The effect of anti‐Xa monitoring on the safety and efficacy of low‐molecular‐weight heparin anticoagulation therapy: A systematic review and meta‐analysis

Anti-Xa-guided Anticoagulation With Unfractionated Heparin and Thrombosis During Extracorporeal Membrane Oxygenation Support: A Systematic Review and Meta-analysis

OBJECTIVE

The initiation of extracorporeal membrane oxygenation (ECMO) triggers complex coagulation processes necessitating systemic anticoagulation. Therefore, anticoagulation monitoring is crucial to avoid adverse events such as thrombosis and hemorrhage. The main aim of this work was to analyze the association between anti-Xa levels and thrombosis occurrence during ECMO support.

DESIGN

Systematic literature review and meta-analysis (Scopus and PubMed, up to July 29, 2023).

SETTING

All retrospective and prospective studies.

PARTICIPANTS

Patients receiving ECMO support.

INTERVENTION

Anticoagulation monitoring during ECMO support.

MEASUREMENTS AND MAIN RESULTS

A total of 16 articles with 1,968 patients were included in the review and 7 studies in the meta-analysis (n = 374). Patients with thrombosis had significantly lower mean anti-Xa values (standardized mean difference -0.36, 95% confidence interval [CI] -0.62 to -0.11, p < 0.01). Furthermore, a positive correlation was observed between unfractionated heparin infusion and anti-Xa levels (pooled estimate of correlation coefficients 0.31, 95% CI 0.19 to 0.43, p < 0.001). The most common adverse events were major bleeding (42%) and any kind of hemorrhage (36%), followed by thromboembolic events (30%) and circuit or oxygenator membrane thrombosis (19%). More than half of the patients did not survive to discharge (52%).

CONCLUSIONS

This work revealed significantly lower levels of anti-Xa in patients experiencing thromboembolic events and a positive correlation between anti-Xa and unfractionated heparin infusion. Considering the contemplative limitations of conventional monitoring tools, further research on the role of anti-Xa is warranted. New trials should be encouraged to confirm these findings and determine the most suitable monitoring strategy for patients receiving ECMO support.

How enoxaparin underdosing and sex contribute to achieving therapeutic anti-Xa levels

Introduction

Anti-Xa serves as a clinical surrogate for assessing the efficacy and bleeding risk in patients treated with enoxaparin for thromboembolic events. Evidence from the literature and empirical observations suggest that patients are underdosed in clinical practice to avoid bleeding complications. This study aimed to investigate such underdosing of enoxaparin and its potential impact on achieving therapeutic anti-Xa levels.

Methods

This multicentric, retrospective, observational study included patients with acute ischemic stroke due to atrial fibrillation. All patients received enoxaparin in the therapeutic setting with subsequent anti-Xa measurements. The one-sample, one-tailed Wilcoxon signed-rank test was used to identify a significant difference between the doses administered and the recommended daily dose. Logistic regression model analysis was performed to identify additional predictors affecting achievement of the therapeutic anti-Xa target range. Stepwise forward-backward selection with Akaike's information criterion as metric was applied to refine the logistic regression model.

Results

A total of 145 patients from the university hospitals of St. Pölten and Tulln in Lower Austria were included. The median daily enoxaparin dose administered was 1.23 mg/kg, resulting in an overall target range achievement rate of 66%. As compared to recommended therapeutic doses, significant underdosing of enoxaparin was evident in both participating centers (p < 0.001). The calculated threshold dose to achieve the therapeutic target range with a 90% probability was 1.5 mg/kg enoxaparin daily. Female sex was found to be a strong independent predictor of achieving a therapeutic target range (OR 9.44; 95% CI 3.40-30.05, p < 0.001).

Conclusion

Despite the underdosing observed in both centers, therapeutic anti-Xa levels were achieved with lower than recommended doses of enoxaparin, and women required even lower doses than men. These findings warrant further confirmation by prospective studies.

A retrospective study of the management and outcomes of pregnancies with inherited antithrombin deficiency

INTRODUCTION

Antithrombin (AT) deficiency is a rare but highly thrombogenic inherited thrombophilia. Its association with adverse pregnancy outcomes (APO) is undefined. There is limited guidance on managing AT deficiency in pregnancy. Some significant issues remain controversial, including risk assessment for prophylactic anticoagulation, anticoagulant therapy, and monitoring. Our goal was to examine if the antepartum management of patients with AT deficiency affected their pregnancy outcomes.

MATERIALS AND METHODS

This retrospective, single-center observational study included pregnant women with inherited AT deficiency in Peking Union Medical College Hospital between 2013 and 2024.

RESULTS

Seventeen pregnancies in 6 women with AT deficiency were identified. A total of 7 pregnancies received adjusted-dose low-molecular-weight heparin (LMWH) and were monitored by anti-Xa level, AT activity, and D-dimer. There were 5 live births (all received LMWH), 7 second-trimester abortions (1 received LMWH), and 5 early pregnancy losses (1 received LMWH). There were 5 abruptio placentae events (3 received LMWH) and 7 thrombotic events (2 received LMWH).

CONCLUSIONS

AT deficiency is at least an important partial factor contributing to APO. It is suggested to make a full assessment of AT patients both for venous thrombus embolism and APO risk. We observed a high prevalence of heparin resistance and a positive correlation between adequate anticoagulation and pregnancy outcome based on tight monitoring with anti-Xa level and timely adjustment of the LMWH dosage.

Monitoring anti-Xa levels in elderly medical patients undergoing thromboprophylaxis: A prospective cohort study

INTRODUCTION

Given the rising incidence of venous thromboembolism (VTE) and insufficient thromboprophylaxis dosing evidence in certain patients, the precise monitoring of anti-Xa (aFXa) levels is crucial. The aim of this study is to investigate the achievement of prophylactic aFXa levels in medical inpatients who were receiving parenteral anticoagulant and to evaluate the impact of various factors on aFXa levels.

METHODS

This is a single-center observational cohort study conducted on patients admitted to the Department of Internal Medicine at the University Hospital of Heraklion, Greece, from March to August 2023. These individuals received low-molecular-weight heparins thromboprophylaxis owing to an increased risk of VTE. Data regarding demographics, past medical history, and somatometric and laboratory findings were recorded. The established range for peak prophylactic aFXa levels was defined as 0.2-0.5 IU/mL.

RESULTS

In this study, we enrolled 150 individuals [91 (60.7%) women] with a mean age of 80.0 ± 14.1 years. Sixty-two (41.4%) patients exhibited non-prophylactic peak aFXa levels. Supratherapeutic levels were observed in all underweight patients and subtherapeutic levels in 12 of 13 obese patients in class II and III. A multivariate linear regression analysis revealed that body weight, cancer, and the Charlson Comorbidity Index (CCI) were independent factors influencing aFXa levels.

CONCLUSIONS

Our study reveals a substantial portion of medical elderly inpatients on thromboprophylaxis with non-prophylactic aFXa levels, with a notable prevalence among underweight and severely obese patients. Body weight, cancer, and CCI were identified as independent factors influencing aFXa levels, advocating for tailored thromboprophylaxis strategies. Further research is warranted to validate personalized dosing approaches and to enhance clinical decision-making. Geriatr Gerontol Int 2024; 24: 587-594.

Thrombosis prophylaxis following trauma

PURPOSE OF REVIEW

This review explores the persistent occurrence of venous thromboembolic events (VTE) in major trauma patients despite standard thrombosis prophylaxis with low-molecular-weight heparin (LMWH) or unfractionated heparin (UFH). It investigates the inadequacies of standard pharmacologic prophylaxis and proposes alternative approaches not covered in current trauma guidelines.

RECENT FINDINGS

Recent studies highlight the effectiveness of monitoring and adjusting subcutaneous LMWH doses based on anti-Xa levels for the purpose of reducing VTE in trauma patients. The need for dose adaptation arises due to factors like fluctuating organ function, varying antithrombin levels, interaction with plasma proteins, and altered bioavailability influenced by oedema or vasopressor use. Additionally, promising alternatives such as intravenous LMWH, UFH, and argatroban have shown success in intensive care settings.

SUMMARY

The standard dosing of subcutaneous LMWH is often insufficient for effective thrombosis prophylaxis in trauma patients. A more personalised approach, adjusting doses based on specific effect levels like anti-Xa or choosing an alternative mode of anticoagulation, could reduce the risk of insufficient prophylaxis and subsequent VTE.

Clinical outcomes associated with anti-Xa-monitored enoxaparin for venous thromboembolism prophylaxis

STUDY OBJECTIVE

The objective of the study was to assess clinical outcomes (composite of any venous thromboembolism [VTE], any bleeding, and mortality) associated with anti-Xa monitoring in the 30 days following enoxaparin initiation for VTE prophylaxis.

DESIGN

Retrospective cohort study.

SETTING

Hospital within an academic healthcare system.

PATIENTS

Propensity score-matched hospitalized adults receiving enoxaparin for VTE prophylaxis.

INTERVENTION

Low-molecular-weight heparin anti-Xa monitoring.

MEASUREMENTS AND MAIN RESULTS

During the 13-month study period, a total of 6611 patients received enoxaparin for VTE prophylaxis, 301 in the anti-Xa monitored group and 6310 in the unmonitored group (4.6% received monitoring). The mean age was 52.9 years and 52% of patients were male. The mean body mass index was 31 kg/m2 and the mean creatinine clearance was 109 mL/min. Twenty percent of patients had active cancer. The most common indication for enoxaparin prophylaxis was hospitalization for medical illness (52%) followed by nonorthopedic surgery (37%). The adjusted odds ratio for the primary outcome comparing monitored to unmonitored patients was 1.26 (95% confidence interval, 0.75-2.11). None of the between-group differences in the individual components of the composite outcome were statistically significant.

CONCLUSIONS

Thirty-day clinical outcomes in patients receiving enoxaparin for VTE prophylaxis were not improved by anti-Xa monitoring. Our results support current evidence-based guideline recommendations against anti-Xa monitoring for patients receiving enoxaparin for VTE prophylaxis.

Multicenter study evaluating target attainment of anti-Factor Xa levels using various enoxaparin prophylactic dosing practices in adult trauma patients

STUDY OBJECTIVE

Enoxaparin is standard of care for venous thromboembolism (VTE) prophylaxis in adult trauma patients, but fixed-dose protocols are suboptimal. Dosing based on body mass index (BMI) or total body weight (TBW) improves target prophylactic anti-Xa level attainment and reduces VTE rates. A novel strategy using estimated blood volume (EBV) may be more effective based on results of a single-center study. This study compared BMI-, TBW-, EBV-based, and hybrid enoxaparin dosing strategies at achieving target prophylactic anti-Factor Xa (anti-Xa) levels in trauma patients.

DESIGN

Multicenter, retrospective review.

DATA SOURCE

Electronic health records from participating institutions.

PATIENTS

Adult trauma patients who received enoxaparin twice daily for VTE prophylaxis and had at least one appropriately timed anti-Xa level (collected 3 to 6 hours after the previous dose after three consecutive doses) from January 2017 through December 2020. Patients were excluded if the hospital-specific dosing protocol was not followed or if they had thermal burns with > 20% body surface area involvement.

INTERVENTION

Dosing strategy used to determine initial prophylactic dose of enoxaparin.

MEASUREMENTS

The primary end point was percentage of patients with peak anti-Xa levels within the target prophylactic range (0.2-0.4 units/mL).

MAIN RESULTS

Nine hospitals enrolled 742 unique patients. The most common dosing strategy was based on BMI (43.0%), followed by EBV (29.0%). Patients dosed using EBV had the highest percentage of target anti-Xa levels (72.1%). Multiple logistic regression demonstrated EBV-based dosing was significantly more likely to yield anti-Xa levels at or above target compared to BMI-based dosing (adjusted odds ratio (aOR) 3.59, 95% confidence interval (CI) 2.29-5.62, p < 0.001). EBV-based dosing was also more likely than hybrid dosing to yield an anti-Xa level at or above target (aOR 2.30, 95% CI 1.33-3.98, p = 0.003). Other pairwise comparisons between dosing strategy groups were nonsignificant.

CONCLUSIONS

An EBV-based dosing strategy was associated with higher odds of achieving anti-Xa level within target range for enoxaparin VTE prophylaxis compared to BMI-based dosing and may be a preferred method for VTE prophylaxis in adult trauma patients.

Large variation in anti-factor Xa levels with nadroparin as thromboprophylaxis in COVID-19 and non-COVID-19 critically ill patients

PURPOSE

Critically ill COVID-19 and non-COVID-19 patients receive thromboprophylaxis with the LMWH nadroparin. Whether a standard dosage is adequate in attaining the target anti-FXa levels (0.20-0.50 IU/ml) in these groups is unknown.

METHODS

This study was a prospective, observational study in the ICU of a large general teaching hospital in the Netherlands. COVID-19 and non-COVID-19 patients admitted to the ICU who received LMWH in a prophylactic dosage of 2850 IU, 5700 IU or 11400 IU subcutaneously were eligible for the study. Anti-FXa levels were determined 4 h after administration. Relevant laboratory parameters, prespecified co-variates and clinical data were extracted from the electronic health record system. The primary goal was to evaluate anti-FXa levels in critically ill patients on a prophylactic dosage of nadroparin. The second goal was to investigate whether covariates had an influence on anti-FXa levels.

RESULTS

A total of 62 patients were included in the analysis. In the COVID-19 group and non-COVID-19 group, 29 (96%) and 12 patients (38%) reached anti-FXa levels above 0.20 IU/ml, respectively. In the non-COVID-19 group, 63% of the patients had anti-FXA levels below the target range. When adjusted for nadroparin dosage a significant relation was found between body weight and the anti-FXa level (p = 0.013).

CONCLUSION

A standard nadroparin dosage of 2850 IU sc in the critically ill patient is not sufficient to attain target anti-FXa levels in the majority of the studied patient group. We suggest a standard higher dosage in combination with body-weight dependent dosing as it leads to better exposure to nadroparin.

CLINICAL TRIALS REGISTRATION

Retrospectively registered, ClinicalTrials.gov ID NTC 05926518 g, date of registration 06/01/23, unique ID 2020/1725.

Efficacy and Safety of Rivaroxaban Versus Enoxaparin in Prevention of Recurrence of Venous Thrombo-Embolism Events in Cancer Patients: A Meta-Analysis

OBJECTIVE

To examine the effectiveness of rivaroxaban compared to enoxaparin in patients diagnosed with cancer and venous thromboembolism.

METHODS

A search of Pub Med, Scopus, and Google Scholar, from inception through April 2023 was conducted. Articles comparing rivaroxaban with enoxaparin in patients with cancer and VTE/PE/DVT were included. Review Manager Version 5.2 was utilised for the analysis of the following outcomes; VTE, PE, DVT, major bleeding, and mortality.

RESULTS

A total of 8 articles and 2276 patients were included in the final analysis. Pooled analysis showed that rivaroxaban had a statistically insignificant reduced association with VTE occurrence (RR:0.83, 95% CI:0.58-1.18, P:0.3) as well as a statically insignificant reduction in major bleeding (RR:0.79, 95% CI:0.53-1.18, P:0.25). Analysis showcased that there was an insignificant reduction of mortality rivaroxaban as compared to enoxaparin (RR:0.74, 95% CI: 0.46-1.20, P:0.23).

CONCLUSION

Rivaroxaban can serve as a viable alternative to enoxaparin, with no appreciable drawbacks, for preventing and managing VTE in patients with malignancy.

Anti-Xa level monitoring of low-molecular-weight heparin during intermittent venovenous hemofiltration

Low-molecular-weight heparin (LMWH) is an anticoagulant used to prevent clotting during blood purification treatments. This study aimed to evaluate the clinical use of the anti-factor Xa level (anti-Xa) for monitoring LMWH anticoagulant levels during intermittent venovenous hemofiltration (IVVHF). This prospective observational study enrolled patients who required IVVHF for renal failure in Beijing Hospital between May 2019 and February 2021. The LMWH anticoagulation was assessed by the coagulation grade of the filter and line. One hundred and ten participants were included. There were 90 patients with a filter and line coagulation grade of ≤ 1 and 20 patients with grade > 1. The anti-Xa level of 0.2 IU/mL was a critical value. The multivariable logistic regression analysis showed that anti-Xa level > 0.2 IU/mL (odd ratio [OR] = 2.263; 95% CI: 1.290-4.871, P = 0.034) and cardiovascular disease (OR = 10.028; 95% CI: 1.204-83.488; P = 0.033) were independently associated with the coagulation grade of the filter and line. Anti-Xa level could monitor LMWH anticoagulation during IVVHF.

The Thresholds of Caprini Score Associated With Increased Risk of Venous Thromboembolism Across Different Specialties: A Systematic Review

OBJECTIVE

Estimation of the specific thresholds of the Caprini risk score (CRS) that are associated with the increased incidence of venous thromboembolism (VTE) across different specialties, including identifying the highest level of risk.

BACKGROUND

Accurate risk assessment remains an important but often challenging aspect of VTE prophylaxis. One well-established risk assessment model is CRS, which has been validated in thousands of patients from many different medical and surgical specialties.

METHODS

A search of MEDLINE and the Cochrane Library was performed in March 2022. Manuscripts that reported on (1) patients admitted to medical or surgical departments and (2) had their VTE risk assessed by CRS and (3) reported on the correlation between the score and VTE incidence, were included in the analysis.

RESULTS

A total of 4562 references were identified, and the full text of 202 papers was assessed for eligibility. The correlation between CRS and VTE incidence was reported in 68 studies that enrolled 4,207,895 patients. In all specialties, a significant increase in VTE incidence was observed in patients with a CRS of ≥5. In most specialties thresholds of ≥7, ≥9, and ≥11 to 12 were associated with dramatically increased incidences of VTE. In COVID-19, cancer, trauma, vascular, general, head and neck, and thoracic surgery patients with ≥9 and ≥11 to 12 scores the VTE incidence was extremely high (ranging from 13% to 47%).

CONCLUSION

The Caprini score is being used increasingly to predict VTE in many medical and surgical specialties. In most cases, the VTE risk for individual patients increases dramatically at a threshold CRS of 7 to 11.

Efficacy and Safety of Anti-Xa-Guided Versus Fixed Dosing of Low Molecular Weight Heparin for Prevention of Venous Thromboembolism in Trauma Patients: A Systematic Review and Meta-Analysis

PURPOSE

Trauma patients are at high risk of venous thromboembolism (VTE). We summarize the comparative efficacy and safety of anti-Xa-guided versus fixed dosing for low molecular weight heparin (LMWH) for the prevention of VTE in adult trauma patients.

METHODS

We searched Medline and Embase from inception through June 1, 2022. We included randomized controlled trials or observational studies comparing anti-Xa-guided versus fixed dosing of LMWH for thromboprophylaxis in adult trauma patients. We incorporated primary data from 2 large observational cohorts. We pooled effect estimates using a random-effects model. We assessed risk of bias using the ROBINS-I tool for observational studies and assessed certainty of findings using GRADE methodology.

RESULTS

We included 15 observational studies involving 10,348 patients. No randomized controlled trials were identified. determined that, compared to fixed LMWH dosing, anti-Xa-guided dosing may reduce deep vein thrombosis [adjusted odds ratio (aOR); 0.52, 95% CI: 0.40-0.69], pulmonary embolism (aOR: 0.48, 95% CI: 0.30-0.78) or any VTE (aOR: 0.54, 95% CI: 0.42-0.69), though all estimates are based on low certainty evidence. There was an uncertain effect on mortality (aOR: 1.06, 95% CI: 0.85-1.32) and bleeding events (aOR: 0.84, 95% CI: 0.50-1.39), limited by serious imprecision. We used several sensitivity and subgroup analyses to confirm the validity of our assumptions.

CONCLUSION

Anti-Xa-guided dosing may be more effective than fixed dosing for prevention of deep vein thrombosis, pulmonary embolism, and VTE for adult trauma patients. These promising findings justify the need for a high-quality randomized study with the potential to deliver practice changing results.

The right time to measure anti-Xa activity in critical illness: pharmacokinetics of therapeutic dose nadroparin

Background

Peak anti-Xa activity of low-molecular-weight heparin nadroparin is measured 3 to 5 hours after subcutaneous injection. In critically ill patients, physiological changes and medical therapies may result in peak activities before or after this interval, possibly impacting dosing.

Objectives

The primary objective was to determine the percentage of critically ill patients with adequately estimated peak activities drawn 3 to 5 hours after subcutaneous administration of a therapeutic dose of nadroparin. Adequate was defined as a peak activity of ≥80% of the actual peak anti-Xa activity. If ≥80% of patients had adequately estimated peak activities in the 3- to 5-hour interval, measurement in this interval was regarded as acceptable. The secondary objective was to determine the pharmacokinetic profile of nadroparin.

Methods

In this single-center, prospective study, we evaluated anti-Xa activities in patients admitted to a general intensive care unit. After ≥4 equal doses of nadroparin, anti-Xa activity was measured according to a 12- to 24-hour sampling scheme.

Results

In 25 patients, anti-Xa activities drawn between 3 and 5 hours after administration ranged 80% to 100% of the actual peak activity. Compared to the threshold level of an adequate estimation in at least 20 patients (≥80%), measuring anti-Xa activities in the 3- to 5-hour interval is an acceptable method (1-tailed binomial test; P < .02). We found a large interindividual variability for nadroparin exposure (mean ± SD area-under-the-curve_0-12h, 10.3 ± 4.8 IU·h/mL) and delayed elimination (t_1/2 range, 4.0-120.9 hours) despite adequate renal function.

Conclusion

In critically ill patients, measuring anti-Xa activity in a 3- to 5-hour interval after subcutaneous injection of therapeutic nadroparin is an acceptable method to estimate the actual peak anti-Xa activity.

Association of aPTT-Guided Anticoagulation Monitoring with Thromboembolic Events in Patients Receiving V-A ECMO Support: A Systematic Review and Meta-Analysis

BACKGROUND

The initiation of extracorporeal membrane oxygenation (ECMO) is associated with complex inflammatory and coagulatory processes, raising the need for systemic anticoagulation. The balance of anticoagulatory and procoagulant factors is essential, as therapeutic anticoagulation confers a further risk of potentially life-threatening bleeding. Therefore, our study aims to systematize and analyze the most recent evidence regarding anticoagulation monitoring and the thromboembolic events in patients receiving veno-arterial ECMO support.

METHODS

Using the PRISMA guidelines, we systematically searched the Scopus and PubMed databases up to October 2022. A weighted effects model was employed for the meta-analytic portion of the study.

RESULTS

Six studies comprising 1728 patients were included in the final analysis. Unfractionated heparin was used for anticoagulation, with an activated partial thromboplastin time (aPTT) monitoring goal set between 45 and 80 s. The majority of studies aimed to investigate the incidence of adverse events and potential risk factors for thromboembolic and bleeding events. None of the authors found any association of aPTT levels with the occurrence of thromboembolic events. Finally, the most frequent adverse events were hemorrhage (pooled 43%, 95% CI 28.4; 59.5) and any kind of thrombosis (pooled 36%, 95% CI 21.7; 53.7), and more than one-half of patients did not survive to discharge (pooled 54%).

CONCLUSIONS

Despite the tremendous development of critical care, aPTT-guided systemic anticoagulation is still the standard monitoring tool. We did not find any association of aPTT levels with thrombosis. Further evidence and new trials should clarify the true incidence of thromboembolic events, along with the best anticoagulation and monitoring strategy in veno-arterial ECMO patients.

Critical appraisal of evidence for anti-Xa monitoring and dosing of low-molecular-weight heparin in renal insufficiency

INTRODUCTION

Several guidelines advise to monitor therapeutic LMWH therapy with peak anti-Xa concentrations in renal insufficiency with subsequent dose adjustments. A better understanding of the clinical association between peak anti-Xa concentrations and clinical outcomes is mandatory, because misunderstanding this association could lead to erroneous, and potentially even harmful, LMWH dose adjustments.

AREAS COVERED

We reviewed the evidence of the widely applied therapeutic window for anti-Xa peak concentrations and report on the evidence for pharmacokinetic dose reduction in renal insufficiency, limitations of peak and trough anti-Xa concentration monitoring.

EXPERT OPINION

The added value of peak anti-Xa monitoring in patients with renal insufficiency, receiving a dose reduced for pharmacokinetic changes, is not supported by data. Enoxaparin and nadroparin should be adjusted to 50-65% and 75-85% of the original dose for patients with a creatinine clearance (CrCL) of <30 ml/min and 30-60 ml/min, respectively. Tinzaparin should be adjusted to around 50% of the original dose for patients with a CrCL of <30 ml/min. In case anti-Xa monitoring is applied, trough concentration anti-Xa monitoring is preferred over peak monitoring, aiming at a maximum concentration of 0.4 IU/mL for once-daily dosed tinzaparin and 0.5 IU/mL for twice-daily dosed enoxaparin and nadroparin.

Low-Molecular-Weight Heparin Resistance and Its Viscoelastic Assessment in Critically Ill COVID-19 Patients

Critically ill COVID-19 patients present an inflammatory and procoagulant status with a high rate of relevant macro- and microvascular thrombosis. Furthermore, high rates of heparin resistance have been described; yet, individualized anticoagulation by drug monitoring has not been sufficiently researched. We analyzed data from critically ill COVID-19 patients treated at Innsbruck Medical University Hospital with routinely adapted low-molecular-weight heparin (LMWH) doses according to anti-Xa peak levels, and regularly performed ClotPro analyses (a viscoelastic hemostatic whole blood test). A total of 509 anti-Xa peak measurements in 91 patients were categorized as below (<0.008 IU/mL/mg), within (0.008-0-012 IU/mL/mg) or above (> 0.012 IU/mL/mg) expected ranges with respect to the administered LMWH doses. Besides intergroup comparisons, correlations between anti-Xa levels and ClotPro clotting times (CTs) were performed (226 time points in 84 patients). Anti-Xa peak levels remained below the expected range in the majority of performed measurements (63.7%). Corresponding patients presented with higher C-reactive protein and D-dimer but lower antithrombin levels when compared with patients achieving or exceeding the expected range. Consequently, higher enoxaparin doses were applied in the sub-expected anti-Xa range group. Importantly, 47 (51.6%) patients switched between groups during their intensive care unit (ICU) stay. Anti-Xa levels correlated weakly with IN test CT and moderately with Russell's viper venom (RVV) test CT. Critically ill COVID-19 patients present with a high rate of LMWH resistance but with a variable LMWH response during their ICU stay. Therefore, LMWH-anti-Xa monitoring seems inevitable to achieve adequate target ranges. Furthermore, we propose the use of ClotPro's RVV test to assess the coagulation status during LMWH administration, as it correlates well with anti-Xa levels but more holistically reflects the coagulation cascade than anti-Xa activity alone.

Monitoring of Enoxaparin during Hemodialysis Covered by Regional Citrate Anticoagulation in Acute Kidney Injury: A Prospective Cohort Study

Background: Current guidelines recommend the monitoring of anti-factor Xa (anti-Xa) levels to avoid an accumulation of low-molecular-weight heparins in patients with acute kidney injury, but there is no evidence on how to proceed with such monitoring during continuous renal replacement therapy. Against this background, we investigated the potential accumulation of enoxaparin administered subcutaneously for venous thromboembolism prophylaxis in critically ill patients during continuous renal replacement therapy covered by regional citrate anticoagulation. Methods: Anti-Xa levels were measured at baseline (≤12 h before renal replacement therapy) and on three consecutive days (A to C) when enoxaparin had reached trough levels. Supplementary testing included modified assays of rotational thromboelastometry known to be highly sensitive for low-molecular-weight heparins. Results: The 16 men and 13 women included were adults comparable in age, body mass index, thromboembolism risk assessment, and clinical severity of the disease. Throughout the four examinations, the median trough levels of anti-Xa remained below the detection limit of the test (<0.1 IU mL⁻¹), with interquartile ranges of <0.1 to 0.14 IU mL⁻¹ at baseline and <0.1 to 0.16 IU mL⁻¹ on days A/B/C. All rotational thromboelastometry parameters of clot initiation and clot formation dynamics did not significantly change from baseline to day C. Conclusions: Neither anti-Xa levels nor modified assays of rotational thromboelastometry revealed any accumulation of enoxaparin administered for thromboprophylaxis during continuous renal replacement therapy covered by regional citrate anticoagulation. Although generally recommended in patients with acute kidney injury, monitoring of anti-Xa levels should be questioned in this defined setting.

Anti-Xa Monitoring of Low-Molecular-Weight Heparin during Pregnancy: A Systematic Review

Low-molecular-weight heparin (LMWH) is commonly used for preventing or treating venous thromboembolic disease (VTE) during pregnancy. The physiological changes in maternal metabolism have led to discussions on optimal LMWH dosing strategy and possible need for monitoring. The aim of this systematic review is to summarize and discuss whether LMWH dose adjustment according to anti-Xa provides superior effectiveness and safety compared with weight adjusted or fixed dosed LMWH in pregnant women. A systematic literature search was performed in PubMed, Embase, and Scopus on September 26, 2020. The study is reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Effectiveness was defined as episodes of thrombosis and safety as bleeding episodes. In total, 33 studies were included: 4 randomized controlled studies and 29 cohort studies. Prophylactic dosing strategies employing weight dosed, fixed dosed, or anti-Xa adjusted LMWH dosing performed equal in effectiveness and safety. In pregnant women with VTE or high thromboembolic risk, therapeutic weight-adjusted LMWH and weight plus anti-Xa-adjusted LMWH provided equal results in terms of effectiveness and safety. Pregnant women with mechanical heart valves (MHVs) received therapeutic anti-Xa-adjusted LMWH with four out of seven studies presenting mean peak anti-Xa within target ranges. Still, pregnant women with MHV experienced both thrombosis and bleeding with anti-Xa in target. Based on the results of this systematic review, current evidence does not support the need for anti-Xa monitoring when using LMWH as thromboprophylaxis or treatment during pregnancy. Nonetheless, the need for anti-Xa monitoring in pregnant women with MHV may need further scrutiny.