Anti-Xa Activity After Enoxaparin Prophylaxis In Hospitalized Patients Weighing Less Than Fifty-Five Kilograms

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.

Venous Thromboembolism Prophylaxis in Low Body Weight Critically Ill Patients

OBJECTIVE

To compare bleeding and thromboembolic events in low body weight patients receiving reduced-dose venous thromboembolism (VTE) prophylaxis versus standard-dose VTE prophylaxis.

DESIGN

Multicenter, retrospective, cohort study.

SETTING

Five Ascension Health Hospitals.

PATIENTS

Adult, critically ill, low body weight (≤50 kg) patients who received either reduced-dose VTE prophylaxis (n = 140) or standard-dose VTE prophylaxis (n = 279) for at least 48 h.

INTERVENTION

Reduced-dose prophylaxis (enoxaparin 30 mg daily or heparin 5000 units every 12 h subcutaneously) or standard-dose prophylaxis (enoxaparin 40 mg daily, enoxaparin 30 mg every 12 h, or heparin 5000 units every 8 h subcutaneously).

MEASUREMENTS AND MAIN RESULTS

A total of 419 patients were included with a mean weight of 45.1 ± 4.2 kg in the standard-dose group and 44.0 ± 5.1 kg in the reduced-dose prophylaxis group (P = .02). The primary endpoint, composite bleeding, was significantly lower in patients receiving reduced-dose prophylaxis (5% vs 12.5%, P = .02). After adjusting for confounding factors, results remained consistent demonstrating reduced composite bleeding with reduced-dose prophylaxis (odds ratio: 0.36, 95% confidence interval: 0.14-0.96). Major bleeding events occurred in 3.6% of reduced-dose patients compared with 8.6% in standard-dose patients (P = .056). Clinically relevant nonmajor bleeding (5.4% vs 2.9%, P = .24) and VTE (2.2% vs 0%, P = .08) events were similar between groups.

CONCLUSIONS

A reduced-dose VTE prophylaxis strategy in low body weight, critically ill patients was associated with a lower risk of composite bleeding and similar rate of thromboembolism.

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.

Enoxaparin for VTE thromboprophylaxis during inpatient rehabilitation care: assessment of the standard fixed dosing regimen

BACKGROUND

We aimed to examine the efficiency of fixed daily dose enoxaparin (40 mg) thromboprophylaxis strategy for patients undergoing inpatient rehabilitation.

METHODS

This was an observational, prospective, cohort study that included 63 hospitalized patients undergoing rehabilitative treatment following sub-acute ischemic stroke (SAIS) or spinal cord injury (SCI), with an indication for thromboprophylaxis. Anti-Xa level measured three hours post-drug administration (following three consecutive days of enoxaparin treatment or more) was utilised to assess in vivo enoxaparin activity. An anti-Xa level between 0.2-0.5 U/ml was considered evidence of effective antithrombotic activity.

RESULTS

We found sub-prophylactic levels of anti-Xa (<0.2 U/ml) in 19% (12/63). Results were within the recommended prophylactic range (0.2-0.5 U/ml) in 73% (46/63) and were supra-prophylactic (>0.5 U/ml) in 7.9% (5/63) of patients. Anti-Xa levels were found to inversely correlate with patients' weight and renal function as defined by creatinine clearance (CrCl) (p<0.05).

CONCLUSIONS

Our study confirmed that a one-size-fits-all approach for venous thromboembolism (VTE) prophylaxis may be inadequate for rehabilitation patient populations. The efficacy of fixed-dose enoxaparin prophylaxis is limited and may be influenced by renal function and weight. This study suggests that anti-Xa studies and prophylactic enoxaparin dose adjustments should be considered in certain patients, such as those who are underweight, overweight and or have suboptimal renal function.

TRIAL REGISTRATION

No. NCT103593291, registered August 2018.

Rivaroxaban versus nadroparin for thromboprophylaxis following thoracic surgery for lung cancer: A randomized, noninferiority trial

The benefit of rivaroxaban in thromboprophylaxis after oncologic lung surgery remains unknown. To evaluate the efficacy and safety of rivaroxaban, patients who underwent thoracic surgery for lung cancer were enrolled, and randomly assigned to rivaroxaban or nadroparin groups in a 1:1 ratio; anticoagulants were initiated 12-24 h after surgery and continued until discharge. Four hundred participants were required according to a noninferiority margin of 2%, assuming venous thromboembolism (VTE) occurrence rates of 6.0% and 12.6% for patients in the rivaroxaban and nadroparin groups, respectively. The primary efficacy outcome was any VTE during the treatment and 30-day follow-up periods. The safety outcome was any on-treatment bleeding event. Finally, 403 patients were randomized (intention-to-treat [ITT] population), with 381 included in per-protocol (PP) population. The primary efficacy outcomes occurred in 12.5% (25/200) of the rivaroxaban group and 17.7% (36/203) of the nadroparin group (absolute risk reduction, -5.2%; 95% confidence interval [CI], [-12.2-1.7]), indicating the noninferiority of rivaroxaban in ITT population. Sensitivity analysis was performed in the PP population and yielded similar results, confirming the noninferiority of rivaroxaban. In the safety analysis population, the incidence of any on-treatment bleeding events did not differ significantly between the groups (12.2% for rivaroxaban vs. 7.0% for nadroparin; relative risk [RR], 1.9; 95% CI, [0.9-3.7]; p = .08), including major bleeding (9.7% vs. 6.5%; RR, 1.6 [95% CI, 0.9-3.7]; p = .24), and nonmajor bleeding (2.6% vs. 0.5%; RR, 5.2 [95% CI, 0.6-45.2]; p = .13). Rivaroxaban for thromboprophylaxis after oncologic lung surgery was shown to be noninferior to nadroparin.

Supraprophylactic Anti-Factor Xa Levels Are Associated with Major Bleeding in Neurosurgery Patients Receiving Prophylactic Enoxaparin

BACKGROUND

Prior studies demonstrated reduced risk for venous thromboembolism (VTE) in neurosurgical patients secondary to prophylaxis with both heparin and low-molecular-weight heparin. The ability to monitor low-molecular-weight heparin by obtaining anti-factor Xa (anti-Xa) serum levels provides an opportunity to evaluate safety and efficacy. The aim of this study was to describe characteristics of patients who have anti-Xa levels outside of the goal range (0.2-0.4/0.5 IU/mL) and investigate incidence of major bleeding and VTE.

METHODS

A single-center, retrospective, observational study was conducted on neurosurgical patients receiving enoxaparin for VTE prophylaxis between August 2019 and December 2020. Significance testing was conducted via Fisher exact test and independent samples t test.

RESULTS

The study included 85 patients. Patients were less likely to have an anti-Xa level in the goal range if they were male, had a higher weight, or were morbidly obese. Three neuroendovascular patients (3.5%) experienced a major bleed. Serum anti-Xa levels were significantly higher in patients who experienced major bleeds compared with patients who did not (0.45 ± 0.16 IU/mL vs. 0.28 ± 0.09 IU/mL, P = 0.003). Patients with a supraprophylactic anti-Xa level (>0.5 IU/mL) were more likely to experience a major bleed (P = 0.005). One VTE event occurred: the patient experienced a pulmonary embolism with anti-Xa level at goal.

CONCLUSIONS

Anti-Xa-guided enoxaparin dosing for VTE prophylaxis in neurosurgical patients may help prevent major bleeding. These data suggest that a higher anti-Xa level may predispose patients to major bleeding. Further evaluation is needed to identify the goal anti-Xa level for VTE prophylaxis in this population.

Venous Thromboembolism Prophylaxis in Underweight Hospitalized Patients

There is limited evidence about optimal anticoagulant dosing for venous thromboembolism (VTE) prophylaxis in underweight patients. The purpose of this study was to characterize dosing strategies used in underweight patients and compare the incidence of bleeding and VTE to patients receiving a standard dose. This multi-center retrospective study evaluated medicine patients who weighed 45 kilograms or less and received VTE prophylaxis with unfractionated heparin or enoxaparin. We categorized subjects into groups as either standard or reduced dose and compared the incidence of bleeding and VTE between groups. Of the 300 patients included in the outcome analysis, 40.7% received a reduced dose regimen, most often enoxaparin 30 mg daily. Standard dose was associated with major bleeding compared with reduced dose, when adjusted for age, gender and admission hemoglobin (odds ratio 4.73, 95% confidence interval 1.05 to 21.34). Incidence of clinically relevant non-major bleeding (2.4% vs. 1.1%) and VTE (0.6% vs. 0%) were similar between groups. Anticoagulant dose reduction for VTE prophylaxis in underweight hospitalized medicine patients is common practice and associated with less major bleeding.

Weight-adjusted versus fixed dose heparin thromboprophylaxis in hospitalized obese patients: A systematic review and meta-analysis

BACKGROUND

Fixed dose unfractionated or low molecular weight heparin is the recommended treatment for venous thromboembolism (VTE) prevention in hospitalized patients. However, its efficacy has been questioned in obese population. Results of previous studies on weight-adjusted doses of heparin for VTE prevention are contradictory. Different anticoagulant regimens are used in clinical practice, but their role remains to be elucidated.

AIMS

To clarify the efficacy and safety of weight-adjusted dose heparin for VTE prevention in obese subjects hospitalized for medical and surgical conditions.

METHODS

Twelve studies were identified as reporting VTE occurrence, major or minor bleeding and anti-Xa levels. A random-effect meta-analysis was conducted to derive odds ratios (OR) comparing fixed vs weight adjusted-doses heparins on VTE occurrence, bleeding, anti-Xa levels. Medical and surgical patients, prospective vs retrospective and quality of studies were extracted for moderators and meta-regression analysis.

RESULTS

Weight-adjusted dose heparin administration was not associated with reduced VTE occurrence (6320/13317 patients, OR 1.03, 95% C.I. 0.79 to 1.35), nor increased bleeding (5840/10906 patients, OR 0.84, 95% C.I. 0.65 to 1.08), but it was associated with higher anti-Xa levels (284/294 patients, ES 2.04, 95% C.I. 1.16 to 2.92, p<0.0001). A significant heterogeneity was present for comparison of anti-Xa levels (I²=94%, p=0.0001) but not for VTE occurrence or bleeding (I²=7.6% and 12.8% respectivel). None of the moderators explained the heterogeneity of the results among primary studies.

CONCLUSION

Weight-adjusted dose as compared to fixed-dose of heparins in the prevention of VTE in obese patients was not associated with a lower risk of VTE nor a higher risk of bleeding.

Pharmacological and clinical application of heparin progress: An essential drug for modern medicine

Heparin is the earliest and most widely used anticoagulant and antithrombotic drug that is still used in a variety of clinical indications. Since it was discovered in 1916, after more than a century of repeated exploration, heparin has not been replaced by other drugs, but a great progress has been made in its basic research and clinical application. Besides anticoagulant and antithrombotic effects, heparin also has antitumor, anti-inflammatory, antiviral, and other pharmacological activities. It is widely used clinically in cardiovascular and cerebrovascular diseases, lung diseases, kidney diseases, cancer, etc., as the first anticoagulant medicine in COVID-19 exerts anticoagulant, anti-inflammatory and antiviral effects. At the same time, however, it also leads to a lot of adverse reactions, such as bleeding, thrombocytopenia, elevated transaminase, allergic reactions, and others. This article comprehensively reviews the modern research progress of heparin compounds; discusses the structure, preparation, and adverse reactions of heparin; emphasizes the pharmacological activity and clinical application of heparin; reveals the possible mechanism of the therapeutic effect of heparin in related clinical applications; provides evidence support for the clinical application of heparin; and hints on the significance of exploring the wider application fields of heparin.

Anti-Factor Xa Levels in Low-weight Surgical Patients Receiving Enoxaparin for Venous Thromboembolism Prophylaxis: A Prospective Cohort Study

Enoxaparin is indicated for thromboprophylaxis in non-orthopedic surgical patients at a fixed dose of 40 mg daily. According to the US Food and Drug Administration’s enoxaparin prescribing information, this dose exposes low-weight patients (males < 57 kg, females < 45 kg) to a higher risk of bleeding. This study aimed to determine the rate of achieving a prophylactic peak anti-factor Xa (AFXa) level in low-weight surgical patients using enoxaparin 30 mg daily. Low-weight patients admitted for abdominopelvic or noncardiac thoracic surgery from May 2018 to May 2019 were prospectively studied. After receiving daily enoxaparin 30 mg, peak AFXa levels were assessed for achieving a prophylactic level (0.2-0.5 IU/mL). In 121 patients, the proportion of achieving a prophylactic peak AFXa level was 66.1%. More females (84.8%) achieved a prophylactic level compared to males (54.7%, P = .001). All out-of-range peak AFXa levels (33.9%) were sub-prophylactic. The median peak AFXa level was lower in males (0.24 [0.1-0.47] IU/mL) than females (0.31 [0.1-0.5] IU/mL; P < .001). On univariate analysis, female sex and weight were associated with achieving a prophylactic peak AFXa level. On multivariate analysis, only female sex was independently associated with an adequate prophylactic AFXa level (odds ratio 3.17, 95% CI: 1.32-11.94; P = .014). Four venous thromboembolism events (3.3%) were observed in patients with sub-prophylactic peak AFXa levels (9.7%). Two-thirds of low-weight surgical patients achieved a prophylactic peak AFXa level using daily enoxaparin 30 mg. This dose is likely to provide adequate thromboprophylaxis in low-weight females.

Prophylactic unfractionated heparin and hemorrhage in neurocritically ill underweight patients: A case series and review of the literature

PURPOSE

Three cases of major bleeding associated with thromboprophylactic unfractionated heparin (UFH) therapy in underweight neurocritically ill patients are reported.

SUMMARY

Three underweight patients (body mass index of <18.5 kg/m2) were treated in the intensive care unit with major bleeds associated with UFH thromboprophylaxis. Two of the patients, a 76-year-old female and a 56-year-old female, had hemorrhages on presentation; the third patient, a 29-year-old male, developed bleeding during his admission. All 3 patients had past medical histories consisting of acute neurologic conditions within 6 weeks of presentation, including subdural hematoma, subarachnoid hemorrhage, and obstructive hydrocephalus secondary to a brain mass. All hemorrhages developed following the receipt of prophylactic UFH at doses of 5,000 units every 8 to 12 hours, which translated to high weight-based dosages (>300 units/kg/d). Additionally, hemorrhages were associated with prolonged activated partial thromboplastin time, which declined following heparin discontinuation. The major bleeds following UFH administration included an acute on chronic subdural hematoma, acute rectus sheath hematoma, and cerebellar hematoma. Stabilization of the subdural hematoma was achieved without the use of protamine and the patient was discharged in stable condition. The other 2 patients expired secondary to their hemorrhagic events. Naranjo nomogram scores for the patients indicated that heparin was the probable cause of bleed in 2 cases and a possible cause in 1 case.

CONCLUSION

Three major hemorrhages developed following the administration of UFH. Underweight patients with neurologic injury may require increased clinical vigilance, reduced doses, and pharmacodynamic monitoring to improve safety outcomes associated with thromboprophylaxis.

[Diagnostic and therapeutic management of venous thromboembolic disease in obese patients]

Despite the high proportion of obese patients this population remains understudied in the field of venous thromboembolic disease (VTE). Obesity is a risk factor for pulmonary embolism and/or deep vein thrombosis, especially when it is associated with other risk factors for VTE. Currently there is no validated diagnostic algorithm for VTE in the population of obese patients. Moreover, imaging examinations can be of poor quality and inconclusive. In the prevention of VTE, data concerning obese patients are mainly based on low-level studies. Apart from the context of bariatric surgery, an adjustment of heparin doses according to the weight of the patient is proposed only on a case-by-case basis. According to the current guidelines, therapeutic fixed dose oral anticoagulants should not be prescribed for patients with weights exceeding 120kg or a body mass index>40kg/m². Heparin doses should be weight adjusted and monitored with anti-Xa activity. Anti vitamin K can be prescribed but require INR monitoring. Therefore, new studies specifically dedicated to obese patients are required in the field of VTE for better diagnostic and therapeutic management.

Underdosing of Prophylactic Enoxaparin Is Common in Orthopaedic Trauma and Predicts 90-Day Venous Thromboembolism

OBJECTIVES

To determine the feasibility and impact of real-time anti-factor Xa (aFXa) level monitoring and enoxaparin dose adjustment in orthopaedic trauma. To examine the adequacy of standard fixed-dose enoxaparin chemoprophylaxis and to examine whether patient-specific factors influence enoxaparin metabolism.

DESIGN

Prospective cohort.

SETTING

Academic Level-I trauma center.

PATIENTS

Postoperative adult orthopaedic trauma patients undergoing acute fracture or nonunion surgery of the pelvis, acetabulum, or lower extremity placed on 30 mg of enoxaparin twice daily.

INTERVENTION

Peak steady-state aFXa levels were drawn with a goal range of 0.2-0.4 IU/mL. Patients with out-of-range levels underwent a 10-mg dose adjustment followed by repeat aFXa draws.

MAIN OUTCOME MEASURES

Peak and trough aFXa levels, 90-day venous thromboembolism, and bleed events.

RESULTS

Of 109 enrolled patients, 43% had inadequate initial peak aFXa levels (aFXa < 0.2 IU/mL) with standard dosing. Higher gross weight, acetabular surgery, and operation length predicted low aFXa levels (P < 0.001, 0.006, 0.004, respectively). Dose adjustment increased the proportion of patients with in-range aFXa levels from 53.2% to 87.8% (P < 0.001). Patients with low aFXa levels during hospitalization or at discharge had significantly higher 90-day deep vein thrombosis and pulmonary embolism rates compared to those with adequate aFXa levels (deep vein thrombosis 12% vs. 1.36%; P = 0.023, pulmonary embolism 8% vs. 0%; P = 0.027). There were no major bleed events.

CONCLUSIONS

Patients receiving inadequate enoxaparin chemoprophylaxis were at significantly increased risk of 90-day venous thromboembolism. Standard fixed-dose enoxaparin provided inadequate chemoprophylaxis in 43% of postoperative orthopaedic trauma patients, which significantly improved with dose adjustment. Weight, acetabular surgery, and operation length predicted inadequate enoxaparin prophylaxis.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Enoxaparin Dosing for Venous Thromboembolism Prophylaxis in Low Body Weight Patients

Background:

The appropriate dose of enoxaparin for venous thromboembolism (VTE) prophylaxis in low body weight patients is unknown.

Objective:

The aim of this study is to evaluate the impact of enoxaparin dosing on major and minor bleeding events in low body weight patients.

Methods:

This was a retrospective cohort study of patients weighing less than 45 kg receiving subcutaneous (SC) enoxaparin for VTE prevention. The primary objective was to determine whether enoxaparin dose was associated with major and minor bleeding. The secondary objective was to determine the incidence of VTE by enoxaparin dose.

Results:

There were 173 patients included in the study, of which 37 patients received 2 different courses of enoxaparin during hospitalization, resulting in 210 enoxaparin courses. Among all enoxaparin courses, 16.2% were associated with major bleeding and 5.2% with minor bleeding. There was no difference in the incidence of major bleeding by dose (enoxaparin 30 mg SC daily, 30 mg SC twice daily, or 40 mg SC daily; P = .409). Patients who experienced major bleeding were older (54.9 ± 16.1 years) than patients who did not (48.4 ± 18.4 years) (P = .043). There was no difference in the incidence of minor bleeding by dosing schedule (P = .14). No patients experienced a VTE.

Conclusion and Relevance:

The risk of bleeding was similar by enoxaparin dose but increased with age in low body weight patients. Given the low incidence of VTE in this study, it is reasonable to consider decreasing the prophylactic enoxaparin dose in low body weight patients, especially in the elderly population.

Enoxaparin Thromboprophylaxis Dosing and Anti-Factor Xa Levels in Low-Weight Patients

INTRODUCTION

Enoxaparin is a widely used anticoagulant to prevent venous thromboembolism (VTE). A fixed dose is recommended for VTE prophylaxis. However, fixed prophylactic doses of enoxaparin in low-weight patients may be close to the weight-based dosing recommended for VTE treatment.

OBJECTIVE

To evaluate peak anti-factor Xa (aFXa) levels in low-weight patients receiving enoxaparin for VTE prophylaxis.

METHODS

Retrospective cohort of adult patients weighing < 55 kg who were hospitalized at Loma Linda University Medical Center between January 2008 and February 2017. All patients received enoxaparin for VTE prophylaxis with a peak aFXa level drawn. The primary endpoint was the proportion of patients achieving peak aFXa levels within the goal range of 0.2-0.5 unit/ml.

RESULTS

Of 35 patients receiving enoxaparin for VTE prophylaxis with an appropriately timed peak aFXa level, 74% achieved goal peak aFXa levels and the median daily dose of enoxaparin was 30 mg. The mean weight was approximately 44 kg. No significant correlations between aFXa level and body mass index or body weight were found.

CONCLUSION

A lower dose of enoxaparin may be reasonable in low-weight patients for VTE prophylaxis. There appears to be no safety concerns with reduced enoxaparin dosing in low-weight patients. More robust data are needed to confirm these findings.

Evaluation of prophylactic dosages of Enoxaparin in non-surgical elderly patients with renal impairment

Background

Thromboprophylaxis dosing strategies using enoxaparin in elderly patients with renal disease are limited, while dose adjustments or monitoring of anti-Xa levels are recommended. We sought to evaluate the efficacy and safety of enoxaparin 20 mg versus 30 mg subcutaneously daily by comparing anti-Xa levels, thrombosis and bleeding.

Methods

We conducted a prospective, single-blinded, single-center randomized clinical trial including non-surgical patients, 70 years of age or older, with renal disease requiring thromboprophylaxis. Patients were randomized to receive either 20 mg or 30 mg of enoxaparin. The primary endpoint was peak anti-Xa levels on day 3. Secondary endpoints included trough anti-Xa levels on day 3, achievement of within range prophylactic target peak anti-Xa levels and the occurrence of hemorrhage, thrombosis, thrombocytopenia or hyperkalemia during hospitalization.

Results

Thirty-two patients were recruited and sixteen patients were randomized to each arm. Mean peak anti-Xa level was significantly higher in 30 mg arm (n = 13) compared to the 20 mg arm (n = 11) 0.26 ± 0.11, 95%CI (0.18–0.34), versus 0.14 ± 0.09, 95CI (0.08–0.19) UI/ml, respectively; p = 0.004. Mean trough anti-Xa level was higher in 30 mg arm (n = 10) compared to the 20 mg arm (n = 16), 0.06 ± 0.03, 95CI (0.04–0.08) versus 0.03 ± 0.03, 95CI (0.01–0.05) UI/ml, respectively; p = 0.044. Bleeding events reported in the 30 mg arm were one retroperitoneal bleed requiring multiple transfusions, and in the 20 mg arm one hematuria. No thrombotic events were reported.

Conclusion

Peak anti-Xa levels provided by enoxaparin 20 mg were lower than the desired range for thromboprophylaxis in comparison to enoxaparin 30 mg.

Trial registration

The trial was retrospectively registered on ClinicalTrials.gov identifier: NCT03158792. Registered: May 18, 2017.

Enoxaparin Dosing at Extremes of Weight: Literature Review and Dosing Recommendations

OBJECTIVE

To review the literature on both thromboprophylaxis and treatment of venous thromboembolism (VTE) with enoxaparin in low- and high-body-weight patients and to make dosing and monitoring recommendations in these patient populations.

DATA SOURCES

A search using PubMed was conducted (1995 to January 2018) using the following key words: enoxaparin, body weight, AND thromboprophylaxis, or AND treatment. Additional references were identified from a review of citations.

STUDY SELECTION AND DATA EXTRACTION

Studies included examined the effect of body weight and/or body mass index (BMI) on VTE, bleeding, enoxaparin dosing, and/or anti-Xa concentrations for thromboprophylaxis and treatment-dose enoxaparin. Studies in pediatric and pregnant patients were excluded.

DATA SYNTHESIS

Optimal enoxaparin dosing strategies for VTE prophylaxis and treatment for patients at extremes of weight have not yet been elucidated by clinical trials; however, data suggest that standard dosing regimens may not be appropriate in these patients. Relevance to Patient Care and Clinical Practice: This review provides a thorough discussion on both thromboprophylaxis and treatment of VTE with enoxaparin in low- and high-body-weight patients. It includes dosing recommendations to guide clinicians caring for these patient populations.

CONCLUSIONS

Patients at extremes of weight require special consideration to determine appropriate enoxaparin doses. Specifically, low-body-weight patients may benefit from 30 mg subcutaneously daily for VTE prophylaxis, and standard weight-based dosing for VTE treatment. Conversely, in patients with BMIs ≥40 kg/m², 40 mg subcutaneously twice daily is recommended, with consideration for higher doses in patients with BMIs ≥50 kg/m².

Prophylactic enoxaparin doses may be inadequate in patients undergoing abdominal cancer surgery

BACKGROUND

The incidence of venous thromboembolism has increased in patients following cancer surgery despite the increased use of prophylactic anticoagulants, suggesting standard doses may be inadequate. We sought to determine the adequacy of enoxaparin prophylaxis in patients undergoing abdominal cancer surgery.

METHODS

Peak and trough anti-Xa levels were measured in patients receiving enoxaparin thromboprophylaxis (40 mg daily or 30 mg twice daily, at the surgeon's discretion) after undergoing open abdominal cancer surgery at a single institution.

RESULTS

Fifty-five patients received enoxaparin 40 mg daily (group 1), 18 received 30 mg twice daily (group 2; total n = 73). There were no significant differences in gender, age, body mass index, creatinine clearance, diagnosis, or procedure between the two groups. Thirty-nine patients (53.4%) had inadequate peak anti-Xa levels (<0.2 IU/mL) and 69 patients (94.5%) had inadequate trough levels (≤0.1 IU/mL). Group 2 had lower mean peak levels (0.14 ± 0.02 IU/mL) than group 1 (0.22 ± 0.01, P = 0.003), and higher mean trough levels (0.06 ± 0.017) than group 1 (0.02 ± 0.004, P = 0.033). Group 2 had lower incidence of adequate peak anti-Xa levels than group 1 when adjusting for gender, age, body mass index, and preoperative creatinine clearance (OR 0.23, P = 0.039).

CONCLUSIONS

The majority of patients had inadequate anti-Xa levels following abdominal cancer surgery, calling into question standard prophylactic enoxaparin dosing.