Monitoring low molecular weight heparins at therapeutic levels: dose-responses of, and correlations and differences between aPTT, anti-factor Xa and thrombin generation assays

Adsorbed polymer conjugates to adaptively inhibit blood coagulation activation by medical membranes

Adaptive drug release can combat coagulation and inflammation activation at the blood-material interface with minimized side effects. For that purpose, poly(styrene-alt-maleic-anhydride) copolymers were conjugated to heparin via coagulation-responsive linker peptides and shown to tightly adsorb onto poly(ethersulfone) (PES)-surfaces from aqueous solutions as monolayers. Coagulation-responsive release of unfractionated as well as low molecular weight heparins from the respective coatings was demonstrated to be functionally beneficial in human plasma and whole blood incubation with faster release kinetics resulting in stronger anticoagulant effects. Coated poly(ethersulfone)/poly(vinylpyrrolidone) (PES/PVP) flat membranes proved the technology to offer an easy, effective and robust anticoagulant interfacial functionalization of hemodialysis membranes. In perspective, the modularity of the adaptive release system will be used for inhibiting multiple activation processes.

Being precise with anticoagulation to reduce adverse drug reactions: are we there yet?

Anticoagulants are potent therapeutics widely used in medical and surgical settings, and the amount spent on anticoagulation is rising. Although warfarin remains a widely prescribed oral anticoagulant, prescriptions of direct oral anticoagulants (DOACs) have increased rapidly. Heparin-based parenteral anticoagulants include both unfractionated and low molecular weight heparins (LMWHs). In clinical practice, anticoagulants are generally well tolerated, although interindividual variability in response is apparent. This variability in anticoagulant response can lead to serious incident thrombosis, haemorrhage and off-target adverse reactions such as heparin-induced thrombocytopaenia (HIT). This review seeks to highlight the genetic, environmental and clinical factors associated with variability in anticoagulant response, and review the current evidence base for tailoring the drug, dose, and/or monitoring decisions to identified patient subgroups to improve anticoagulant safety. Areas that would benefit from further research are also identified. Validated variants in VKORC1, CYP2C9 and CYP4F2 constitute biomarkers for differential warfarin response and genotype-informed warfarin dosing has been shown to reduce adverse clinical events. Polymorphisms in CES1 appear relevant to dabigatran exposure but the genetic studies focusing on clinical outcomes such as bleeding are sparse. The influence of body weight on LMWH response merits further attention, as does the relationship between anti-Xa levels and clinical outcomes. Ultimately, safe and effective anticoagulation requires both a deeper parsing of factors contributing to variable response, and further prospective studies to determine optimal therapeutic strategies in identified higher risk subgroups.

Pharmacogenomic Considerations for Anticoagulant Prescription in Patients with Hereditary Haemorrhagic Telangiectasia

Hereditary haemorrhagic telangiectasia (HHT) is a vascular dysplasia that commonly results in bleeding but with frequent indications for therapeutic anticoagulation. Our aims were to advance the understanding of drug-specific intolerance and evaluate if there was an indication for pharmacogenomic testing. Genes encoding proteins involved in the absorption, distribution, metabolism, and excretion of warfarin, heparin, and direct oral anticoagulants (DOACs) apixaban, rivaroxaban, edoxaban, and dabigatran were identified and examined. Linkage disequilibrium with HHT genes was excluded, before variants within these genes were examined following whole genome sequencing of general and HHT populations. The 44 genes identified included 5/17 actionable pharmacogenes with guidelines. The 76,156 participants in the Genome Aggregation Database v3.1.2 had 28,446 variants, including 9668 missense substitutions and 1076 predicted loss-of-function (frameshift, nonsense, and consensus splice site) variants, i.e., approximately 1 in 7.9 individuals had a missense substitution, and 1 in 71 had a loss-of-function variant. Focusing on the 17 genes relevant to usually preferred DOACs, similar variant profiles were identified in HHT patients. With HHT patients at particular risk of haemorrhage when undergoing anticoagulant treatment, we explore how pre-emptive pharmacogenomic testing, alongside HHT gene testing, may prove beneficial in reducing the risk of bleeding and conclude that HHT patients are well placed to be at the vanguard of personalised prescribing.

Apply Anticoagulants after Discharge not Benefit to the Incidence of Symptomatic Thrombus in High-Altitude Areas: A Retrospective Study

OBJECTIVE

Many guidelines indicate that continuous use of anticoagulant drugs reduces the incidence of venous thrombus (VT), but no studies show the effect on the incidence of symptomatic venous thrombus (SVT) in total knee arthroplasty (TKA) patients after discharge. This study aimed to investigate whether it is necessary to apply anticoagulants to TKA patients after discharge.

METHODS

Patients who met the exclusion criteria requirement, underwent TKA by the same surgical team and received anticoagulant therapy after the operation were eligible for the study. Finally, a total of 567 TKA patients were recruited as participants. The patients were divided into two groups. The patients in group A were taken low molecular heparin for 5-10 days after surgery, which included but was not limited to low molecular weight heparin calcium injection (0.4 mL, ih, Qd), calcium dioxin injection (0.6 mL, ih, Qd), or enoxaparin sodium injection (0.4 mL, ih, Qd), and the patients needed to continue oral anticoagulant drug (10 mg, po, Qd) for 7-21 days after discharge. The patients in group B only took low molecular heparin 5-10 days after surgery and no treatment after discharge. The baseline characteristics of patients, total complications of SVT include lower limb vascular pain (LLVP), lower limb vascular pain no fester (LLVPNF), lower limbs swelling (LLS), lower limb fester (LLF), and death by thrombosis (DT), bleeding and mortality following discharged were compared between two groups.

RESULTS

The study showed that the incidence of SVT patients had no significant difference between the two groups (p = 0.489). Moreover, the incidence of LLVP (p = 0.265), LLS (p = 0.84), LLVPNF (p = 0.213), LLF (p = 0.907), DT (p = 0.907), death from other causes, and bleeding (p = 0.323) had no significant differences between the two groups. However, the incidence of SVT in patients with smoking (p = 0.0001 or 0.0011) or drinking (p = 0.0002 or 0.0001) was significantly increased.

CONCLUSION

There is not enough evidence showing that the TKA patients given anticoagulants after discharge had benefits in decreasing the risk of SVT. Furthermore, smoking and drinking would significantly increase the risk of SVT in TKA patients.

Acquired Hemophilia A Masquerading as Bleeding on Anticoagulation: A Case Report Including Key Laboratory Considerations

We report a case of a patient with recurrent hematomas while on anticoagulation for a pulmonary embolism and a prolonged hospital stay due to a delayed diagnosis for acquired hemophilia A. Acquired hemophilia A is a rare autoimmune bleeding disorder with autoantibodies directed against coagulation factor VIII (FVIII), leading to an acquired FVIII deficiency. A prolonged isolated activated partial thromboplastin time (aPTT) in a bleeding patient warrants workup for acquired hemophilia A. This is specifically challenging in patients with thrombosis on anticoagulation and can lead to significant delays in diagnosis and associated morbidities. The case highlights the need for further awareness of this disease, potential laboratory pitfalls when conducting and interpreting coagulation assays, and the management considerations in a patient with a simultaneous thrombotic and hemorrhagic condition.

Population Pharmacokinetics and Probability of Target Attainment Analysis of Nadroparin in Different Stages of COVID-19

BACKGROUND AND OBJECTIVE

The risk of thrombotic complications in critical patients with COVID-19 remains extremely high, and multicenter trials failed to prove a survival benefit of escalated doses of low-molecular-weight heparins (nadroparin calcium) in this group. The aim of this study was to develop a pharmacokinetic model of nadroparin according to different stages of COVID-19 severity.

METHODS

Blood samples were obtained from 43 patients with COVID-19 who received nadroparin and were treated with conventional oxygen therapy, mechanical ventilation, and extracorporeal membrane oxygenation. We recorded clinical, biochemical, and hemodynamic variables during 72 h of treatment. The analyzed data comprised 782 serum nadroparin concentrations and 219 anti-Xa levels. We conducted population nonlinear mixed-effects modeling (NONMEM) and performed Monte Carlo simulations of the probability of target attainment for reaching 0.2-0.5 IU/mL anti-Xa levels in study groups.

RESULTS

We successfully developed a one-compartment model to describe the population pharmacokinetics of nadroparin in different stages of COVID-19. The absorption rate constant of nadroparin was 3.8 and 3.2 times lower, concentration clearance was 2.22 and 2.93 times higher, and anti-Xa clearance was 0.87 and 1.1 times higher in mechanically ventilated patients and the extracorporeal membrane oxygenation group compared with patients treated with conventional oxygen, respectively. The newly developed model indicated that 5.900 IU of nadroparin given subcutaneously twice daily in the mechanically ventilated patients led to a similar probability of target attainment of 90% as 5.900 IU of subcutaneous nadroparin given once daily in the group supplemented with conventional oxygen.

CONCLUSIONS

Different nadroparin dosing is required for patients undergoing mechanical ventilation and extracorporeal membrane oxygenation to achieve the same targets as those for non-critically ill patients.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov identifier no. NCT05621915.

Weight-adjusted dosing of tinzaparin for thromboprophylaxis in obese medical patients

Background

The optimal dose of tinzaparin for prophylaxis in obese medical patients is not well defined.

Objectives

To evaluate the anti-Xa activity in obese medical patients on tinzaparin prophylaxis adjusted for actual bodyweight.

Methods

Patients with a body mass index of ≥30 kg/m² treated with 50 IU/kg tinzaparin once daily were prospectively included. Anti-Xa and anti-IIa activity; von Willebrand factor antigen and von Willebrand activity; factor VIII activity; D-dimer, prothrombin fragments; and thrombin generation were measured 4 hours after subcutaneous injection between days 1 and 14 after the initiation of tinzaparin prophylaxis.

Results

We included 121 plasma samples from 66 patients (48.5% women), with a median weight of 125 kg (range, 82-300 kg) and a median body mass index of 41.9 kg/m² (range, 30.1-88.6 kg/m²). The target anti-Xa activity of 0.2 to 0.4 IU/mL was achieved in 80 plasma samples (66.1%); 39 samples (32.2%) were below and 2 samples (1.7%) above the target range. The median anti-Xa activity was 0.25 IU/mL (IQR, 0.19-0.31 IU/mL), 0.23 IU/mL (IQR, 0.17-0.28 IU/mL), and 0.21 IU/mL (IQR, 0.17-0.25 IU/mL) on days 1 to 3, days 4 to 6, and days 7 to 14, respectively. The anti-Xa activity did not differ among the weight groups (P = .19). Injection into the upper arm compared to the abdomen resulted in a lower endogenous thrombin potential, a lower peak thrombin, and a trend to a higher anti-Xa activity.

Conclusion

Dosing of tinzaparin adjusted for actual bodyweight in obese patients achieved anti-Xa activity in the target range for most patients, without accumulation or overdosing. In addition, there is a significant difference in thrombin generation depending on the injection site.

Venous thromboembolism and anticoagulation in spinal cord lesion rehabilitation inpatients: A 10-year retrospective study

BACKGROUND

Venous thromboembolism (VTE) is a concern following the onset of spinal cord lesions (SCL).

OBJECTIVES

To assess the current efficacy and risks of anticoagulation after SCL and consider changes in thromboprophylaxis.

METHODS

This retrospective cohort study included individuals admitted to inpatient rehabilitation within 3 months of SCL onset. Main outcome measures were the incidence of deep vein thrombosis (DVT), pulmonary embolism (PE), bleeding, thrombocytopenia, or death, which occurred within 1 year of the SCL onset.

RESULTS

VTE occurred in 37 of the 685 patients included in the study (5.4%, 95% CI 3.7-7.1%, 2.8% PE), and in 16 of 526 patients who received prophylactic anticoagulation at rehabilitation (3%, 95% CI 1.6-4.5%, 1.1% PE, with at least 1 fatality). Of these 526, 1.3% developed clinically significant bleeding and 0.8% thrombocytopenia. Prophylactic anticoagulation, most commonly 40 mg/day, continued until a median period of 6.4 weeks after SCL onset (25% -75% percentiles 5.8-9.7), but in 29.7%, VTE occurred more than 3 months after SCL onset.

CONCLUSION

The VTE prophylaxis used for the present cohort contributed to a considerable but limited reduction of VTE incidence. The authors recommend conducting a prospective study to assess the efficacy and safety of an updated preventive anticoagulation regimen.

Thrombin generation assays to personalize treatment in bleeding and thrombotic diseases

Treatment of bleeding and thrombotic disorders is highly standardized and based on evidence-based medicine guidelines. These evidence-based treatment schemes are well accepted but may lead to either insufficient treatment or over-dosing, because the individuals' hemostatic properties are not taken into account. This can potentially introduce bleeding or thrombotic complications in individual patients. With the incorporation of pharmacokinetic (PK) and pharmacodynamic (PK-PD) parameters, based on global assays such as thrombin generation assays (TGAs), a more personalized approach can be applied to treat either bleeding or thrombotic disorders. In this review, we will discuss the recent literature about the technical aspects of TGAs and the relation to diagnosis and management of bleeding and thrombotic disorders. In patients with bleeding disorders, such as hemophilia A or factor VII deficiency, TGAs can be used to identify patients with a more severe bleeding phenotype and also in the management with non-replacement therapy and/or bypassing therapy. These assays have also a role in patients with venous thrombo-embolism, but the usage of TGAs in patients with arterial thrombosis is less clear. However, there is a potential role for TGAs in the monitoring of (long-term) antithrombotic therapy, for example with the use of direct oral anticoagulants. Finally this review will discuss controversies, limitations and knowledge gaps in relation to the introduction of TGAs to personalize medicine in daily medical practice.

Anticoagulation Monitoring with Activated Partial ThromboPlastin Time and Anti-Xa Activity in Intensive Care Unit Patients: Interest of Thrombin Generation Assay

Current guidelines recommend monitoring the anticoagulant effect of unfractionated heparin (UFH) by measuring anti-Xa activity rather than activated partial thromboplastin time (aPTT) in intensive care unit (ICU) patients. The primary objective of this study was to evaluate the correlation of aPTT, anti-Xa activity, and thrombin generation in UFH-treated ICU patients. A prospective observational pilot study was conducted in adult surgical ICU patients treated with UFH. aPTT and anti-Xa activity were monitored daily. The therapeutic target was aPTT between 50 s and 84 s, and/or anti-Xa between 0.3 and 0.7 U/mL. Correlation among aPTT, anti-Xa activity, and thrombin generation was determined by measuring endogenous thrombin potential (ETP), with the inflammatory response evaluated. C-reactive protein (CRP) was used as a marker of inflammatory response. The plasma of 107 samples from 30 ICU patients was analyzed. The correlation between aPTT and anti-Xa activity was 0.66, CI95% [0.54;0.76] (p < 0.0001). Although thrombin generation, aPTT, and anti-Xa were correlated with inflammatory responses, the correlation was higher with thrombin generation and anti-Xa activity compared to aPTT. When aPTT was in a therapeutic range, a low thrombin generation was observed but was 50% inhibited when anti-Xa was in a therapeutic range. Coagulation testing with aPTT, anti-Xa correlated with thrombin generation. A 50% decrease in thrombin generation was observed when anti-Xa was within a therapeutic range. Further work is needed to evaluate coagulation biomarker responses and clinical outcomes in specific ICU populations.

Role of Physical Therapists in the Management of Individuals at Risk for or Diagnosed With Venous Thromboembolism: Evidence-Based Clinical Practice Guideline 2022

No matter the practice setting, physical therapists work with patients who are at risk for or who have a history of venous thromboembolism (VTE). In 2016, the first clinical practice guideline (CPG) addressing the physical therapist management of VTE was published with support by the American Physical Therapy Association's Academy of Cardiovascular and Pulmonary Physical Therapy and Academy of Acute Care, with a primary focus on lower extremity deep vein thrombosis (DVT). This CPG is an update of the 2016 CPG and contains the most current evidence available for the management of patients with lower extremity DVT and new key action statements (KAS), including guidance on upper extremity DVT, pulmonary embolism, and special populations. This document will guide physical therapist practice in the prevention of and screening for VTE and in the management of patients who are at risk for or who have been diagnosed with VTE. Through a systematic review of published studies and a structured appraisal process, KAS were written to guide the physical therapist. The evidence supporting each action was rated, and the strength of statement was determined. Clinical practice algorithms based on the KAS were developed that can assist with clinical decision-making. Physical therapists, along with other members of the health care team, should implement these KAS to decrease the incidence of VTE, improve the diagnosis and acute management of VTE, and reduce the long-term complications of VTE.

Anti-factor X Activity Levels with Continuous Intravenous Infusion and Subcutaneous Administration of Enoxaparin after Coronary Artery Bypass Grafting: a Randomized Clinical Trial

BACKGROUND

Low-molecular-weight heparin enoxaparin is widely used in pharmacological thromboprophylaxis after coronary artery bypass grafting (CABG). The aim of this study was to compare anti-factor X activity (anti-Xa) levels when the thromboprophylactic dose of enoxaparin was provided after CABG, with two different administration routes: continuous intravenous infusion (CIV) and subcutaneous bolus (SCB) injection. We hypothesized that the current standard method of SCB administration might lead to lower anti-Xa levels than recommended in other patient groups, due to reduced bioavailability.

METHODS

In this prospective, randomized, controlled clinical trial, 40 patients scheduled for elective CABG were randomized to receive 40 mg of enoxaparin per day either as CIV or SCB for 72 h. Enoxaparin was initiated 6-10 h after CABG. Anti-Xa levels were measured 12-14 times during the study period. The primary outcome i.e. the maximum anti-Xa concentration over 0-24 h (C_max0-24h ), was calculated from these measured values. Secondary outcomes were C_max25-72h and the trough concentration of anti-Xa after 72 h of enoxaparin initiation (C_72h ).

RESULTS

Twenty patients were randomized to the CIV-group and 19 to the SCB-group. The median anti-Xa C_max0-24h was significantly lower in the CIV-group than in the SCB-group: 0.15 [interquartile range (IQR) 0.13-0.19] IU/mL versus 0.25 (IQR 0.18-0.32) IU/mL, p < 0.005. The median anti-Xa C_max25-72h was 0.12 (IQR, 0.1-0.17) IU/mL versus 0.23 (IQR 0.19-0.31) IU/mL, respectively, p < 0.005. At 72 h, there was no difference between the groups in their anti-Xa levels.

CONCLUSIONS

In this low-risk CABG patient population, SCB administration of a thromboprophylactic dose of enoxaparin provided anti-Xa levels that are considered sufficient for thromboprophylaxis in other patient groups. CIV administration resulted in lower anti-Xa levels compared to the SCB route.

Therapeutically dosed low molecular weight heparins in renal impairment: a nationwide survey

PURPOSE

International guidelines vary in their recommendations whether or not to reduce the therapeutic dose of low molecular weight heparins (LMWHs) in renal impairment. The use of anti-Xa monitoring as a basis of dose adjustments is also a matter of debate. As this may lead to variations in treatment policies, we aimed to study the treatment policies of therapeutically dosed LMWHs in renal impairment in Dutch hospitals.

METHODS

An 11-item survey was distributed between June 2020 and March 2021 to hospital pharmacists, representing Dutch hospital organisations. Primary outcomes were the dosing regimens of therapeutically dosed LMWHs in renally impaired patients. Secondary outcomes were the proportion of hospitals that used anti-Xa monitoring and the anti-Xa target range used.

RESULTS

There was a response from 56 of 69 (81%) Dutch hospital organisations where in each case a hospital pharmacist completed the survey. In these hospitals, 77 LMWH regimens were in use. In 76 of 77 (99%) regimens, a regular dose reduction was used at the start of treatment. Fifty-five of these hospitals used a dose reduction if estimated glomerular filtration rate (eGFR) < 50 ml/min and 17 used a dose reduction if eGFR < 30 ml/min. Anti-Xa levels were not routinely monitored in 40% of regimens, while 22% monitored anti-Xa if eGFR < 50 ml/min, 27% if eGFR < 30 ml/min and 10% in other eGFR cutoff values. Target ranges of 1.0-2.0 IU/ml (once daily) and 0.5/0.6-1.0 IU/ml (twice daily) were used in 69% of regimens that included monitoring of anti-Xa.

CONCLUSION

Treatment policies show substantial diversity in therapeutically dosed LMWHs in renally impaired patients. The most commonly used treatment regimen was a regular dose reduction if eGFR is < 50 ml/min, without anti-Xa monitoring.

Heparins for prevention and treatment of venous thromboembolism in cirrhosis: Research advances

Current evidence suggests that liver cirrhosis may increase the risk of venous thromboembolism (VTE). In cirrhosis, common types of VTE include portal vein thrombosis (PVT), deep vein thrombosis, and pulmonary embolism (PE). Heparins are the most commonly prescribed anticoagulants for the prevention and treatment of VTE. However, the indications, choice, dosage, and monitoring of heparins in cirrhosis remain inconclusive. This paper aims to review the advances in the research of heparins for the prevention and treatment of VTE in cirrhosis to optimize the treatment strategy.

Monitoring of heparin therapy beyond the anti-Xa activity assay: Evaluation of a thrombin generation assay

INTRODUCTION

Global coagulation assays may be of added value to the anti-Xa assay for monitoring heparin therapy. Unlike most testing methods, the thrombin generation assay (TGA) has the ability to assess the overall function of the hemostatic system, which provides information on the anticoagulation status of patients. We compared the TGA, measured with ST Genesia^® STG-DrugScreen^® reagent, with the anti-Xa assay for monitoring heparin therapy in inflammatory and non-inflammatory patients. We also determined reference values for STG-DrugScreen^® thrombin generation (TG) parameters.

METHODS

Reference values were determined on 120 healthy donors. Furthermore, a spiking experiment with unfractionated heparin (UFH) and low molecular weight heparin (LMWH) was performed, and samples of patients receiving UFH or LMWH were analyzed with ST Genesia^® and the anti-Xa assay.

RESULTS

High discrepancy between TG parameters and anti-Xa activity was observed for low LMWH anti-Xa levels. TG parameters were affected in 36/46 (time to peak) to 42/46 (peak height) patients during UFH therapy with sub-target anti-Xa activity levels.

CONCLUSION

TGA seems insufficiently sensitive for low concentrations of LMWH. There may be an added value of the TGA for monitoring UFH in so-called heparin-resistant patients. Therefore, the TGA has the potential to be introduced as an additional tool for monitoring heparin therapy.

"In Less than No Time": Feasibility of Rotational Thromboelastometry to Detect Anticoagulant Drugs Activity and to Guide Reversal Therapy

Anticoagulant drugs (i.e., unfractionated heparin, low-molecular-weight heparins, vitamin K antagonists, and direct oral anticoagulants) are widely employed in preventing and treating venous thromboembolism (VTE), in preventing arterial thromboembolism in nonvalvular atrial fibrillation (NVAF), and in treating acute coronary diseases early. In certain situations, such as bleeding, urgent invasive procedures, and surgical settings, the evaluation of anticoagulant levels and the monitoring of reversal therapy appear essential. Standard coagulation tests (i.e., activated partial thromboplastin time (aPTT) and prothrombin time (PT)) can be normal, and the turnaround time can be long. While the role of viscoelastic hemostatic assays (VHAs), such as rotational thromboelastometry (ROTEM), has successfully increased over the years in the management of bleeding and thrombotic complications, its usefulness in detecting anticoagulants and their reversal still appears unclear.

International multicenter, multiplatform study to validate Taipan snake venom time as a lupus anticoagulant screening test with ecarin time as the confirmatory test: Communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies

BACKGROUND

Lupus anticoagulant (LA) assays are compromised in anticoagulated patients, and existing strategies to overcome the interferences have limitations. The prothrombin-activating Taipan snake venom time (TSVT) screening test and ecarin time (ET) confirmatory test are innately insensitive to vitamin K antagonists (VKA) and direct factor Xa inhibitors (DFXaI).

OBJECTIVES

Validate standardized TSVT/ET reagents for LA detection, in a multicenter, multiplatform study.

PATIENTS/METHODS

Six centers from four countries analyzed samples with TSVT/ET from 81 nonanticoagulated patients with LA, patients with established antiphospholipid syndrome (APS), and proven persistent LA who were either not anticoagulated (n = 120) or were anticoagulated with VKAs (n = 180) or DFXaIs (n = 71). Additionally, 339 nonanticoagulated LA-negative patients, and 575 anticoagulated non-APS patients (172 VKA, 403 DFXaI) were tested. Anticoagulant spiking experiments were performed and 112 samples containing potential interferences (i.e., direct thrombin inhibitors) were tested. Results were evaluated against locally derived cutoffs. Imprecision was evaluated.

RESULTS

Cutoffs were remarkably similar despite use of different analyzers and donor populations. Cutoffs for TSVT ratio, ET ratio, percent correction, and normalized TSVT ratio/ET ratio ranged between 1.08 and 1.10, 1.09 and 1.12, 9.3% and 14.8%, and 1.10 and 1.15, respectively. Coefficients of variation for TSVT and ET ratios were ≤5.0%. TSVT/ET exhibited sensitivity, specificity, and negative and positive predictive values of 78.2%/95.0%/86.3%/91.5%, respectively, with established APS as the LA-positive population, and 86.9%/95.0%/76.8%/97.4%, respectively, with triple-positive APS. Interference was seen with direct thrombin inhibitors, unfractionated heparin, and low molecular weight heparins, but not VKAs or DFXaIs.

CONCLUSIONS

TSVT/ET are validated for LA detection in nonanticoagulated patients and those on VKAs or DFXaIs.

Prophylactic Low-Molecular-Weight Heparin Versus Unfractionated Heparin in Spine Surgery (PLUSS): A Pilot Matched Cohort Study

BACKGROUND

Despite a proven superior efficacy of prophylactic low-molecular-weight heparin (LMWH) over unfractionated heparin (UFH) in the majority of surgical specialties, chemoprophylactic techniques after spine surgery have not been established because of the fear of epidural hematomas with LMWH.

OBJECTIVE

To determine the efficacy of LMWH vs UFH in the prevention of venous thromboembolism (VTE) events, balanced against the risk of epidural hematoma.

METHODS

This is the first matched cohort design that directly compares prophylactic LMWH to UFH after spine surgery for degenerative/deformity pathologies at a tertiary academic center. Prospectively collected patients receiving prophylactic LMWH and a historical cohort of patients receiving prophylactic UFH (prior to 2017) were matched in 1:1 ratio based on age ±5 yr, American Society of Anesthesiologists classification, location in the spinal column, and type of surgery.

RESULTS

Of 562 patients, VTE events equaled 1.4% (n = 8): 1.4% (n = 4) with LMWH was exactly equal to 1.4% (n = 4) with UFH. Epidural hematomas reached 0.8% (n = 5): 1.4% (n = 4) with UFH vs 0.3% (n = 1) with the LMWH (P = .178). Utilizing adjusted odds ratio (ORadj), the type of chemoprophylaxis after spine surgery failed to predict VTE events. Similarly, the chemoprophylactic technique failed to predict epidural hematoma in the multivariable regression analysis, although UFH trended toward a higher complication rate (ORadj = 3.15 [0.48-20.35], P = .227).

CONCLUSION

Chemoprophylactic patterns failed to predict VTE. Although no differences in epidural hematoma rates were detected, our analysis does highlight a trend toward a safer profile with LMWH vs UFH. LMWH may be a safe alternative to UFH in spine surgery.

Heparin - Messias or Verschlimmbesserung?

A heightened risk of thrombosis noted early on with the severe acute respiratory syndrome coronavirus 2 infection led to the widespread use of heparin anticoagulation in the coronavirus disease 2019 (COVID-19) pandemic. However, reports soon started appearing in the literature where an apparent failure of heparin to prevent thrombotic events was observed in hospitalized patients with this viral infection. In this review, we explore the likely mechanisms for heparin failure with particular relevance to COVID-19. We also explore the role of anti-Xa assays and global hemostatic tests in this context. The current controversy of dosing heparin in this disease is detailed with some possible mechanistic reasons for anticoagulant failure. We hope that lessons learnt from the use of heparin in COVID-19 could assist us in the appropriate use of this anticoagulant in the future.

Thrombin Generation and Platelet Function in ICU Patients Undergoing CVVHD Using Regional Citrate Anticoagulation

Background: To investigate pro- and anticoagulant alterations in uremic critically ill patients prior to and during continuous renal replacement therapy. In addition to the conventional thrombin generation assay (TGA), we performed a thrombomodulin-modified variant to better elucidate procoagulant imbalances. Platelet function was determined via multiple electrode aggregometry (MEA) to round off hemostatic analysis.

Methods: We prospectively enrolled patients at surgical intensive care units (ICU) with acute kidney injury undergoing continuous veno-venous hemodialysis using regional citrate anticoagulation. TGA and platelet function testing were performed at baseline (≤ 12 h prior to continuous renal replacement therapy) and on 3 consecutive days (day A–C) of extracorporeal therapy.

Results: We did not observe significant changes in thrombin generation after start or during renal replacement therapy. Ratios of endogenous thrombin potential in patients were significantly increased (p < 0.001) compared to standardized plasma of healthy donors confirming the assumed procoagulant alterations in ICU patients. Test results of the conventional TGA differed significantly (p < 0.05) from those of the thrombomodulin-modified assay. The area under the curve remained below MEA reference values during the entire observation period, indicating a persistent reduction in platelet function.

Conclusion: In summary, in-depth analysis using standard and modified TGA, as well as calculation of endogenous thrombin potential (ETP) ratios, revealed no further aggravation of the procoagulatory shift in the critically ill patient during CVVHD using regional citrate anticoagulation. MEA ruled out the potential impact of platelets.

Clinical Trial Registration: German Clinical Trials Register (DRKS00004336), 29 August 2012; www.drks.de.

Updates on Anticoagulation and Laboratory Tools for Therapy Monitoring of Heparin, Vitamin K Antagonists and Direct Oral Anticoagulants

Anticoagulant drugs have been used to prevent and treat thrombosis. However, they are associated with risk of hemorrhage. Therefore, prior to their clinical use, it is important to assess the risk of bleeding and thrombosis. In case of older anticoagulant drugs like heparin and warfarin, dose adjustment is required owing to narrow therapeutic ranges. The established monitoring methods for heparin and warfarin are activated partial thromboplastin time (APTT)/anti-Xa assay and prothrombin time – international normalized ratio (PT-INR), respectively. Since 2008, new generation anticoagulant drugs, called direct oral anticoagulants (DOACs), have been widely prescribed to prevent and treat several thromboembolic diseases. Although the use of DOACs without routine monitoring and frequent dose adjustment has been shown to be safe and effective, there may be clinical circumstances in specific patients when measurement of the anticoagulant effects of DOACs is required. Recently, anticoagulation therapy has received attention when treating patients with coronavirus disease 2019 (COVID-19). In this review, we discuss the mechanisms of anticoagulant drugs—heparin, warfarin, and DOACs and describe the methods used for the measurement of their effects. In addition, we discuss the latest findings on thrombosis mechanism in patients with COVID-19 with respect to biological chemistry.

Updates in Anticoagulation Therapy Monitoring

In the past six decades, heparin and warfarin were the primary anticoagulants prescribed for treatment and prophylaxis of venous thromboembolism worldwide. This has been accompanied by extensive clinical knowledge regarding dosing, monitoring, and reversal of these anticoagulants, and the resources required to do so have largely been readily available at small and large centers alike. However, with the advent of newer oral and parenteral anticoagulants such as low molecular weight heparins, factor Xa inhibitors, and direct thrombin inhibitors in recent years, new corresponding practice guidelines have also emerged. A notable shift in the need for monitoring and reversal agents has evolved as well. While this has perhaps streamlined the process for physicians and is often desirable for patients, it has also left a knowledge and resource gap in clinical scenarios for which urgent reversal and monitoring is necessary. An overview of the currently available anticoagulants with a focus on the guidelines and available tests for anticoagulant monitoring will be discussed in this article.

Continuous intravenous infusion of enoxaparin controls thrombin formation more than standard subcutaneous administration in critically ill patients. A sub-study of the ENOKSI thromboprophylaxis RCT

INTRODUCTION

Standard subcutaneous low-molecular-weight heparin (LMWH) thromboprophylaxis yields low anti-factor Xa activity in patients in the intensive care unit (ICU). The aim of the study was to assess coagulation status in ICU patients randomized to receive enoxaparin thromboprophylaxis either as a standard subcutaneous bolus (SCB) or continuous intravenous infusion (CII) for 3 consecutive days after the initiation of LMWH thromboprophylaxis.

MATERIALS AND METHODS

Thirty-eight patients were studied by conventional coagulation variables: prothrombin fragment F 1+2 (F 1+2) representing FXa inhibition and antithrombin (AT). Additionally, 18 patients were analyzed by the thrombin generation assay-calibrated automated thrombogram (TGA-CAT). Blood samples were collected before the initiation of the LMWH thromboprophylaxis (ie, baseline), at 51 h, and at 72 h.

RESULTS

At beginning, no differences in coagulation biomarkers were observed. The levels of F 1+2 were significantly lower at 51 and 72 h in the CII group than in the SCB group. AT levels increased during the follow-up in the CII group, unlike in the SCB group. TGA-CAT was poor in some patients overall. In a subset of patients at 51 h lag time (4.3 vs 7.5 min, respectively, P < 0.05) and time to peak (7.7 vs 14.3 min, respectively, P < 0.05) were prolonged in the SCB group. At 72 h, however, peak thrombin was lower in the CII than in the SCB group: 271 vs 356 nM, respectively (P < 0.05).

CONCLUSIONS

Enoxaparin thromboprophylaxis administered by CII inhibited more prominently FXa and preserved better the AT level, compared with standard subcutaneous care.

Coronavirus Historical Perspective, Disease Mechanisms, and Clinical Outcomes: JACC Focus Seminar

The emergence of a new coronavirus disease (coronavirus disease 2019 [COVID-19]) has raised global concerns regarding the health and safety of a vulnerable population. Infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) incites a profound inflammatory response leading to tissue injury and organ failure. COVID-19 is characterized by the bidirectional relationship between inflammation and thrombosis. The clinical syndrome is propelled by inflammation producing acute lung injury, large-vessel thrombosis, and in situ microthrombi that may contribute to organ failure. Myocardial injury is common, but true myocarditis is rare. Elderly patients, those with established cardiovascular disease, and mechanically ventilated patients face the highest mortality risk. Therapies for COVID-19 are evolving. The antiviral drug remdesivir, dexamethasone, transfusion of convalescent plasma, and use of antithrombotic therapy are promising. Most require additional prospective studies. Although most patients recover, those who survive severe illness may experience persistent physical and psychological disabilities.

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Severe acute respiratory syndrome coronavirus 2 infection (COVID-19) is a global pandemic affecting millions of people worldwide.

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Clinical sequelae result largely from an intense inflammatory response triggering large-vessel and microvascular thrombosis.

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No therapy has been universally effective for COVID-19, but systemic anticoagulation, remdesivir, and corticosteroids hold promise.

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Long-term sequelae of COVID-19 are variable and incompletely defined, but physical and psychological disabilities can persist.

Thromboprophylaxis in a patient with COVID-19 and severe hemophilia A on emicizumab prophylaxis

COVID-19 can be associated with coagulopathy (CAC, COVID-19-associated coagulopathy) with a high prothrombotic risk based on an intense inflammatory response to viral infection leading to immunothrombosis through different procoagulant pathways. Emerging evidence suggests that the use of heparin in these patients could be associated with lower mortality. Emicizumab is a bispecific humanized monoclonal antibody that bridges activated factor IX and factor X, thereby restoring the function of missing factor VIIIa in hemophilia A. The use of emicizumab has been associated with thrombotic events in patients who also received high cumulative amounts of activated prothrombin complex concentrates. Although this risk is extremely low, there is a lack of evidence on whether CAC increases the thrombotic risk in patients on emicizumab prophylaxis. We present the case of a patient with severe hemophilia A in prophylaxis treatment with emicizumab; due to the potential thrombotic risk we decided to administer low molecular weight heparin as prophylaxis treatment without any thrombotic or bleeding complications.

Prevention and Treatment of Venous Thromboembolism Associated with Coronavirus Disease 2019 Infection: A Consensus Statement before Guidelines

Coronavirus disease 2019 (COVID-19) has caused a global pandemic in just a few months, causing millions infected. Nearly 20% of COVID-19 patients present severe coagulation abnormalities, which may occur in almost all of the severe and critical ill COVID-19 cases. Concomitant venous thromboembolism (VTE), a potential cause of unexplained deaths, has been frequently reported in COVID-19 cases, but its management is still challenging due to the complexity between antithrombotic therapy and coagulation disorders. Based on frontline practical experience and comprehensive literature review, here a panel of experts and physicians from China and Europe developed an evidence and opinion-based consensus on the prophylaxis and management of VTE associated with COVID-19. This statement aims for clinicians treating COVID-19 and provides practical recommendations in detailed situations, for example, how to choose thromboprophylactic measures for patients with diverse severity of disease and bleeding risk, or which kind of anticoagulant should be prescribed. With limited experience on COVID19-associated VTE, this expert consensus statement should be helpful for clinicians worldwide with specific suggestions.

Rivaroxaban and Dabigatran for Suppression of Mechanical Heart Valve-Induced Thrombin Generation

BACKGROUND

Patients with mechanical heart valves (MHVs) require warfarin to prevent thromboembolism. Dabigatran was less effective than warfarin in patients with MHVs, which prompted a black box warning against the use of direct oral anticoagulants for this indication. However, rivaroxaban and apixaban, which inhibit factor Xa, have not been evaluated in patients with MHVs. To determine whether rivaroxaban and apixaban would be effective, we used MHV-induced thrombin generation assays to compare them with warfarin either alone or in combination with dabigatran.

METHODS

Thrombin generation in the absence or presence of MHV leaflets or sewing ring segments (SRSs) was quantified. Studies were done in control plasma; plasma from patients on warfarin; plasma containing varying concentrations of rivaroxaban, apixaban, or dabigatran alone; or plasma containing rivaroxaban plus dabigatran.

RESULTS

Mean endogenous thrombin potential (ETP) increased 1.2-fold, 1.5-fold, and 1.8-fold in the presence of leaflets, Teflon (Terumo Aortic (Sunrise, FL)) SRSs, or Dacron (Terumo Aortic (Sunrise, FL)) SRSs, respectively. Rivaroxaban and apixaban reduced ETP at concentrations above 50 ng/mL but were less effective than warfarin. When rivaroxaban and dabigatran were combined, they suppressed ETP in a more than additive manner.

CONCLUSIONS

Whereas warfarin suppresses MHV-induced thrombin generation, MHVs induce the generation of factor Xa in concentrations that overwhelm clinically relevant concentrations of rivaroxaban or apixaban. When used in combination, rivaroxaban and dabigatran are more effective than either agent is alone, suggesting that concomitant inhibition of factor Xa and thrombin is better than inhibition of either clotting enzyme alone.

Monitoring anti-Xa levels in patients with cancer-associated venous thromboembolism treated with bemiparin

OBJECTIVE

To analyze the relationship between therapeutic (weight-adjusted) dose of bemiparin and anti-Xa activity in patients with venous thromboembolism (VTE) and cancer in comparison with a cohort of patients with VTE without cancer, and its relationship with outcomes.

MATERIALS AND METHODS

This is a prospective cohort study that comprised a cohort of patients with cancer-associated VTE and a cohort of non-cancer patients with VTE, all of them treated with bemiparin. The ethics committee approved the study and informed consent was obtained from the patients.

RESULTS

One hundred patients were included (52 with cancer and 48 without cancer), with a median follow-up of 9.8 months. Mean anti-Xa activity was 0.89 (± 0.33) UI/mL in oncological patients and 0.83 (± 0.30) UI/mL in non-cancer patients (mean difference - 0.05 95% CI - 0.18; 0.06). A multiple linear regression model showed that anti-Xa peak was associated with the dose/kg independently of possible confounding variables (presence of cancer, age, sex and eGFR-estimated Glomerular Filtration Rate), in a way that for every 1 UI of dose/kg increase, the anti-Xa peak activity increased 0.006 UI/mL (95% CI 0.003; 0.009) (p < 0.001). The predictive capacity of anti-Xa peak in the oncology cohort showed an area under the ROC curve of 0.46 (95% CI 0.24-0.68), 0.70 (95% CI 0.49-0.91) and 0.74 (95% CI 0.44-0.94) for death, first bleeding and recurrence of VTE, respectively, and none was statistically significant.

CONCLUSION

In patients with venous thromboembolism treated with bemiparin, anti-Xa levels were not influenced by the presence of cancer.

Cartridge-Based Thromboelastography Can Be Used to Monitor and Quantify the Activity of Unfractionated and Low-Molecular-Weight Heparins

Thromboelastography is increasingly utilized in the management of bleeding and thrombotic complications where heparin management remains a cornerstone. This study assessed the feasibility of the cartridge-based TEG ^® 6s system (Haemonetics Corp., Braintree, Massachusetts, United States) to monitor and quantify the effect of unfractionated and low-molecular-weight heparin (UFH and LMWH). Blood samples from healthy donors were spiked with UFH ( n  = 23; 0–1.0 IU/mL) or LMWH (enoxaparin; n  = 22; 0–1.5 IU/mL). Functional fibrinogen maximum amplitude (CFF.MA), RapidTEG activated clotting time (CRT.ACT), and kaolin and kaolin with heparinase reaction time (CK.R and CKH.R) were evaluated for their correlation with heparin concentrations, as well as the combination parameters ΔCK.R − CKH.R, ratio CK.R/CKH.R, and ratio CKH.R/CK.R. Nonlinear mixed-effect modelling was used to study the relationship between concentrations and parameters, and Bayesian classification modelling for the prediction of therapeutic ranges. CK.R and CRT.ACT strongly correlated with the activity of LMWH and UFH ( p  < 0.001). Using combination parameters, heparin activity could be accurately quantified in the range of 0.05 to 0.8 IU/mL for UFH and 0.1 to 1.5 IU/mL for LMWH. CRT.ACT was able to quantify heparin activity at higher concentrations but was only different from the reference range ( p  < 0.05) at >0.5 IU/mL for UFH and >1.5 IU/mL for LMWH. Combination parameters classified blood samples into subtherapeutic, therapeutic, and supratherapeutic heparin ranges, with an accuracy of >90% for UFH, and >78% for LMWH. This study suggests that TEG 6s can effectively monitor and quantify heparin activity for LMWH and UFH. Additionally, combination parameters can be used to classify blood samples into therapeutic ranges based on heparin activity.

Unfractionated Heparin with Sequential Enoxaparin in Patients with Complex Coronary Artery Lesions during Percutaneous Coronary Intervention

Background:

Unfractionated heparin (UFH), despite its limitations, has been used as the primary anticoagulant alternative during the percutaneous coronary intervention (PCI). Some studies indicated that intravenous enoxaparin could be an effective and safe option. Our team used enoxaparin alone at one time according to the guidelines (Class IIA) and found a little catheter thrombosis during PCI. We recommend a new anticoagulation strategy using enoxaparin in combination with UFH. Enoxaparin has a more predictable anticoagulant response with no need of repeatedly monitoring anticoagulation during PCI. This retrospective study aimed to evaluate the efficacy and safety of using enoxaparin in combination with UFH in PCI patients with complex coronary artery disease.

Methods:

Between January 2015 and April 2017, 600 PCI patients who received intravenous UFH at an initial dose of 3000 U plus intravenous enoxaparin at a dose of 0.75 mg/kg (observation group) and 600 PCI patients who received UFH at a dose of 100 U/kg (control group) were consecutively included in this retrospective study. The endpoints were postoperative 48-h thrombolysis in myocardial infarction (TIMI) bleeding and transfusion and 30-day and 1-year major adverse cardio-cerebrovascular events (MACCE).

Results:

Baseline clinical, angiographic, and procedural characteristics were similar between groups, except there was less stent implantation per patient in the observation group (2.13 vs. 2.25 in the control group, P = 0.002). TIMI bleeding (3.3% vs. 4.7%) showed no significant difference between the observation group and control group. During the 30-day follow-up, the rate of MACCE was 0.9% in the observation group and 1.5% in the control group. There was no significant difference in the rates of MACCE, death, myocardial infarction, target vessel revascularization, cerebrovascular event, and angina within 30 days and 1 year after PCI between groups as well as in the subgroup analysis of transfemoral approach.

Conclusions:

UFH with sequential enoxaparin has similar anticoagulant effect and safety as UFH in PCI of complex coronary artery disease.

Thrombodynamics-A new global hemostasis assay for heparin monitoring in patients under the anticoagulant treatment

BACKGROUND

Heparin therapy and prophylaxis may be accompanied by bleeding and thrombotic complications due to individual responses to treatment. Dosage control based on standard laboratory assays poorly reflects the effect of the therapy. The aim of our work was to compare the heparin sensitivity of new thrombodynamics (TD) assay with sensitivity of other standard and global coagulation tests available to date.

STUDY POPULATION AND METHODS

A total of 296 patients with high risk of venous thromboembolism (deep vein thrombosis (DVT), early postoperative period, hemoblastosis) were enrolled in the study. We used a case-crossover design to evaluate the sensitivity of new thrombodynamics assay (TD) to the hemostatic state before and after unfractionated heparin (UFH) and low-molecular-weight heparin (LMWH) therapy/prophylaxis and to compare it with the activated partial thromboplastin time (APTT), anti-Xa activity test, thrombin generation test (TGT) and thromboelastography (TEG). A receiver operating characteristic (ROC) curve analysis was used to evaluate changes before and after heparin prophylaxis and therapy. Blood was sampled before heparin injection, at the time of maximal blood heparin concentration and before the next injection.

RESULTS

Hypercoagulation before the start of heparin treatment was detected by TD, TGT and TEG but not by APTT. The area under the ROC curve (AUC) was maximal for TD and anti-Xa, intermediate for TGT and TEG and minimal for APTT.

CONCLUSIONS

These results indicate that TD has a high sensitivity to the effects of UFH and LMWH after both prophylactic and therapeutic regimes and may be used for heparin monitoring.

Correlation between activated partial thromboplastin time and anti-Xa activity in patients who received low-molecular weight heparin as anticoagulation for haemodialysis

Plasma anti-Xa activity, the recommended test to monitor low-molecular weight heparin (LMWH) therapy, is not readily available in many laboratories. In our clinical trials on the use of LMWH as anticoagulation for haemodialysis, a consistent prolongation of APTT in addition to the elevated anti-Xa activity was observed in the patients after LMWH administration. Hence, the paired anti-Xa activity and APTT data were re-analyzed. The APTT ratio, which was the proportional change in APTT from the baseline value after LMWH administration, was found to have a strong correlation with anti-Xa activity (coefficient of determination, R ²  = 0.72, P < 0.001). In the receiver operating characteristic analysis, the APTT ratio was also found to be an excellent predictor of therapeutic anti-Xa activity ≧0.5 IU/mL (area under curve = 0.93, P < 0.001). The sensitivity was 88% and the specificity was 83.3% when an APTT ratio ≧1.4 was used as the cut point to predict the achievement of therapeutic anti-Xa activity. Our results illustrated that APTT is a potentially useful screening test to assess the degree of anticoagulation achieved by LMWH during haemodialysis, if the testing for plasma anti-Xa activity is not available.

Bilateral Patellar Tendon Rupture

The knee is the most complex and largest joint in the body. Injuries to any part of this joint affect the entire body. There are multiple injuries that can occur to the knee, with the most common being ligament and meniscus tears. A not-so-common injury to the knee is a patellar tendon rupture. A bilateral patellar tendon rupture is extremely rare. A case study of a 43-year-old man who sustained a bilateral patellar tendon rupture while playing softball is used to present this devastating injury. This discussion includes the incidence and diagnosis of the tear, surgical repair, as well as a description of the comprehensive rehabilitation process necessary to allow the patient to return to normal physical activity. Risks and complications of this surgery and the expected outcomes are also presented.

The Role of Tinzaparin in Oncology

Current guidelines recommend low-molecular-weight heparin treatment in patients with cancer with established venous thromboembolism (VTE). The aim of this article was to study the pharmacological properties and effectiveness of tinzaparin in patients with cancer as well as its potential anticancer properties. A search of PubMed and ScienceDirect databases up to March 2016 was carried out to identify published studies that detect the properties and use of tinzaparin in oncology. Protamine sulfate partially (60% to 65%) neutralized tinzaparin’s anti-Xa activity. No dose adjustment of tinzaparin is needed even in patients with severe renal impairment and Creatinine Clearance ≥20 mL/min. Tinzaparin demonstrated a statistically significant decline in VTE recurrence at 1 year post the index thromboembolic event. A statistically significant reduction in minor bleeding rates was also described, whereas major bleeding events did not decrease in patients with cancer treated with tinzaparin versus those who received vitamin K antagonists. Tinzaparin treatment in patients suffering from deep vein thrombosis reduced the incidence of postthrombotic syndrome and venous ulcers. Tinzaparin’s ability to prevent both metastatic dissemination of cancer cells and tumor angiogenesis has been delineated in preclinical research. Current data show that tinzaparin is safe and efficacious either for short-term or for long-term treatment of VTE in patients with cancer. Clinical trials are needed in order to examine the utility of tinzaparin in primary prevention of VTE and validate its potential anticancer advantages exhibited in preclinical research.

Weight-Based Dosing for Once-Daily Enoxaparin Cannot Provide Adequate Anticoagulation for Venous Thromboembolism Prophylaxis

BACKGROUND

Surgeons commonly provide enoxaparin prophylaxis to high-risk patients to decrease venous thromboembolism risk. The authors' prior work demonstrated that most patients receive inadequate venous thromboembolism prophylaxis, based on anti-factor Xa level, when enoxaparin 40 mg/day is provided and that peak anti-factor Xa level correlates with weight. This study models a weight-based strategy for daily enoxaparin prophylaxis and its impact on anti-factor Xa levels.

METHODS

The authors enrolled plastic surgery patients who received enoxaparin 40 mg/day and had anti-factor Xa levels drawn. The enoxaparin dose of 40 mg was converted to a milligram-per-kilogram dose for each patient. Stratified analysis examined the milligram-per-kilogram dose that produced low, in-range, and high anti-factor Xa levels to identify the appropriate milligram-per-kilogram dose to optimize venous thromboembolism prevention and bleeding events.

RESULTS

Among 94 patients, weight-based dosing ranged from 0.28 to 0.94 mg/kg once daily. For peak and trough anti-factor Xa levels, there was nearly complete overlap for milligram-per-kilogram dosing that produced low versus in-range anti-factor Xa levels. For peak anti-factor Xa, there was nearly complete overlap for milligram-per-kilogram dosing that produced in-range versus high anti-factor Xa levels. Mean milligram-per-kilogram dose was not significantly different between patients who did or did not have postoperative venous thromboembolism (0.41 mg/kg versus 0.52 mg/kg; p = 0.085) or clinically relevant bleeding (0.48 mg/kg versus 0.51 mg/kg; p = 0.73).

CONCLUSIONS

Alterations in enoxaparin dose magnitude based on patient weight cannot allow a high proportion of patients to achieve appropriate anti-factor Xa levels when once-daily enoxaparin prophylaxis is provided. Future research should examine the impact of increased enoxaparin dose frequency on anti-factor Xa levels, venous thromboembolism events, and bleeding.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Pre- to postoperative coagulation profile of 307 patients undergoing oesophageal resection with epidural blockade over a 10-year period in a single hospital: implications for the risk of spinal haematoma

Background

Epidural anaesthesia and analgesia are indicated for oesophageal surgery. A rare but serious complication is spinal haematoma, which can occur on insertion, manipulation or withdrawal of catheters. Evidence and guidelines are vague regarding which tests are appropriate and how to interpret their results. We aimed to describe how routine coagulation test results change during oesophagectomy’s perioperative course.

Methods

Following ethical approval, we retrospectively identified patients who had undergone oesophagectomy between 2002 and 2012. Blood test results and details of operations, haemorrhage and complications were recorded and analysed with Excel and R. A literature search was conducted using the PubMed terms ‘epidural’ AND ‘coagulation’ AND English language. Relevant articles published in 2000 and after were included.

Results

Three hundred and seven patients received a thoracic epidural infusion with bupivacaine and morphine while 51 received an intravenous morphine infusion. Tests taken preoperatively and before the planned withdrawal of the epidural catheter demonstrated increases in all three measures: aPTT (activated partial thromboplastin time), PT-INR (prothrombin international normalised ratio) and platelet count (Plc). Postoperative thrombocytopenia was almost non-existent while aPTT or PT-INR was elevated above the reference range in 129/307 patients: aPTT was elevated in 116/307 while PT-INR was elevated in 32/307. This is too small a sample to allow meaningful estimation of risk of spinal haematoma: it may be as high as 2.3%. The literature search returned 275 articles, of which 57 were relevant. Twenty-one concerned the natural history of postoperative coagulation; 16, the incidence of and risk factors for spinal haematoma; and 5, evaluation of specific blood tests. Postoperative coagulation is characterised by thrombocytosis and transient moderately abnormal routine coagulation test results. Viscoelastic tests are not validated in the stable postoperative setting.

Conclusions

Screening for coagulopathy before removal of epidural catheters is of unclear benefit since elevated aPTT and PT-INR are usual and may not indicate hypocoagulation. A thorough clinical assessment is important. We nevertheless recommend caution when being presented with elevated routine tests of coagulation before withdrawing an epidural catheter: viscoelastic haemostatic tests may have a role in testing before withdrawal of epidural catheters but they are so far not validated. Future research should include advanced coagulation analysis as soon as a patient is unfortunate enough to have a spinal haematoma.

Electronic supplementary material

The online version of this article (10.1186/s13741-017-0070-7) contains supplementary material, which is available to authorized users.

Performance of a new-generation continuous autotransfusion device including fat removal and consequences for quality controls

BACKGROUND AND OBJECTIVES

Cell salvage plays a key role in blood conservation. To maintain high performance, quality management is recommended. Accordingly, a new-generation autotransfusion device was tested for its performance and compared with its predecessor. Two different calculations of quality parameters were applied.

MATERIALS AND METHODS

In an experimental study, the continuous autotransfusion devices CATSmart and Continuous Autotransfusion System (C.A.T.S) plus were tested using banked blood adjusted to a haematocrit of 20% and anticoagulated with heparin 5 U/L. Test blood was processed using an emergency programme, a high-quality programme/smart wash programme and a low-volume wash programme. Samples were taken after the production of 200 mL of red blood cells (RBC) and after the final emptying of the separation chamber. In an additional set of tests, blood containing 1·25% fat was processed with both devices to examine fat removal.

RESULTS

Both devices demonstrated an equally high performance with regards to product hematocrit (Hct); RBC recovery; and elimination rates of protein, heparin and fat. The high fat elimination rate (>99·8%) reported for C.A.T.S plus was confirmed for CATSmart, regardless of the used programme. Samples taken during the ongoing process show a higher haematocrit and RBC recovery rate than samples taken after the final emptying of the separation chamber. Interface sensors were not affected by fat in the blood.

CONCLUSIONS

The new-generation autotransfusion device CATSmart is not inferior to its predecessor and shows high performance with regards to RBC recovery, plasma and fat elimination in all programme modes. Samples for quality controls should be taken during blood processing.

Thrombin generation and intracranial atherosclerotic disease in patients with a transient ischaemic attack

BACKGROUND

Intracranial atherosclerotic disease (ICAD) is responsible for at least 10% of transient ischaemic attacks (TIA). Thrombin generation has been shown to be associated with several atherosclerotic conditions and may be relevant in the pathogenesis of TIA from ICAD.

OBJECTIVE

To evaluate the association between thrombin generation and ICAD in patients with TIA.

MATERIALS AND METHODS

Consecutive patients with confirmed diagnosis of TIA by vascular neurologist were enrolled. Within 24h from diagnosis, all the patients underwent: blood samples including thrombin generation search, electrocardiography, brain CT scan, blood pressure (BP) measurement, supra-aortic echo-Doppler, transcranial Doppler (TCD) and standard echocardiogram. Thrombin generation was measured as endogenous thrombin potential (ETP) in platelet-rich plasma (PRP) and in platelet-poor plasma (PPP), in the presence and in the absence of thrombomodulin (TM).

RESULTS

120 patients (male 52.5%), aged 69±16years were enrolled. Ten patients on warfarin treatment had significantly lower ETP than the others. Among the remaining, ETP in the presence or absence of TM did not differ according to TOAST classification aetiology (large vessel vs. cardioembolic vs. lacunar vs. others). In PRP, ETP was similar in patients with ICAD and in those without (1748±160 vs. 1851±36nM·min, p=0.393), whereas, ETP measured in presence of thrombomodulin was higher in patients with than in those without ICAD (2045±99 vs. 1715±41nM·min, p=0.011). In PPP, ETP was similar in patients with ICAD and in those without, whereas thrombin peak was higher in patients with ICAD than in those without both in the presence (165±17 vs. 130±5nM, p=0.036) and in the absence of TM (178±19 vs. 142±5nM, p=0.037).

CONCLUSION

ETP measured in presence of TM is enhanced in patients with ICAD, supporting that thrombomodulin-protein C pathways is relevant in TIA from ICAD. These hypothesis-generating data suggest that thrombin generation may be relevant in cerebral ischaemia from intracranial disease, and justify larger studies.

Current Controversies in Lupus Anticoagulant Detection

Antiphospholipid syndrome is an autoimmune, acquired thrombophilia diagnosed when vascular thrombosis or pregnancy morbidity are accompanied by persistent antiphospholipid antibodies. Lupus anticoagulants (LA) are one of the criteria antibodies but calibration plasmas are unavailable and they are detected by inference based on antibody behaviour in a medley of coagulation-based assays. Elevated screening tests suggest the presence of a LA, which is confirmed with mixing tests to evidence inhibition and confirmatory tests to demonstrate phospholipid-dependence. At least two screening tests of different principle must be used to account for antibody heterogeneity and controversy exists on whether assays, in addition to dilute Russell's viper venom time and activated partial thromboplastin time, should be employed. A variety of approaches to raw data manipulation and interpretation attract debate, as does inclusion or exclusion of mixing studies in circumstances where the presence of a LA is already evident from other results. Therapeutic anticoagulation compromises coagulation-based assays but careful data interpretation and use of alternative reagents can detect or exclude LA in specific circumstances, and this aspect of LA detection continues to evolve. This review focuses on the main areas of debate in LA detection.

Coagulative safety of epidural catheters after major upper gastrointestinal surgery: advanced and routine coagulation analysis in 38 patients

BACKGROUND

The risk of spinal haematoma in patients receiving epidural catheters is estimated using routine coagulation tests, but guidelines are inconsistent in their recommendations on what to do when results indicate slight hypocoagulation. Postoperative patients are prone to thrombosis, and thromboelastometry has previously shown hypercoagulation in this setting. We aimed to better understand perioperative haemostasis by comparing results from routine and advanced tests, hypothesizing that patients undergoing major upper gastrointestinal surgery would be deficient in vitamin K-dependent coagulation factors because of malnutrition, or hypocoagulative because of accumulation of low molecular weight heparin (LMWH).

METHODS

Thirty-eight patients receiving epidural analgesia for major upper gastrointestinal surgery were included. We took blood at the time of preoperative epidural catheterization and at catheter withdrawal. Prothrombin time-international normalized ratio (PT-INR), activated partial thromboplastin time (aPTT) and platelet count (Plc) were analysed, and also albumin, proteins induced by vitamin K absence (PIVKA-II), rotational thromboelastometry (ROTEM®), multiple electrode aggregometry (Multiplate®) and activities of factors II, VII, IX, X, XI, XII and XIII.

RESULTS

Postoperative coagulation was characterized by thrombocytosis and hyperfibrinogenaemia. Mean PT-INR increased significantly from 1.0 ± 0.1 to 1.2 ± 0.2 and mean aPTT increased significantly from 27 ± 3 to 30 ± 4 s. Activity of vitamin K-dependent factors did not decrease significantly: FIX and FX activity increased. FXII and FXIII decreased significantly. Mean Plc increased from 213 ± 153 × 10⁶/L while all mean ROTEM-MCFs (maximal clot firmnesses) especially FIBTEM-MCF increased significantly to above the reference interval. All mean ROTEM® clotting times were within their reference intervals both before and after surgery. ROTEM® (HEPTEM minus INTEM) results were spread around 0. There were significant correlations between routine tests and the expected coagulation factors, but not any of the viscoelastic parameters or PIVKA-II. Multiplate® area under curve and EXTEM-MCF correlated significantly to Plc as did EXTEM-MCF to fibrinogen, FIX, FX and FXIII; and FIBTEM-MCF to Plc, FII, FXI and FXIII.

CONCLUSIONS

The increase in PT-INR may be caused by decreased postoperative FVII while the elevated aPTT may be caused by low FXII. The mild postoperative hypocoagulation indicated by routine tests is not consistent with thromboelastometry. The relevance of ROTEM® and Multiplate® in the context of moderately increased routine tests remains unclear. Trial registration number is not applicable since this is not a clinical trial.

The Antithrombotic Potential of Tinzaparin and Enoxaparin Upon Thrombin Generation Triggered In Vitro by Human Ovarian Cancer Cells IGROV1

BACKGROUND

A documented relationship between ovarian cancer and thrombosis does exist. Low-molecular-weight heparins (LMWHs) are cornerstone drugs in the primary prevention and treatment of venous thromboembolic events in patients with cancer. However, cancer cells may alter the efficiency of these antithrombotic agents.

OBJECTIVE

We aimed to characterize the procoagulant phenotype of human epithelial ovarian adenocarcinoma cells, IGROV1, and to compare the capacity of tinzaparin and enoxaparin to inhibit thrombin generation triggered by these cells.

METHODS

Thrombin generation induced by different concentrations of IGROV1 cells on platelet poor plasma (PPP) was assessed by the calibrated automated thrombogram assay. Tissue factor (TF) expression was studied using Western blot analysis. Then, the experimental model of thrombin generation was used to compare the inhibitory effect of clinically relevant concentrations of both tinzaparin and enoxaparin. The inhibitory concentration 50 (IC50) of the mean rate index and the endogenous thrombin potential and the 2-fold increase in lag time were analyzed on the basis of the anti-Xa and anti-IIa activities of the LMWHs.

RESULTS

IGROV1 cells suspended into PPP resulted in a significant increase in thrombin generation in the absence of any exogenous source of TF and phospholipids. Tissue factor was expressed by IGROV1 cells. Tinzaparin was a more potent inhibitor of thrombin generation than enoxaparin. The inhibition of thrombin generation induced by IGROV1 cancer cells depended mainly on the anti-Xa activity of the LMWHs.

CONCLUSION

This experimental study in ovarian cancer cells demonstrates that the antithrombotic activity of LMWHs is not completely predicted by the anti-Xa or anti-IIa activities measured in PPP.

Argatroban for anticoagulation of a blood salvage system - an ex-vivo study

BACKGROUND

Blood salvage systems help to minimize intraoperative transfusion of allogenic blood. So far no data is available on the use of argatroban for anticoagulation of such systems. We conducted an ex-vivo trial to evaluate the effectiveness of three different argatroban doses as compared to heparin and to assess potential residual anticoagulant in the red cell concentrates.

METHODS

With ethical approval and individual informed consent, blood of 23 patients with contraindications for use of blood salvage systems during surgery was processed by the Continuous-Auto-Transfusion-System (C.A.T.S. ® Cell Saver System, Fresenius Kabi, Bad Homburg, Germany) using 5,50 or 250 mg of argatroban or 25.000 U of heparin in 1000 ml saline for anticoagulation of the system. Emergency and high-quality washing modes were applied in random order. Patency of the system and residual amount of anticoagulants in the re-transfusion bag were measured. The collected blood was not re-infused, but only used for analysis of hematocrit, heparin and argatroban concentrations.

RESULTS

Patency of the system was provided by all anticoagulants except for 3/8 cases with 5 mg of argatroban. Residual anticoagulant was found in 2/10 (20 %) heparin samples in two different patients (1 emergency and 1 high-quality washing) and in all argatroban samples. High quality washing eliminated 89-95 % and emergency washing 60-90 % of the initial argatroban concentration. Residual argatroban concentrations ranged from 55 ng ml(-1) to 6810 ng ml(-1), with initial argatroban concentrations of 5 and 250 mg, respectively.

CONCLUSION

The C.A.T.S. does not reliably remove heparin and should therefore not be used in HIT patients. Anticoagulation with 50 and 250 mg argatroban, maintains the systems patency and is significantly removed during washing. In this ex-vivo study a concentration of 50 μg ml(-1) argatroban provided the best ratio of system patency and residual argatroban concentration. Additional dose-finding studies with different blood salvage systems are needed to evaluate the optimal argatroban concentration.