Anticoagulation Medications, Monitoring, and Outcomes in Patients with Cardiogenic Shock Requiring Temporary Mechanical Circulatory Support

Cardiogenic shock (CS) is a syndrome of low cardiac output resulting in critical end-organ hypoperfusion and hypoxia. The mainstay of management involves optimizing preload, afterload and contractility. In medically refractory cases, temporary percutaneous mechanical support (MCS) is used as a bridge to recovery, surgical ventricular assist device, or transplant. Anticoagulation is recommended to prevent device-related thromboembolism. However, MCS can be fraught with hemorrhagic complications, compounded by incident multisystem organ failure often complicating CS. Currently, there are limited data on optimal anticoagulation strategies that balance the risk of bleeding and thrombosis, with most centers adopting local antithrombotic stewardship practices. In this review, we detail anticoagulation protocols, including anticoagulation agents, therapeutic monitoring, and complication mitigation in CS requiring MCS. This review is intended to provide an evidence-based framework in this population at high risk for in-hospital bleeding and mortality.

Evaluation of anti-XA-guided versus APTT-guided management of intravenous unfractionated heparin in patients requiring a durable ventricular assist device

OBJECTIVE

The objective of this study was to compare the effectiveness and safety of anti-Xa-guided management versus aPTT-guided management of intravenous (IV) unfractionated heparin (UFH) in patients with a durable ventricular assist device (VAD).

MATERIALS AND METHODS

This was a retrospective study conducted at a single academic medical center. Patients were included if they had a durable VAD and were managed using aPTT-guided UFH management from May 2019 to May 2020 or were managed using anti-Xa-guided UFH management from May 2021 to December 2021. The primary outcome of the study was the median time to goal anticoagulation post-initiation of UFH. Secondary outcomes included the percentage of time within the therapeutic range and the incidence of thromboembolic and bleeding complications.

RESULTS

The study included 23 patients, 12 of whom were managed using anti-Xa-guided UFH, and 11 were managed using aPTT-guided UFH. The treatment arm using anti-Xa-guided UFH demonstrated a faster time to therapeutic anticoagulation goal range with a median time of 21.3 h [IQR = 12.2-34.8] compared to 37.3 h [IQR = 41-74] in the aPTT-guided UFH treatment arm (P = 0.03). In addition, the anti-Xa-guided UFH arm had a higher percentage of time within the therapeutic range, 76 % [IQR = 64.25-96.25] compared to 53 % [IQR = 41-74] in the aPTT-guided UFH arm (P = 0.04). Both arms had no significant differences in major bleeding events (P = 0.59) or clinically relevant minor bleeding events (P = 0.60) among patients. There was no incidence of thromboembolic events in either treatment arm.

CONCLUSION

Based on this single-center experience, anti-Xa-guided UFH management resulted in a faster time to therapeutic anticoagulation and a longer time within the desired therapeutic range. The results suggest that anti-Xa-guided monitoring may be superior to UFH-guided monitoring in patients with a durable VAD.

Evaluating the Use of Unfractionated Heparin with Intra-Aortic Balloon Counterpulsation

BACKGROUND

Evidence supporting anticoagulation with unfractionated heparin (UFH) in patients with an intra-aortic balloon pump (IABP) to prevent limb ischaemia remains limited, while bleeding risks remain high. Monitoring heparin in this setting with anti-factor Xa (anti-Xa) is not previously described.

OBJECTIVES

The study objective is to describe the incidence of thromboembolic and bleeding events with the use of UFH in patients with an IABP utilising monitoring with both anti-Xa and activated partial thromboplastin time (aPTT).

METHODS

This is a retrospective study of adults who received an IABP and UFH for ≥24 hours. Electronic medical records were reviewed for pertinent data. The primary outcome was the incidence of limb ischaemia during IABP. Secondary outcomes included myocardial infarction, thrombus on IABP, or stroke. Exploratory outcomes included any venous thromboembolism and bleeding events.

RESULTS

Of 159 patients, 88% received an IABP for cardiogenic shock and median duration of IABP support was 118 hours (interquartile range, 67-196). Limb ischaemia occurred in four of 159 patients (2.5%). Strokes occurred in 3.8% of the cohort, and bleeding events occurred in 33%. Despite anticoagulation use in all patients, 11% experienced a venous thromboembolism, with most identified upon asymptomatic screening with concern for heparin-induced thrombocytopenia. We found no differences in outcomes that occurred with a hybrid anti-Xa and aPTT versus aPTT monitoring alone.

CONCLUSIONS

We observed a high rate of thrombotic and bleeding complications with the use of UFH in patients with an IABP. Use of anti-Xa versus aPTT for monitoring was not associated with complications. These data suggest safer anticoagulation strategies are needed in this setting.

Anti-Xa Assay Monitoring Improves the Precision of Anticoagulation in Venovenous Extracorporeal Membrane Oxygenation

Unfractionated heparin (UFH) is the most used anticoagulant in patients receiving veno-venous extracorporeal membrane oxygenation (VV-ECMO). Its therapeutic levels are monitored using activated partial thromboplastin time ratio (aPTTr) or antifactor Xa (anti-Xa) assay. This was a retrospective, single-center, cohort study where all adult patients with viral etiology respiratory failure requiring VV-ECMO from January 2, 2015 to January 31, 2022 were included. Anticoagulation was monitored using aPTTr (until November 1, 2019) or anti-Xa assay (after November 1, 2019). We compared the accuracy and precision of anticoagulation monitoring tests using time in therapeutic range (TTR) and variance growth rate (VGR), respectively, and their impact on bleeding and thrombotic events (BTEs). A total of 254 patients, 74 in aPTTr and 180 in anti-Xa monitoring groups, were included with a total of 4,992 ECMO-person days. Accuracy was comparable: mean TTR of 47% in aPTTr and 51% in anti-Xa groups ( p = 0.28). Antifactor Xa monitoring group demonstrated improved precision with a lower variance (median VGR 0.21 vs. 1.61 in aPTTr, p < 0.05). Secondary outcome of less heparin prescription changes (adjusted rate ratio [RR] = 1.01, p = 0.01), fewer blood transfusions (adjusted RR = 0.78, p < 0.05), and ECMO circuit changes (adjusted RR = 0.68, p < 0.05) were seen with anti-Xa monitoring.

Anti-factor Xa as the preferred assay to monitor heparin for the treatment of pulmonary embolism

INTRODUCTION

The mainstay of acute pulmonary embolism (PE) treatment is anticoagulation. Timely anticoagulation correlates with decreased PE-associated mortality, but the ability to achieve a therapeutic activated partial thromboplastin time (aPTT) with unfractionated heparin (UFH) remains limited. Although some institutions have switched to a more accurate and reproducible test to assess for heparin's effectiveness, the anti-factor Xa (antiXa) assay, data correlating a timely therapeutic antiXa to PE-associated clinical outcomes remains scarce. We evaluated time to a therapeutic antiXa using intravenous heparin after PE response team (PERT) activation and assessed clinical outcomes including bleeding and recurrent thromboembolic events.

METHODS

This was a retrospective cohort study at NYU Langone Health. All adult patients ≥18 years with a confirmed PE started on IV UFH with >2 antiXa levels were included. Patients were excluded if they received thrombolysis or alternative anticoagulation. The primary endpoint was the time to a therapeutic antiXa level of 0.3-0.7 units/mL. Secondary outcomes included recurrent thromboembolism, bleeding and PE-associated mortality within 3 months.

RESULTS

A total of 330 patients with a PERT consult were identified with 192 patients included. The majority of PEs were classified as sub massive (64.6%) with 87% of patients receiving a bolus of 80 units/kg of UFH prior to starting an infusion at 18 units/kg/hour. The median time to the first therapeutic antiXa was 9.13 hours with 93% of the cohort sustaining therapeutic anticoagulation at 48 hours. Recurrent thromboembolism, bleeding and mortality occurred in 1%, 5% and 6.2%, respectively. Upon univariate analysis, a first antiXa <0.3 units/ml was associated with an increased risk of mortality [27.78% (5/18) vs 8.05% (14/174), p = 0.021].

CONCLUSION

We observed a low incidence of recurrent thromboembolism or PE-associated mortality utilizing an antiXa titrated UFH protocol. The use of an antiXa based heparin assay to guide heparin dosing and monitoring allows for timely and sustained therapeutic anticoagulation for treatment of PE.

Laboratory Monitoring of Heparin Anticoagulation in Hemodialysis: Rationale and Strategies

Unfractionated heparin (UFH) and low-molecular-weight heparins (LMWHs) are commonly used to prevent clotting of the hemodialysis extracorporeal circuit and optimize hemodialysis adequacy. There is no consensus on the optimal dosing for UFH and LMWHs during hemodialysis. In clinical practice, semiquantitative clotting scoring of the dialyzer and venous chamber may help to guide UFH and LMWH dose adjustment. Laboratory monitoring has not been shown to improve clinical outcomes and is therefore not routinely indicated in most hemodialysis patients. It might, however, be considered in select patients, such as those with extremes of body weight or history of repeated clotting or bleeding. Methods for laboratory monitoring include the activated partial thromboplastin time, activated clotting time, and antifactor Xa assays for UFH and antifactor Xa assay for LMWHs. Target ranges for anticoagulation in hemodialysis have been suggested but not clearly defined. When utilizing these tests, issues such as availability, standardization, interfering factors, and interpretation must be considered. In this narrative review, we discuss the rationale and methods of monitoring anticoagulation in hemodialysis.

Application of anti-Xa assay in monitoring unfractionated heparin therapy in contemporary antithrombotic management

INTRODUCTION

Unfractionated heparin remains the most widely used agent in the prevention and acute treatment of thrombosis. Pharmacological complexities of this intriguing agent mandate frequent monitoring of its anticoagulant properties to maintain safe and effective hematological outcomes. Although activated partial thromboplastin time has been the standard test to monitor unfractionated heparin therapy for many decades, the anti-Xa assay has emerged as a substitute or adjunct in many institutions.

AREAS COVERED

This brief report outlines the key features of anti-Xa assay in monitoring unfractionated heparin in acute management of thrombosis in various contemporary settings, with emphasis on evidence for clinical outcomes. PubMed.gov database was utilized to obtain the pertinent literature.

EXPERT OPINION

The anti-Xa activity is primarily a reflection of UFH concentration and does not account for other hematological variables frequently present in contemporary anticoagulation management. The advantage of the anti-Xa assay in monitoring UFH therapy is predicated upon its limitations to account for global physiological hemostasis. There are significant disease and drug interactions that may potentially result in false in-vitro analysis of anti-Xa activity. Routine application of the anti-Xa assay is not evidence-based at this time.

Comparison of clinical outcomes using activated partial thromboplastin time versus antifactor-Xa for monitoring therapeutic unfractionated heparin: A systematic review and meta-analysis

INTRODUCTION

Continuous intravenous unfractionated heparin (UFH) is a mainstay of therapeutic anticoagulation in the acute setting. The two most common laboratory tests for monitoring UFH are the activated partial thromboplastin time (aPTT) and antifactor Xa (anti-Xa) heparin assay. We reviewed the available evidence to evaluate if the choice of monitoring test for UFH therapy is associated with a difference in the clinical outcomes of bleeding, thrombosis, or mortality.

MATERIALS AND METHODS

MEDLINE, Cochrane database, and conference abstracts from the Society of Critical Care Medicine, the American Society of Hematology, and the American College of Clinical Pharmacy were searched for all studies comparing aPTT and anti-Xa monitoring for therapeutic UFH that evaluated outcomes for bleeding, thrombotic events, or mortality. Risk of bias was assessed with the Cochrane Risk of Bias Tool and Newcastle Ottawa Scale. Pooled relative risk ratios were calculated using an inverse variance-weighted random-effects model.

RESULTS

Ten studies (n = 6677) were included for analysis. The use of anti-Xa compared to aPTT was not associated with an increased risk of bleeding (RR 1.03; 95% CI 0.8-1.22 I² = 4%) or an increased risk of thrombotic events (RR 0.99; 95% CI 0.76-1.30, I² = 3%). There was no difference in mortality within individual studies but the data were not suitable for pooled analysis.

CONCLUSIONS

Pooled data comparing aPTT vs. anti-Xa for monitoring therapeutic UFH did not suggest differences in the outcomes of bleeding or thrombosis.

From Activated Partial Thromboplastin Time to Antifactor Xa and Back Again

OBJECTIVES

Monitoring is essential to safe anticoagulation prescribing and requires close collaboration among pathologists, clinicians, and pharmacists.

METHODS

We describe our experience in the evolving strategy for laboratory testing of unfractionated heparin (UFH).

RESULTS

An intrainstitutional investigation revealed significant discordance between activated partial thromboplastin time (aPTT) and antifactor Xa (anti-Xa) assays, prompting a transition from the former to the latter in 2013. With the increasing use of oral factor Xa inhibitors (eg, apixaban, rivaroxaban, edoxaban, betrixaban), which interfere with the anti-Xa assay, we adapted our protocol again to incorporate aPTT in patients admitted on oral Xa inhibitors who require transition to UFH.

CONCLUSIONS

Our experience demonstrates key challenges in anticoagulation and highlights the importance of clinical pathologists in helping health systems adapt to the changing anticoagulation landscape.

Running after Activated Clotting Time Values in Patients Receiving Direct Oral Anticoagulants: A Potentially Dangerous Race. Results from a Prospective Study in Atrial Fibrillation Catheter Ablation Procedures

Background: Activated Clotting Time (ACT) guided heparinization is the gold standard for titrating unfractionated heparin (UFH) administration during atrial fibrillation (AF) ablation procedures. The current ACT target (300 s) is based on studies in patients receiving a vitamin K antagonist (VKA). Several studies have shown that in patients receiving Direct Oral Anticoagulants (DOACs), the correlation between ACT values and UFH delivered dose is weak. Objective: To assess the relationship between ACT and real heparin anticoagulant effect measured by anti-Xa activity in patients receiving different anticoagulant treatments. Methods: Patients referred for AF catheter ablation in our centre were prospectively included depending on their anticoagulant type. Results: 113 patients were included, receiving rivaroxaban (n = 30), apixaban (n = 30), dabigatran (n = 30), and VKA (n = 23). To meet target ACT, a higher UFH dose was required in DOAC than VKA patients (14,077.8 IU vs. 9565.2 IU, p < 0.001), leading to a longer time to achieve target ACT (46.5 min vs. 27.3 min, p = 0.001). The correlation of ACT and anti-Xa activity was tighter in the VKA group (Spearman correlation ρ = 0.53), compared to the DOAC group (ρ = 0.19). Despite lower ACT values in the DOAC group, this group demonstrated a higher mean anti-Xa activity compared to the VKA group (1.56 ± 0.39 vs. 1.14 ± 0.36; p = 0.002). Conclusion: Use of a conventional ACT threshold at 300 s during AF ablation procedures leads to a significant increase in UFH administration in patients treated with DOACs. This increase corresponds more likely to an overdosing than a real increase in UFH requirement.

Review of Medical Therapies for the Management of Pulmonary Embolism

Traditionally, the management of patients with pulmonary embolism has been accomplished with anticoagulant treatment with parenteral heparins and oral vitamin K antagonists. Although the administration of heparins and oral vitamin K antagonists still plays a role in pulmonary embolism management, the use of these therapies are limited due to other options now available. This is due to their toxicity profile, clearance limitations, and many interactions with other medications and nutrients. The emergence of direct oral anticoagulation therapies has led to more options now being available to manage pulmonary embolism in inpatient and outpatient settings conveniently. These oral therapeutic options have opened up opportunities for safe and effective pulmonary embolism management, as more evidence and research is now available about reversal agents and monitoring parameters. The evolution of the pharmacological management of pulmonary embolism has provided us with better understanding regarding the selection of anticoagulants. There is also a better understanding and employment of anticoagulants in pulmonary embolism in special populations, such as patients with liver failure, renal failure, malignancy, and COVID-19.

Monitoring unfractionated heparin therapy: Lack of standardization of anti-Xa activity reagents

INTRODUCTION

One of the main advantages of using anti-Xa instead of activated partial thromboplastin time in monitoring of unfractionated heparin (UFH) therapy relies on its hypothesized standardization, with a unique therapeutic range defined to be 0.30 to 0.70 IU/mL. The aim of the present study was to compare the inter-reagent agreement of anti-Xa activity.

METHODS

Citrate tubes were obtained from 104 inpatients on UFH. Plasma samples were stored frozen in aliquots at -70°C before being shipped to three accredited coagulation laboratories to be evaluated for anti-Xa activity using their routine assay(s). Pooled normal plasmas spiked with dilutions of the 6th International Standard of UFH to achieve anti-Xa activities up to 1.0 IU/mL were evaluated using the same techniques.

RESULTS

In the plasmas from patients on UFH, the median anti-Xa activity ranged from 0.37 IU/mL with one reagent to 0.57 IU/mL with another; results were in between (0.45 IU/mL) using two other reagents. Comparisons of results obtained using the different reagents demonstrated unacceptable bias up to 0.24 IU/mL between some reagents (41% difference). The concordance as whether anti-Xa activities measured using different reagents were within or outside the therapeutic range was between 0.411 and 0.939 (kappa). Similar discrepancy was demonstrated for anti-Xa activities when evaluating normal plasma spiked with the International Standard. A discrepancy of the same order of magnitude was demonstrated in the 2017 External Quality Assessment Program provided by the External Quality Control in Assays and Tests exercises.

CONCLUSIONS

The reported discrepancy between test results obtained using different anti-Xa assays clearly suggests a lack of standardization of that assay with potentially significant impact on the patients' anticoagulation.

Effectiveness of a Calculation-Free Weight-Based Unfractionated Heparin Nomogram With Anti-Xa Level Monitoring Compared With Activated Partial Thromboplastin Time

BACKGROUND

Accurate monitoring of intravenous unfractionated heparin (UFH) is essential to mitigate the risk of adverse drug events associated with dosing errors. Although recent data support anti-factor Xa (anti-Xa) monitoring preferentially over activated partial thromboplastin time (aPTT) to improve time to therapeutic anticoagulation, the utility of incorporating anti-Xa monitoring with a calculation-free weight-based UFH nomogram has not been formally evaluated.

OBJECTIVE

The primary objective of this study was to evaluate the time to therapeutic anticoagulation of a calculation-free weight-based UFH nomogram integrated with anti-Xa monitoring versus a historical control of aPTT monitoring utilizing manual dose calculations.

METHODS

This was a retrospective analysis of patients with anti-Xa monitoring and a novel calculation-free weight-based UFH nomogram compared with a historical control with aPTT monitoring and manual calculations.

RESULTS

A total of 103 patients in the aPTT cohort and 100 patients in the anti-Xa cohort were analyzed. The anti-Xa cohort achieved goal therapeutic target 3.8 hours sooner than the aPTT cohort (P = 0.03). Patients with anti-Xa monitoring required 1 fewer adjustment per 2.5 patient-days of UFH with the venous thromboembolism nomogram (P = 0.02). Patients in the aPTT cohort required more infusion interruptions because of supratherapeutic values (P = 0.007) and boluses because of subtherapeutic values (P = 0.044). There were no differences in rates of thromboembolism, major bleeding, or clinically relevant nonmajor bleeding between the cohorts.

CONCLUSION AND RELEVANCE

This study demonstrated that anti-Xa UFH monitoring integrated with a calculation-free nomogram results in faster time to therapeutic anticoagulation and fewer dose adjustments compared with aPTT monitoring with manual calculations.

Design and Implementation of an Anti-Factor Xa Heparin Monitoring Protocol

BACKGROUND

The VA Northeast Ohio Healthcare System introduced a new nurse-driven anti-factor Xa (anti-Xa) protocol for monitoring unfractionated heparin to replace the previous activated partial thromboplastin time protocol.

OBJECTIVE

To design, implement, and evaluate the efficacy of the anti-Xa monitoring protocol.

METHODS

An interdisciplinary team of providers collaborated to develop and implement a nurse-driven, facility-wide anti-factor Xa protocol for monitoring unfractionated heparin therapy. The effectiveness of this protocol was evaluated by retrospective analysis.

RESULTS

We reviewed 100 medical records for compliance with the new anti-Xa monitoring protocol. We then evaluated 178 patients whose anticoagulation was monitored with the anti-Xa assay to determine the time to therapeutic range. We found that 80% of patients receiving the anti-Xa protocol achieved therapeutic anticoagulation within 24 hours, as compared with 54% of patients receiving the activated partial thromboplastin time protocol (P < .001). Protocol conversion also yielded a decrease in blood draws, dose adjustments, and potential calculation errors.

CONCLUSIONS

Monitoring intravenous heparin therapy with the anti-Xa assay rather than activated partial thromboplastin time resulted in a shorter time to therapeutic anticoagulation, longer maintenance of therapeutic levels, and fewer laboratory tests and heparin dosage changes. We believe the current practice of monitoring heparin treatment with activated partial thromboplastin time assays should be reexamined.

Correlation Among Antifactor Xa, Activated Partial Thromboplastin Time, and Heparin Dose and Association with Pediatric Extracorporeal Membrane Oxygenation Complications

Anticoagulation is essential during extracorporeal membrane oxygenation (ECMO) to prevent catastrophic circuit clotting. Several assays exist to monitor unfractionated heparin (UFH), the most commonly used anticoagulant during ECMO, but no single test or combination of tests has consistently been proven to be superior. This retrospective observational study examines the correlation among antifactor Xa level, activated partial thromboplastin time (aPTT), and UFH dose and the association between antifactor Xa level and aPTT with survival and hemorrhagic and thrombotic complications. Sixty-nine consecutive neonatal and pediatric ECMO patients from September 2012 to December 2014 at a single institution were included. Spearman rank correlation was used to compare antifactor Xa level, aPTT, and UFH dose. Significant but poor correlation exists between antifactor Xa level and UFH dose ρ = 0.1 (p < 0.0001) and aPTT and UFH dose ρ = 0.26 (p < 0.0001). Antifactor Xa level and aPTT were weakly correlated to each other ρ = 0.38 (p < 0.0001). In an univariate analysis, there was no difference between survival and antifactor Xa level, aPTT, or UFH dose. Multiple anticoagulation tests may be superior to a single test during ECMO.

Evaluating anticoagulation sensitivity among elderly patients managed with an institution’s heparin protocol using initial anti-factor Xa levels

Purpose

The purpose of this study was to assess an institution’s heparin protocols in elderly and nonelderly adult populations to see if a response difference was observed.

Methods

This was a retrospective cohort study of hospitalized adults who were prescribed unfractionated heparin due to surgery, acute coronary syndrome (ACS), or deep vein thrombosis/pulmonary embolism (DVT/PE) from February 11, 2016, through August 1, 2017. Patients were divided into nonelderly adults 18 to 69 years of age and elderly patients 70 years of age or older. The anti-factor Xa (anti-Xa) level after protocol initiation was compared to the institution’s goal range of 0.3 to 0.7 IU/mL. Outcomes of each protocol in the elderly population were compared to outcomes in their nonelderly counterparts to determine if there was a difference in heparin response.

Results

A total of 325 patients were included in the analysis, comprising 150 elderly and 175 nonelderly adults. Elderly patients had a higher initial anti-Xa levels than did their nonelderly adult counterparts in the ACS, DVT/PE, and surgery protocols, with P values of 0.02, &lt;0.001, and 0.01, respectively. Only the ACS protocol demonstrated increased frequency of above-target-level anti-Xa levels in the elderly (P = 0.03).

Conclusion

Elderly patients had significantly higher initial anti-Xa levels than did nonelderly adult patients across all protocols. This study identifies the need to further study elderly patients’ increased heparin sensitivity to determine if a separate dosing protocol is needed.

The effect of heparin infusion intensity on outcomes for bridging hospitalized patients with atrial fibrillation

Background

Perioperative bridging in atrial fibrillation (AF) is associated with low thromboembolic rates but high bleeding rates. Recent guidance cautions the practice of bridging except in high risk patients. However, the practice of bridging varies widely and little data exist regarding appropriate anticoagulation intensity when using intravenous unfractionated heparin (UFH).

Hypothesis

To determine if high intensity UFH infusion regimens are associated with increased bleeding rates compared to low intensity regimens for bridging patients with AF.

Methods

We conducted a single center retrospective cohort study of admitted patients with non‐valvular AF receiving UFH for ≥24 hours. UFH intensities were chosen at the providers' discretion. The primary endpoint was the rate of bleeding defined by the International Society on Thrombosis and Hemostasis during UFH infusion or within 24 hours of discontinuation. The secondary endpoint was a composite of cardiovascular events, arterial thromboembolism, venous thromboembolism, myocardial infarctions and death during UFH infusion.

Results

A total of 497 patients were included in this analysis. Warfarin was used in 82.1% and direct acting oral anticoagulants in 14.1% of patients. The rate of any bleed was higher among high intensity compared to low intensity UFH regimens (10.5% vs 4.9%, odds ratio = 2.29, 95% confidence interval = 1.07‐4.90). Major bleeding was significantly higher among high intensity compared to low intensity UFH regimens. There was no difference in composite thrombotic events or death.

Conclusions

Low intensity UFH infusions, targeting lower anticoagulation targets, were associated with decreased bleeding rates without a signal of increased thromboembolic events in hospitalized AF patients.

Clinical outcomes with unfractionated heparin monitored by anti-factor Xa vs. activated partial Thromboplastin time

Anti-factor Xa (anti-Xa) monitoring of unfractionated heparin (UFH) is associated with less time to achieve therapeutic anticoagulation compared to the activated partial thromboplastin time (aPTT). However, it is unknown whether clinical outcomes differ between these methods of monitoring. The aim of this research was to compare the rate of venous thrombosis and bleeding events in patients that received UFH monitored by anti-Xa compared to the aPTT. A retrospective review of electronic health records identified adult patients that received UFH given intravenously (IV) for ≥2 days, with either anti-Xa or aPTT monitoring at an academic tertiary care hospital. This was a pre/post study design conducted between January 1 to December 30, 2014 (aPTT), and January 1 to December 30, 2016 (anti-Xa). All UFH adjustments were based on institutional nomograms. The primary outcome was venous thrombosis and the secondary outcome was bleeding, both of which occurred between UFH administration and discharge from the index hospitalization. A total of 2500 patients were in the anti-Xa group and 2847 patients aPTT group. Venous thrombosis occurred in 10.2% vs 10.8% of patients in the anti-Xa and aPTT groups, respectively (P = .49). Bleeding occurred in 33.7% vs 33.6% of patients in the anti-Xa and aPTT groups, respectively (P = .94). Anti-Xa monitoring was not an independent predictor of either outcome in multivariate logistic regression analyses. Our study found no difference in clinical outcomes between anti-Xa and aPTT-based monitoring of UFH IV.

Comparing Anti-Factor Xa and Activated Partial Thromboplastin Levels for Monitoring Unfractionated Heparin

Background: Lab tests such as activated partial thromboplastin time (aPTT) or anti-factor Xa (anti-Xa) levels are typically used to monitor intravenous unfractionated heparin (IV heparin), with recent evidence suggesting that anti-Xa levels may provide a more accurate measure of anticoagulation. Objective: The Lexington Veterans Affairs Health Care System transitioned from using aPTT to anti-Xa levels in January 2017. This study was conducted to evaluate the efficacy and safety of this change. Methods: This was a retrospective cohort study comparing all patients receiving IV heparin per protocol for at least 24 hours from August 1, 2016, to January 31, 2017 (aPTT group), and February 1, 2017, to July 31, 2017 (anti-Xa group). The primary objective was a comparison of IV heparin doses required to achieve goal range between the 2 cohorts. Secondary objectives included a comparison of time to therapeutic goal, percentage of time within goal range, number of rate changes until therapeutic goal, and adverse outcomes, such as number of bleeds. Results: A total of 155 patients were included in this study. Significantly higher IV heparin doses were required to achieve therapeutic goal in the anti-Xa group, despite significantly fewer IV heparin rate changes required. Anti-Xa monitoring was not associated with an increased risk of adverse events. Conclusion and Relevance: Significantly higher IV heparin doses were required to achieve therapeutic anti-Xa levels after transitioning from an aPTT-based protocol in the largely unstudied veteran population. However, the transition from aPTT to anti-Xa monitoring appears safe and efficacious in these patients.

Performance of Anti-Factor Xa Versus Activated Partial Thromboplastin Time for Heparin Monitoring Using Multiple Nomograms

The purpose of this study was to compare the performance of anti-factor Xa concentration versus activated partial thromboplastin time (aPTT) monitoring with multiple indication-specific heparin nomograms. This was a prospective, nonrandomized study with historical control at a large academic medical center. A total of 201 patients who received intravenous heparin in the cardiology units were included. The prospective cohort included patients (n = 101) with anti-factor Xa (anti-Xa) monitoring, and the historical control group included patients (n = 100) who had aPTT monitoring. Patients in the prospective group had both anti-Xa and aPTT samples drawn, but anti-Xa was used for dosing adjustment. The anti-Xa cohort achieved a significantly faster time to therapeutic range (P < .01) and required fewer dose adjustments per 24-hour period compared to the aPTT control (P = .01). Results were consistent across heparin nomograms. The overall discordance rate between the 2 tests was 49%. No significant differences in clinical outcomes were observed. In summary, anti-Xa monitoring improved the time to therapeutic anticoagulation and led to fewer dose adjustments compared to the aPTT with multiple indication-based heparin nomograms.

Comparison of Antifactor Xa and Activated Partial Thromboplastin Time Monitoring for Heparin Dosing in Vascular Surgery Patients: A Single-Center Retrospective Study

BACKGROUND

Vascular surgery patients often require anticoagulation with intravenous unfractionated heparin monitored through antifactor Xa (anti-Xa) levels or the activated partial thromboplastin time (aPTT). This study compares the 2 monitoring strategies in terms of major bleeding events in the vascular surgery population.

METHODS

This was a single-center, retrospective study that included patients treated with a pharmacy-managed heparin protocol monitored by either anti-Xa or aPTT after vascular surgery. The primary outcome was the percentage of patients experiencing major bleeding events after procedure. Secondary outcomes evaluated minor bleeding episodes, postprocedure packed red blood cell transfusions, and the incidence of thrombotic events. In a secondary analysis, simultaneously measured anti-Xa and aPTT values were identified and analyzed for discordance.

RESULTS

Major bleeding occurred in 12/72 patients (17%) on the anti-Xa-monitored protocol versus 5/62 patients (8%) on the aPTT-monitored protocol (P = 0.19). Minor bleeding episodes were documented in 10% of the patients in the anti-Xa group versus 6% in the aPTT group (P = 0.54). There were no significant differences between the 2 groups in packed red blood cell transfusions and thrombotic events. Of 109 pairs of simultaneously measured anti-Xa and aPTT values, 39 pairs (36%) showed relatively high aPTT values compared with corresponding anti-Xa levels. Nine patients who had these discordant test results experienced bleeding while their heparin drip was titrated based on lower anti-Xa values.

CONCLUSIONS

The use of anti-Xa levels for heparin titration showed higher rates of major bleeding complications in vascular surgery patients compared with aPTT monitoring, but no significant difference was identified in this study. Vascular surgery patients with relatively high aPTT to anti-Xa values may have an increased risk of bleeding complications when heparin is titrated based on anti-Xa levels.

Therapeutic monitoring of unfractionated heparin - trials and tribulations

INTRODUCTION

Heparin is one of the oldest biological medicines with an established role in prevention and treatment of arterial and venous thromboembolism. Published therapeutic ranges for unfractionated heparin (UFH) mostly precede the large increase in the number of activated partial thromboplastin time (APTT) reagent/instrument combinations that now show wide variability. Areas covered: This paper explores the use of UFH, the development of heparin therapeutic ranges (HTRs), and the strengths and limitations of the methods used to monitor heparin's anticoagulant effect. Expert commentary: Despite longstanding use of UFH for management of thromboembolic conditions, the optimal test for monitoring UFH remains undetermined. Although used extensively for monitoring UFH, routine APTT-derived HTRs are based on limited science that may have little relevance to current laboratory practice. Anti-FXa levels may provide better and more reliable HTRs; however, even these levels show considerable inter-laboratory variation, and there are insufficient clinical studies proving improved clinical efficacy. Alternative tests for monitoring UFH reported over time have not been proven effective nor feasible, secondary to technical or cost issues, or lack of general adoption. Thus, despite limited evidence of clinical utility, an uncomfortable marriage of convenience represented by heparin laboratory monitoring is unlikely to be terminated in the immediate future.

Should we abandon the APTT for monitoring unfractionated heparin?

INTRODUCTION

The activated partial thromboplastin time (APTT) is commonly used to monitor unfractionated heparin (UFH) but may not accurately measure the amount of heparin present. The anti-Xa assay is less susceptible to confounding factors and may be a better assay for this purpose.

MATERIALS AND METHODS

The validity of the APTT for monitoring UFH was assessed by comparing with an anti-Xa assay on 3543 samples from 475 patients (infants [n=165], children 1-15years [n=60] and adults [n=250]) receiving treatment dose UFH.

RESULTS

Overall concordance was poor. The highest concordance (66%; 168/254) was seen in children. Concordance (51.8%) or discordance (48.4%) was almost equal in adult patients. Among adult patients whose anti-Xa level was within 0.3-0.7IU/mL, only 38% had an APTT in the therapeutic range whilst 56% were below and 6% were above therapeutic range. Children and adult patients with anti-Xa of 0.3-0.7IU/mL but sub- therapeutic APTT had significantly higher fibrinogen levels compared to those with therapeutic or supra-therapeutic APTT.

CONCLUSIONS

When the anti-Xa level was 0.3-0.7IU/mL, the majority of samples from infants demonstrated a supra-therapeutic APTT, whilst adults tended to have a sub-therapeutic APTT. This may lead to under anticoagulation in infants or over anticoagulation in adults with risk of bleeding if APTT is used to monitor UFH. These results further strengthen existing evidence of the limitation of APTT in monitoring UFH. Discordance of APTT and anti-Xa level in adults and children may be due to elevation of fibrinogen level.

The impact of pharmacy monitoring and intervention in patients receiving intravenous heparin

Background Intravenous unfractionated heparin (IV UFH) has a narrow therapeutic index and poses a high risk of bleeding. Objective To determine the impact of pharmacy monitoring and intervention on adherence to and appropriate implementation of IV UFH protocol. Setting A 438 bed hospital specializing in cardiac services. Methods This is a retrospective chart review study. Pre-pharmacy intervention data were collected from November 2013 to January 2014 and compared to post-pharmacy intervention data obtained between August 2014 and October 2014. Patients were included if they received IV UFH for at least 24 hours. The first three daytime laboratory draws were collected for each patient and analyzed using generalized estimating equations to quantify the association between pharmacy monitoring and adherence to the institution's protocol. Main outcome measures Designation of appropriate protocol, accurate selection of initial infusion rate, timing of anti-Xa levels within 60 min of anticipated due time, change of infusion rate within 120 min of laboratory result, and appropriate adjustment of infusion rates. Results A total of 195 data points were included. The initial selection of infusion rate and subsequent adjustments were more appropriate in the post-intervention period with an odds ratio of 8.36 (95% CI 2.41-29.01, p value = 0.0008), and 4.66 (95% CI 1.41-15.43, p value = 0.0118), respectively. Conclusion The results of this study indicate that pharmacy monitoring of IV UFH therapy has improved adherence to an institution's protocol and is associated with more accurate selection of initial infusion rates and adjustment of infusions based upon laboratory results.

Protocolled Redefinition of the Therapeutic Range for Unfractionated Heparin: Lost in Translation?

BACKGROUND

Protocolled treatment with unfractionated heparin (UFH) is a subject of ongoing debate. Even though international guidelines prescribe calibration of the activated partial thromboplastin time (aPTT) to 0.3 to 0.7 U/mL anti-Xa activity to establish an UFH therapeutic range, evidence for this approach remains scarce. In this study, we evaluated different strategies to delineate the UFH therapeutic range and analyzed the effects on patient therapeutic classification.

METHODS

In 109 patient samples, the aPTT was measured with 2 different reagents, both of which used mechanical clot detection. The UFH therapeutic range was determined using 3 previously described methods: calibration of the aPTT to 0.3 to 0.7 U/mL anti-Xa activity, application of 1.5 to 2.5 times the control aPTT, or using 0.3 to 0.7 U/mL anti-Xa activity directly. We also applied the UFH therapeutic range of a second hospital to our patient population.

RESULTS

Application of the guideline-prescribed anti-Xa calibration method would result in patients receiving increased UFH dosage in comparison to our previous UFH nomogram. Between-method and between-laboratory variations in aPTT and anti-Xa activity assays are a likely cause of these discrepancies. Additionally, we show that individual patient characteristics, such as weight and UFH treatment duration, likely contribute to the discordance between different strategies to establish an UFH therapeutic range.

CONCLUSION

No consensus is reached between different strategies to define the UFH therapeutic range, which could result in relevant differences in UFH doses applied in patients. Clinicians and laboratory specialists should critically evaluate UFH monitoring protocols and be aware of their shortcomings.

Disseminated Intravascular Coagulation

Anesthesiologists may encounter patients with disseminated intravascular coagulation, a potential complication of severe sepsis or major trauma. This practical guide discusses the clinical approach, laboratory diagnosis, and current management of this condition.