Dosing of unfractionated heparin in obese patients with venous thromboembolism

Gerinnungsdiagnostik im klinischen Alltag – Teil 2

Während bei einer Vitamin-K-Antagonisten-Therapie die Therapieüberwachung (International Normalized Ratio [INR]) obligat ist, gilt dies für direkte orale Antikoagulanzien (DOAK) oder niedermolekulares Heparin (NMH) nur in ausgewählten klinischen Szenarien. Bei DOAK steht die Bestimmung von Tal- und Spitzenspiegeln des Medikaments im Plasma im Vordergrund, bei NMH die Anti-Xa-Aktivität. Der Zeitpunkt der Probenabnahme in Relation zur Einnahme ist für die Bewertung essenziell. Eine neu aufgetretene Thrombozytopenie im Rahmen stationärer Behandlungen ist häufig. Einordnung der Grunderkrankung, Tag des Auftretens sowie Erfassung medikamentöser Einflüsse und ihrer Dynamik ermöglichen oft die Eingrenzung der Ursache. Die Thrombophilietestung nach venöser Thromboembolie wird aufgrund fehlender therapeutischer Konsequenz zunehmend seltener durchgeführt. Ein Antiphospholipidsyndrom darf aber nicht übersehen werden, da sowohl die Therapiedauer als auch die Wahl des Antikoagulans davon abhängen.

Emergency Department Management of Acute Venous Thromboembolism in Patients With Obesity With Intravenous Unfractionated Heparin and Anti-Xa Monitoring

BACKGROUND

Unfractionated heparin (UFH) remains a frequently utilized agent in the emergency department (ED) for management of acute venous thromboembolism (VTE). While various protocols of UFH dosing have been proposed for patients with obesity, the optimal dosing and monitoring strategy is unclear.

OBJECTIVE

This study aims to compare the time to the first therapeutic anti-Xa level in obese acute VTE patients following the use of either total body weight (TBW) or adjusted body weight-based (AdjBW) dosing of UFH in the ED, and to analyze the impact of different dosing strategies on patient outcomes.

METHODS

Inclusion criteria included adult patients with a BMI > 30 kg/m², and suspected VTE managed with UFH per institutional protocol utilizing a bolus dose followed by maintenance infusion and anti-Xa monitoring. The primary outcome was time to the first therapeutic anti-Xa level in the group dosed per TBW compared with the group dosed per AdjBW. Safety outcomes included incidence of bleeding events, protamine administration, and mortality.

RESULTS

There were 32 patients included in the study. Patients dosed per TBW achieved a median time to first therapeutic anti-Xa level of 14.5 hours compared with 15 hours in the AdjBW group (P = .613). The median therapeutic UFH infusion rate was 16 units/kg/hr in the TBW group compared with 13.5 units/kg/hr in the AdjBW group (P < .001). Safety outcomes were not significantly different between groups.

CONCLUSION

Patients presenting to the ED with acute VTE may be managed with UFH using either a TBW or AdjBW dosing strategy.

Impact of Protocolized Pharmacist Intervention on Critical Activated Partial Thromboplastin Time Values With Heparin Infusions

Background: Unfractionated heparin (UFH) infusions are commonly managed with nurse-driven nomograms titrated to activated partial thromboplastin time (aPTT). In some patients, anti-Xa values may be more appropriate measures of anticoagulation. At the present institution, an update to the nurse-driven aPTT nomogram requires pharmacist notification and clinical assessment for critically supratherapeutic aPTT results. Objective: The purpose of this study was to evaluate the efficacy and safety of the nomogram update. Methods: A single-center, retrospective, pre-post analysis was conducted in patients treated with UFH who experienced a critical aPTT during the 6 months preceding and following the nomogram update. Patients with erroneous critical aPTT results were excluded. The primary endpoint was the time in therapeutic range (Rosendaal method) from the first critical aPTT until UFH discontinuation. Secondary endpoints included the proportion of patients transitioned to anti-Xa monitoring and the incidence of Bleeding Academic Research Consortium (BARC) 2, 3, 5 bleeding. Data were analyzed by the χ² test. The study was institutional review board approved. Results: Of 277 UFH infusions, 142 belonged to the pre-implementation group and 135 to the post-implementation group. Baseline aPTTs were similar between the 2 groups. Time in therapeutic range was 58.1% versus 62.4% of between groups (P = .467). UFH was transitioned to pharmacist-driven anti-Xa monitoring in 16.2% versus 40.3% of patients (P < .001). BARC 2, 3, 5 bleeding occurred in 23.2% versus 13.4% of patients (P < .001). Conclusions: Application of these data suggest improved safety and efficacy outcomes with directed pharmacist management of UFH in patients with critically elevated aPTTs.

Development of Selective FXIa Inhibitors Based on Cyclic Peptides and Their Application for Safe Anticoagulation

Coagulation factor XI (FXI) has emerged as a promising target for the development of safer anticoagulation drugs that limit the risk of severe and life-threatening bleeding. Herein, we report the first cyclic peptide-based FXI inhibitor that selectively and potently inhibits activated FXI (FXIa) in human and animal blood. The cyclic peptide inhibitor (K_i = 2.8 ± 0.5 nM) achieved anticoagulation effects that are comparable to that of the gold standard heparin applied at a therapeutic dose (0.3-0.7 IU/mL in plasma) but with a substantially broader estimated therapeutic range. We extended the plasma half-life of the peptide via PEGylation and demonstrated effective FXIa inhibition over extended periods in vivo. We validated the anticoagulant effects of the PEGylated inhibitor in an ex vivo hemodialysis model with human blood. Our work shows that FXI can be selectively targeted with peptides and provides a promising candidate for the development of a safe anticoagulation therapy.

Statistical Analysis of Inter-attribute Relationships in Unfractionated Heparin Injection Problems

Unfractionated heparin (UFH) is commonly used in the intensive care unit (ICU) to prevent blood clotting. Recently, many researchers focus on the development of data- driven methods to solve UFH related problems, which usually involves time series analysis. The performance of data-driven methods depends on whether the inter-correlation of attributes (or variables) in the dataset is closely examined and addressed. This study performs attribute selection, optimal time delay and inter-attributes relations on ICU time series data, in order to provide insights of time series data for UFH related problems. Medical records of 3211 patients with 22 attributes extracted from MIMIC (Medical Information Mart for Intensive Care) III database are used for the experiment. Experimental result shows that some of commonly selected attributes in the literature are less sensitive to the variations of UFH injection. Furthermore, some attributes are inter-dependent, which can increase the complexity of data-driven models, implying that the number of attributes could be reduced. There are 9 attributes found highly related and fast responding in 22 commonly used attributes. This study shows strong potential to provide clinicians with information about sensitive attributes that can help determine the UFH injection policy in ICU.

[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.

Unfractionated heparin infusion for treatment of venous thromboembolism based on actual body weight without dose capping

Controversy exists regarding the use of dose capping of weight-based unfractionated heparin (UFH) infusions in obese and morbidly obese patients. The primary objective of this study was to compare time to first therapeutic activated partial thromboplastin time (aPTT) in hospitalized patients receiving UFH for acute venous thromboembolism (VTE) among three body mass index (BMI) cohorts: non-obese (< 30 kg/m2), obese (30–39.9 kg/m2), and morbidly obese (⩾ 40 kg/m2). In this single-center, retrospective cohort study, patients were included if they ⩾ 18 years of age, had a documented VTE, and were on an infusion of UFH for at least 24 hours. Weight-based UFH doses were calculated using actual body weight. A total of 423 patients met the inclusion criteria, with 230 (54.4%), 146 (34.5%), and 47 (11.1%) patients in the non-obese, obese, and morbidly obese cohorts, respectively. Median times to therapeutic aPTT were 16.4, 16.6, and 17.1 hours in each cohort. Within 24 hours, the cumulative incidence rates for therapeutic aPTT were 70.7% for the non-obese group, 69.9% for the obese group, and 61.7% for the morbidly obese group (obese vs non-obese: HR = 1.02, 95% CI: 0.82–1.26, p = 0.88; morbidly obese vs non-obese: HR = 0.87, 95% CI: 0.62–1.21, p = 0.41). There was no significant difference in major bleeding events between BMI groups (obese vs non-obese, p = 0.91; morbidly obese vs non-obese, p = 0.98). Based on our study, heparin dosing based on actual body weight without a dose cap is safe and effective.

Anticoagulation at the extremes of body weight: choices and dosing

INTRODUCTION

The landscape of therapeutic anticoagulation has changed dramatically over the past decade, with availability of direct oral anticoagulants (DOACs), which inhibit factor Xa or thrombin. However, the optimal anticoagulant agent and dosing strategy for patients at both extremes of body weight has not been established for any anticoagulant, including DOACs, vitamin K antagonists (VKA), and the various heparin options. Areas covered: This paper reviews available evidence to assist clinicians in prescribing of anticoagulation therapy at the extremes of body weight. Expert commentary: There are limited data to guide prescribing of all available anticoagulants at the extremes of weight and further research regarding efficacy and safety outcomes in these groups is required. Laboratory monitoring to guide dosing of traditional anticoagulants provides reassurance of 'predictable' efficacy. In contrast agents that are not routinely monitored by laboratory testing provide greater challenges. For example, underweight patients are at risk of receiving higher drug exposures of DOACs, whereas the use of fixed dose DOACs in obese patients may be associated with lower drug exposures.

Heparin Increases Food Intake through AgRP Neurons

Although the widely used anticoagulant drug heparin has been shown to have many other biological functions independent of its anticoagulant role, its effects on energy homeostasis are unknown. Here, we demonstrate that heparin level is negatively associated with nutritional states and that heparin treatment increases food intake and body weight gain. By using electrophysiological, pharmacological, molecular biological, and chemogenetic approaches, we provide evidence that heparin increases food intake by stimulating AgRP neurons and increasing AgRP release. Our results support a model whereby heparin competes with insulin for insulin receptor binding on AgRP neurons, and by doing so it inhibits FoxO1 activity to promote AgRP release and feeding. Heparin may be a potential drug target for food intake regulation and body weight control.

Zhu et al. demonstrate that heparin competes with insulin for insulin receptor binding on AgRP neurons, and by doing so it inhibits FoxO1 activity to promote AgRP release and feeding. Heparin is identified as a potential drug target for food intake regulation and body weight control.

Evaluation of an Unfractionated Heparin Pharmacy Dosing Protocol for the Treatment of Venous Thromboembolism in Nonobese, Obese, and Severely Obese Patients

Background: Despite large interpatient variability in dose response, heparin is utilized for treatment of venous thromboembolism (VTE). Current data on the optimal heparin dosing in obese patients are conflicting. Objective: The objective was to evaluate the time and dose required to achieve a therapeutic activated partial thromboplastin time (aPTT) in nonobese, obese, and severely obese patients using a pharmacist-directed heparin dosing protocol. Methods: This was a retrospective cohort study in a single-center community hospital inpatient setting. Adult patients receiving heparin for VTE treatment from July 1, 2013, to July 31, 2015, were evaluated. Patients were categorized into 3 groups: nonobese (BMI < 30 kg/m2), obese (BMI = 30-39.9 kg/m2), and severely obese (BMI ≥ 40 kg/m2). Data on height, weight, initial bolus dose, initial infusion rate, time to therapeutic aPTT, and therapeutic infusion rate were collected. Dosing body weight (DBW) was utilized for patients 20% over their ideal body weight (IBW). The primary outcome was time to therapeutic aPTT. Results: Analysis included 298 patients. Median times to therapeutic aPTT (hours:minutes) in the nonobese, obese, and severely obese were 15:00 (interquartile range [IQR] = 8:05-23:21), 15:40 (IQR = 9:22-25:10), and 15:22 (IQR = 7.54-23:40), respectively ( P = 0.506). There was no difference in bleeding among the nonobese (14%), obese (13.9%), or severely obese groups (7.9%; P = 0.453). No adverse thrombotic events occurred during hospitalization. Conclusion: Using a DBW for heparin dosing in patients 20% over their IBW resulted in similar times to therapeutic aPTT and adverse events in the nonobese, obese, and severely obese.

Development of a pharmacist-driven protocol for automatic medication dosage adjustments in obese patients

PURPOSE

A hospital protocol utilizing automatic dosage adjustments and pharmacist consultations to optimize the use of certain medications in obese patients is described.

SUMMARY

After conducting a literature search focused on medication dosing in obese patients, pharmacists at a large community hospital developed a list of commonly ordered medications appropriate for inclusion in a pharmacy-driven institutional protocol for automatic medication dosage adjustment in adult patients with obesity. Evidence-based recommendations on initial dosing of eight antimicrobials and two anticoagulant agents according to weight and renal function were formulated. Under the protocol, pharmacists receive electronic alerts regarding protocol-eligible patients during initial order verification and automatically adjust medication dosages as appropriate. For patients prescribed anticoagulants at specified dosage levels, clinical pharmacists consult with prescribers to help ensure safe and effective initial and ongoing therapy. Multidisciplinary educational initiatives were conducted prior to protocol implementation. During two designated three-week postimplementation data collection periods, pharmacists received a total of 372 protocol-eligible medication orders. Pharmacists adjusted a total of 149 dosages and verified an additional 183 dosages consistent with the protocol as originally ordered. Clinical pharmacy consults were completed for 10-15% of patients, with laboratory monitoring ordered in 25-30% of those cases (all patients were found to have appropriate test values). There have been no documented adverse drug reactions in patients whose medication dosages were adjusted per protocol.

CONCLUSION

Pharmacists implemented weight- and renal function-based dosage adjustments for obese patients in 40% of evaluated protocol-eligible cases to achieve 89% compliance with the protocol. Heparin and cefazolin were the medications most likely to require obesity-related dosage adjustments.

Unfractionated heparin dosing for therapeutic anticoagulation in critically ill obese adults

PURPOSE

Research evaluating unfractionated heparin (UFH) dosing in obese critically ill populations is limited. This study aimed to determine optimal weight-based and total therapeutic infusion rates of UFH in this population.

METHODS

This retrospective cohort study compared adults on UFH infusions in intensive care units from May 2011 through October 2013 across 3 weight strata: 95 to 104 kg (control), 105 to 129 kg (high weight), and greater than or equal to 130 kg (higher weight). Primary outcomes included total and weight-based infusion rates for therapeutic anticoagulation.

RESULTS

To achieve therapeutic activated partial thromboplastin times, higher weight patients had higher mean infusion rates compared with control (2017 vs 1582 U/h; P = .002). Mean weight-based therapeutic infusion rate was lower in the higher weight group compared with control (13.1 vs 15.8 U kg(-1) h(-1); P = .008). Post hoc analyses indicated mean weight-based infusion rate to achieve therapeutic anticoagulation was 15 U kg(-1) h(-1) in patients less than 165 kg and 13 U kg(-1) h(-1) in patients greater than 165 kg.

CONCLUSIONS

Patients greater than or equal to 130 kg have lower weight-based heparin requirements compared with patients 95 to 104 kg. This difference appears to be driven by patients greater than 165 kg. Patients greater than 165 kg have lower weight-based heparin requirements, whereas patients from 105 to 164 kg have weight-based requirements similar to a normal-weight patient population. Initiating heparin at appropriate weight-based doses for obese patients may optimize anticoagulation.

Weight based heparin dosing for thromboembolic disease is associated with earlier anticoagulation in surgical patients

INTRODUCTION

Achievement of early therapeutic anticoagulation with unfractionated heparin (UFH) is associated with improved outcomes in thromboembolic disease. Weight based UFH expedites time to therapeutic anticoagulation. Treatment with UFH is challenging in surgical patients due to their high propensity for bleeding. We sought to test the hypothesis that an initial weight based UFH infusion in surgical patients increases the percentage of patients who achieve early therapeutic anticoagulation without increasing the risk of hemorrhagic events.

METHODS

Using a non-concurrent retrospective cohort study design, adult surgical patients receiving UFH for venous thromboembolism (VTE) at a tertiary care center were included. Two groups were identified: the weight based (WB) and the under-dosed (UD) heparin groups. For our primary outcome, we compared percentage of patients in each group that achieved a therapeutic PTT within 24 h. Secondary outcomes included the incidence of supratherapeutic PTT levels, hemorrhagic events, and complications associated with VTE.

RESULTS

73 subjects met study criteria, which included 8 subjects in the WB group and 65 in the UD group. The demographic, baseline laboratory, admitting service and type of VTE were similar between the 2 groups. The percentages of WB and UD subjects who achieved a therapeutic PTT within 24 h were 75% and 28%, respectively (p < 0.01). There was no difference in the incidence of supratherapeutic PTT or hemorrhagic events.

CONCLUSION

Surgical patients who received an initial weight based UFH infusion achieved earlier therapeutic anticoagulation compared to under-dosed UFH without increasing the occurrence of supratherapeutic PTT levels or hemorrhagic events.

Effect of extremes of body weight on the pharmacokinetics, pharmacodynamics, safety and tolerability of apixaban in healthy subjects

AIM

Apixaban is an oral, direct, factor-Xa inhibitor approved for thromboprophylaxis in patients who have undergone elective hip or knee replacement surgery and for prevention of stroke and systemic embolism in patients with non-valvular atrial fibrillation. This open label, parallel group study investigated effects of extremes of body weight on apixaban pharmacokinetics, pharmacodynamics, safety and tolerability.

METHOD

Fifty-four healthy subjects were enrolled [18 each into low (≤50 kg), reference (65-85 kg) and high (≥120 kg) body weight groups]. Following administration of a single oral dose of 10 mg apixaban, plasma and urine samples were collected for determination of apixaban pharmacokinetics and anti-factor Xa activity. Adverse events, vital signs and laboratory assessments were monitored.

RESULTS

Compared with the reference body weight group, low body weight had approximately 27% [90% confidence interval (CI): 8-51%] and 20% (90% CI: 11-42%) higher apixaban maximum observed plasma concentration (Cmax) and area under the concentration-time curve extrapolated to infinity (AUC(0,∞)), respectively, and high body weight had approximately 31% (90% CI: 18-41%) and 23% (90% CI: 9-35%) lower apixaban Cmax and AUC(0,∞) , respectively. Apixaban renal clearance was similar across the weight groups. Plasma anti-factor Xa activity showed a direct, linear relationship with apixaban plasma concentration, regardless of body weight group. Apixaban was well tolerated in this study.

CONCLUSION

The modest change in apixaban exposure is unlikely to require dose adjustment for apixaban based on body weight alone. However, caution is warranted in the presence of additional factors (such as severe renal impairment) that could increase apixaban exposure.

A real-world, multicenter assessment of drugs requiring weight-based calculations in overweight, adult critically ill patients

Prescribing appropriate doses of drugs requiring weight-based dosing is challenging in overweight patients due to a lack of data. With 68% of the US population considered overweight and these patients being at an increased risk for hospitalization, clinicians need guidance on dosing weight-based drugs. The purpose of this study was to identify “real-world” dose ranges of high-risk medications administered via continuous infusion requiring weight-based dosing and determine the reasons for dosing changes (ineffectiveness or adverse drug reactions). A prospective, multicenter, observational study was conducted in four intensive care units at three institutions. A total of 857 medication orders representing 11 different high-risk medications in 173 patients were reviewed. It was noted that dosing did not increase in proportion to weight classification. Overall, 14 adverse drug reactions occurred in nine patients with more in overweight patients (9 of 14). A total of 75% of orders were discontinued due to ineffectiveness in groups with higher body mass indexes. Ineffectiveness leads to dosing adjustments resulting in the opportunity for medication errors. Also, the frequent dosing changes further demonstrate our lack of knowledge of appropriate dosing for this population. Given the medications' increased propensity to cause harm, institutions should aggressively monitor these medications in overweight patients.

Heparin Dosing in Obese Pediatric Patients in the Cardiac Catheterization Laboratory

Background:

Unfractionated heparin (UFH) dosing may need to be adjusted when used in obese patients. The prevalence of pediatric obesity is increasing and, to our knowledge, no data exist to determine the effect of obesity on UFH therapy in children.

Objective:

To determine whether obese pediatric patients who receive a weight-based dose of UFH in the cardiac catheterization laboratory exhibit an enhanced response compared with those of normal body habitus.

Methods:

The records of pediatric patients who underwent a cardiac catheterization procedure from September 2006 to September 2010 at Texas Children's Hospital were reviewed. Patients were included if they had received a bolus dose of UFH during their procedure, and had pre- and post-UFH bolus activated clotting time (ACT) values determined. Patients were identified as obese if their body mass index (BMI) was at the 95th percentile or more for age and sex and were matched by age, sex, and catheterization procedure to a control group of patients with a BMI lower than the 95th percentile. Differences in demographic, UFH, and ACT variables were compared between obese and nonobese paired groups.

Results:

Seventy-eight patients (39 obese) met study criteria; 46 (58.9%) patients were male. The primary catheterization procedure was radiofrequency ablation (n = 32). There was no statistically significant difference in the mean (SD) dose per kilogram of UFH administered (72.3 [24.9] vs 63.6 [23.6] units/kg; p = 0.12) and no statistically significant difference in the time after the UFH bolus that the ACT was measured (52 [26] vs 56 [26] minutes; p = 0.59) between the 2 groups. No statistically significant difference was noted in the percent change in ACT after UFH bolus in obese compared to nonobese pediatric patients (196% [106] vs 165% [97]; p = 0.17).

Conclusions:

No significant difference in response to UFH was identified in obese pediatric patients compared to nonobese pediatric patients as measured by ACT in the cardiac catheterization laboratory.