How useful is the monitoring of (low molecular weight) heparin therapy by anti-Xa assay? A laboratory perspective

Smaller nadroparin dose reductions required for patients with renal impairment: A multicenter cohort study

BACKGROUND

Guidelines advise 50 % and 25 % dose reduction of the therapeutic nadroparin dose (86 IU/kg) in patients with eGFR 15-29 and 30-60 ml/min respectively. For monitoring, peak anti-Xa levels are suggested. Data lack whether this results in therapeutic anti-Xa levels or in anti-Xa levels that are comparable to those of patients without renal impairment.

AIMS

To determine dose ranges in patients with renal impairment that result in therapeutic anti-Xa levels and to determine the percentage of the 86 IU/kg dose that results in anti-Xa levels normally occurring in patients without renal impairment.

METHODS

A retrospective cohort study was conducted in five hospitals. Patients ≥18 years of age, with an eGFR ≥ 15 ml/min were included. The first correctly sampled peak (i.e. 3-5 h after ≥ third administration, regardless of dose per patient) was included. Simulated prediction models were developed using multiple linear regression.

RESULTS

770 patients were included. eGFR and hospital affected the association between dose and anti-Xa level. The doses for peak anti-Xa levels of 0.75 IU/ml differed substantially between hospitals and ranged from 55 to 91, 65-359 and 68-168 IU/kg in eGFR 15-29, 30-60 and > 60 ml/min/1.73m2, respectively. In eGFR 15-29 and 30-60 ml/min/1.73m2, doses of 75 % and 91 % of 86 IU/kg respectively, were needed for anti-Xa levels normally occurring in patients with eGFR > 60 ml/min.

CONCLUSION

We advise against anti-Xa based dose-adjustments as long as anti-Xa assays between laboratories are not harmonized and an anti-Xa target range is not validated. A better approach might be to target levels similar to eGFR > 60 ml/min/1.73m2, which are achieved by smaller dose reductions.

Evolution of Hemostasis Testing: A Personal Reflection Covering over 40 Years of History

There is no certainty in change, other than change is certain. As Seminars in Thrombosis and Hemostasis celebrates 50 years of publication, I felt it appropriate to reflect on my own 40-year plus scientific career. My career in the thrombosis and hemostasis field did not start until 1987, but the subsequent 35 years reflected a period of significant change in associated disease diagnostics. I started in the Westmead Hospital "coagulation laboratory" when staff were still performing manual clotting tests, using stopwatches, pipettes, test tubes, and a water bath, which we transported to the hospital outpatient department to run our weekly warfarin clinic. Several hemostasis instruments have come and gone, including the Coag-A-Mate X2, the ACL-300R, the MDA-180, the BCS XP, and several StaR Evolution analyzers. Some instruments remain, including the PFA-100, PFA-200, the AggRAM, the CS-5100, an AcuStar, a Hydrasys gel system, and two ACL-TOP 750s. We still have a water bath, but this is primarily used to defrost frozen samples, and manual clotting tests are only used to teach visiting medical students. We have migrated across several methodologies in the 45-year history of the local laboratory. Laurel gel rockets, used for several assays in the 1980s, were replaced with enzyme-linked immunosorbent assay assays and most assays were eventually placed on automated instruments. Radio-isotopic assays, used in the 1980s, were replaced by an alternate safer method or else abandoned. Test numbers have increased markedly over time. The approximately 31,000 hemostasis assays performed at the Westmead-based laboratory in 1983 had become approximately 200,000 in 2022, a sixfold increase. Some 90,000 prothrombin times and activated partial thromboplastic times are now performed at this laboratory per year. Thrombophilia assays were added to the test repertoires over time, as were the tests to measure several anticoagulant drugs, most recently the direct oral anticoagulants. I hope my personal history, reflecting on the changes in hemostasis testing over my career to date in the field, is found to be of interest to the readership, and I hope they forgive any inaccuracies I have introduced in this reflection of the past.

Quality performance for indirect Xa inhibitor monitoring in patients using international external quality data

Objectives Chromogenic anti-activated factor X (FXa) assays are currently the "gold standard" for monitoring indirect anticoagulants. However, anti-FXa has been shown to vary according to the choice of reagents. In the present study, the performance of anti-FXa measurement was evaluated in order to gain more insight into the clinical applications. Furthermore, the longitudinal coefficient of variation (CV) was studied to investigate whether there is improvement over time. Methods Laboratory tests results were evaluated for samples spiked with unfractionated heparin (UFH), low-molecular-weight-heparin (LMWH), fondaparinux and danaparoid sodium. External quality assessment (EQA) data from multiple years were used from more than 100 laboratories. Results Comparison of the results for all methods showed significant differences in measured values between the frequently used methods (ANOVA: p < 0.001). The largest differences were observed for LMWH and UFH measurements. These differences may be caused by differences in method composition, such as the addition of dextran sulphate. Substantial interlaboratory variation in anti-FXa monitoring was observed for all parameters, particularly at low concentrations. Our results showed that below 0.35 IU/mL, the CVs for UFH and LMWH increase dramatically and results below this limit should be used with caution. Conclusions Our study demonstrates that the choice of the anti-FXa method is particularly important for UFH and LMWH measurement. The variation in measurements may have an effect on clinical implications, such as therapeutic ranges. Furthermore, the longitudinal EQA data demonstrated a constant performance and, in at least 50% of the cases, improvement in the CV% of the anti-Xa results over time.

ISTH DIC subcommittee communication on anticoagulation in COVID-19

Hypercoagulability is an increasingly recognized complication of SARS-CoV-2 infection. As such, anticoagulation has become part and parcel of comprehensive COVID-19 management. However, several uncertainties exist in this area, including the appropriate type and dose of heparin. In addition, special patient populations, including those with high body mass index and renal impairment, require special consideration. Although the current evidence is still insufficient, we provide a pragmatic approach to anticoagulation in COVID-19, but stress the need for further trials in this area.

American Society of Hematology 2018 guidelines for management of venous thromboembolism: optimal management of anticoagulation therapy

BACKGROUND

Clinicians confront numerous practical issues in optimizing the use of anticoagulants to treat venous thromboembolism (VTE).

OBJECTIVE

These evidence-based guidelines of the American Society of Hematology (ASH) are intended to support patients, clinicians and other health care professionals in their decisions about the use of anticoagulants in the management of VTE. These guidelines assume the choice of anticoagulant has already been made.

METHODS

ASH formed a multidisciplinary guideline panel balanced to minimize potential bias from conflicts of interest. The McMaster University GRADE Centre supported the guideline development process, including updating or performing systematic evidence reviews. The panel prioritized clinical questions and outcomes according to their importance for clinicians and patients. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to assess evidence and make recommendations, which were subject to public comment.

RESULTS

The panel agreed on 25 recommendations and 2 good practice statements to optimize management of patients receiving anticoagulants.

CONCLUSIONS

Strong recommendations included using patient self-management of international normalized ratio (INR) with home point-of-care INR monitoring for vitamin K antagonist therapy and against using periprocedural low-molecular-weight heparin (LMWH) bridging therapy. Conditional recommendations included basing treatment dosing of LMWH on actual body weight, not using anti-factor Xa monitoring to guide LMWH dosing, using specialized anticoagulation management services, and resuming anticoagulation after episodes of life-threatening bleeding.

Guidance for the practical management of the heparin anticoagulants in the treatment of venous thromboembolism

Venous thromboembolism (VTE) is a serious and often fatal medical condition with an increasing incidence. Despite the changing landscape of VTE treatment with the introduction of the new direct oral anticoagulants many uncertainties remain regarding the optimal use of traditional parenteral agents. This manuscript, initiated by the Anticoagulation Forum, provides clinical guidance based on existing guidelines and consensus expert opinion where guidelines are lacking. This specific chapter addresses the practical management of heparins including low molecular weight heparins and fondaparinux. For each anticoagulant a list of the most common practice related questions were created. Each question was addressed using a brief focused literature review followed by a multidisciplinary consensus guidance recommendation. Issues addressed included initial anticoagulant dosing recommendations, recommended baseline laboratory monitoring, managing dose adjustments, evidence to support a relationship between laboratory tests and meaningful clinical outcomes, special patient populations including extremes of weight and renal impairment, duration of necessary parenteral therapy during the transition to oral therapy, candidates for outpatient treatment where appropriate and management of over-anticoagulation and adverse effects including bleeding and heparin induced thrombocytopenia. This article concludes with a concise table of clinical management questions and guidance recommendations to provide a quick reference for the practical management of heparin, low molecular weight heparin and fondaparinux.

Appropriate enoxaparin dose for venous thromboembolism prophylaxis in patients with extreme obesity

OBJECTIVE

To evaluate the appropriate dose of enoxaparin for venous thromboembolism (VTE) prophylaxis in patients with extreme obesity.

METHODS

A literature search was performed using MEDLINE (1950-April 2013) to analyze all English-language articles that evaluated incidence of VTE and/or anti-Xa levels with enoxaparin for thromboprophylaxis in patients with extreme obesity.

RESULTS

Eight studies were included in the analysis. Six of the studies were done in patients undergoing bariatric surgery. Mean body mass index ranged from 44.9 to 63.4 kg/m(2) within studies. Studies done with bariatric surgery patients utilized doses of enoxaparin that ranged from the standard dose of 30 mg subcutaneous (SQ) every 12 hours to 60 mg SQ every 12 hours. Other studies evaluated doses ranging from 40 mg SQ every 24 hours to 0.5 mg/kg/day. Only 3 studies evaluated the incidence of VTE as the primary endpoint; the other studies evaluated anti-Xa levels. The studies showed that appropriate anti-Xa levels were achieved more often with higher than standard doses of enoxaparin. One study showed that enoxaparin 40 mg SQ every 12 hours decreased the incidence of VTE in patients undergoing bariatric surgery compared to standard doses. Overall risk of bleeding was similar between study groups.

CONCLUSIONS

Higher than standard doses of enoxaparin may be needed for patients with extreme obesity. Patients undergoing bariatric surgery may benefit from enoxaparin 40 mg SQ every 12 hours. Additional large randomized, controlled trials are needed to determine the efficacy and safety of higher than standard doses of enoxaparin for VTE prophylaxis in patients with extreme obesity.

Current State of Knowledge on Oral Anticoagulant Reversal Using Procoagulant Factors

OBJECTIVE:

To discuss current trends and challenges in the use of procoagulants for treating bleeding caused by use of oral anticoagulants.

DATA SOURCES:

Literature searches of PubMed (MEDLINE), Google, and Medscape were conducted in February 2013. There were no date limitations. Search terms included anticoagulation agents, anticoagulation reversal, anticoagulation reversal agents, apixaban, clinical studies, dabigatran, 3-factor PCCs, 4-factor PCCs, FEIBA, fresh frozen plasma, human studies, pharmacology, prescribing information, rFVIIa, rivaroxaban, vitamin K, and warfarin.

DATA SYNTHESIS:

Warfarin has been the mainstay for the treatment and prevention of primary and secondary thrombosis in patients with cardiovascular disorders such as atrial fibrillation, deep vein thrombosis, pulmonary embolism, and stroke. Three oral anticoagulants have recently become available in the US: a direct thrombin inhibitor, dabigatran etexilate, and 2 direct factor Xa inhibitors, rivaroxaban and apixaban. Reversal strategies for anticoagulant-associated bleeding are well established for warfarin; however, strategies to stop bleeding in a patient who has taken one of the newer anticoagulants are less clear. In the US, agents available for oral anticoagulant reversal include activated prothrombin complex concentrate (APCC), 3-factor PCCs, and recombinant activated factor VII (rFVIIa). Few studies have evaluated the 3-factor PCCs, and current evidence for APCC and rFVIIa as reversal agents for dabigatran and rivaroxaban is based primarily on laboratory or animal studies, or on small studies in healthy humans and case reports.

CONCLUSIONS:

Patients contemplating using the new oral anticoagulants should be informed about specific clinical situations that could pose a bleeding risk such as the need for emergency surgery because no reliable antidote is available to stop the bleeding, which could prove fatal.

The new oral anticoagulants and the future of haemostasis laboratory testing

The tests currently employed within most haemostasis laboratories to monitor anticoagulant therapy largely comprise the prothrombin time (PT)/ International Normalised Ratio (INR) and the activated partial thromboplastin time (APTT). These are respectively used to monitor Vitamin K antagonists (VKAs) such as warfarin, and unfractionated heparin. Additional tests that laboratories may also employ for assessing or monitoring unfractionated heparin include thrombin time (TT) and the anti-Xa assay, which can also be used to monitor low molecular weight heparin. Several new anti-thrombotic agents have recently emerged, or are in the final process of clinical evaluation. These novel drugs that include Dabigatran etexilate and Rivaroxaban would not theoretically require monitoring; however, testing is useful in specific situations. The tests currently used to monitor VKAs and heparin are typically either too sensitive or too insensitive to the new drugs to be used as 'typically performed in laboratories', and may thus require some methodological adjustments to increase or decrease their sensitivity. Alternately, different tests may be better employed in these assessments. Whatever the case, laboratories may soon be performing a reduced or possibly increased number of tests, the same kind of tests but perhaps differently, or conceivably different assay panels. Specific laboratory guidance on the choice of the appropriate test to be ordered according to the drug being administered, as well as on appropriate interpretation of test results, will also be necessary. The current report reviews the current state of play and provides a glimpse to the possible future of the coagulation laboratory.

Mitral stenosis and pregnancy: Current concepts in anaesthetic practice

The incidence of rheumatic mitral stenosis is grossly reduced in India. Still, among heart disease complicating pregnancy, rheumatic mitral stenosis occupies a greater segment. The unique physiological changes in pregnancy and the pathological impact of mitral stenosis over pregnancy and labour are discussed in detail. A multidisciplinary approach in the diagnosis and management reduces the mortality and morbidity during peripartum. The labour analgesia technique and the evidence-based regional and general anaesthesia techniques are discussed at length in this article.

Discrepant results from laboratories impact patients receiving heparin or antithrombin therapy

Despite improvements achieved in laboratory medicine over the years, discrepant results from different clinical laboratories are still a source of imminent risk to patients and the pharmaceutical industry. The problem is aggravated by a disconnect between the in vitro diagnostic community and clinicians or drug developers. This is the sequel to a previous report where data from proficiency testing, originally established as a tool for good laboratory practice, were used to highlight the size of the problem, and its possible impact on patients and pharmaceutical trials. Results from three laboratory tests commonly used as tools to monitor patients undergoing therapy with heparin or antithrombin agents, activated partial thromboplastin time, anti-factor Xa and thrombin time, were investigated. Unfortunately, data show that, owing to an absence of standardization approaches or a reasonable technique to harmonize results from different laboratories, results for the same sample, if analyzed by different laboratories or even by one laboratory employing different platforms or reagents, can be extremely different and misleading.

Monitoring of low molecular weight heparin anticoagulation during haemodialysis with a Sonoclot Analyzer

OBJECTIVES

Sonoclot was used in this study to monitor low molecular weight heparin (LMWH) during haemodialysis.

MATERIAL AND METHODS

Two different intravenous doses (standard / half-dose) of dalteparin were studied in eight patients. Blood was sampled for coagulation analyses with Sonoclot, thrombin-antithrombin (TAT) and anti-Xa. A visual fibrin deposition score (VFS) in the venous drip chamber was also evaluated.

RESULTS

All patients completed their dialysis. There was a progressive increase in TAT levels, which correlated to the dalteparin dose. Significant differences (p<0.05) were found for TAT, VFS and Sonoclot celite-activated clotting time (SonACT) between the different LMWH dosages. TAT and Sonoclot correlated to each other, but not to the VFS. SonACT was significantly increased at two hours, with the high dalteparin dose compared to the lower dose.

CONCLUSION

Both Sonoclot and TAT failed to predict the VFS. No patient had any clinical clotting events and all dialyses were completed successfully.

Dosing Low Molecular Weight Heparins in Kidney Disease

The low molecular weigh heparins (LMWHs) are primarily eliminated renally, and current literature indicates that there is a reduction in clearance and an increase in half-life of LMWHs in patients with severe chronic kidney disease (CKD) associated with elevated anti-Xa levels and an increased risk of bleeding. It therefore becomes clinically prudent to evaluate dosing adjustments in CKD. The American College of Chest Physicians (ACCP), in its 2008 consensus statement, recommends 5 possible approaches to dosing LMWH in patients with severe CKD. In evaluating the individual compounds, enoxaparin, dalteparin, and tinzaparin, this article attempts to address the preferred dosing strategies.

Extended thromboprophylaxis reduces incidence of postoperative venous thromboembolism in laparoscopic bariatric surgery

BACKGROUND

Venous thromboembolism (VTE) after laparoscopic bariatric surgery is a significant cause of morbidity and mortality. The objective of the present study was to study the incidence of symptomatic VTE in extended thromboprophylaxis regimens using dalteparin at an independent hospital in England, United Kingdom.

METHODS

A prospective database of all patients undergoing bariatric surgery was retrospectively analyzed. All patients underwent VTE prophylaxis regimen using perioperative and extended postoperative low-molecular-weight heparin (dalteparin 2500 IU preoperatively, followed by 5000 IU daily postoperatively). The treatment period was 1 week for laparoscopic gastric banding or 3 weeks for all other procedures. Inferior vena cava filters were used in selected patients with thrombophilia, a history of pulmonary embolism, or >1 episode of deep vein thrombosis. The endpoint was the incidence of symptomatic VTE.

RESULTS

A total of 735 patients underwent laparoscopic bariatric surgery, all of whom received dalteparin. The postoperative VTE incidence was 0%. The 30-day and 90-day all-cause mortality rate was 0%. A total of 3 adverse bleeding events occurred.

CONCLUSION

An extended VTE prophylaxis regimen using low-molecular-weight heparin is simple and effective and was associated with a low incidence of bleeding complications.

Anticoagulation: Low-Molecular-Weight Heparins in Renal Impairment and Obesity: Available Evidence and Clinical Practice Recommendations Across Medical and Surgical Settings

Objective

To develop practical recommendations for the use of low-molecular-weight heparins (LMWHs) as prophylaxis and treatment of venous thromboembolism and acute coronary syndromes in patients with impaired renal function or obesity.

Data Sources

Multiple MEDLINE searches were performed (November 2008) to identify studies for inclusion, using a comprehensive list of search terms including, but not limited to, LMWH, enoxaparin, dalteparin, tinzaparin, obesity, weight, renal, kidney, elderly, monitoring, and anti-Xa.

Study Selection And Data Extraction

Only articles published in English that were relevant for this review were included.

Data Synthesis

In the majority of patients, standardized prophylaxis or treatment doses of LMWHs can be used without the need for monitoring and adjusting regimens. For patients with severe renal impairment (estimated creatinine clearance [CrCl] <30 mL/min), doses of some LMWHs should be adjusted or unfractionated heparin should be used instead. CrCl should be estimated using the Cockcroft-Gault method. Differences are noted in the degree of accumulation of various LMWHs in patients with moderate-to-severe renal impairment, and thus, the degree of dose adjustment may differ among the various LMWHs. Increasing the prophylactic doses of LMWH may be appropriate in morbidly obese patients (body mass index ≥40 kg/m2). The use of total body weight is appropriate for therapeutic doses of LMWH in obese patients. Laboratory monitoring of the anticoagulation effect of LMWHs is generally not necessary, but should be considered in patients with morbid obesity (weight >190 kg), those with severe renal impairment, and those with moderate renal impairment with prolonged (>10 days) LMWH use. When anti-Xa activity is monitored, it should be determined using a chromogenic method and a calibration curve based on the LMWH used.

Conclusions

Additional data are needed for specific dose guiding in obese and renally impaired patients, who are often excluded from larger clinical trials. Practice recommendations are made based on available evidence and authors' clinical opinions.

Prophylaxis of thromboembolism in bariatric surgery with parnaparin

BACKGROUND

There are limited data on appropriate dosing of low-molecular-weight heparins (LMWHs) for venous thromboembolism (VTE) prophylaxis in bariatric surgery. The primary objective of this preliminary study was to evaluate the preoperative effects of increasing doses of the LMWH parnaparin on coagulation in severely obese patients undergoing bariatric surgery.

METHODS

Severely obese patients (BMI > 50 kg/m(2)) were administered three increasing single doses of parnaparin (3200, 4250, and 6400 IU) on the three consecutive days leading up to biliointestinal bypass surgery. Activated partial thromboplastin time (APTT), anti-factor IIa and anti-factor Xa levels were measured 1 h before and 4 h after dosing. The highest dose (6400 IU/day) was continued from the day of surgery until day 30 (recovery period). Intermittent pneumatic compression and stockings were applied during surgery and the recovery period, respectively. Lower limb echoDoppler and phleboscintigraphy, and pulmonary scintigraphy were used for VTE detection.

RESULTS

Ten patients (mean BMI 52.4 kg/m(2)) were recruited into this study. During the preoperative dosing phase, parnaparin dose-dependently prolonged APTT, with the 6400 IU dose significantly prolonging APTT versus the lower doses. Meanwhile, anti-factor Xa and anti-factor IIa activity was increased by the 4250 and 6400 IU doses. After surgery, one patient with heparin resistance experienced pulmonary embolization. No bleeding complications were observed.

CONCLUSION

The dose-response data reported in this preliminary study suggest that parnaparin doses of 4250 and 6400 IU may provide effective prophylaxis for VTE in patients undergoing bariatric surgery. However, given the small number of patients, larger, well-controlled trials are required to confirm these findings.

Enoxaparin Use in the Neonatal Intensive Care Unit: Experience Over 8 Years

STUDY OBJECTIVE

To evaluate the effectiveness and safety of enoxaparin therapy in a neonatal intensive care unit (NICU).

DESIGN

Retrospective chart review.

SETTING

Level III NICU in a Canadian academic center.

PATIENTS

All neonates treated with enoxaparin while in the NICU between January 1, 1998, and June 1, 2006.

MEASUREMENTS AND MAIN RESULTS

Data abstracted included patient demographics, diagnosis of thrombosis and its progression, enoxaparin dosages with corresponding antifactor Xa levels, and adverse events. Sixteen neonates (four term, 12 preterm) were treated with enoxaparin at a mean +/- SD initial subcutaneous dose of 1.41 +/- 0.15 mg/kg every 12 hours. The target therapeutic range (antifactor Xa level 0.5-1.0 U/ml) was achieved by 12 infants at a mean +/- SD dose of 1.92 +/- 0.43 mg/kg every 12 hours, after a mean of 5.6 days (range 1-15 days). Preterm infants required a higher dose (per kilogram) compared with term infants to maintain therapeutic antifactor Xa levels (mean +/- SD 1.94 +/- 0.39 vs 1.65 +/- 0.14 mg/kg every 12 hrs, p<0.001). Enoxaparin doses were more strongly correlated to antifactor Xa levels in term infants (r(2)=0.51, p<0.001) compared with preterm infants (r(2)=0.20, p<0.001). Ten (71%) of 14 thromboembolic events resolved, either partially or completely, at a mean of 39 days (range 8-61 days) of enoxaparin therapy. Nine infants (56%) experienced minor local adverse effects at the site of the indwelling subcutaneous catheter (induration, bruises, hematomas, or leakage). Systemic adverse events that were possibly related to enoxaparin therapy included osteopenia (one infant), scleral hemorrhage (one), and minor gastrointestinal tract bleeding (three) found in gastric feeding tubes. No adverse effects were associated with antifactor Xa levels greater than 1.0 U/ml.

CONCLUSION

Enoxaparin may be effective in the treatment of neonatal thrombosis. An initial dosage of 1.5 mg/kg every 12 hours is likely inadequate to obtain therapeutic antifactor Xa levels rapidly and differs for term and preterm neonates. Therapeutic levels in preterm infants may be more variable, and the pharmacokinetics of this drug in preterm infants requires further evaluation. Future studies in neonates should prospectively evaluate a higher starting dose of enoxaparin to document effectiveness, acceptance, compliance with treatment guidelines, and adverse effects.