The risk of thromboembolic events in kidney transplant patients

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.

Immunosuppressive therapy and oral anticoagulation in kidney transplant recipients: Direct oral anticoagulants versus vitamin-k antagonists

BACKGROUND

direct oral anticoagulants (DOACs) are an alternative to conventional antagonist of vitamin-K (AVK). However, immune suppressive drugs (ISDs) may interfere with DOACs pharmacokinetic.

AIM OF THIS STUDY

evaluate safety and efficacy profile of DOACs compared to AVK in kidney transplant recipients (KTRs) treated with ISDs.

METHODS

a multi-center study from 4 Italian University hospitals enrolling consecutive KTRs on DOACs or AVK was carried out. Sixty-six patients on DOACs were compared with fifty patients on AVK with similar clinical features. Serial evaluation of renal function and serum levels of ISDs during 18 months follow-up (FU) was performed.

RESULTS

Mean age of DOACs patients was 67±9 and mean eGFR was 58,3± 30,4mL/min/1.73m2. ISDs included tacrolimus (n=47, 71%), cyclosporin (n=13, 20%), everolimus (n=10, 7%) and sirolimus (n=4, 6%). After 14 days of DOACs therapy initiation there was a slight increase of serum levels of tacrolimus (+0.19±0.67 p=0.80) and cyclosporine (+0.12±0.25 p=0.94) not statistically significant. Levels of Tacrolimus and cyclosporin were stable at serial evaluation during 18-months follow-up. There were no thromboembolic events among patients treated with DOACs or AVK and no differences in term of major bleeding (6% vs 4% p=0.69), at long-term follow-up. There was no difference in term of eGFR decline from start therapy to 18 months FU between DOACs vs AVK therapy (-3.9±1 vs -3.8±2 p=0.82).

CONCLUSION

DOACs have similar safety and efficacy than AVK among KTRs treated with ISDs. However, careful evaluation of potential drug interaction and ISDs serum levels is needed.

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.

Risk and factors associated with venous thromboembolism following abdominal transplantation

Background

Venous thromboembolism (VTE) remains under-studied among patients undergoing kidney, liver and pancreas (abdominal) transplantation. We characterized the risk and predictors of VTE using a nationally-representative cohort.

Methods

The 2014-2019 Nationwide Readmissions Database was queried to identify all adults undergoing abdominal transplantation. Patients who developed pulmonary embolism or deep venous thrombosis were considered the VTE cohort (others: nonVTE). Multivariable models were developed to identify factors linked with VTE and assess the independent associations between VTE and key outcomes.

Results

Of ~141,977 transplant recipients, 1.9 % (2722) developed VTE. The VTE cohort was similarly female (39.2 vs 38.0, p = 0.51), but more often demonstrated a higher Elixhauser comorbidity index (4.19 ± 1.40 vs 3.93 ± 1.39, p < 0.001).After adjustment, congestive heart failure (AOR 1.54, 95%CI 1.25-1.91), cardiac arrhythmias (AOR 1.54, 95%CI 1.34-1.78), peripheral vascular disease (AOR 1.29, 95%CI 1.02-1.63), coagulopathies (AOR 1.63, 95%CI 1.38-1.92), previous history of VTE (AOR 1.14, 95%CI 1.06-1.22), and heparin-induced thrombocytopenia (AOR 2.61, 95%CI 2.07-3.28) were associated with VTE. The development of VTE was linked with significantly greater in-hospital mortality (AOR 4.56, 95%CI 2.07-10.10), as well as infectious (AOR 2.59, 95%CI 1.55-4.21), cardiac (AOR 2.59, 95%CI 1.39-4.82), and respiratory (AOR 1.78, 95%CI 1.21-2.63) complications. VTE was further associated with increased length of stay (+8.18 days, 95%CI +1.32-15.41), expenditures (+$42,000, 95%CI $24,800-59,210), and odds of VTE upon readmission (AOR 4.51, 95%CI 1.32-15.41).

Conclusions

VTE after abdominal transplantation is linked with significantly greater in-hospital mortality, complications, resource utilization, and risk of VTE at readmission. Novel risk assessments and prophylaxis protocols are needed to reduce VTE incidence and sequelae.

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.

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.

Deep vein thrombosis in the setting of Klippel-Trenaunay syndrome and sirolimus treatment

Klippel-Trenaunay syndrome (KTS) is a congenital vascular disorder characterized by the triad of cutaneous capillary malformation, lymphatic and venous anomalies, and soft tissue and bone overgrowth. Sirolimus is a mechanistic target of rapamycin inhibitor used as an immunosuppressive drug. It has also been used to improve and treat vascular malformations that can predispose to intravascular coagulopathy. We have described the case of a patient with KTS receiving a therapeutic anticoagulation dose, for whom sirolimus was initiated, and who had presented with an extensive venous thromboembolism. Correlations between the use of sirolimus in patients with KTS are limited, and cautious use and monitoring could be necessary.

Incidence, risk factors, and outcomes of post-transplant erythrocytosis after kidney transplantation

The incidence, risk factors, and outcomes of kidney transplant recipients (KTRs) with post-transplant erythrocytosis (PTE) in the modern era of strong, protocolized immunosuppressive management are unknown. In this study, we aim to identify the incidence and risk factors of PTE and outcomes associated with PTE. This study examined adult KTRs transplanted at our hospital between 01/2001 and 12/2016. Controls were KTRs without PTE and selected in a 1:5 ratio using incident density sampling. Patient survival, graft survival, and vascular thromboembolism (VTE) incidence were outcomes of interest. Of 4,317 kidney transplants during the study period, 214 (5%) had PTE and were compared with controls. In the multivariate analysis, recipients with older age (HR: 0.97, 95% CI 0.96-0.99, p = .001) were less likely to develop PTE, while male gender (HR: 3.2; 95% CI: 1.92-5.3, p < .001) and non-preemptive transplant (HR: 3.86, 95% CI 1.56-9.56, p = .003) were associated with increased risk of PTE. After adjustment for confounding factors, PTE was not associated with patient mortality (HR: 0.99, 95% CI 0.69-1.42, p = .97), graft failure (HR: 1.11, 95% CI 0.68-1.80, p = .69), or VTE (HR: 1.07, 95% CI 0.59-1.96, p = .81). The incidence of PTE is still substantial in this era, but with proper management PTE does not impact patient or graft survival.

Ischemic Stroke in a Young Patient with Nephrotic Syndrome and Antiphospholipid Syndrome

We report a case of a 21-year-old man with underlying nephrotic syndrome (NS) secondary to minimal change disease, who developed an ischemic stroke with left hemiparesis. He received intravenous thrombolysis followed by a mechanical thrombectomy. After mechanical thrombectomy, he developed acute kidney injury which subsequently required haemodialysis. Further workup revealed that he had concomitant antiphospholipid syndrome (APS) and NS. He was started on vitamin K antagonist anticoagulant. This case report illustrates the importance of workup in identifying causes of ischemic stroke in a young patient.

Alternative Diagnostic Strategy for the Assessment and Treatment of Pulmonary Embolus: A Case Series

Introduction

Ferumoxytol-enhanced magnetic resonance angiography (FeMRA) can be used as an alternate and safe method to diagnose patients with compromised renal function who present with acute pulmonary embolus in the emergency department (ED) setting.

Case Report

A 62-year old man with a history of renal transplant and lymphoproliferative disease described new onset of breathlessness. His clinical symptoms were suggestive of pulmonary embolus. He underwent FeMRA in the ED to avoid exposure to intravenous iodinated contrast. FeMRA demonstrated a left main pulmonary artery embolus, which extended to the left interlobar pulmonary artery. Afterward, the patient initiated anticoagulation therapy. With preserved renal function he was able to continue his outpatient chemotherapy regimen.

Conclusion

This case highlights a safe imaging technique for emergency physicians to diagnose pulmonary embolus and subsequently guide anticoagulation therapy for patients in whom use of conventional contrast is contraindicated.

Incidence and outcome of isolated distal deep vein thrombosis in kidney transplant recipients

Purpose

Isolated distal deep vein thrombosis (IDDVT) is a localized lesion; nonetheless, the risk of proximal vein propagation makes it difficult to decide on the treatment protocol—that is, whether immediate anticoagulation after diagnosis or surveillance via serial imaging should be employed. This study aimed to investigate the appropriate treatment protocol for IDDVT in kidney transplant recipient (KTR).

Methods

Surveillance for venous thromboembolism (VTE) was performed using duplex ultrasonography (DUS) before transplant surgery and at 1 week, 2 weeks, 1 month, 3 months, 6 months, and 1 year after transplant surgery. Dual mechanical prophylaxis was administered to prevent VTE.

Results

In total, 60 out of 829 patients (7.2%) developed VTE, with 49 cases (81.6%) of IDDVT. Among IDDVT patients, 15 patients were treated using anticoagulation-first strategy, whereas the remaining 34 patients were treated using surveillance-first strategy. No patient in either group exhibited thrombus extension into the proximal vein or recurrence within 1 year from transplant surgery.

Conclusion

In Korean KTR, extension of IDDVT into the proximal vein could be prevented safely and effectively by serial DUS surveillance along with the maintenance of mechanical prophylaxis. However, the patients who have high thrombus burden or are difficult to get repeated DUS require the use of anticoagulation in early stages.

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.

Renal Transplantation Is Associated with Increased Complications Following Spinal Fusion Operations: Analysis of a National Database

BACKGROUND

Improved postoperative care for renal transplant recipients has advanced both duration and overall quality of life. However, degenerative spinal pathology is increasingly prevalent after transplant. Outcomes following spinal fusion among the renal transplant population in the United States are rarely addressed.

METHODS

The Healthcare Cost and Utilization Project National Inpatient Sample database was employed. Cases in years 2008-2014 for patients ≥18 years old receiving spinal fusion, exploration/decompression, and/or spinal revision/re-fusion surgeries were included. Cases were divided into kidney transplant recipients (KTR) and non-kidney transplant recipients. Complications, demographics, and socioeconomic outcomes were compared between cohorts.

RESULTS

Of 579,726 patients who met inclusion criteria, 685 (0.1%) were KTRs. The KTR population was older and included more men compared with the non-kidney transplant recipient population (60.1 years vs. 56.6 years, P < 0.001; 58% male vs. 45.5% male, P < 0.001). KTRs experienced higher total complication rates (29.8% vs. 18.9%, P < 0.001). Prevalence of acute posthemorrhagic anemia and need for transfusion was markedly higher for KTRs (15.8% vs. 9.1%, P < 0.001; 13.6% vs. 6.2%, P < 0.001). Multivariate analysis revealed longer length of stay (median 1.23 days, interquartile range 0.94-1.53, P < 0.001), lower routine discharge (odds ratio = 0.57, 95% confidence interval 0.48-0.69, P < 0.001), and higher discharge to alternative care facilities (odds ratio = 1.91, 95% confidence interval 1.57-2.33, P < 0.001) for KTRs. The inpatient course for KTRs undergoing spinal operations was significantly costlier ($87,445 vs. $71,589, P < 0.001).

CONCLUSIONS

History of renal transplant was associated with increased inpatient medical and socioeconomic complications following spinal fusion. Physicians and patients must understand and respect the potentially increased perioperative challenges facing KTRs.

Chronic mesenteric ischaemia masked by candida esophagitis in a renal transplant patient

Chronic mesenteric ischaemia is a severe disease that is often missed due to its non-specific presentation. Immunosuppressed patients are at risk for infectious gastrointestinal disease, which may further obscure the diagnosis of chronic mesenteric ischaemia. In this case, a patient's symptoms and diagnostic workup were consistent with candida esophagitis. Worsening leukocytosis despite treatment, however, prompted re-evaluation ultimately revealing a superior mesenteric artery thrombus causing mesenteric ischaemia. The patient required urgent surgical intervention for the management of his disease.

Preemptively and non-preemptively transplanted patients show a comparable hypercoagulable state prior to kidney transplantation compared to living kidney donors

To prevent renal graft thrombosis in kidney transplantation, centres use different perioperative anticoagulant strategies, based on various risk factors. In our centre, patients transplanted preemptively are considered at increased risk of renal graft thrombosis compared to patients who are dialysis-dependent at time of transplantation. Therefore these patients are given a single dose of 5000 IU unfractionated heparin intraoperatively before clamping of the vessels. We questioned whether there is a difference in haemostatic state between preemptively and non-preemptively transplanted patients and whether the distinction in intraoperative heparin administration used in our center is justified. For this analysis, citrate samples of patients participating in the VAPOR-1 trial were used and several haemostatic and fibrinolytic parameters were measured in 29 preemptively and 28 non-preemptively transplanted patients and compared to 37 living kidney donors. Sample points were: induction anaesthesia (T1), 5 minutes after reperfusion (T2) and 2 hours postoperative (T3). At T1, recipient groups showed comparable elevated levels of platelet factor 4 (PF4, indicating platelet activation), prothrombin fragment F1+2 and D-dimer (indicating coagulation activation) and Von Willebrand Factor (indicating endothelial activation) compared to the donors. The Clot Lysis Time (CLT, a measure of fibrinolytic potential) was prolonged in both recipient groups compared to the donors. At T3, F1+2, PF4 and CLT were higher in non-preemptively transplanted recipients compared to preemptively transplanted recipients. Compared to donors, non-preemptive recipients showed a prolonged CLT, but comparable levels of PF4 and D-dimer. In conclusion pre-transplantation, preemptively and non-preemptively transplanted patients show a comparable enhanced haemostatic state. A distinction in intraoperative heparin administration between preemptive and non-preemptive transplantation does not seem justified.

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.

Influence of Kidney Transplant Status on Warfarin Dose, Anticoagulation Control, and Risk of Hemorrhage

STUDY DESIGN

To assess whether warfarin dose requirement, anticoagulation control, and risk of hemorrhage differ in kidney transplant recipients (KTRs) compared with patients without kidney transplants (non-KTRs).

DESIGN

Analysis of data from the Warfarin Pharmacogenetics Cohort, a prospective cohort of first-time warfarin users followed at two anticoagulation clinics.

SETTING

Two outpatient anticoagulation clinics at two large, academic, tertiary care hospitals.

PATIENTS

Adults aged 20 years or older starting warfarin for anticoagulation with a therapeutic international normalized ratio (INR) goal of 2-3 who were KTRs (n=65) or non-KTRs (n=1630).

MEASUREMENTS AND MAIN RESULTS

Warfarin dose requirement, anticoagulation control, and risk of hemorrhage were assessed in each group. KTRs required an approximately 20% lower warfarin dose (4.7 vs 5.6 mg/day, p=0.0005) compared with non-KTRs. Genetic variants had similar effects on dose in both groups. Mean percentage of time in therapeutic range (PTTR) was similar among KTRs and non-KTRs. Although the proportion of patients achieving good anticoagulation control (PTTR ≥ 60%) was low in both groups, it was similar among KTRs and non-KTRs. KTRs had a higher risk of major hemorrhage (hazard ratio 2.1, p=0.0081), but this difference was not statistically significant after controlling for kidney function, clinical, and genetic factors.

CONCLUSION

KTRs initiating warfarin require lower doses and closer monitoring to optimize anticoagulation therapy. Additional studies are needed to confirm these findings.

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%.

Antiphospholipid Syndrome: Role of Vascular Endothelial Cells and Implications for Risk Stratification and Targeted Therapeutics

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by venous thromboembolism, arterial thrombosis, and obstetric morbidities in the setting of persistently positive levels of antiphospholipid antibodies measured on 2 different occasions 12 weeks apart. Patients with APS are at increased risk for accelerated atherosclerosis, myocardial infarction, stroke, and valvular heart disease. Vascular endothelial cell dysfunction mediated by antiphospholipid antibodies and subsequent complement system activation play a cardinal role in APS pathogenesis. Improved understanding of their pathogenic function could help in the risk stratification of patients with APS and provide new molecular therapeutic targets.

Posttransplant Lymphoproliferative Disease and Inhibitors of Mammalian Target of Rapamycin: When a Quick Look Back Can Change the Perspective

Posttransplant lymphoproliferative disease represents a heterogeneous group of diseases characterized by uncontrolled proliferation of lymphocytes, favored by immunosuppression. Several risk factors for its development have been described, with Epstein-Barr virus infection being a main cause of early-onset forms and chronic antigen stimulation of donors and/or accumulated immunosuppression as key factors of later forms of lymphocyte transformation. The present clinical case presents a patient diagnosed with posttransplant lymphoproliferative disease 3 years after renal transplant who had a potentially lethal complication related to conversion to inhibitors of mammalian target of rapamycin. Because clinical studies that establish the most suitable treatment are lacking, it is recommended to identify the strategy, defining possible risks versus benefits of conversion to inhibitors of mammalian target of rapamycin in cases of posttransplant lymphoproliferative disease, and to maintain a high level of surveillance in case of possible secondary effects that can be verified after their introduction.

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.

Differences in coagulation in clotting of vascular access in hemodialysis patients

Arteriovenous graft (AVG) thrombosis is a frequent cause of graft failure. We evaluated coagulation protein concentrations, platelet function, and viscoelasticity factors in 20 hemodialysis (HD) patients with AVGs. The goal was to determine whether significant differences in protein concentrations, platelet function, and viscoelasticity factors exist among dialysis patients requiring frequent AVG declot procedures vs. those who do not. Twenty HD patients were enrolled: 10 frequent clotters (>3 declots in the previous year) and 10 were nonclotters. Patients on antiplatelets or chronic anticoagulation were excluded. Laboratories were drawn pretreatment and heparinase was added to counteract any potential heparin effect. Coagulation protein concentrations including tissue factor (TF), thrombin/antithrombin III complex (TAT), and prothrombin fragment 1 + 2 (F(1+2)) were assayed. The time to clot onset was measured by force onset time (FOT). Platelet contractile force (PCF) measured the force produced by platelets during clot retraction, whereas clot rigidity was measured as clot elastic modulus (CEM). FOT, CEM, and PCF were measured by Hemodyne. Both groups had upregulation of the TF pathway, as TF, TAT, and F(1+2) levels were similarly increased over baseline levels. Hemodialysis patients with frequent AVG clotting had higher levels of both PCF and CEM compared with nonclotters. Additionally, the frequent clotters had a lower FOT relative to nonclotters, although both were considered in the normal range. Our study suggests that HD patients with recurrent AVG thrombotic events form clots with higher tensile strength compared with HD patients without recurrent graft thrombosis.