venous thromboembolism (VTE), which may impact solid organ transplant outcomes. We evaluated the incidence of VTE and other complications after liver transplantation stratified by hyperlipidemia status and statin use using a retrospective cohort study approach. We reviewed all primary orthotopic liver transplantation (OLT) records from January 2014 to December 2019 from our center. Intraoperative deaths were excluded. Recipient, donor clinical and demographic data were collected. We developed risk-adjusted models to assess the effect of statin use on the occurrence of VTE, hepatic artery complications (HACs), graft failure, and death, accounting for clinical covariates and competing risks. A total of 672 OLT recipients were included in the analysis. Of this cohort, 11.9% (n = 80) received statin therapy. A total of 47 patients (7.0%) had VTE events. HACs occurred in 40 patients (6.0%). A total of 42 (6.1%) patients experienced graft loss, whereas 9.1% (n = 61) of the cohort died during the study interval. Eighty OLT recipients (29.8%) were treated with statins. In the statin treated group, 0% of patients had VTE versus 7.9% of those not on statins (P = 0.02). HACs were identified in 1.2% of the statin group and 6.8% of the nonstatin group. Untreated hyperlipidemia was associated with a 2.1-fold higher risk of HACs versus patients with no hyperlipidemia status (P = 0.05). Statin therapy was associated with significantly better risk-adjusted thromboembolic event-free survival (absence of VTE, cerebrovascular accident, myocardial infarction, HACs, and death); hazard ratio, 2.7; P = 0.01. These data indicate that statin therapy is correlated with a lower rate of VTE and HACs after liver transplantation.

Can direct oral anticoagulants be used in kidney transplant recipients?

BACKGROUND

Kidney transplant recipients(KTRs) are at an increased risk of venous thromboembolism (VTE) and atrial fibrillation(AF). Direct oral anticoagulants (DOACs) have shown important advantages over vitamin K antagonists; however, in KTRs, concerns regarding interactions and use in severe kidney disease may limit their use. This evaluation describes a large UK kidney transplant center's experience of DOACs in KTRs with CrCl > 15 mL/min.

METHODS

Electronic records were reviewed for all adult KTRs at Manchester University Foundation Trust Hospitals taking DOACs between January 2018 and October 2020 with VTE or AF. The primary outcome was trough and peak DOAC levels within the expected reference ranges and secondary outcomes included bleeding and thrombotic events.

RESULTS

In 31 KTRs taking DOACS, eight patients had a CrCl < 30 mL/min. Overall, 94% (62/66) of DOAC levels were within the recommended ranges. There were no thrombotic events and four bleeding events (two major and two clinically relevant non-major bleeds). The overall bleeding rate was 6.9 per 100 patient-years at risk.

CONCLUSIONS

There was no evidence of a significant interaction of apixaban or rivaroxaban with CNIs based on expected DOAC and CNI levels. Their use was found to be safe and effective with no VTE events and bleeding episodes similar to published trial data.

Interventions for preventing thrombosis in solid organ transplant recipients

BACKGROUND

Graft thrombosis is a well-recognised complication of solid organ transplantation and is one of the leading causes of graft failure. Currently there are no standardised protocols for thromboprophylaxis. Many transplant units use unfractionated heparin (UFH) and fractionated heparins (low molecular weight heparin; LMWH) as prophylaxis for thrombosis. Antiplatelet agents such as aspirin are routinely used as prophylaxis of other thrombotic conditions and may have a role in preventing graft thrombosis. However, any pharmacological thromboprophylaxis comes with the theoretical risk of increasing the risk of major blood loss following transplant. This review looks at benefits and harms of thromboprophylaxis in patients undergoing solid organ transplantation.

OBJECTIVES

To assess the benefits and harms of instituting thromboprophylaxis to patients undergoing solid organ transplantation.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 10 November 2020 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) and quasi-RCTs designed to examine interventions to prevent thrombosis in solid organ transplant recipients. All donor types were included (donor after circulatory (DCD) and brainstem death (DBD) and live transplantation). There was no upper age limit for recipients in our search.

DATA COLLECTION AND ANALYSIS

The results of the literature search were screened and data collected by two independent authors. Dichotomous outcome results were expressed as risk ratio (RR) with 95% confidence intervals (CI). Random effects models were used for data analysis. Risk of bias was independently assessed by two authors using the risk of bias assessment tool. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

We identified nine studies (712 participants). Seven studies (544 participants) included kidney transplant recipients, and studies included liver transplant recipients. We did not identify any study enrolling heart, lung, pancreas, bowel, or any other solid organ transplant recipient. Selection bias was high or unclear in eight of the nine studies; five studies were at high risk of bias for performance and/or detection bias; while attrition and reporting biases were in general low or unclear. Three studies (180 participants) primarily investigated heparinisation in kidney transplantation. Only two studies reported on graft vessel thrombosis in kidney transplantation (144 participants). These small studies were at high risk of bias in several domains and reported only two graft thromboses between them; it therefore remains unclear whether heparin decreases the risk of early graft thrombosis or non-graft thrombosis (very low certainty). UFH may make little or no difference versus placebo to the rate of major bleeding events in kidney transplantation (3 studies, 155 participants: RR 2.92, 95% CI 0.89 to 9.56; I² = 0%; low certainty evidence). Sensitivity analysis using a fixed-effect model suggested that UFH may increase the risk of haemorrhagic events compared to placebo (RR 3.33, 95% CI 1.04 to 10.67, P = 0.04). Compared to control, any heparin (including LMWH) may make little or no difference to the number of major bleeding events (3 studies, 180 participants: RR 2.70, 95% CI 0.89 to 8.19; I² = 0%; low certainty evidence) and had an unclear effect on risk of readmission to intensive care (3 studies, 180 participants: RR 0.68, 95% CI 0.12 to 3.90, I² = 45%; very low certainty evidence). The effect of heparin on our other outcomes (including death, patient and graft survival, transfusion requirements) remains unclear (very low certainty evidence). Three studies (144 participants) investigated antiplatelet interventions in kidney transplantation: aspirin versus dipyridamole (1), and Lipo-PGE₁ plus low-dose heparin to "control" in patients who had a diagnosis of acute rejection (2). None of these reported on early graft thromboses. The effect of aspirin, dipyridamole and Lipo PGE₁ plus low-dose heparin on any outcomes is unclear (very low certainty evidence). Two studies (168 participants) assessed interventions in liver transplants. One compared warfarin versus aspirin in patients with pre-existing portal vein thrombosis and the other investigated plasmapheresis plus anticoagulation. Both studies were abstract-only publications, had high risk of bias in several domains, and no outcomes could be meta-analysed. Overall, the effect of any of these interventions on any of our outcomes remains unclear with no evidence to guide anti-thrombotic therapy in standard liver transplant recipients (very low certainty evidence).

AUTHORS' CONCLUSIONS

Overall, there is a paucity of research in the field of graft thrombosis prevention. Due to a lack of high quality evidence, it remains unclear whether any therapy is able to reduce the rate of early graft thrombosis in any type of solid organ transplant. UFH may increase the risk of major bleeding in kidney transplant recipients, however this is based on low certainty evidence. There is no evidence from RCTs to guide anti-thrombotic strategies in liver, heart, lung, or other solid organ transplants. Further studies are required in comparing anticoagulants, antiplatelets to placebo in solid organ transplantation. These should focus on outcomes such as early graft thrombosis, major haemorrhagic complications, return to theatre, and patient/graft survival.

Venous thromboembolism in solid-organ transplant recipients: Findings from the RIETE registry

BACKGROUND

Venous thromboembolism (VTE) represents a relevant cause of morbidity in patients with solid-organ transplant (SOT), but there are scarce data on the management and outcomes in these patients.

METHODS

RIETE is a worldwide, ongoing observational registry of patients with objectively confirmed, acute VTE. We used the RIETE database to compare the clinical characteristics, treatment and outcomes in SOT recipients vs. non-recipients.

RESULTS

From January 2001 to December 2019, 83,210 patients were enrolled in RIETE. Of these, 329 (0.4%) were SOT recipients: in the kidney 221, liver 41, lung 28 and heart 25. Median duration of anticoagulation was similar in SOT recipients and non-recipients (174 vs. 182 days). During anticoagulation, 1180 patients developed deep vein thrombosis (DVT) recurrences, 1028 pulmonary embolism (PE) recurrences, 2392 had major bleeding, 3119 non-major bleeding and 8157 died. SOT recipients had a higher rate of major bleeding (hazard ratio [HR]: 2.55; 95% CI: 1.62-3.84) and clinically relevant non-major bleeding (HR: 1.94; 95% CI: 1.23-2.93) than non-recipients, with no differences in the rates of DVT recurrences (HR: 0.96; 95% CI: 0.30-2.32), PE recurrences (HR: 1.11; 95% CI: 0.35-2.67) or death (HR: 0.98; 95% CI: 0.67-1.40). On multivariable analysis, only liver transplant recipients were at an increased risk for major bleeding compared to non-recipients (adjusted HR: 3.17; 95% CI: 1.02-9.87).

CONCLUSIONS

Treatment of VTE in SOT recipients is associated with an increased risk of bleeding compared to non-recipients. This is mainly due to the influence of liver transplant recipients. In non-liver SOT recipients, the risk for bleeding was similar to that in non-recipients.

Absence of interaction between rivaroxaban, tacrolimus and everolimus in renal transplant recipients with deep vein thrombosis or atrial fibrillation

No data are available on rivaroxaban use in renal transplant recipients and on its surmised interaction with immunosuppressants. The aim was to investigate potential interactions between rivaroxaban and immunosuppressants in this setting. Renal transplant recipients with a stable renal function treated with rivaroxaban and tacrolimus with or without everolimus were investigated. All drugs and creatinine concentrations were determined daily for 2 weeks after the start of anticoagulation. Blood samples were drawn at 8.00 am and 3-4 h later for trough and peak concentrations, respectively. Bleeding and thrombotic events were recorded during a minimum follow-up of 6 months. In 8 renal transplant patients, rivaroxaban levels showed a predictable pharmacokinetic trend, both at C_trough (30-61 μg/L) and at C_peak (143-449 μg/L), with limited variability in the 25th-75th percentile range. Tacrolimus (C_trough 3-13 μg/L; C_peak 3-16 μg/L), everolimus (C_trough 3-11 μg/L; C_peak 5-17 μg/L) and creatinine concentrations were stable as well. Immunosuppressors variability before and after rivaroxaban were 30% and 30% for tacrolimus, 27% and 29% for everolimus, respectively, as well as 14% and 3% for creatinine. For rivaroxaban monitoring, the reference change value better performed in identifying significant variations of its concentration. No patient had bleeding or thrombotic events, worsening of renal graft function, and signs of immunosuppressants toxicity during a mean follow-up of 23 (9-28) months. In conclusion, rivaroxaban does not seem to interact with tacrolimus and everolimus in renal transplant recipients. Both anticoagulant and immunosuppressive effects seem warranted, without major bleeding complications and effect on the graft function.

Incidence of Direct Oral Anticoagulant Prescriptions in Kidney Transplant Recipients in Ontario, Canada

BACKGROUND

Kidney transplant recipients (KTRs) are routinely excluded from direct oral anticoagulant (DOAC) trials. Given the lack of safety and efficacy data in this population, we examined real-world prescribing practices of DOACs in KTRs.

METHODS

We conducted a retrospective cohort study using linked administrative data sets in Ontario, Canada. All adult KTRs (n = 5580) from June 23, 2009, to March 31, 2017, were included. The primary outcomes were the first prescription for a DOAC or warfarin. Patients were censored on graft failure, death, or end of follow-up.

RESULTS

The mean age was 55 (SD, 14) years; 63% were male, and 65% had received a deceased donor kidney. Over a median follow-up of 5.5 and 4.7 years, 224 KTRs (4.0%) and 824 KTRs (14.8%) were prescribed DOACs and warfarin, respectively. The rates of DOAC and warfarin prescriptions were 8.1 and 32.6 per 1000 person-years, respectively. Older age, receipt of a kidney transplant in more recent years, and higher baseline estimated glomerular filtration rate were associated with DOAC prescription compared with warfarin. Patients with multiple comorbidities and a history of deep venous thromboembolism had a lower risk of DOAC prescription compared with warfarin. When examined by era, the incidence rate of both DOAC and warfarin prescriptions increased significantly over time.

CONCLUSIONS

Despite limited safety and efficacy data, DOACs are prescribed to KTRs. However, warfarin still remains more commonly prescribed in this selected patient population. Anticoagulant prescriptions overall are on the rise in KTRs. Further study is needed to determine the safety and efficacy of DOACs in KTRs.

Anticoagulation management strategies in heart transplantation

Anticoagulation before, during, and after heart transplantation (HT) presents unique challenges to clinicians. Bleeding and thrombotic morbidity continues to affect this patient population throughout all phases of the HT journey. Reversal is commonly required since patients are commonly bridged to HT with left ventricular assist devices, which require chronic anti platelet and anticoagulation. Caution must be exercised in patients requiring cardiopulmonary bypass during surgery who are at risk of complications from heparin induced thrombocytopenia. The reported incidence of venous thromboembolism following HT is high, particularly during the first post-HT year, most likely due to surgery, biopsies, specific immunosuppression (mTOR inhibitors) and immobilization. It is crucial to maintain long-term oral anticoagulation after the first venous thromboembolism event, especially when risk factors exist. A major issue, and one for which there remains considerable debate, is the optimal treatment of such complications, particularly upper extremity venous thrombosis. For both warfarin and the thrombin inhibitors or Factor Xa inhibitors, the clinician must determine potential drug interactions based on the HT drug regimen, and then develop a patient-specific management strategy.

Perioperative antithrombotic therapy does not increase the incidence of early postoperative thromboembolic complications and bleeding in kidney transplantation - a retrospective study

Perioperative antithrombotic therapy could play a role in preventing thromboembolic complications (TEC) after kidney transplantation (KTx), but little is known on postoperative bleeding risks. This retrospective analysis comprises 2000 single‐organ KTx recipients transplanted between 2011 and 2016 in the two largest transplant centers of the Netherlands. TEC and bleeding events were scored ≤7 days post‐KTx. Primary analyses were for associations of antithrombotic therapy with incidence of TEC and bleeding. Secondary analyses were for associations of other potential risk factors. Mean age was 55 ± 14 years, 59% was male and 60% received a living donor kidney. Twenty‐one patients (1.1%) had a TEC. Multiple donor arteries [OR 2.79 (1.15–6.79)] and obesity [OR 2.85 (1.19–6.82)] were identified as potential risk factors for TEC. Bleeding occurred in 88 patients (4.4%) and incidence varied significantly between different antithrombotic therapies (P = 0.006). Cardiovascular disease [OR 2.01 (1.18–3.42)], pre‐emptive KTx [OR 2.23 (1.28–3.89)], postoperative heparin infusion [OR 1.69 (1.00–2.85)], and vitamin K antagonists [OR 6.60 (2.95–14.77)] were associated with an increased bleeding risk. Intraoperative heparin and antiplatelet therapy were not associated with increased bleeding risk. These regimens appear to be safe for the possible prevention of TEC without increasing the risk for bleeding after KTx.

Drug-Drug Interaction Study of Apixaban with Cyclosporine and Tacrolimus in Healthy Volunteers

Apixaban is metabolized by cytochrome P450 (CYP) 3A4 in the liver and intestine, undergoes direct intestinal excretion, and is a substrate to permeability glycoprotein (P-gp) and breast cancer resistance protein (BCRP) transporters. We examined the drug interactions between cyclosporine and tacrolimus (combined inhibitors of CYP3A4, P-gp, and BCRP) with apixaban in 12 healthy adult male volunteers. Apixaban 10 mg was administered orally alone, in combination with 100 mg cyclosporine or 5 mg tacrolimus. Co-administration with cyclosporine resulted in increase in apixaban maximum plasma concentration (Cmax ) and area under the plasma concentration-time curve from time zero to the last quantifiable concentration (AUC(0-tlast) ) with associated geometric mean ratios (GMRs) and 90% confidence intervals (CIs) of 143% (112, 183) and 120% (97, 148), respectively. Co-administration with tacrolimus resulted in reduction in apixaban Cmax and AUC(0-tlast) with associated GMRs (90% CI) of 87% (69, 112) and 78% (63, 97), respectively. The observed changes in apixaban exposure margins with cyclosporine or tacrolimus are within the range of the historical clinical development program, therefore, apixaban dose adjustments are not warranted.

Venous thromboembolism, factor VIII and chronic kidney disease

Chronic kidney disease (CKD) affects 30 million Americans and is associated with approximately a two-fold increased risk of venous thromboembolism (VTE). There is a graded increased risk of VTE across declining kidney function, as measured by estimated glomerular filtration rate (eGFR) and albuminuria. When patients with end-stage kidney disease (ESKD) experience VTE they are more likely than the general population to be hospitalized and they have a higher mortality. The incidence and consequences of VTE may also differ depending on the cause of kidney disease. In addition, kidney transplant patients with VTE are at a greater risk for death and graft loss than transplant patients without VTE. The reasons that patients with CKD are at increased risk of VTE are not well understood, but recent data suggest that factor VIII is a mediator. Factor VIII is an essential cofactor in the coagulation cascade and a strong risk factor for VTE in general. It is inversely correlated with eGFR and prospective studies demonstrate that factor VIII activity predicts incident CKD and rapid eGFR decline. The etiology of CKD may also influence factor VIII levels. This review summarizes the epidemiology VTE in CKD and reviews the biochemistry of factor VIII and determinants of its levels, including von Willebrand factor and ABO blood group. We explore mechanisms by which the complications of CKD might give rise to higher factor VIII and suggests future research directions to understand how factor VIII and CKD are linked.

Effect of the Direct Oral Anticoagulants Rivaroxaban and Apixaban on the Disposition of Calcineurin Inhibitors in Transplant Recipients

BACKGROUND

Calcineurin inhibitors (CNIs) and direct oral anticoagulants (DOACs) share certain metabolic pathways, but whether DOACs influence CNI exposure has not been assessed.

METHODS

A single-center retrospective analysis was performed including 39 organ recipients treated with the combination of a CNI and rivaroxaban (n = 29) or apixaban (n = 10). Dose-corrected CNI trough concentrations (C0/D) during 200 days before and after DOAC initiation were recorded (n = 261), together with covariates known to influence CNI disposition such as steroid dose and hematocrit. The average C0/D before and during DOAC therapy was compared using paired samples t test. Multivariable mixed models were constructed to estimate the effect of DOAC and other predictors on C0/D at each time point.

RESULTS

Group average C0/D was not significantly different before and during DOAC therapy for any CNI-DOAC combination (P = 0.089-0.761), although C0/D changed >20% in 19/39 patients (13 increases, 6 decreases). In multivariable analysis, independent predictors of tacrolimus C0/D were methylprednisolone dose (P = 0.039) and concomitant use of a CYP3A inhibitor (P = 0.007). The subgroup analysis per DOAC showed a limited but significant effect of rivaroxaban on tacrolimus C0/D (9.2% increase, P = 0.042). Independent predictors of ciclosporin C0/D were age (P = 0.018) and use of any DOAC (12.1% increase, P = 0.020).

CONCLUSIONS

Apixaban, and particularly rivaroxaban, may cause a limited (<20%) increase in CNI trough concentration, an effect that is unlikely to trigger a dose change. It may be prudent to perform an additional CNI trough concentration measurement 5-7 days after DOAC initiation, but preemptive CNI dose changes are not warranted based on these observations.

Venous Thromboembolism and the Risk of Death and Graft Loss in Kidney Transplant Recipients

BACKGROUND

The implications of venous thromboembolism (VTE) for morbidity and mortality in kidney transplant recipients are not well described.

METHODS

We conducted a retrospective study using linked healthcare databases in Ontario, Canada to determine the risk and complications of VTE in kidney transplant recipients from 2003 to 2013. We compared the incidence rate of VTE in recipients (n = 4,343) and a matched (1:4) sample of the general population (n = 17,372). For recipients with evidence of a VTE posttransplant, we compared adverse clinical outcomes (death, graft loss) to matched (1:2) recipients without evidence of a VTE posttransplant.

RESULTS

During a median follow-up of 5.2 years, 388 (8.9%) recipients developed a VTE compared to 254 (1.5%) in the matched general population (16.3 vs. 2.4 events per 1,000 person-years; hazard ratio [HR] 7.1, 95% CI 6.0-8.4; p < 0.0001). Recipients who experienced a posttransplant VTE had a higher risk of death (28.5 vs. 11.2%; HR 4.1, 95% CI 2.9-5.8; p < 0.0001) and death-censored graft loss (13.1 vs. 7.5%; HR 2.3, 95% CI 1.4-3.6; p = 0.0006) compared to matched recipients who did not experience a posttransplant VTE.

CONCLUSIONS

Kidney transplant recipients have a sevenfold higher risk of VTE compared to the general population with VTE conferring an increased risk of death and graft loss.

The postoperative venous thromboembolism (TREVO) study - risk and case mortality by surgical specialty

INTRODUCTION AND OBJECTIVES

Venous thromboembolism, risk of which is increased in surgical patients, is a preventable cause of morbidity and death. The primary objective of this study was to estimate the incidence of symptomatic postoperative venous thromboembolism in adults at a tertiary university hospital, overall and by surgical specialty. The secondary objective was to analyze severity of and mortality from thromboembolic events.

METHODS

We performed a retrospective study to identify cases of in-hospital postoperative venous thromboembolism, encoded by the International Classification of Diseases, Ninth Revision, according to the Joint Commission International criteria. Adult patients admitted for surgery in 2008-2012 were included.

RESULTS

Among 67 635 hospitalizations, 90 cases of postoperative symptomatic venous thromboembolism were identified, corresponding to an incidence of 1.33/1000 admissions (95% confidence interval [CI] 1.1-1.6/1000). Neurosurgery had the highest risk (4.07/1000), followed by urological surgery and general surgery (p<0.001). There were 50 cases of pulmonary embolism, 11 of which were fatal. Of the 90 cases, 12.2% occurred under neuraxial anesthesia and 55.1% in patients with American Society of Anesthesiology III physical status. At least 37.7% of patients with events received a prophylactic dose of injectable anticoagulant postoperatively. The overall risk decreased from 2008 to 2012. Venous thromboembolism-associated mortality during hospitalization was 21.1% (95% CI 13.6-30.4).

CONCLUSIONS

The incidence of postoperative symptomatic venous thromboembolism was 1.33/1000. Neurosurgery showed the greatest risk. Mortality was 21.1%.

Cardiovascular disease risk in patients receiving organ transplantation: a national cohort study

Although organ transplantation is the definitive treatment for end-stage organ failure, the post-transplant outcomes can be substantially influenced by cardiovascular complications. A national cohort study was performed to estimate risks of cardiovascular diseases in those with heart, lung, kidney, and liver transplantation. This cohort study consisted of 5978 solid organ transplantations identified using the Taiwan National Health Insurance Database. Cardiovascular and mortality risks in transplant recipients were evaluated using standardized incidence ratios, excess absolute risks, and standardized mortality ratios as compared to those in the general population. In heart, kidney, and liver recipients, the standardized incidence ratios of overall cardiovascular diseases were 9.41 (7.75-11.44), 3.32 (2.29-3.77), and 1.4 (1.15-1.7) and the overall standardized mortality ratios were 5.23 (4.54-6.03), 1.48 (1.34-1.63), and 3.95 (3.64-4.28), respectively. Except for heart organ recipients who were at highest risk for coronary artery disease with a standardized incidence ratio of 13.12 (10.57-16.29), kidney and liver organ recipients had a ninefold increased risk in developing deep vein thrombosis post-transplant. In conclusion, solid organ transplant patients are at risk of cardiovascular disease, in particular, deep vein thrombosis, which may warrant early identification of high-risk patients in addition to prompt and adequate thromboprophylaxis perioperatively.

Symptomatic Venous Thromboembolism and Major Bleeding After Renal Transplantation: Should We Use Pharmacologic Thromboprophylaxis?

BACKGROUND

Venous thromboembolism (VTE) is a major health issue that may result in complications such as post-thrombotic syndrome, pulmonary hypertension, and death. Appropriate thromboprophylaxis in individuals undergoing kidney transplantation remains unclear. The aim of this study was to determine the prevalence of symptomatic VTE and major bleeding within 90 days after renal transplantation (RT).

METHODS

This was a retrospective study on consecutive patients undergoing RT at Hospital Privado Córdoba, Argentina, from January 1, 2006, to December 31, 2013. Exclusion criteria were age <18 years and combined organ transplantation. Pharmacologic or mechanical thromboprophylaxis was not used routinely. Symptomatic VTE and major bleeding were documented.

RESULTS

A total of 511 RTs were performed; 62 patients received combined organ transplantation, and 8 patients (1.5%) were lost to follow-up. Overall, follow-up was completed on 441 patients, 4 (0.9%) of whom developed deep venous thrombosis and 14 (3%) of whom died. The most frequent causes of death were septic shock and severe hemorrhage. Duration of surgery >4 hours (P = .006) and a history of VTE (P < .001) were associated with VTE. Twenty-three patients (5.2%) had major bleeding, 2 (0.4%) died from bleeding complications, and 17 (3.85%) required a reoperation to control bleeding.

CONCLUSIONS

This study shows a low prevalence of symptomatic VTE in patients undergoing RT despite not having used thromboprophylaxis routinely. Major bleeding was significant, and despite the high risk of VTE assigned by the Caprini score, which suggests pharmacologic prophylaxis, our data raise questions about the appropriate prophylaxis for these patients.

Measures of Kidney Disease and the Risk of Venous Thromboembolism in the REGARDS (Reasons for Geographic and Racial Differences in Stroke) Study

BACKGROUND

Kidney disease has been associated with venous thromboembolism (VTE) risk, but results conflict and there is little information regarding blacks.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

30,239 black and white adults 45 years or older enrolled in the REGARDS (Reasons for Geographic and Racial Differences in Stroke) Study 2003 to 2007.

PREDICTORS

Estimated glomerular filtration rate (eGFR) using the combined creatinine-cystatin C (eGFR_cr-cys) equation and urinary albumin-creatinine ratio (ACR).

OUTCOMES

The primary outcome was adjudicated VTE, and secondary outcomes were provoked and unprovoked VTE, separately. Mortality was a competing-risk event.

RESULTS

During 4.6 years of follow-up, 239 incident VTE events occurred over 124,624 person-years. Cause-specific HRs of VTE were calculated using proportional hazards regression adjusted for age, sex, race, region of residence, and body mass index. Adjusted VTE HRs for eGFR_cr-cys of 60 to <90, 45 to <60, and <45 versus ≥90mL/min/1.73m² were 1.28 (95% CI, 0.94-1.76), 1.30 (95% CI, 0.77-2.18), and 2.13 (95% CI, 1.21-3.76). Adjusted VTE HRs for ACR of 10 to <30, 30 to <300, and ≥300 versus <10mg/g were 1.14 (95% CI, 0.84-1.56), 1.15 (95% CI, 0.79-1.69), and 0.64 (95% CI, 0.25-1.62). Associations were similar for provoked and unprovoked VTE.

LIMITATIONS

Single measurement of eGFR and ACR may have led to misclassification. Smaller numbers of events may have limited power.

CONCLUSIONS

There was an independent association of low eGFR (<45 vs ≥90mL/min/1.73m²) with VTE risk, but no association of ACR and VTE.

Trends of pulmonary embolism before and after kidney transplantation in black versus white patients

BACKGROUND

Pulmonary embolism (PE) is an important cause of in-hospital mortality and is common in renal transplantation and maintenance dialysis patients. PE incidence is higher among patients who are black; however, differences in trends of incidence and outcomes of PE by race among patients on dialysis and after renal transplantation is not well known.

METHODS

In this observational study, the incidences of PE hospitalizations and mortality were studied in those with renal transplant, on maintenance dialysis, and in general population. Incidences were compared across racial groups. Renal transplantation status as a predictor of mortality was also examined.

RESULTS

The incidences of PE in general population, dialysis, and renal transplant groups were 70.5, 518.8, and 158.8 per 100,000 population, respectively. Incidence was higher in blacks across all groups. The age-adjusted incidence of PE admissions increased over time in all groups with greater increase in blacks in non-transplant groups (the slope in dialysis for blacks was 112.1 versus that for whites at 49.4; P = .001; the slope in general population for blacks was 9.3 versus 3.4 for whites; P = .003). The mortality rate in general population was not significantly different than renal transplant group (3.4% versus 1.9%, P = .2); however, was lower than 6.8% seen in dialysis group (P < .001). The mortality rate was not different between whites and blacks. Maintenance dialysis was an independent predictor of mortality (odds ratio [OR] 1.94; 95% confidence interval [CI] 1.62-2.32).

CONCLUSIONS

PE in those with renal transplant is more common than in general population but less common than those on maintenance dialysis. The mortality rate for PE hospitalizations is equivocal between renal transplant and general population but higher for patients on dialysis. The incidence of PE hospitalizations is not only higher among blacks, but is increasing disproportionately in this group among those who are on maintenance dialysis and within general population.

Late-onset renal vein thrombosis: A case report and review of the literature

INTRODUCTION

Renal vein thrombosis, a rare complication of renal transplantation, often causes graft loss. Diagnosis includes ultrasound with Doppler, and it is often treated with anticoagulation or mechanical thrombectomy. Success is improved with early diagnosis and institution of treatment.

PRESENTATION OF CASE

We report here the case of a 29 year-old female with sudden development of very late-onset renal vein thrombosis after simultaneous kidney pancreas transplant. This resolved initially with thrombectomy, stenting and anticoagulation, but thrombosis recurred, necessitating operative intervention. Intraoperatively the renal vein was discovered to be compressed by a large ovarian cyst.

DISCUSSION

Compression of the renal vein by a lymphocele or hematoma is a known cause of thrombosis, but this is the first documented case of compression and thrombosis due to an ovarian cyst.

CONCLUSION

Early detection and treatment of renal vein thrombosis is paramount to restoring renal allograft function. Any woman of childbearing age may have thrombosis due to compression by an ovarian cyst, and screening for this possibility may improve long-term graft function in this population.

Mechanical thromboprophylaxis is sufficient to prevent the lower extremity deep vein thrombosis after kidney transplantation

Purpose

Deep vein thrombosis (DVT) is a severe and common complication that occurs after the major operation. Despite the commonality of DVT there is limited data on the incidence of DVT after kidney transplantation (KT). Furthermore, most studies have been retrospective in design and were conducted in western countries. The aim of this study was to evaluate the incidence of lower extremity DVT with mechanical thromboprophylaxis within 1 month of KT in Korea.

Methods

A total of 187 consecutive patients who underwent KT were included in this study. Patients used a graduated elastic stocking (n = 93) or an intermittent pneumatic compression device (n = 94) to prevent DVT. The frequency of DVT during the first month after KT was evaluated using serial color duplex ultrasound on postoperative days 7 ± 2, 14 ± 2, and 28 ± 3. All patients were tested for eight thrombophilic factors before KT.

Results

DVT occurred in four patients (2.1%) during the first month after KT. All DVT developed in the graduated elastic stocking group. Interestingly, none of the patients had the factor V Leiden mutation or the prothrombin gene 20210A mutation.

Conclusion

The incidence of DVT in this study was relatively lower than that of western populations. We did not encounter a factor V Leiden mutation or a prothrombin gene 20210A mutation in our study population. These findings suggest that inherited thrombophilic risk factors may be partially responsible for the difference in DVT incidence rates between different nationalities and/or ethnicities.

Treatment with everolimus is associated with a procoagulant state

INTRODUCTION

Renal transplant recipients are at increased risk of venous thromboembolic events, which is in part caused by their treatment with maintenance immunosuppressive drugs. Because we observed an increased incidence of venous thromboembolic events in renal transplant recipients treated with the mTOR inhibitor (mTORi) everolimus, we aimed to identify prothrombotic mechanisms of this immunosuppressive drug.

MATERIALS AND METHODS

In a single center study, nested in a multi-center randomized controlled trial, we measured parameters of coagulation, anti-coagulation and fibrinolysis in renal transplant recipients, receiving the mTORi everolimus (n=16, mTOR group) and compared them to a similar patient group, receiving a calcineurin inhibitor and/or mycophenolate sodium (n=20, non-mTOR group). All patients were at least 6 months following transplantation with a stable transplant function.

RESULTS

The use of an mTORi was associated with significantly higher levels of von Willebrand factor, prothrombin fragment 1+2, thrombin-activatable fibrinolysis inhibitor and plasminogen activator inhibitor-1 as compared to a non-mTORi based immunosuppressive regimen.

CONCLUSIONS

Treatment with an mTORi leads to increased endothelial activation, thrombin formation and impaired fibrinolysis in renal transplant recipients. This suggests an increased risk of thrombotic events in renal transplant recipients treated with mTOR inhibitors. A prospective study to establish the precise risk of thrombotic events in these patients is urgently needed.

Splanchnic vein thrombosis following renal transplantation: a case report

Background

Recurrent episodes of venous thrombosis have been closely correlated with JAK2 V617F mutation. Upto date, JAK2 gene mutation has not been defined as a prothrombic risk factor in renal transplant recipients. Herein; we present a case of portosplenic vein thrombosis in a primary renal transplant recipient with JAK2 V617F mutation who had no history of prior venous thromboembolism or thrombophilia.

Case presentation

A 59 year old female caucasian patient with primary kidney transplant admitted with vague abdominal pain at left upper quadrant. Abdominal doppler ultrasound and magnetic resonance imaging angiography demonstrated splanchnic vein thrombosis (SVT). The final diagnosis was SVT due to MPD (essential thrombocytosis, ET) with JAK2 V617F mutation. After 3 months of treatment with warfarin (≥5 mg/day, to keep target INR values of 1.9-2.5), control MRI angiography and doppler USG demonstrated partial (>%50) resolution of thrombosis with recanalization of hepatopedal venous flow. The patient is still on the same treatment protocol without any complication.

Conclusion

JAK2 V617F mutation analysis should be a routine procedure in the diagnosis and treatment of kidney transplant patients with thrombosis in uncommon sites.

Platelet Hyperaggregability is Highly Prevalent in Patients With Chronic Kidney Disease

Background:

Platelet hyperaggregation is known to be associated with arterial and venous thromboembolic events. The prevalence of platelet hyperaggregation in patients with chronic kidney disease (CKD) has not been described to date.

Methods:

Platelet hyperaggregation in patients with renal disease was defined by comparison of platelet aggregation patterns to non-CKD patients without thromboembolic disorders and healthy controls.

Results:

Among the 30 hemodialysis patients and 34 renal transplant recipients, 20 (67%) and 28 (82%) showed significantly decreased median Δ-epinephrine aggregation and increased 0.5 mol/L epinephrine response (65% and 54%) compared to healthy controls and non-CKD patients. In concordance to the laboratory finding of platelet hyperaggregability, renal transplant recipients showed a high rate of thromboembolic events (normal platelet aggregation: 0 events and platelet hyperaggregation: 30 events in 13 of 28 patients).

Conclusions:

Patients with CKD exhibit a hitherto unappreciated high prevalence of platelet hyperaggregability indicating sticky platelet syndrome. Laboratory testing of platelet hyperaggregability may supplement the assessment of thromboembolic complications in patients with CKD.

Risk factors for early hemorrhagic and thrombotic complications after kidney transplantation

INTRODUCTION

Clotting disturbances resulting from chronic renal failure do not remit immediately after successful kidney transplantation (KTx). Hemorrhagic and thrombotic complications after KTx increase the risk of transplanted kidney loss. The aim of the study was to analyze the influence of clotting system disturbances and applied antithrombotic prophylaxis on the development of hemorrhagic and thrombotic complications among KTx patients in the early postoperative period.

MATERIALS AND METHODS

Sixty seven KTx patients underwent measurement of plasma activated partial thromboplastin time (APTT); international normalized ratio; fibrinogen and D-dimer concentration; activity of antitrombin III; protein C and S, VIII, IX; and von Willebrand factors, as well as platelet counts.

RESULTS

A perigraft hematoma developed in 25.4% patients, of whom 4.5% required reoperation. Lower antithrombin III activity (96.2±27.6 vs 112.3±17.4, P=.02) on postoperative day (POD) 7 and higher fibrinogen concentration (4.41±2.03 vs 3.35±0.87, P=.01) and platelet count (269.8±117.5 vs 215.8±64.8, P=.03) on POD 14 were noted in recipients with a hematoma compared to those free of this complication. A perigraft hematoma developed in 57.9% patients undergoing antithrombotic prophylaxis and in 12.5% without this treatment (P=.0002). Among patients receiving unfractionated heparin, we observed extension of APTT on POD 1 (45.9±53.2 vs 30.9±7.5 seconds, P=.04), higher von Willebrand factor activity on POD 7 (348.8±122.2 vs 218.5±125.5, P=.02), and higher D-dimer concentrations POD 7 and 14 (1662±894 vs 757±708, P=.002 and 1614±1372 vs 672±532, P=.003, respectively). No significant differences were observed as regards to analyzed parameters between patients receiving low-molecular-weight heparin versus those not receiving antithrombotic prophylaxis.

CONCLUSIONS

Disturbances in analyzed parameters of hemostasis did not increase the risk of hemorrhagic and thrombotic complications in the early period after KTx. Antithrombotic prophylaxis increases the risk of hemorrhagic complications and should be introduced only for selected renal transplant recipients.

Organ transplants do not escape paradoxical embolisms

Acute renal allograft dysfunction in the first weeks after transplantation primarily requires examination for acute rejection, drug-associated injury, pre-renal failure due to exsiccosis/dehydration, and post-renal problems such as urinary tract obstruction. In rare instances, main renal artery or vein thrombosis may be found, e.g. due to acute rejection of the vessels. Herein, we describe the clinical course of a patient with a recent renal transplantation who presented with an acute enigmatic renal allograft failure which, after intensive diagnostic efforts, emerged as paradoxical embolism with extensive allograft ischemia in consequence of a venous thrombosis and a patent foramen ovale - a so far unreported case.