Evaluation of Heparin Anticoagulation Protocols in Post-Renal Transplant Recipients (EHAP-PoRT Study)

Predictive Value of HAS-BLED Score Regarding Bleeding Events and Graft Survival following Renal Transplantation

Objective: Due to the high prevalence and incidence of cardio- and cerebrovascular diseases among dialysis-dependent patients with end-stage renal disease (ERSD) scheduled for kidney transplantation (KT), the use of antiplatelet therapy (APT) and/or anticoagulant drugs in this patient population is common. However, these patients share a high risk of complications, either due to thromboembolic or bleeding events, which makes adequate peri- and post-transplant anticoagulation management challenging. Predictive clinical models, such as the HAS-BLED score developed for predicting major bleeding events in patients under anticoagulation therapy, could be helpful tools for the optimization of antithrombotic management and could reduce peri- and postoperative morbidity and mortality. Methods: Data from 204 patients undergoing kidney transplantation (KT) between 2011 and 2018 at the University Hospital Leipzig were retrospectively analyzed. Patients were stratified and categorized postoperatively into the prophylaxis group (group A)—patients without pretransplant anticoagulation/antiplatelet therapy and receiving postoperative heparin in prophylactic doses—and into the (sub)therapeutic group (group B)—patients with postoperative continued use of pretransplant antithrombotic medication used (sub)therapeutically. The primary outcome was the incidence of postoperative bleeding events, which was evaluated for a possible association with the use of antithrombotic therapy. Secondary analyses were conducted for the associations of other potential risk factors, specifically the HAS-BLED score, with allograft outcome. Univariate and multivariate logistic regression as well as a Cox proportional hazard model were used to identify risk factors for long-term allograft function, outcome and survival. The calibration and prognostic accuracy of the risk models were evaluated using the Hosmer−Lemshow test (HLT) and the area under the receiver operating characteristic curve (AUC) model. Results: In total, 94 of 204 (47%) patients received (sub)therapeutic antithrombotic therapy after transplantation and 108 (53%) patients received prophylactic antithrombotic therapy. A total of 61 (29%) patients showed signs of postoperative bleeding. The incidence (p < 0.01) and timepoint of bleeding (p < 0.01) varied significantly between the different antithrombotic treatment groups. After applying multivariate analyses, pre-existing cardiovascular disease (CVD) (OR 2.89 (95% CI: 1.02−8.21); p = 0.04), procedure-specific complications (blood loss (OR 1.03 (95% CI: 1.0−1.05); p = 0.014), Clavien−Dindo classification > grade II (OR 1.03 (95% CI: 1.0−1.05); p = 0.018)), HAS-BLED score (OR 1.49 (95% CI: 1.08−2.07); p = 0.018), vit K antagonists (VKA) (OR 5.89 (95% CI: 1.10−31.28); p = 0.037), the combination of APT and therapeutic heparin (OR 5.44 (95% CI: 1.33−22.31); p = 0.018) as well as postoperative therapeutic heparin (OR 3.37 (95% CI: 1.37−8.26); p < 0.01) were independently associated with an increased risk for bleeding. The intraoperative use of heparin, prior antiplatelet therapy and APT in combination with prophylactic heparin was not associated with increased bleeding risk. Higher recipient body mass index (BMI) (OR 0.32 per 10 kg/m2 increase in BMI (95% CI: 0.12−0.91); p = 0.023) as well as living donor KT (OR 0.43 (95% CI: 0.18−0.94); p = 0.036) were associated with a decreased risk for bleeding. Regarding bleeding events and graft failure, the HAS-BLED risk model demonstrated good calibration (bleeding and graft failure: HLT: chi-square: 4.572, p = 0.802, versus chi-square: 6.52, p = 0.18, respectively) and moderate predictive performance (bleeding AUC: 0.72 (0.63−0.79); graft failure: AUC: 0.7 (0.6−0.78)). Conclusions: In our current study, we could demonstrate the HAS-BLED risk score as a helpful tool with acceptable predictive accuracy regarding bleeding events and graft failure following KT. The intensified monitoring and precise stratification/assessment of bleeding risk factors may be helpful in identifying patients at higher risks of bleeding, improved individualized anticoagulation decisions and choices of antithrombotic therapy in order to optimize outcome after kidney transplantation.

Impact of intra-abdominal pressure on early kidney transplant outcomes

Increased intra-abdominal pressure (IAP) is common among post-surgical patients and may cause organ dysfunction. However, its impact after kidney transplantation on early postoperative complications and graft recovery remains unclear. We designed a prospective, observational cohort study to describe the prevalence and determinants of IAP, as well as its effect on delayed graft function, postoperative complications, and graft recovery. IAP was measured in 205 kidney transplant recipients every 8 h during the first 72 h after surgery using the urinary bladder technique. Intra-abdominal hypertension was defined as IAP ≥ 12 mmHg. Patients were followed for 6 months or until graft failure/death. Mean IAP was 12 ± 3.3 mmHg within the first 24 h. 78% of subjects presented with intra-abdominal hypertension during the first 72 h. Increased IAP was associated with higher renal resistive index [r = 0.213; P = 0.003] and lower urine output [r =  - 0.237; P < 0.001]. 72 h mean IAP was an independent risk factor for delayed graft function [OR: 1.31; 95% CI: 1.13-1.51], postoperative complications [OR: 1.17; 95% CI: 1.03-1.33], and absence of graft function recovery [HR for graft function recovery: 0.94; 95% CI: 0.88-0.99]. Increased IAP was highly prevalent after transplantation and was independently associated with delayed graft function, postoperative complications, and absence of graft function recovery. Routine IAP monitoring should be considered post-transplantation to facilitate early recognition of relevant complications.

Ex-vivo Kidney Machine Perfusion: Therapeutic Potential

Kidney transplantation remains the gold standard treatment for patients suffering from end-stage kidney disease. To meet the constantly growing organ demands grafts donated after circulatory death (DCD) or retrieved from extended criteria donors (ECD) are increasingly utilized. Not surprisingly, usage of those organs is challenging due to their susceptibility to ischemia-reperfusion injury, high immunogenicity, and demanding immune regulation after implantation. Lately, a lot of effort has been put into improvement of kidney preservation strategies. After demonstrating a definite advantage over static cold storage in reduction of delayed graft function rates in randomized-controlled clinical trials, hypothermic machine perfusion has already found its place in clinical practice of kidney transplantation. Nevertheless, an active investigation of perfusion variables, such as temperature (normothermic or subnormothermic), oxygen supply and perfusate composition, is already bringing evidence that ex-vivo machine perfusion has a potential not only to maintain kidney viability, but also serve as a platform for organ conditioning, targeted treatment and even improve its quality. Many different therapies, including pharmacological agents, gene therapy, mesenchymal stromal cells, or nanoparticles (NPs), have been successfully delivered directly to the kidney during ex-vivo machine perfusion in experimental models, making a big step toward achievement of two main goals in transplant surgery: minimization of graft ischemia-reperfusion injury and reduction of immunogenicity (or even reaching tolerance). In this comprehensive review current state of evidence regarding ex-vivo kidney machine perfusion and its capacity in kidney graft treatment is presented. Moreover, challenges in application of these novel techniques in clinical practice are discussed.

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.

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.