Guide to anticoagulant therapy: Heparin : a statement for healthcare professionals from the American Heart Association

A Nanoscale Tool for Photoacoustic-Based Measurements of Clotting Time and Therapeutic Drug Monitoring of Heparin

Heparin anticoagulation therapy is an indispensable feature of clinical care yet has a narrow therapeutic window and is the second most common intensive care unit (ICU) medication error. The active partial thromboplastin time (aPTT) monitors heparin but suffers from long turnaround times, a variable reference range, limited utility with low molecular weight heparin, and poor correlation to dose. Here, we describe a photoacoustic imaging technique to monitor heparin concentration using methylene blue as a simple and Federal Drug Administration-approved contrast agent. We found a strong correlation between heparin concentration and photoacoustic signal measured in phosphate buffered saline (PBS) and blood. Clinically relevant heparin concentrations were detected in blood in 32 s with a detection limit of 0.28 U/mL. We validated this imaging approach by correlation to the aPTT (Pearson's r = 0.86; p < 0.05) as well as with protamine sulfate treatment. This technique also has good utility with low molecular weight heparin (enoxaparin) including a blood detection limit of 72 μg/mL. We then used these findings to create a nanoparticle-based hybrid material that can immobilize methylene blue for potential applications as a wearable/implantable heparin sensor to maintain drug levels in the therapeutic window. To the best of our knowledge, this is the first use of photoacoustics to image anticoagulation therapy with significant potential implications to the cardiovascular and surgical community.

Heparin-binding protein is important for vascular leak in sepsis

BACKGROUND

Elevated plasma levels of heparin-binding protein (HBP) are associated with risk of organ dysfunction and mortality in sepsis, but little is known about causality and mechanisms of action of HBP. The objective of the present study was to test the hypothesis that HBP is a key mediator of the increased endothelial permeability observed in sepsis and to test potential treatments that inhibit HBP-induced increases in permeability.

METHODS

Association between HBP at admission with clinical signs of increased permeability was investigated in 341 patients with septic shock. Mechanisms of action and potential treatment strategies were investigated in cultured human endothelial cells and in mice.

RESULTS

Following adjustment for comorbidities and Acute Physiology and Chronic Health Evaluation (APACHE) II, plasma HBP concentrations were weakly associated with fluid overload during the first 4 days of septic shock and the degree of hypoxemia (PaO₂/FiO₂) as measures of increased systemic and lung permeability, respectively. In mice, intravenous injection of recombinant human HBP induced a lung injury similar to that observed after lipopolysaccharide injection. HBP increased permeability of vascular endothelial cell monolayers in vitro, and enzymatic removal of luminal cell surface glycosaminoglycans (GAGs) using heparinase III and chondroitinase ABC abolished this effect. Similarly, unfractionated heparins and low molecular weight heparins counteracted permeability increased by HBP in vitro. Intracellular, selective inhibition of protein kinase C (PKC) and Rho-kinase pathways reversed HBP-mediated permeability effects.

CONCLUSIONS

HBP is a potential mediator of sepsis-induced acute lung injury through enhanced endothelial permeability. HBP increases permeability through an interaction with luminal GAGs and activation of the PKC and Rho-kinase pathways. Heparins are potential inhibitors of HBP-induced increases in permeability.

Extended enoxaparin monotherapy for acute symptomatic pulmonary embolism

We investigated the efficacy and safety of extended enoxaparin monotherapy in symptomatic patients with acute pulmonary embolism (PE). We randomized 40 patients in a 1:1 allocation to enoxaparin monotherapy (1 mg/kg twice daily for 10-18 days, and then 1.5 mg/kg once daily until day 90) ( n = 20) or to enoxaparin 1.0 mg/kg twice daily as a bridge to warfarin with a target international normalized ratio of 2.0-3.0 for 90 days (at least 10 doses of enoxaparin overlapping with warfarin for at least 4 days) ( n = 20). All patients underwent echocardiography, cardiac troponin I (TnI), and brain natriuretic peptide testing to identify patients with an increased likelihood of adverse clinical outcomes. The end-points were newly diagnosed deep venous thrombosis (DVT) or PE and bleeding events through day 90. In 15 patients on extended enoxaparin therapy, we used repeated measure analysis of variance (ANOVA) to investigate differences in anti-Xa levels obtained at 2, 4, 8 and 12 weeks. The patients’ mean age was 52 ± 17 years; the most common comorbidities were obesity (58%), hypertension (30%), concomitant DVT (30%) and cancer (15%). Twelve (30%) patients had elevated cardiac TnI >0.1 mg/l and 11 (28%) had moderate or severe right ventricular dysfunction on echocardiography. Ten (25%) patients received thrombolysis with a continuous infusion of 100 mg alteplase prior to randomization. During a 90-day follow-up, one patient from the enoxaparin monotherapy group suffered symptomatic distal DVT; one from the warfarin group had recurrent symptomatic PE (p= 1.0). None of the study patients had major hemorrhage; two warfarin group patients had minor bleeding compared with none in the enoxaparin monotherapy group (p= 0.49). Repeated measure ANOVA did not reveal significant differences in anti-Xa levels over time (p= 0.217). In patients with acute symptomatic PE, extended enoxaparin monotherapy is feasible and warrants further investigation in a large clinical trial.

Comparison of Time to Therapeutic aPTT in Patients Who Received Continuous Unfractionated Heparin After Implementation of Pharmacy-wide Intervention Alerts

Background: For patients on continuous IV unfractionated heparin (UFH), failing to achieve a therapeutic aPTT by 24 hours can be associated with increased morbidity. A pharmacy clinical surveillance system (PCSS) subtherapeutic aPTT alert was implemented at our institution to improve achievement of therapeutic aPTT goals by 24 hours. Objective: The primary objective was the time to achieve the minimum goal aPTT before and after the alert implementation. The secondary objectives were to examine the percentage of patients who achieved the minimum goal aPTT by 24 hours and the number of dose changes to achieve the minimum goal aPTT. Methods: A single-center retrospective study was conducted to include all adult inpatients receiving a continuous UFH infusion during a 3-month period prior to the implementation of a subtherapeutic aPTT alert and a 3-month period after implementation. Results: 317 patients were included in the analysis. The average time to achieve the minimum goal aPTT was 21.8 hours prior to alert implementation and 15.4 hours after implementation (p = .002). The percent of patients who achieved the minimum goal aPTT by 24 hours was 65.7% prior to alert implementation and 82.4% after implementation (p = .035). The average number of dose changes necessary to achieve aPTT value to the minimum goal aPTT prior to alert implementation was 1.67 and 1. 98 after implementation (p = .68). Conclusion: This analysis showed that implementation of a PCSS subtherapeutic aPTT alert for patients on continuous UFH infusions may ensure patients reach goal aPTT faster and facilitate a higher percent of patients who achieve the minimum goal aPTT by 24 hours.

Control of IBMIR Induced by Fresh and Cryopreserved Hepatocytes by Low Molecular Weight Dextran Sulfate Versus Heparin

Rapid destruction of hepatocytes after hepatocyte transplantation has hampered the application of this procedure clinically. The instant blood-mediated inflammatory reaction (IBMIR) is a plausible underlying cause for this cell loss. The present study was designed to evaluate the capacity of low molecular weight dextran sulfate (LMW-DS) to control these initial reactions from the innate immune system. Fresh and cryopreserved hepatocytes were tested in an in vitro whole-blood model using ABO-compatible blood. The ability to elicit IBMIR and the capacity of LMW-DS (100 μg/ml) to attenuate the degree of activation of the cascade systems were monitored. The effect was also compared to conventional anticoagulant therapy using unfractionated heparin (1 IU/ml). Both fresh and freeze-thawed hepatocytes elicited IBMIR to the same extent. LMW-DS reduced the platelet loss and maintained the cell counts at the same degree as unfractionated heparin, but controlled the coagulation and complement systems significantly more efficiently than heparin. LMW-DS also attenuated the IBMIR elicited by freeze-thawed cells. Therefore, LMW-DS inhibits the cascade systems and maintains the cell counts in blood triggered by both fresh and cryopreserved hepatocytes in direct contact with ABO-matched blood. LMW-DS at a previously used and clinically applicable concentration (100 μg/ml) inhibits IBMIR in vitro and is therefore a potential IBMIR inhibitor in hepatocyte transplantation.

New Functional Tools for Antithrombogenic Activity Assessment of Live Surface Glycocalyx

OBJECTIVE

It is widely accepted that the presence of a glycosaminoglycan-rich glycocalyx is essential for endothelialized vasculature health; in fact, a damaged or impaired glycocalyx has been demonstrated in many vascular diseases. Currently, there are no methods that characterize glycocalyx functionality, thus limiting investigators' ability to assess the role of the glycocalyx in vascular health.

APPROACH AND RESULTS

We have developed novel, easy-to-use, in vitro assays that directly quantify live endothelialized surface's functional heparin weights and their anticoagulant capacity to inactivate Factor Xa and thrombin. Using our assays, we characterized 2 commonly used vascular models: native rat aorta and cultured human umbilical vein endothelial cell monolayer. We determined heparin contents to be ≈10 000 ng/cm(2) on the native aorta and ≈10-fold lower on cultured human umbilical vein endothelial cells. Interestingly, human umbilical vein endothelial cells demonstrated a 5-fold lower anticoagulation capacity in inactivating both Factor Xa and thrombin relative to native aortas. We verified the validity and accuracy of the novel assays developed in this work using liquid chromatography-mass spectrometry analysis.

CONCLUSIONS

Our assays are of high relevance in the vascular community because they can be used to establish the antithrombogenic capacity of many different types of surfaces such as vascular grafts and transplants. This work will also advance the capacity for glycocalyx-targeting therapeutics development to treat damaged vasculatures.

Isolation and Characterization of Heparin From Tuna Skins

This study characterized heparin isolated from tuna skins. Glycosaminoglycans were isolated from tuna skin after digestion using anion exchange resin. Heparin was eluted from the resin by sodium chloride gradient and was further fractionated by acetone fractionation. Anticoagulant activity was determined using the activated partial thromboplastin time and Heptest assays. Potency was determined using amidolytic antifactor IIa and antifactor Xa assays. The presence of heparin in the extracted tuna skin glycosaminoglycans was confirmed using13C-nuclear magnetic resonance. The activated partial thromboplastin time and Heptest clotting times were doubled at concentrations of about 4 and 1 µg/mL, respectively. The clotting time prolongation and antiprotease activity induced by tuna heparin was readily neutralized by 25 µg/mL protamine sulfate. These results demonstrate that biologically active heparin with properties similar to clinical grade heparin can be derived from tuna skin, a raw material with otherwise relatively little economic value.

Off-pump coronary artery bypass grafting using continuous heparin infusion

Objectives

Levels of anticoagulation during off-pump coronary artery bypass grafting (OPCAB) remain controversial. Prolonged activated clotting time (ACT) during OPCAB increases blood loss during surgery and can also cause paradoxical increase in postoperative myocardial infarction. Shorter ACT can increase thrombotic complication. Maintaining a steady ACT level is challenging. We have used continuous heparin infusion after initial bolus during OPCAB to maintain a steady low target ACT. The objective of the present study was to assess the effectiveness and safety of heparin infusion in maintaining a steady target ACT level.

Methods

This was a prospective study of consecutive OPCAB patients. ACT was measured after initial bolus dose of heparin. Once ACT of more than 200 seconds was achieved, heparin infusion was started to maintain the required level of anticoagulation. CPK-MB was measured in operation room, 6 and 24 hours postoperatively to rule out ischemic complication.

Results

ACT could be maintained in target range with heparin infusion in 80.1% patients (161/201). Of the 40 patients with one or more ACT reading less than 200 seconds, 38 patients were managed by increasing the dose of heparin infusion and only 2 patients required additional bolus dose of heparin.

Conclusions

Heparin infusion maintains a steady target ACT level and avoids peaks and troughs associated with bolus doses. Lower level of anticoagulation using continuous heparin infusion does not increase ischemic complications. This is the first ever study of use of heparin infusion during OPCAB. We may conclude that heparin infusion is a safe anticoagulation strategy for OPCAB.

Development of a population pharmacokinetic-pharmacodynamic model of a single bolus dose of unfractionated heparin in paediatric patients

BACKGROUND

Unfractionated heparin (UFH) is the anticoagulant of choice in paediatric patients undergoing a variety of cardiac procedures. There are currently no population pharmacokinetic-pharmacodynamic (PKPD) models for UFH in paediatrics.

OBJECTIVE

The aim of the present study was to develop and evaluate a PKPD model of UFH in paediatrics.

METHODS

Data from 64 children who received 75-100 IU kg(-1) of UFH during cardiac angiography were analysed. Five blood samples were collected at baseline and at 15, 30, 45 and 120 min postdose. The UFH concentration was quantified using a protamine titration assay. The UFH effect was quantified using activated partial thromboplastin time (aPTT). A PKPD model was fitted using nonlinear mixed-effects modelling. Patient covariates such as gender, weight (WT) and fat-free mass (FFM) were tested. The final model was evaluated using the likelihood ratio test and visual predictive checks (VPCs).

RESULTS

A one-compartment model with linear elimination provided the best fit for the dose-concentration data. FFM was a significant covariate on clearance. A linear model provided the best fit for the concentration-effect data using aPTT as a biomarker for effect. The models performed well using VPCs. However, when used to simulate UFH infusion (at a much lower dose), the model overpredicted target aPTT responses.

CONCLUSIONS

A PKPD model to describe the time course of the UFH effect was developed in a paediatric population. FFM was shown to describe drug disposition well. However, when applied to smaller UFH infusion doses, the model overpredicted target aPTT responses. This unsuccessful extrapolation may be attributed to a possible nonlinear relationship for heparin PKPD.

Comparison of the Effects of Subcutaneous Versus Continuous Infusion of Heparin on Key Inflammatory Parameters Following Sepsis

Background

Sepsis is the result of the interaction between inflammatory mediators and coagulation pathway. Unfractionated heparin may play a role as an anti-inflammatory agent beyond its anticoagulatory effect in sepsis. As a result, it may cause reduction in organ failure rate in patients with sepsis due to its impact on both inflammatory and coagulation process.

Objectives

The aim of this study was to evaluate the anti-inflammatory effects of heparin in sepsis. Plasma plasminogen activator inhibitor-1 (PAI-1) as an inflammatory mediator and urinary necoutrophil gelatinase-associated lipocalin (NGAL) as a marker of kidney injury were investigated.

Patients and Methods

This prospective, randomized controlled trial was conducted in a 32-bed intensive care unit. Thirty patients with sepsis were randomized to receive heparin infusion of 500 units/hour or 5000 units of heparin three times a day, subcutaneously. The plasma level of PAI-1 and urinary level of NGAL were determined at day 0, 2 and 7.

Results

The infusion group had a lower plasma PAI-1 level compared to the subcutaneous group at day 7 (11.3 ± 1.6 vs. 16.5 ± 4.2; P = 0.003). The urinary NGAL level was lower in the infusion group at day 2 (131.3 ± 11.9 vs. 151.2 ± 20.6; P = 0.014); however, at day 7 the NGAL level was decreased in the subcutaneous group as much as the infusion group and there was no significant difference between the two groups. There was no significant difference in the acute physiology and chronic health evaluation (APACHE) II and sequential organ failure assessment (SOFA) scores between the two groups at day 0, 2 and 7.

Conclusions

Low-dose heparin infusion compared to subcutaneous heparin can decrease the plasma PAI-1 and urinary NGAL levels more rapidly. It can be related to anti-inflammatory effects of heparin, which may be more prominent in infusion route.

Heparin supplement counteracts the prohemostatic effect of prothrombin complex concentrate and factor IX concentrate: An in vitro evaluation

INTRODUCTION

Coagulation factor concentrates like factor IX (FIX) and prothrombin complex concentrate (PCC) can contain anticoagulant substances that may hamper their procoagulant effectiveness in the treatment of hemophilia B or reversal of oral anticoagulation, as well as the laboratory assessment thereof. The aim of the present study was to evaluate the influence of anticoagulant heparin supplement on the prohemostatic potential of different PCCs and FIX concentrates.

MATERIALS AND METHODS

Prohemostatic potential was evaluated in vitro employing PT/aPTT, thrombography (TGA) and thromboelastography (TEG) with FIX deficient plasma, vitamin K antagonist (VKA)-anticoagulated plasma and plasma anticoagulated with rivaroxaban.

RESULTS

Most PCCs contained heparin, while heparin was detected in 1 out of 4 examined FIX concentrates. All heparin-containing clotting factor concentrates showed severely hampered prohemostatic effects when therapeutic doses were added to anticoagulated plasmas. Upon heparin removal, comparable prohemostatic effects were observed. Of importance is the notion that the anticoagulant effect of heparin was enhanced by rivaroxaban, resulting in a 7 fold increased PT sensitivity towards heparin in the presence of 500μg/L rivaroxaban.

CONCLUSIONS

Compositional differences between clotting factor concentrates should be taken into account. Therapeutic levels of heparin may be co-infused when treating emergency bleeds with high prohemostatic drug doses, particularly those recommended in the reversal of non-VKA anticoagulants such as rivaroxaban by PCC. Given the relative short half-life of heparin compared to vitamin K-dependent clotting factors, an anticoagulant heparin effect shortly after concentrate infusion should be considered clinically and while interpreting laboratory coagulation parameters.

Spontaneous Coassembly of Biologically Active Nanoparticles via Affinity Binding of Heparin-Binding Proteins to Alginate-Sulfate

Controlled delivery of heparin-binding (HB) proteins represents a challenge in regenerative medicine strategies. Here, we describe the features of novel nanoparticles (NPs), spontaneously coassembled due to affinity interactions between HB proteins and the semisynthetic anionic polysaccharide, alginate-sulfate. The NPs efficiently encapsulated and protected the proteins from proteolysis. Injection of a combination of NPs encapsulating multiple therapeutic growth factors promoted effective and long-term tissue repair in animal models of severe ischemia (murine model of hindlimb ischemia and acute myocardial infarction in rats). This simple yet efficient NP fabrication method is amenable for clinical use.

Warfarin initiation nomograms for venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE) is a common condition in hospital patients. Considerable controversy is ongoing regarding optimal initial warfarin dosing for patients with acute deep venous thrombosis (DVT) and pulmonary embolism (PE). Achieving a therapeutic international normalized ratio (INR) with warfarin as soon as possible is important because this minimizes the duration of parenteral medication necessary to attain immediate anticoagulation, and it potentially decreases the cost and inconvenience of treatment. Although a 5-mg loading-dose nomogram tends to prevent excessive anticoagulation, a 10-mg loading-dose nomogram may achieve a therapeutic INR more quickly. This is an update of a review first published in 2013.

OBJECTIVES

To evaluate the efficacy of a 10-mg warfarin nomogram compared with a 5-mg warfarin nomogram among patients with VTE.

SEARCH METHODS

For this update the Cochrane Vascular Trials Search Co-ordinator searched the Specialised Register (last searched September 2015) and the Cochrane Register of Studies (CENTRAL (2015, Issue 8). Clinical trials databases were also searched. The review authors searched PubMed (last searched 11 June 2015) and LILACS (last searched 11 June 2015). In addition, the review authors contacted pharmaceutical companies.

SELECTION CRITERIA

Randomized controlled studies comparing warfarin initiation nomograms of 10 and 5 mg in patients with VTE.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. The review authors contacted study authors for additional information.

MAIN RESULTS

Four trials involving 494 participants were included. Three studies involving 383 participants provided data on the proportion of participants who had achieved a therapeutic INR by day five. Significant benefit of a 10-mg warfarin nomogram was observed (risk ratio (RR) 1.27, 95% confidence interval (CI) 1.05 to 1.54; moderate quality evidence), although with substantial heterogeneity (I(2) = 90%). The review authors analyzed each study separately because it was not possible to perform a subgroup analysis by inpatient or outpatient status. One study showed significant benefit of a 10-mg warfarin nomogram for the proportion of outpatients with VTE who had achieved a therapeutic INR by day five (RR 1.78, 95% CI 1.41 to 2.25), with the number needed to treat for an additional beneficial outcome (NNTB = 3, 95% CI 2 to 4); another study showed significant benefit of a 5-mg warfarin nomogram in outpatients with VTE (RR 0.58, 95% CI 0.36 to 0.93) with NNTB = 5 (95% CI 3 to 28); a third study, consisting of both inpatients and outpatients, showed no difference (RR 1.08, 95% CI 0.65 to 1.80).No difference was observed in recurrent venous thromboembolism at 90 days when the warfarin nomogram of 10 mg was compared with the warfarin nomogram of 5 mg (RR 1.48, 95% CI 0.39 to 5.56; 3 studies, 362 participants, low quality evidence); no difference was observed in major bleeding at 14 to 90 days (RR 0.97, 95% CI 0.27 to 3.51; 4 studies, 494 participants, moderate quality evidence). No difference was observed in minor bleeding at 14 to 90 days (RR 0.52, 95% CI 0.15 to 1.83; 2 studies, 243 participants, very low quality evidence) or in length of hospital stay (mean difference (MD) -2.3 days, 95% CI -7.96 to 3.36; 1 study, 111 participants, low quality evidence).

AUTHORS' CONCLUSIONS

In patients with acute thromboembolism (DVT or PE) aged 18 years or older, considerable uncertainty surrounds the use of a 10-mg or a 5-mg loading dose for initiation of warfarin to achieve an INR of 2.0 to 3.0 on the fifth day of therapy. Heterogeneity among analyzed studies, mainly caused by differences in types of study participants and length of follow-up, limits certainty surrounding optimal warfarin initiation nomograms.

Marine Non-Glycosaminoglycan Sulfated Glycans as Potential Pharmaceuticals

Sulfated fucans (SFs) and sulfated galactans (SGs) are currently the marine non-glycosaminoglycan (GAG) sulfated glycans most studied in glycomics. These compounds exhibit therapeutic effects in several pathophysiological systems such as blood coagulation, thrombosis, neovascularization, cancer, inflammation, and microbial infections. As analogs of the largely employed GAGs and due to some limitations of the GAG-based therapies, SFs and SGs comprise new carbohydrate-based therapeutics available for clinical studies. Here, the principal structural features and the major mechanisms of action of the SFs and SGs in the above-mentioned pathophysiological systems are presented. Discussion is also given on the current challenges and the future perspectives in drug development of these marine glycans.

Randomized Comparison of Continuous Versus Intermittent Heparin Infusion During Catheter Ablation of Atrial Fibrillation

OBJECTIVES

This study tested the hypothesis that continuous heparin infusions would be favorable for maintaining heparin concentrations during radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF).

BACKGROUND

Heparin infusions are essential for RFCA of AF. There is a paucity of data on the details for the optimal heparin infusion during RFCA of AF.

METHODS

A total of 333 patients undergoing AF ablation were consecutively enrolled and randomized to intermittent or continuous heparin infusion. A heparin bolus of 100 U/kg was injected just prior to transseptal puncture. The heparin concentration necessary to maintain an optimal activated clotting time (ACT) (300 to 400 s) was determined and checked every 30 min during the procedure. The primary endpoint of the study was the frequency of the maintenance of an optimal intraprocedural ACT.

RESULTS

The frequency of an optimal ACT in the continuous group was significantly higher than that in the intermittent group (64.0% vs. 57.6%, respectively, p < 0.01), whereas the total heparin level was significantly lower in the continuous group (13,162 ± 4,634 U vs. 15,837 ± 5,243 U, respectively, p < 0.01). The standard deviation of the ACT was significantly smaller in the continuous group than in the intermittent group (49 ± 30 vs. 33 ± 18, respectively, p < 0.01). Ninety-six patients had new oral anticoagulants (NOACs) before the procedure, and an optimal ACT at the first ACT check was less frequent than in patients taking warfarin (12.5% vs. 59.1%, respectively, p < 0.01). There were no significant differences in periprocedural bleeding or thromboembolic complications between the groups.

CONCLUSIONS

During AF ablation, a continuous heparin infusion was superior to an intermittent heparin infusion for maintaining an optimal ACT range. (Randomized Comparison of Continuous and Intermittent Heparin Infusion During Catheter Ablation of Atrial Fibrillation [COHERE]; NCT01935557).

A systematic review and meta-analysis of systemic intraoperative anticoagulation during arteriovenous access formation for dialysis

PURPOSE

Surgical arteriovenous fistula (AVF) or graft (AVG) is preferred to a central venous catheter for dialysis access. Surgical access may suffer thrombosis early after placement and systemic anticoagulation during surgical access formation may increase patency rates but would be expected to increase bleeding-related complications. A systematic review and meta-analysis of randomised controlled trials was conducted to examine the impact of systemic anticoagulation on access surgery perioperative bleeding and patency rates.

METHODS

We included randomised controlled trials testing systemic anticoagulation during access formation versus a control group without systemic anticoagulation reporting bleeding complications and access patency. Medline, Embase, CENTRAL and CINAHL were searched up to March 2015. Risk of bias was assessed using the Cochrane risk of bias tool and the Jadad score. Meta-analysis was performed using Cochrane Revman® software.

RESULTS

Searches identified 445 reports of which four randomised studies involving 411 participants were included. Three studies pertained to AVF only and one included both AVF and AVG. Systemic anticoagulation led to increased bleeding events in all access [four trials; risk ratio (RR) 7.18; confidence interval (CI), 2.41 to 21.38; p<0.001]. Patency was not improved for all access (four trials; RR, 0.64; CI, 0.37 to 1.09; p = 0.10) but was improved when AVF analysed alone (three trials; RR, 0.57; CI, 0.33 to 0.97; p = 0.04).

CONCLUSIONS

The use of intraoperative systemic anticoagulation during access formation is associated with a highly significant increased risk of bleeding-related complications. A significant improvement in AVF patency was seen, though not when AVF and AVG were analysed together.

Leakage of central venous catheter locking fluid by hemodynamic transport

Central venous catheters are often filled when not in use with an anticoagulating fluid, usually heparinized saline, known as the locking fluid. However, the use of the locking fluid is associated with known risks because of "leakage" of the lock. A new hypothesis is proposed here to explain the lock fluid leakage: that the leakage is due to advective and diffusive mass transfer by blood flow around the catheter tip in situ. On the basis of previous in vitro experiments, the leakage mechanism has been hypothesized to be fluid motion driven by buoyancy forces between the heavier blood and the lighter locking fluid. The current hypothesis is justified by a simple one-dimensional mass transfer model and more sophisticated three-dimensional computational hemodynamic simulations of an idealized catheter. The results predict an initial, fast (<10 seconds) advection-dominated phase, which may deplete up to 10% of the initial lock, followed by a slow diffusion-limited phase which predicts an additional 1-2% of leakage during a 48 hour period. The current results predict leakage rates that are more consistent with published in vivo data when compared with the buoyancy hypothesis predictions, which tend to grossly overestimate leakage rates.

Enhancing kidney function with thrombolytic therapy following donation after cardiac death: a multicenter quasi-blinded prospective randomized trial

Kidneys from donors after cardiac death (DCD) are at risk for inferior outcomes, possibly due to microthrombi and additional warm ischemia. We describe an organ procurement organization-wide trial utilizing thrombolytic tissue plasminogen activator (tPA) during machine pulsatile perfusion (MPP). A kidney from each recovered kidney pair was prospectively randomized to receive tPA (50 mg Alteplase) or no tPA (control) in the MPP perfusate. From 2011 to 2013, 24 kidneys were placed with enrolled recipients from 19 DCD kidney donors. There were no significant differences for absolute values of flow or resistance while undergoing MPP between the groups, nor rates of achieving discrete flow and resistance targets. While there was a trend toward lower creatinine and higher glomerular filtration rates in the tPA group at 3, 6, 9, and 12 months, these differences were not significant. Delayed graft function (DGF) rates were 41.7% in the tPA group vs. 58.4% in the control group (OR 0.51, 95%CI 0.10-2.59, p = 0.68). Death-censored graft survival was similar between the groups. In this pilot study, encouraging trends are seen in kidney allograft function independent of MPP parameters following DCD kidney transplantation for those kidneys receiving thrombolytic tPA and MPP, compared with standard MPP.

Production of decellularized porcine lung scaffolds for use in tissue engineering

There is a growing body of work dedicated to producing acellular lung scaffolds for use in regenerative medicine by decellularizing donor lungs of various species. These scaffolds typically undergo substantial matrix damage due to the harsh conditions required to remove cellular material (e.g., high pH, strong detergents), lengthy processing times, or pre-existing tissue contamination from microbial colonization. In this work, a new decellularization technique is described that maintains the global tissue architecture, key matrix components, mechanical composition and cell-seeding potential of lung tissue while effectively removing resident cellular material. Acellular lung scaffolds were produced from native porcine lungs using a combination of Triton X-100 and sodium deoxycholate (SDC) at low concentrations in 24 hours. We assessed the effect of matrix decellularization by measuring residual DNA, biochemical composition, mechanical characteristics, tissue architecture, and recellularization capacity.

Strict management of a pregnant patient with giant coronary artery aneurysm due to Kawasaki disease

Coronary artery aneurysms (CAA) may occur in Kawasaki disease (KD). Patients with giant CAA (diameter >8 mm), in particular, have higher risk of myocardial infarction. Previous reports have demonstrated the necessity of anticoagulation therapy in such cases. The management of patients with KD complicated by giant CAA later in life, however, remains controversial. Here, we describe the strict management in the case of a 28-year-old pregnant Japanese woman with KD with giant CAA (diameter, 11 mm). Instead of warfarin, the patient was given low-dose aspirin and i.v. unfractionated heparin during pregnancy to prevent thrombosis in the giant CAA. At 38 weeks of gestation, she had spontaneous delivery of a healthy baby. No thrombotic or bleeding complications were observed. The strict anticoagulation therapy resulted in successful pregnancy and delivery without any adverse events.

Multicenter study on hemorrhagic risk of heparin bridging therapy for periendoscopic thromboprophylaxis

Background

For endoscopic interventions, heparin bridging therapy is recommended in patients who are at high risk from interruption of antithrombotic therapy. Although heparin bridging has been reported to be effective in preventing thrombosis, several reports have raised concerns about increased risk of bleeding. The aim of this study was to clarify complications of hepari  bridging therapy in therapeutic endoscopy.

Methods

A nationwide multicenter survey using questionnaire was performed about patients undergoing therapeutic endoscopy with heparin bridging. Patients who underwent therapeutic endoscopy without heparin bridging therapy were considered as controls. Compliance scores of heparin bridging therapy guideline were employed, and association was analyzed between the score and occurrence of post-procedural bleeding.

Results

The incidence of post-procedural bleeding was significantly higher (13.5 %, 33/245) in the heparin group compared with the control group (2.7 %, 299/11102)(p < 0.001). Thrombosis occurred in 1 patient each in the two groups. In the heparin group, post-procedural bleeding was more likely to be delayed bleeding. Dose adjustment of heparin was a significant factor contributing to bleeding. The compliance score of heparin bridging therapy guideline was significantly higher in those who suffered bleeding.

Conclusions

Heparin bridging therapy significantly increased the risk of post-procedural bleeding compared with the control. The bleeding risk was associated with greater adherence with guidelines for heparin bridging therapy.

Heparin-engineered mesoporous iron metal-organic framework nanoparticles: toward stealth drug nanocarriers

The specific modification of the outer surface of the promising porous metal-organic framework nanocarriers (nanoMOFs) preserving their characteristic porosity is still a major challenge. Here a simple, fast, and biofriendly method for the external functionalization of the benchmarked mesoporous iron(III) trimesate nanoparticles MIL-100(Fe) with heparin, a biopolymer associated with longer-blood circulation times is reported. First, the coated nanoparticles showed intact crystalline structure and porosity with improved colloidal stability under simulated physiological conditions, preserving in addition its encapsulation and controlled release capacities. The effect of the heparin coating on the nanoMOF interactions with the biological environment is evaluated through cell uptake, cytotoxicity, oxidative stress, cytokine production, complement activation, and protein adsorption analysis. These results confirmed that the heparin coating endowed the nanoMOFs with improved biological properties, such as reduced cell recognition, lack of complement activation, and reactive oxygen species production. Overall, the ability to coat the surface of the nanoMOFs using a simple and straight-forward approach could be taken as a way to enhance the versatility and, thus, the potential of porous MOF nanoparticles in biomedicine.

Allosteric inhibition of factor XIa. Sulfated non-saccharide glycosaminoglycan mimetics as promising anticoagulants

Recent development of sulfated non-saccharide glycosaminoglycan mimetics, especially sulfated pentagalloyl glucopyranoside (SPGG), as potent inhibitors of factor XIa (FXIa) (J. Med. Chem. 2013; 56:867-878 and J. Med. Chem. 2014; 57:4805-4818) has led to a strong possibility of developing a new line of factor XIa-based anticoagulants. In fact, SPGG represents the first synthetic, small molecule inhibitor that appears to bind in site remote from the active site. Considering that allosteric inhibition of FXIa is a new mechanism for developing a distinct line of anticoagulants, we have studied SPGG's interaction with FXIa with a goal of evaluating its pre-clinical relevance. Comparative inhibition studies with several glycosaminoglycans revealed the importance of SPGG's non-saccharide backbone. SPGG did not affect the activity of plasma kallikrein, activated protein C and factor XIIIa suggesting that SPGG-based anticoagulation is unlikely to affect other pathways connected with coagulation factors. SPGG's effect on APTT of citrated human plasma was also not dependent on antithrombin or heparin cofactor II. Interestingly, SPGG's anticoagulant potential was diminished by serum albumin as well as factor XI, while it could be reversed by protamine or polybrene, which implies possible avenues for developing antidote strategy. Studies with FXIa mutants indicated that SPGG engages Lys529, Arg530 and Arg532, but not Arg250, Lys252, Lys253 and Lys255. Finally, SPGG competes with unfractionated heparin, but not with polyphosphates and/or glycoprotein Ibα, for binding to FXIa. These studies enhance understanding on the first allosteric inhibitor of FXIa and highlight its value as a promising anticoagulant.

Anticoagulation management associated with extracorporeal circulation

The use of extracorporeal circulation requires anticoagulation to maintain blood fluidity throughout the circuit, and to prevent thrombotic complications. Additionally, adequate suppression of hemostatic activation avoids the unnecessary consumption of coagulation factors caused by the contact of blood with foreign surfaces. Cardiopulmonary bypass represents the greatest challenge in this regard, necessitating profound levels of anticoagulation during its conduct, but also quick, efficient reversal of this state once the surgical procedure is completed. Although extracorporeal circulation has been around for more than half a century, many questions remain regarding how to best achieve anticoagulation for it. Although unfractionated heparin is the predominant agent used for cardiopulmonary bypass, the amount required and how best to monitor its effects are still unresolved. This review discusses the use of heparin, novel anticoagulants, and the monitoring of anticoagulation during the conduct of cardiopulmonary bypass.

Polysulfated trehalose as a novel anticoagulant agent with dual mode of action

Physiological hemostatic balance is a coordinated outcome of counteracting coagulation and fibrinolytic systems. An imbalance of procoagulant and anticoagulant factors may result in life threatening thromboembolism. Presently, anticoagulant administration is the first line of therapy for the treatment of these conditions and several anticoagulants have been approved, including various forms of heparin. However, the polyanionic nature and multispecificity of heparin pose several complications. Generally, the polysulfated compounds with antithrombotic potential are thought to have feasible synthetic procedures with much less bleeding, thus having favourable safety profiles. Here we report the synthesis of a novel compound, trehalose octasulfate and the assessment of its anticoagulation potential. Molecular docking of trehalose and trehalose octasulfate with antithrombin showed a specificity switch in binding affinity on sulfation, where trehalose octasulfate interacts with critical residues of AT that are either directly involved in heparin binding or in the conformational rearrangement of AT on heparin binding. An in vitro analysis of trehalose octasulfate demonstrated prolonged clotting time. Lead compound when intravenously injected in occlusion induced thrombotic rats showed remarkable reduction in the size and weight of the clot at a low dose. Delay in coagulation time was observed by analysing blood plasma isolated from rats preinjected with trehalose octasulfate. A decrease in Adenosine 5′-Diphosphate (ADP) induced platelet aggregation indicated a probable dual anticoagulant and antiplatelet mechanism of action. To summarize, this study presents trehalose octasulfate as a novel, effective, dual acting antithrombotic agent.

In vitro evaluation and in vivo demonstration of a biomimetic, hemocompatible, microfluidic artificial lung

Despite the promising potential of microfluidic artificial lungs, current designs suffer from short functional lifetimes due to surface chemistry and blood flow patterns that act to reduce hemocompatibility. Here, we present the first microfluidic artificial lung featuring a hemocompatible surface coating and a biomimetic blood path. The polyethylene-glycol (PEG) coated microfluidic lung exhibited a significantly improved in vitro lifetime compared to uncoated controls as well as consistent and significantly improved gas exchange over the entire testing period. Enabled by our hemocompatible PEG coating, we additionally describe the first extended (3 h) in vivo demonstration of a microfluidic artificial lung.

Potential antidotes for reversal of old and new oral anticoagulants

The prescription of new oral anticoagulants is on the rise. As opposed to vitamin K antagonists and heparins the new agents have single targets in the coagulation cascade, more predictable pharmacokinetics and they lack validated and available antidotes. In general, the new agents have similar or lower bleeding risk than vitamin K antagonists, especially risk of intracranial bleeding. Risk factors for bleeding are typically the same for old and new anticoagulants. Old age, renal dysfunction and concomitant antiplatelet agents seem to be recurring risk factors. Adequate supportive care and temporary removal of all antithrombotic agents constitute the basis for management of serious bleeding complications. With the exception of vitamin K (for vitamin K antagonists) and protamine (for heparin) the same array of prohemostatic agents--unactivated or activated prothrombin complex concentrate, and activated factor VIIa--have been tried for almost all anticocoagulants in different models, and for some agents also in patients, with varying success. Hemodialysis can reduce the level of dabigatran efficiently and activated charcoal may be used for very recent oral ingestion of lipophilic agents. In view of the shorter half life of the new agents compared to warfarin the need for reversal agents may be less critical. Nevertheless, highly specific reversal agents for the thrombin- and factor Xa-inhibitors are under development and might be available within two years.

Absence of pharmacodynamic interaction between inclacumab and heparin in healthy smokers

Inclacumab is a novel monoclonal antibody directed against P-selectin in development for the prevention and treatment of atherosclerotic cardiovascular diseases. It is likely to be used concomitantly with heparin in patients undergoing percutaneous coronary intervention. Coadministration of both drugs may potentially increase the bleeding risk associated with heparin. This crossover study evaluated the potential pharmacodynamic interaction between inclacumab and unfractionated heparin in 18 healthy smokers. Owing to the long elimination of inclacumab (half-life of approximately 18 days), a 2-period, one-sequence study design was used. Subjects received an intravenous bolus injection of unfractionated heparin (5000 IU) on days 1 and 8 and an intravenous infusion of inclacumab (20 mg/kg) on day 8. Blood samples were collected on days 1 and 8 for pharmacodynamic effects of unfractionated heparin (anti-FXa and anti-FIIa activities, activated partial thromboplastin time and tissue factor pathway inhibitor) and over 6 months for pharmacokinetics of inclacumab. Sixteen subjects were eligible for pharmacodynamic analysis. Inclacumab had no clinically significant pharmacodynamic interaction with unfractionated heparin. With the exception of the minor but statistically significant increase of the maximum effect [Emax] of anti-FIIa activity, pharmacodynamic parameters (areas under the effect curve [AUElast] and Emax of anti-FXa) were almost similar on days 1 and 8. The 90% confidence intervals of geometric mean ratios of day 8 to day 1 for AUElast and Emax were however all contained within bioequivalence boundaries. The data demonstrate that the anticoagulant effect of unfractionated heparin was not affected by the administration of inclacumab.

Nanomimics of host cell membranes block invasion and expose invasive malaria parasites

The fight against most infectious diseases, including malaria, is often hampered by the emergence of drug resistance and lack or limited efficacies of vaccines. Therefore, new drugs, vaccines, or other strategies to control these diseases are needed. Here, we present an innovative nanotechnological strategy in which the nanostructure itself represents the active substance with no necessity to release compounds to attain therapeutic effect and which might act in a drug- and vaccine-like dual function. Invasion of Plasmodium falciparum parasites into red blood cells was selected as a biological model for the initial validation of this approach. Stable nanomimics-polymersomes presenting receptors required for parasite attachment to host cells-were designed to efficiently interrupt the life cycle of the parasite by inhibiting invasion. A simple way to build nanomimics without postformation modifications was established. First, a block copolymer of the receptor with a hydrophobic polymer was synthesized and then mixed with a polymersome-forming block copolymer. The resulting nanomimics bound parasite-derived ligands involved in the initial attachment to host cells and they efficiently blocked reinvasion of malaria parasites after their egress from host cells in vitro. They exhibited efficacies of more than 2 orders of magnitude higher than the soluble form of the receptor, which can be explained by multivalent interactions of several receptors on one nanomimic with multiple ligands on the infective parasite. In the future, our strategy might offer interesting treatment options for severe malaria or a way to modulate the immune response.

Heparin-independent, PF4-dependent binding of HIT antibodies to platelets: implications for HIT pathogenesis

Antibodies specific for platelet factor 4 (PF4)/heparin complexes are the hallmark of heparin-induced thrombocytopenia and thrombosis (HIT), but many antibody-positive patients have normal platelet counts. The basis for this is not fully understood, but it is believed that antibodies testing positive in the serotonin release assay (SRA) are the most likely to cause disease. We addressed this issue by characterizing PF4-dependent binding of HIT antibodies to intact platelets and found that most antibodies testing positive in the SRA, but none of those testing negative, bind to and activate platelets when PF4 is present without any requirement for heparin (P < .0001). Binding of SRA-positive antibodies to platelets was inhibited by chondroitinase ABC digestion (P < .05) and by the addition of chondroitin-4-sulfate (CS) or heparin in excess quantities. The findings suggest that although all HIT antibodies recognize PF4 in a complex with heparin, only a subset of these antibodies recognize more subtle epitopes induced in PF4 when it binds to CS, the major platelet glycosaminoglycan. Antibodies having this property could explain "delayed HIT" seen in some individuals after discontinuation of heparin and the high risk for thrombosis that persists for weeks in patients recovered from HIT.

Exopolysaccharides produced by marine bacteria and their applications as glycosaminoglycan-like molecules

Although polysaccharides are ubiquitous and the most abundant renewable bio-components, their studies, covered by the glycochemistry and glycobiology fields, remain a challenge due to their high molecular diversity and complexity. Polysaccharides are industrially used in food products; human therapeutics fall into a more recent research field and pharmaceutical industry is looking for more and more molecules with enhanced activities. Glycosaminoglycans (GAGs) found in animal tissues play a critical role in cellular physiological and pathological processes as they bind many cellular components. Therefore, they present a great potential for the design and preparation of therapeutic drugs. On the other hand, microorganisms producing exopolysaccharides (EPS) are renewable resources meeting well the actual industrial demand. In particular, the diversity of marine microorganisms is still largely unexplored offering great opportunities to discover high value products such as new molecules and biocatalysts. EPS-producing bacteria from the marine environment will be reviewed with a focus on marine-derived EPS from bacteria isolated from deep-sea hydrothermal vents. Information on chemical and structural features, putative pathways of biosynthesis, novel strategies for chemical and enzymatic modifications and potentialities in the biomedical field will be provided. An integrated approach should be used to increase the basic knowledge on these compounds and their applications; new clean environmentally friendly processes for the production of carbohydrate bioactive compounds should also be proposed for a sustainable industry.

A data-driven approach to optimized medication dosing: a focus on heparin

PURPOSE

To demonstrate a novel method that utilizes retrospective data to develop statistically optimal dosing strategies for medications with sensitive therapeutic windows. We illustrate our approach on intravenous unfractionated heparin, a medication which typically considers only patient weight and is frequently misdosed.

METHODS

We identified available clinical features which impact patient response to heparin and extracted 1,511 patients from the multi-parameter intelligent monitoring in intensive care II database which met our inclusion criteria. These were used to develop two multivariate logistic regressions, modeling sub- and supra-therapeutic activated partial thromboplastin time (aPTT) as a function of clinical features. We combined information from these models to estimate an initial heparin dose that would, on a per-patient basis, maximize the probability of a therapeutic aPTT within 4-8 h of the initial infusion. We tested our model's ability to classifying therapeutic outcomes on a withheld dataset and compared performance to a weight-alone alternative using volume under surface (VUS) (a multiclass version of AUC).

RESULTS

We observed statistically significant associations between sub- and supra-therapeutic aPTT, race, ICU type, gender, heparin dose, age and Sequential Organ Failure Assessment scores with mean validation AUC of 0.78 and 0.79 respectively. Our final model improved outcome classification over the weight-alone alternative, with VUS values of 0.48 vs. 0.42.

CONCLUSIONS

This work represents an important step in the secondary use of health data in developing models to optimize drug dosing. The next step would be evaluating whether this approach indeed achieves target aPTT more reliably than the current weight-based heparin dosing in a randomized controlled trial.

Analysis of multiple factors involved in acute progressive cerebral infarction and extra- and intracranial arterial lesions

In order to identify the potential factors involved in the development of acute progressive cerebral infarction (PCI), the association between potential risk factors and extra- and intracranial arterial lesions was investigated. A total of 608 patients underwent cerebral angiography to analyze the morphological characteristics between the PCI and NPCI groups. In addition, data from numerous cases of extra- and intracranial arterial lesions were collected and compared with the control groups, and the associations between the severity of arterial lesions and the potential influential factors were analyzed. In the blood vessels responsible for cerebral infarction, various degrees of atherosclerotic plaques and stenosis were observed. Age, high-density lipoprotein (HDL) levels, glycosylated hemoglobin and blood pressure affected the degrees of hardening, plaques and stenosis. Analysis of cerebral artery stenosis revealed that age, diabetes mellitus and plasma fibrinogen were risk factors for cerebral artery stenosis, while the HDL/low density lipoprotein ratio was a protective factor. Therefore, the results of the present study indicate that the lesions of blood vessels are a major pathological change in PCI and multiple factors are involved in the pathogenesis.

Electrodeposition of nanostructured bioactive hydroxyapatite-heparin composite coatings on titanium for dental implant applications

In this paper we describe the one-pot fabrication of hydroxyapatite (HA)-heparin composites by electrodeposition onto Ti substrates and their characterisation in terms of structure, morphology, heparin content and bioactivity. HA coatings are well known and widely applied osteointegration enhancers, but post-implant healing rate in dental applications is still suboptimal: e.g. coagulation control plays a key role and the incorporation of an anticoagulant is considered a highly desirable option. In this study, we have developed an improved, simple and robust growth procedure for single-phase, pure HA-heparin films of thickness 1/3 μm. HA-heparin, forming nanowires, has the ideal morphology for bone mineralisation. Staining assays revealed homogeneous incorporation of sizable amounts of heparin in the composite films. The bioactivities of the HA and HA-heparin coatings on Ti were compared by HeLa cell proliferation/viability tests and found to be enhanced by the presence of the anticoagulant.

Synthesis and biological evaluation of a unique heparin mimetic hexasaccharide for structure-activity relationship studies

To date, the structure-activity relationship studies of heparin/heparan sulfate with their diverse binding partners such as growth factors, cytokines, chemokines, and extracellular matrix proteins have been limited yet provide early insight that specific sequences contribute to this manifold biological role. This has led to an impetus for the chemical synthesis of oligosaccharide fragments of these complex polysaccharides, which can provide an effective tool for this goal. The synthesis of three heparin mimetic hexasaccharides with distinct structural patterns is described herein, and the influence of the targeted substitution on their bioactivity profiles is studied using in vitro affinity and/or inhibition toward different growth factors and proteins. Additionally, the particularly challenging synthesis of an irregular hexasaccharide is reported, which, interestingly, in spite of being considerably structurally similar with its two counterparts, displayed a unique and remarkably distinct profile in the test assays.