Thrombotic and Hemorrhagic Complications in Patients with Mechanical Heart Valve Prosthesis Attending an Anticoagulation Clinic

Compact Grating-Coupled Biosensor for the Analysis of Thrombin

A compact optical biosensor for direct detection of thrombin in human blood plasma (HBP) is reported. This biosensor platform is based on wavelength spectroscopy of diffraction-coupled surface plasmons on a chip with a periodically corrugated gold film that carries an antifouling thin polymer layer consisting of poly[(N-(2-hydroxypropyl)methacrylamide)-co-(carboxybetaine methacrylamide)] (poly(HPMA-co-CBMAA)) brushes. This surface architecture provides superior resistance to nonspecific and irreversible adsorption of abundant compounds in the analyzed HBP samples in comparison to standard surface modifications. The carboxylate groups along the polymer brushes were exploited for the covalent immobilization of aptamer ligands. These ligands were selected to specifically capture the target thrombin analyte from the analyzed HBP sample in a way that does not activate the coagulatory process at the biosensor surface with poly(HPMA-co-CBMAA) brushes. Direct label-free analysis of thrombin in the medically relevant concentration range (1-20 nM) is demonstrated without the need for diluting the HBP samples or using additional steps for signal enhancement. The reported platform constitutes the first step toward a portable and sensitive point-of-care device for direct detection of thrombin in human blood.

Rivaroxaban versus Warfarin in Patients with Mechanical Heart Valve: Rationale and Design of the RIWA Study

Introduction

Mechanical heart valves (MHV) are extremely durable, but they require permanent use of anticoagulation to prevent thromboembolic events. The only approved therapeutic options are vitamin K antagonists (VKAs), such as warfarin. As a drug class, clinical management is difficult, therefore new alternatives need to be evaluated.

Methods

RIWA is a phase II/III, prospective, open-label, randomized, pilot study designed to investigate oral rivaroxaban 15 mg twice daily compared with dose-adjusted warfarin for the prevention of stroke (ischemic or hemorrhagic) and systemic embolism in patients with MHV, from August 2018 to December 2019. Patients will undergo transesophageal echocardiography at the beginning and the end of the study (follow-up time 90 days). On an explanatory basis, all events will be analyzed, including stroke, peripheral systemic embolism, valve thrombosis, significant bleeding and death.

Discussion

Warfarin and similar VKAs are standard therapy for patients with an MHV. Even with the appropriate use of therapy, the incidence of thromboembolic events is high at 1–4% per year. Furthermore, bleeding risk is significant, ranging from 2 to 9% per year. The new frontier to be overcome in relation to use of the new oral anticoagulants is undoubtedly in patients with MHV. A significant portion of people with MHV worldwide will benefit if noninferiority of these new agents is confirmed.

Trial Registration

ClinicalTrials.gov identifier: NCT03566303. Recruitment Status: Recruiting. First Posted: 25 June 2018. Last Update Posted: 25 June 2018.

Bringing the Benefits of Anticoagulation Management Services to the Community

Background:

While warfarin is efficacious for the prevention of thromboembolic disorders, many patients are undertreated. To optimize therapy, anticoagulation management services (AMSs) deliver a coordinated, focused approach to this care; however, AMSs are limited in their ability to impact patients outside of tertiary care settings.

Objective:

To describe the methods used to develop community-based AMSs across Alberta.

Methods:

Through a three-staged approach, this project created community-based, pharmacist-managed AMSs for patients requiring warfarin therapy. Stage I was the initiation of a central or “core” AMS, located at a quaternary referral centre. Starting with the core enabled us to develop and test the program and create an environment to serve as a training and support centre for future aspects of the program. Next, an educational program was developed and implemented (Stage II) for a diverse group of pharmacists to establish and manage a community-based or “satellite” AMS (Stage III) at their practice site. All three stages are undergoing detailed evaluation, capturing project-specific (patient outcome) data as well as system-level (integration within the health care infrastructure) data.

Conclusion:

By offering a focused, coordinated, and consistent approach to warfarin management, with ongoing collaboration with other providers, the ultimate goal of this program is to optimize patient outcomes. Utilizing pharmacists as central players within a collaborative setting will enhance the use of our current infrastructure. This program may serve as a model for other health regions and other chronic diseases.

Low-Dose Anticoagulation in Chinese Patients with Mechanical Heart Valves

The aim of this study was to provide guidelines for optimal anticoagulation in Chinese patients after mechanical heart valve replacement. A Carbomedics valve was implanted in 178 patients between July 2000 and July 2003. During follow-up, 22 bleeding events and 1 thromboembolic complication occurred. The linearized rates of bleeding and thromboembolism were 5.83% and 0.26% per patient-year, respectively. The linearized mortality rate was 0.79% per patient-year. The final mean international normalized ratio (INR) was 1.68 ± 0.38, however there was a significant variation between the early and late periods of follow-up. For Chinese patients with mechanical heart valves, bleeding was the major complication rather than thromboembolism. Low-dose anticoagulation (international normalized ratio 1.4–2.0) could markedly decrease bleeding and effectively prevent thromboembolism. As the INR was most unstable in the first postoperative month, re-examination of patients in this period is critical.

Dabigatran versus warfarin after bioprosthesis valve replacement for the management of atrial fibrillation postoperatively: protocol

Background

Warfarin and similar vitamin K antagonists have been the standard therapy for patients with mechanical or biological valve prosthesis and atrial fibrillation (AF). Even with the appropriate use of therapy, some studies have reported that there is a high incidence of thromboembolic events, 1%-4% per year. Furthermore, a bleeding risk is significant, ranging from 2% to 9% per year, according to some studies.

Objective

The objective of our study was to examine the effect of dabigatran etexilate versus dose-adjusted warfarin for the prevention of intracardiac thrombus in persistent or permanent AF at least 3 months after aortic and/or mitral bioprosthesis replacement.

Methods

Dabigatran versus warfarin after bioprosthesis valve replacement for the management of atrial fibrillation postoperatively (DAWA) is a phase 2, prospective, open label, randomized exploratory pilot study. The main variable to be observed in this study is intracardiac thrombus. From August 2013 to April 2015, 100 patients, at least 3 months after aortic and/or mitral bioprosthesis replacement and permanent or persistent AF postoperatively, who match eligibility criteria will be selected from Ana Nery Hospital in Salvador-Bahia with a follow-up of three months. Patients were randomly assigned in a 1:1 ratio to receive either dabigatran etexilate or warfarin.

Results

Although the present study has no statistic power to proof non-inferiority, it is expected that the dabigatran etexilate group will be protected as well as the warfarin group from intracardiac thrombus, without increasing the bleeding rates, since we are using safer doses (110 mg bid). The lack of necessity of monitoring INR is also another factor that contributes to a better adherence to the new drug and it can make all the difference in the manner of doing anticoagulation for patients with similar clinical characteristics.

Conclusions

The study is in the recruitment phase. It is possible that dabigatran etexilate is as effective as warfarin in preventing the emergence of intracardiac thrombus in patients with AF and mitral and/or aortic bioprosthesis.

Trial Registration

Clinicaltrials.gov NCT01868243; http://clinicaltrials.gov/ct2/show/NCT01868243 (Archived by WebCite at http://www.webcitation/6OABiuasd).

Quadruple Valve Replacement with Mechanical Valves: An 11-Year Follow-up Study

<p><b>Background:</b> We performed the first quadruple valve replacement with mechanical valves, combined with the correction of complex congenital heart disease on November 17, 1999. We report here the 11-year follow-up study.</p><p><b>Methods:</b> A 47-year-old man with subacute rheumatic endocarditis, a ventricular septal defect, and an obstruction of the right ventricular outflow tract required replacement of the aortic, mitral, tricuspid, and pulmonary valves; repair of the ventricular septal defect; and relief of the obstruction of the right ventricular outflow tract. The surgery was done on November 17, 1999, after careful systemic preparation of the patient. Warfarin therapy with a target international normalized ratio (INR) range of 1.5 to 2.0 was used. Follow-up included monitoring the INR, recording the incidences of thromboembolic and bleeding events, electrocardiography, radiography, and echocardiography evaluations.</p><p><b>Results:</b> The patient's INR was maintained between 1.5 and 2.0. All 4 mechanical prosthetic heart valves worked well. He is in generally good health without any thromboembolic or bleeding complications.</p><p><b>Conclusions:</b> Long-term management is challenging for patients who have experienced quadruple valve replacement with mechanical valves; however, promising results could mean that replacement of all 4 heart valves in 1 operation is feasible in patients with quadruple valve disease, and an INR of 1.5 to 2.0 could be appropriate for Chinese patients with undergoing valve replacement with mechanical valves.</p>

Evidence-based management of anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

High-quality anticoagulation management is required to keep these narrow therapeutic index medications as effective and safe as possible. This article focuses on the common important management questions for which, at a minimum, low-quality published evidence is available to guide best practices.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines in this supplement.

RESULTS

Most practical clinical questions regarding the management of anticoagulation, both oral and parenteral, have not been adequately addressed by randomized trials. We found sufficient evidence for summaries of recommendations for 23 questions, of which only two are strong rather than weak recommendations. Strong recommendations include targeting an international normalized ratio of 2.0 to 3.0 for patients on vitamin K antagonist therapy (Grade 1B) and not routinely using pharmacogenetic testing for guiding doses of vitamin K antagonist (Grade 1B). Weak recommendations deal with such issues as loading doses, initiation overlap, monitoring frequency, vitamin K supplementation, patient self-management, weight and renal function adjustment of doses, dosing decision support, drug interactions to avoid, and prevention and management of bleeding complications. We also address anticoagulation management services and intensive patient education.

CONCLUSIONS

We offer guidance for many common anticoagulation-related management problems. Most anticoagulation management questions have not been adequately studied.

Oral anticoagulant therapy: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

The objective of this article is to summarize the published literature concerning the pharmacokinetics and pharmacodynamics of oral anticoagulant drugs that are currently available for clinical use and other aspects related to their management.

METHODS

We carried out a standard review of published articles focusing on the laboratory and clinical characteristics of the vitamin K antagonists; the direct thrombin inhibitor, dabigatran etexilate; and the direct factor Xa inhibitor, rivaroxaban

RESULTS

The antithrombotic effect of each oral anticoagulant drug, the interactions, and the monitoring of anticoagulation intensity are described in detail and discussed without providing specific recommendations. Moreover, we describe and discuss the clinical applications and optimal dosages of oral anticoagulant therapies, practical issues related to their initiation and monitoring, adverse events such as bleeding and other potential side effects, and available strategies for reversal.

CONCLUSIONS

There is a large amount of evidence on laboratory and clinical characteristics of vitamin K antagonists. A growing body of evidence is becoming available on the first new oral anticoagulant drugs available for clinical use, dabigatran and rivaroxaban.

Warfarin therapeutic monitoring: is 70% time in the therapeutic range the best we can do?

WHAT IS KNOWN AND OBJECTIVE

Warfarin, an oral anticoagulant, which has been in clinical use for over sixty years, remains a challenge for clinicians to utilize, given the multiplicity of items which can limit its efficacy. Our objective is to review the evidence and comment on whether INR control can be better than has been currently reported in various studies.

COMMENT

The duration of time a patient's international normalized ratio (INR) is maintained within the therapeutic range (time in the therapeutic range, TTR) for his or her particular indication for the drug impacts the effectiveness and safety of warfarin therapy. Maintaining a therapeutic INR while on warfarin is difficult, and numerous studies employing various strategies confirm the challenge, but not the impossibility of achieving a TTR above 70%.

WHAT IS NEW AND CONCLUSION

Maintaining a therapeutic INR requires a dedicated multi-faceted approach. With diligence, skill and various therapeutic strategies, a TTR >70% can be achieved.

Evaluation of an electronic warfarin nomogram for anticoagulation of hemodialysis patients

Background

Warfarin nomograms to guide dosing have been shown to improve control of the international normalized ratio (INR) in the general outpatient setting. However, the effectiveness of these nomograms in hemodialysis patients is unknown. We evaluated the effectiveness of anticoagulation using an electronic warfarin nomogram administered by nurses in outpatient hemodialysis patients, compared to physician directed therapy.

Methods

Hemodialysis patients at any of the six outpatient clinics in Calgary, Alberta, treated with warfarin anticoagulation were included. Two five-month time periods were compared: prior to and post implementation of the nomogram. The primary endpoint was adequacy of anticoagulation (proportion of INR measurements within range ± 0.5 units).

Results

Overall, 67 patients were included in the pre- and 55 in the post-period (with 40 patients in both periods). Using generalized linear mixed models, the adequacy of INR control was similar in both periods for all range INR levels: in detail, range INR 1.5 to 2.5 (pre 93.6% (95% CI: 88.6% - 96.5%); post 95.6% (95% CI: 89.4% - 98.3%); p = 0.95); INR 2.0 to 3.0 (pre 82.2% (95% CI: 77.9% - 85.8%); post 77.4% (95% CI: 72.0% - 82.0%); p = 0.20); and, INR 2.5 to 3.5 (pre 84.3% (95% CI: 59.4% - 95.1%); post 66.8% (95% CI: 39.9% - 86.0%); p = 0.29). The mean number of INR measurements per patient decreased significantly between the pre- (30.5, 95% CI: 27.0 - 34.0) and post- (22.3, 95% CI: 18.4 - 26.1) (p = 0.003) period. There were 3 bleeding events in each of the periods.

Conclusions

An electronic warfarin anticoagulation nomogram administered by nurses achieved INR control similar to that of physician directed therapy among hemodialysis patients in an outpatient setting, with a significant reduction in frequency of testing. Future controlled trials are required to confirm the efficacy of this nomogram.

Are the risk factors listed in warfarin prescribing information associated with anticoagulation-related bleeding? A systematic literature review

Warfarin significantly reduces thromboembolic risk, but perceptions of associated bleeding risk limit its use. The evidence supporting the association between bleeding and individual patient risks factors is unclear. This systematic review aims to determine the strength of evidence supporting an accentuated bleeding risk when patients with risk factors listed in the warfarin prescribing information are prescribed the drug. A systematic literature search of MEDLINE and Cochrane CENTRAL was conducted to identify studies reporting multivariate relationships between prespecified covariates and the risk of bleeding in patients receiving warfarin. The prespecified covariates were identified based on patient characteristics for bleeding listed in the warfarin package insert. Each covariate was evaluated for its association with specific types of bleeding. The quality of individual evaluations was rated as 'good', 'fair' or 'poor' using methods consistent with those recommended by the Agency for Healthcare Research and Quality (AHRQ). Overall strength of evidence was determined using the Grading of Recommendations Assessment, Development (GRADE) criteria and categorised as 'insufficient', 'very low', 'low', 'moderate' or 'high'. Thirty-four studies, reporting 134 multivariate evaluations of the association between a covariate and bleeding risk were identified. The majority of evaluations had a low strength of evidence for the association between covariates and bleeding and none had a high strength of evidence. Malignancy and renal insufficiency were the only two covariates that had a moderate strength of evidence for their association with major and minor bleeding respectively. The associations between covariates listed in the warfarin prescribing information and increased bleeding risk are not well supported by the medical literature.

Association between CHADS₂risk factors and anticoagulation-related bleeding: a systematic literature review

OBJECTIVE

To determine the strength of evidence supporting an accentuated bleeding risk when patients with CHADS(2) risk factors (chronic heart failure, hypertension, advanced age, diabetes, and prior stroke/transient ischemic attack) receive warfarin.

METHODS

A systematic literature search of MEDLINE (January 1, 1950, through December 22, 2009) and Cochrane CENTRAL (through December 22, 2009) was conducted to identify studies that reported multivariate results on the association between CHADS(2) covariates and risk of bleeding in patients receiving warfarin. Each covariate was evaluated for its association with a specific type of bleeding. Individual evaluations were rated as good, fair, or poor using methods consistent with those recommended by the Agency for Healthcare Research and Quality. The strength of the associations between each CHADS(2) covariate and a specific type of bleeding was determined using Grading of Recommendations Assessment, Development and Evaluation criteria as insufficient, very low, low, moderate, or high for the entire body of evidence.

RESULTS

Forty-one studies were identified, reporting 127 multivariate evaluations of the association between a CHADS(2) covariate and bleeding risk. No CHADS(2) covariate had a high strength of evidence for association with any bleeding type. For the vast majority of evaluations, the strength of evidence between covariates and bleeding was low. Advanced age was the only covariate that had a moderate strength of evidence for association; this was the strongest independent positive predictor for major bleeding. Similar findings were observed regardless of whether all included studies, or only those evaluating patients with atrial fibrillation, were assessed.

CONCLUSION

The associations between CHADS(2) covariates and increased bleeding risk were weak, with the exception of age. Given the known association of the CHADS(2) score and stroke risk, the decision to prescribe warfarin should be driven more by patients' risk of stroke than by the risk of bleeding.

Clinical outcomes of a pharmacist-managed anticoagulation service for breast cancer patients

Purpose. Report descriptive outcome measures related to the quality of pharmacist-managed anticoagulation care with warfarin in patients with breast cancer since the formation of the anticoagulation management service (AMS).

Methods. Retrospective review of 145 patients with breast cancer (median age 54 years) receiving warfarin therapy for venous thromboembolism (VTE) managed by the pharmacist-run AMS between 1998 and 2005.

Results. The median time followed by the AMS was 151 days. Fifty three percent ( n = 1651) of total lab draws ( n = 3129) were within the target therapeutic INR range 2–3. Recurrent thrombosis occurred in 4.1% of patients. Minor bleeding occurred in 18.6% of patients and major bleeding occurred in three patients (2.1%, gastrointestinal, intra-abdominal, and subdural hematoma).

Conclusion. To date, this is the largest known published database of cancer patients receiving anticoagulation in a pharmacist-managed anticoagulation service. Recurrent VTE rates, major and minor bleeding rates, and percentage of time spent within the therapeutic range are slightly different in our patient population compared to an oncology population receiving warfarin and a non-oncology population with warfarin managed by AMS. Oral anticoagulation with warfarin is an effective, albeit complicated, treatment for venous thromboembolism in the oncology population. Although low-molecular weight heparin (LMWH) therapy is now the preferred treatment for thrombosis in malignancy, warfarin is still relevant in patients who are unable to receive treatment with LMWH. This report provides valuable information supporting coordinated anticoagulation therapy with a pharmacist-managed service in a breast cancer-specific population, and contributes to the growing data supporting the challenging nature of maintaining warfarin anticoagulation in patients with cancer.

Major hemorrhagic and thromboembolic complications in patients with mechanical heart valves receiving oral anticoagulant therapy

INTRODUCTION

Patients with mechanical heart valve prostheses are obligated to receive lifelong oral anticoagulant therapy to prevent thromboembolic complications; however, this treatment is associated with an increased risk of bleeding. The aim of this study was to evaluate the frequency of major hemorrhagic and thromboembolic complications in patients with mechanical heart valves who received oral anticoagulant therapy.

MATERIALS AND METHODS

The analysis involved 225 patients who underwent successful surgery in 2000; the mean (+/-SD) follow-up period was 43.3 +/- 9.2 months. Aortic, mitral, and double valve replacement was performed in 128 (56.7%), 70 (31.1%), and 27 (12.1%) of the patients, respectively. There were 128 men (57.3%), and the mean patient age was 57.9 +/- 18.8 years. The following data were assessed: rate of major hemorrhagic and thromboembolic complications, frequency of international normalized ratio (INR) rate measurements, and percentage of results within the therapeutic range.

RESULTS

Major hemorrhagic and thromboembolic complications occurred in 25 patients (11.1%). Seventeen patients (7.5%) survived, and 8 (3.6%) died of the complications. Major hemorrhagic and thromboembolic complications occurred in 17 patients (7.6%) and 8 patients (3.6%), respectively. The mean time between sequential measurements was 4.3 +/- 3.0 weeks, and of all the INR values collected, 42.4% were within, 31.3% were below, and 26.3% were above the target ranges.

CONCLUSIONS

Patients with a mechanical heart valve prosthesis receiving acenocoumarol are susceptible to major hemorrhagic and thromboembolic complications, some of which lead to death. Despite the danger related to these complications, patients receiving anticoagulant therapy still have difficulty achieving INR values within the therapeutic range.

Penny-wise, pound-foolish? Highmark Medicare Services' proposal for anticoagulation clinic reimbursement

Warfarin is prescribed to millions of Americans for the management of thromboembolism and is a common cause of adverse events. Optimizing warfarin therapy has been the focus of national quality improvement initiatives. Anticoagulation clinics have been demonstrated to result in better outcomes than usual care. Nevertheless, Highmark Medicare Services recently issued a provider bulletin on anticoagulation clinic visit reimbursement that we believe will adversely affect the care for patients on anticoagulation. In this commentary, we review the potential unintended consequences of this proposal and offer alternatives that we believe will increase the efficiency and quality of anticoagulation management.

Necrose cutânea induzida por antagonistas da vitamina K

Os anticoagulantes orais que atuam através do antagonismo à vitamina K são utilizados na prática clínica há muito tempo, porém ainda há dificuldades no seu manejo e na condução das complicações. Entre as complicações, as mais conhecidas são os transtornos hemorrágicos, mas outras também devem ser reconhecidas, tais como a necrose induzida por varfarina. Esta é uma grave, porém rara complicação, cuja fisiopatologia é ainda obscura e cujas causas são indefinidas. Dentre as possíveis causas, as mais prováveis são a deficiência de proteína C e de proteína S, reações de hipersensibilidade e deficiência de fator VII. Há maior incidência desta complicação entre mulheres de meia-idade, acometendo preferencialmente mamas e glúteos. As medidas mais importantes para o tratamento são: suspensão imediata da droga, uso de heparina não fracionada ou de baixo peso molecular em doses terapêuticas, emprego da vitamina K e, eventualmente, infusão de plasma fresco congelado ou de proteína C ativada recombinante.

Novel anticoagulants and the future of anticoagulation

Since its discovery during the first half of the 20th century by biochemists at the University of Wisconsin, warfarin (along with other vitamin K antagonists) has remained the only oral anticoagulant available to patients at risk for thromboembolism. After nearly 6 decades in clinical practice, we have learned much about warfarin. Although it is highly effective for most patients, warfarin has a number of undesirable attributes: significant inter- and intra-patient variability in dose-response, a narrow therapeutic index, a slow pharmacodynamic response, and numerous interactions with both diet as well as other medications. The negative characteristics associated with warfarin have inspired many clinicians, patients, and researchers to wonder if a better alternative can be discovered. To that end, at least three novel anticoagulant compounds are in the late stages of development and several others are progressing through earlier phases of investigation. This review will summarize the latest clinical trial data pertinent to several newer antithrombotic agents and discuss recent developments that impact the safety and challenges associated with warfarin and other vitamin K antagonists (VKA).

Measuring quality of oral anticoagulation care: extending quality measurement to a new field

BACKGROUND

Oral anticoagulation with warfarin is an increasingly common medical intervention. Despite its efficacy, warfarin is difficult to manage, contributing to potential for patient harm. Efforts to measure the quality of oral anticoagulation care have focused disproportionately on the identification of ideal candidates for warfarin therapy, with comparatively little effort in measuring the quality of oral anticoagulation care once therapy has begun. To address this gap in the literature, a MEDLINE search was conducted for all papers relevant to possible quality measures in oral anticoagulation care, including measures of structure, process, and outcomes of care.

LIMITATIONS, CONCERNS, AND CHALLENGES OF QUALITY MEASUREMENT IN ORAL ANTICOAGULATION

Because they do not have intrinsic significance, measures of structure and process should be strongly related to outcomes that matter to merit our interest. Consensus guidelines may provide useful guidance to practicing clinicians but may not represent valid process measures. Outcome measures must be studied with databases that provide sufficient statistical power to reliably demonstrate real differences between providers or sites of care.

CONCLUSION

Oral anticoagulation care, a common and serious condition, is in need of a program of quality measurement. This article suggests a research agenda to begin such a program. Previous research has established the evidence for anticoagulant therapy across a broad spectrum of indications and has helped to achieve consensus on the optimal target intensity for various indications. The next task will be to use this body of evidence to develop valid measures of the structure, process, and outcomes of oral anticoagulation care. Quality indicators provide a framework for quality improvement, two goals of which are to maximize the effectiveness of therapy and to minimize harm.

Evaluation of pharmacist-managed diabetes mellitus under a collaborative drug therapy agreement

PURPOSE

The effect of a pharmacist-managed collaborative drug therapy agreement (CDTA) on diabetes mellitus (DM) management in an outpatient setting is evaluated.

METHODS

Patients with DM were referred by physicians to the pharmacist for either education or clinical management of DM under the CDTA. A retrospective chart review was conducted between September 2001 and December 2005 and included patients who had laboratory values of interest within one year before and after the initial visit and who had more than two documented visits with the pharmacist. After the pharmacist's intervention in the DM management, glycosylated hemoglobin (HbA(1c)) and low-density lipoprotein cholesterol were compared using a paired sample t test. Average costs for inpatient hospitalization and emergency department (ED) admission were also compared.

RESULTS

A total of 110 patients had a mean +/- S.D. of 5.7 +/- 3.9 visits with the pharmacist. A mean reduction in HbA(1c) of 0.7% (p < or = 0.001, n = 93) from 8.9% to 8.2% and a mean reduction in blood glucose of 26.4 mg/dL (p < or = 0.001, n = 99) were achieved. Average costs for inpatient hospitalization and ED admissions were significantly higher in the preintervention period than in the postintervention period for patients with DM as the primary or secondary diagnosis ($2434 versus $636, respectively; p = 0.015). For patients with a primary diagnosis of diabetes, preintervention costs were higher than postintervention costs, but this difference was not significant ($3082 versus $696, respectively; p = 0.100).

CONCLUSION

Pharmacist interventions under a CDTA resulted in significant improvements in glucose and HbA(1c) levels in patients with DM. Postintervention costs for inpatient hospitalization and ED services were significantly less than preintervention costs when DM was a primary or secondary diagnosis for the admission.

Comparison of INR stability between self-monitoring and standard laboratory method: preliminary results of a prospective study in 67 mechanical heart valve patients

INTRODUCTION

Thromboembolic accidents and haemorrhage are the main complications observed during long-term follow-up of mechanical heart valve patients. Several suggestions for improving anticoagulation quality have been made, including international normalised ratio (INR) self-monitoring.

OBJECTIVES

We report the preliminary results of a single-centre, open, randomised study (scheduled population of 200 patients), which compares monthly laboratory monitoring (group A) versus weekly self-monitoring of INR (group B). The primary aim is INR stability improvement within the target range, and the secondary aim is adverse events reduction.

PATIENTS AND METHODS

Between May 2004 and June 2005, 67 patients with an average age of 56.6 years (+/-9.6), were enrolled in the study (group A: 34 patients, group B: 33 patients). The mean follow-up was 47 weeks (+/-11.5). The two groups differed only in the sex ratio (44.1 and 21.2% of women in groups A and B respectively, p=0.0459). Mechanical heart valves were aortic in 73% of patients, mitral in 13.5%, and multiple in 13.5%. Sixty-five patients (97%) were treated with fluindione, the others with acenocoumarol. The intraclass correlation coefficient between the self- and laboratory-monitored INR was 0.75.

RESULTS

The time spent in the INR target range (group A: 53+/-19%, group B: 57+/--19%, p=0.45) and the time spent in the INR therapeutic range, between 2 and 4.5, (group A: 86+/-14%, group B: 91+/-7%, p=0.07) are longer in group B, but not significantly so. For patients outside the range, the absolute mean deviation of INR from the target or therapeutic range (range standardized between 0 and 100) is lower for the self-monitoring group (41.1+/-39.3 and 11.27+/-11.2) than for the control group (62.4+/-72.6 and 39.2+/-52.8). This difference is significant (p=0.0004 and p=0.0005). Eighteen adverse events were reported: 17 haemorrhages, 13 in group A (9 mild, 4 serious) and four in group B (all mild), and one sudden death in group B, two days after the patient's discharge. No thromboembolic events were reported. Six patients (8.8 %), 3 in each group, dropped out of the study.

CONCLUSION

This first study evaluating INR self-monitoring in France shows that this method leads to better stability of the INR within the target range. On the basis of these preliminary data, this appears to be related to a decrease in serious haemorrhages (11.8% serious haemorrhage cases in group A versus 0% in group B, p=0.06, NS).

Pharmacology and management of the vitamin K antagonists: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article concerning the pharmacokinetics and pharmacodynamics of vitamin K antagonists (VKAs) is part of the American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). It describes the antithrombotic effect of the VKAs, the monitoring of anticoagulation intensity, and the clinical applications of VKA therapy and provides specific management recommendations. Grade 1 recommendations are strong and indicate that the benefits do or do not outweigh the risks, burdens, and costs. Grade 2 recommendations suggest that the individual patient's values may lead to different choices. (For a full understanding of the grading, see the "Grades of Recommendation" chapter by Guyatt et al, CHEST 2008; 133:123S-131S.) Among the key recommendations in this article are the following: for dosing of VKAs, we recommend the initiation of oral anticoagulation therapy, with doses between 5 mg and 10 mg for the first 1 or 2 days for most individuals, with subsequent dosing based on the international normalized ratio (INR) response (Grade 1B); we suggest against pharmacogenetic-based dosing until randomized data indicate that it is beneficial (Grade 2C); and in elderly and other patient subgroups who are debilitated or malnourished, we recommend a starting dose of < or = 5 mg (Grade 1C). The article also includes several specific recommendations for the management of patients with nontherapeutic INRs, with INRs above the therapeutic range, and with bleeding whether the INR is therapeutic or elevated. For the use of vitamin K to reverse a mildly elevated INR, we recommend oral rather than subcutaneous administration (Grade 1A). For patients with life-threatening bleeding or intracranial hemorrhage, we recommend the use of prothrombin complex concentrates or recombinant factor VIIa to immediately reverse the INR (Grade 1C). For most patients who have a lupus inhibitor, we recommend a therapeutic target INR of 2.5 (range, 2.0 to 3.0) [Grade 1A]. We recommend that physicians who manage oral anticoagulation therapy do so in a systematic and coordinated fashion, incorporating patient education, systematic INR testing, tracking, follow-up, and good patient communication of results and dose adjustments [Grade 1B]. In patients who are suitably selected and trained, patient self-testing or patient self-management of dosing are effective alternative treatment models that result in improved quality of anticoagulation management, with greater time in the therapeutic range and fewer adverse events. Patient self-monitoring or self-management, however, is a choice made by patients and physicians that depends on many factors. We suggest that such therapeutic management be implemented where suitable (Grade 2B).

Is long-term pharmacist-managed anticoagulation service efficient? A pragmatic randomized controlled trial

BACKGROUND

Some pharmacist-managed anticoagulation services (PMAS) provide initial follow-up to patients on oral anticoagulant, who are transferred to their physician once they are stabilized. This may be as effective as and less expensive than long-term PMAS follow-up.

METHODS

Once PMAS patients were stabilized and ready for discharge, they were randomized to be transferred to their physician or stay with the PMAS. Quality of international normalized ratio (INR) control, incidence of complications, health-related quality of life, use of health care services, and direct incremental cost of PMAS follow-up were evaluated.

RESULTS

One hundred thirty-eight physicians and 250 patients participated. Patients were initially followed at the PMAS for a mean of 11.3 weeks and afterwards were followed by their physician (n = 122) or by the PMAS pharmacists (n = 128) for a mean of 14.9 and 14.5 weeks, respectively. Pharmacist-managed anticoagulation services' and physician's patients were within the exact target range 77.3% and 76.7% of the time (95% CI of the difference -4.9% to 6.0%) and within the extended range 93.0% and 91.6% of the time (95% CI -2.1% to 4.7%), respectively. Pharmacist-managed anticoagulation services patients have seen their family physician less often (95% CI -3.1 to -0.1 visit per year). Number of INR tests, incidence of complications, and health-related quality of life were similar in both groups. The incremental cost of PMAS follow-up was estimated at CAN$123.80 per patient year.

CONCLUSION

Once PMAS patients are well stabilized, maintaining a PMAS follow-up or transferring them to their physician is associated with excellent INR control. However, long-term PMAS follow-up may be more expensive.

Outpatient management of oral vitamin K antagonist therapy: defining and measuring high-quality management

Oral anticoagulation therapy with warfarin is the mainstay of prevention and treatment of thromboembolic disease. However, it remains one of the leading causes of harmful medication errors and medication-related adverse events. The beneficial outcomes of oral anticoagulation therapy are directly dependent upon the quality of dose and anticoagulation management, but the literature is not robust with regards to what constitutes such management. This review focuses on, and attempts to define, the parameters of high-quality anticoagulation management and identifies the appropriate outcome measures constituting high-quality management. Elements discussed include the most fundamental measure, time in therapeutic range, along with other parameters including therapy initiation, time to therapeutic range, dosing management when patients are not in therapeutic range, perioperative dosing management, patient education, and other important outcome measures. Healthcare providers who manage oral anticoagulation therapy should utilize these parameters as a measure of their performance in an effort to achieve high-quality anticoagulation management.

Management of Chinese patients on warfarin therapy in two models of anticoagulation service - a prospective randomized trial

AIM

To compare the treatment outcomes of a clinical pharmacist-managed anticoagulation service with physician-managed service in Chinese patients.

METHODS

A prospective, randomized clinical trial was conducted at the anticoagulation clinic of a teaching hospital in Hong Kong. Patients aged > or = 18 years who would required warfarin therapy for at least 3 months were recruited. Patients were randomized to the pharmacist-managed or physician-managed group. Primary clinical outcome was assessed by the percentage of patient time spent within the target international normalized ratio (INR) range. The incidence of major thromboembolic events (TEs) and major bleeding was assessed as secondary clinical outcomes. The cost per patient per month (cPPPM) was calculated and patient satisfaction was assessed by patient satisfaction questionnaire (PSQ)-18.

RESULTS

One hundred and forty-one patients were recruited at the anticoagulation clinic and 137 patients completed the study. Patients in the pharmacist-managed group (n = 68) were in the target INR 64% of patient time vs. 59% in the physician-managed group (n = 69) (P < 0.001). There was no significant difference in incidence of major TEs or bleeding. The cPPPM in the pharmacist-managed group (76 +/- 95 US dollar) (43 +/- 53 British pound) was lower than in the physician-managed group (98 +/- 158 US dollar) (55 +/- 89 British pound) (P < 0.001). The PSQ-18 score of the pharmacist-managed group (3.8 +/- 0.2) was higher than that of the physician-managed group (3.6 +/- 0.3) (P < 0.001).

CONCLUSION

The pharmacist-managed anticoagulation service was more effective and less costly than the physician-managed service in achieving target anticoagulation control for Chinese patients on warfarin therapy.

A "two-step" educational approach for patients taking oral anticoagulants does not improve therapy control

BACKGROUND AND OBJECTIVE

The educational aspect of oral anticoagulant treatment is considered a possible cause of variability in anticoagulation levels. The aim of this prospective study was to investigate whether the time spent in the therapeutic range (TSTR) by patients taking oral anticoagulants could be improved by two different, consecutive educational approaches on the crucial aspects of oral anticoagulant therapy.

DESIGN AND METHODS

Between May and June 2004, validated interviews were conducted with 240 patients (128 male and 112 female, mean age 50 +/- 12 years) enrolled in the study. Three months later, the patients were randomly allocated to three groups. A course that focused on the questions in the interview was followed by the first group (n = 80); a brochure containing the correct answers to questions was given to the second (n = 81); nothing was provided for the third (n = 79).

RESULTS

A significant difference was found in the TSTR between the quarters preceding and following the interview. Mean TSTR increase was 13%. Patients that were randomly selected to attend the educational course, read a brochure or do nothing showed similar TSTR percentages in the quarter following the interview. A good control of the anticoagulant therapy (TSTR >70%) was maintained, with no significant variation during the following three-quarters.

INTERPRETATION AND CONCLUSIONS

A two-step educational approach for patients on long-term oral anticoagulation does not improve TSTR percentages in the short term.

Individualizing warfarin therapy

Warfarin is the most commonly prescribed oral anticoagulant for the treatment and prevention of thromboembolic events. The correct maintenance dose of warfarin for a given patient is difficult to predict, the drug carries a high risk of toxicity, and variability among patients means that the safe dose range differs widely between individuals. Recent pharmacogenetic studies indicate that the routine incorporation of genetic testing into warfarin therapy protocols could substantially ease both the financial and health risks currently associated with this treatment. In particular, the variability in warfarin dose requirement is now recognized to be due, in large part, to polymorphisms in two genes: cytochrome P450 2C9 and the vitamin K epoxide reductase complex subunit 1. The development of algorithms that integrate all of the relevant genetic and physical factors into comprehensive, individualized predictive models for warfarin dose could be used to translate the results of pharmacogenetic testing into actionable clinical application.

Descriptive analysis of the process and quality of oral anticoagulation management in real-life practice in patients with chronic non-valvular atrial fibrillation: the international study of anticoagulation management (ISAM)

BACKGROUND/OBJECTIVES

Expert oral anticoagulation management is the key to good outcomes and is performed variably in different health care systems throughout the world. We set out to assess the quality of anticoagulation management in five countries in patients receiving vitamin K antagonists (VKAs) for stroke prophylaxis in chronic non-valvular atrial fibrillation (NVAF), and to compare the anticoagulation management practices in these countries.

METHODS AND RESULTS

This was a retrospective, multi-centre cohort study in the United States, Canada, France, Italy, and Spain. About 1,511 patients were randomly recruited from representative practices (routine medical care (RMC) in the US, Canada, and France; anticoagulation clinics in Italy and Spain) and data pertaining to their oral anticoagulation care were abstracted from their medical records. The predominant anticoagulant in use was warfarin in the US, Canada, and Italy; acenocoumarol in Spain; and fluindione in France. Documentation of care was poor in the US, Canada, and France, countries where RMC was studied. Percent INRs or time-in-therapeutic range was greater in the two anticoagulation clinic samples compared with the RMC samples.

CONCLUSION

Oral anticoagulation care varies considerably from country to country. Findings suggest that anticoagulation clinic care (ACC) may provide better outcomes as assessed by international normalized ratio (INR) time-in-range. Physicians tend to under treat more than over treat. Finally, documentation of care is often inadequate. Condensed Abstract Oral anticoagulation management (routine medical care or anticoagulation clinic care) was retrospectively assessed in 5 countries using a uniform, structured assessment tool. Major management differences were detected, especially between anticoagulation clinic care and routine care. Documentation was often a problem in the latter setting. Less time in therapeutic INR range was noted in routine medical care. Findings suggest that anticoagulation clinic care may provide better outcomes as assessed by international normalized ratio (INR) time-in-range. Physicians tend to under treat more than over treat. Finally, documentation of care is often inadequate.

Complicações da terapia anticoagulante com warfarina em pacientes com doença vascular periférica: estudo coorte prospectivo

OBJETIVO: Estudar prospectivamente a freqüência de complicações em pacientes tratados com warfarina e acompanhados no Ambulatório de Anticoagulação da Faculdade de Medicina de Botucatu da Universidade Estadual Paulista. MÉTODOS: Pacientes sorteados entre os agendados para consulta de junho de 2002 a fevereiro de 2004. Na primeira consulta, foi preenchida ficha com dados de identificação e clínicos. A cada retorno, ou quando o paciente procurou o hospital por intercorrência, foi preenchida ficha com a razão normatizada internacional, existência e tipo de intercorrência e condições de uso dos antagonistas da vitamina K. RESULTADOS: Foram acompanhados 136 pacientes (61 homens e 75 mulheres), 99 com tromboembolismo venoso e 37 com doença arterial; 59 pacientes eram de Botucatu, e 77, de outros municípios. Foram registradas 30 intercorrências: nove não relacionadas ao uso da warfarina e 21 complicações hemorrágicas (38,8 por 100 pacientes/ano). Uma hematêmese foi considerada grave (1,9 por 100 pacientes/ano). As demais foram consideradas moderadas ou leves. Não houve óbitos, hemorragia intracraniana ou necrose cutânea. A única associação significante foi da freqüência de hemorragia com nível médio de razão normatizada internacional. CONCLUSÃO: Nossos resultados mostram a viabilidade desse tratamento em pacientes vasculares em nosso meio, mesmo em população de baixo nível socioeconômico, quando tratados em ambulatório especializado.

Guidelines for implementation of patient self-testing and patient self-management of oral anticoagulation. International consensus guidelines prepared by International Self-Monitoring Association for Oral Anticoagulation

AIMS

This document provides health care professionals involved in initiating and monitoring oral anticoagulation therapy with guidelines for the provision of safe and effective patient self-testing/patient self-management of oral anticoagulation.

METHODS AND RESULTS

The consensus group has critically reviewed the literature and compared the results of usual care (UC) vs. anticoagulation clinic and patient self-management/patient self-testing (PSM/PST). The education and training of patients for self-monitoring are described, together with the suitability of patients, the effect on quality of life and cost-effectiveness. The consensus agrees that patient self-testing and patient self-management are effective methods of monitoring oral anticoagulation therapy, providing outcomes at least as good as, and possibly better than, those achieved with an anticoagulation clinic. All patients must be appropriately selected and trained. Currently available self-testing/self-management devices give INR results which are comparable with those obtained in laboratory testing. The most frequent testing frequency is weekly but lower frequency of testing can be justified based on institutional or patient conditions.

CONCLUSIONS

The consensus agrees that there are several points in favour of PST/PSM, for example, a higher degree of medical safety, increased patient education, improved response to changes in lifestyle, increased independence for the patient and improved quality of life.

Major bleeding complications in a specialized anticoagulation service

Major bleeding complications were investigated in 2,460 patients with 3,684 patient-years of warfarin exposure from 2000 to 2003. The most common indications for anticoagulation were atrial fibrillation (30%), venous thromboembolic disease (28%), and mechanical heart valve prosthesis (15%). Eleven patients had 12 nonfatal major bleeding complications, with no fatal bleeds during the study. The incidence of major bleeding complications was 0.12%/year; there were 0.32 bleeds/100 patient-years of coverage. Of the 12 bleeding events, 5 (42%) were intracranial hemorrhages. The average hospitalization cost per patient was dollar 15,988, and the average length of hospitalization was 6.0 days.

Effect of a centralized clinical pharmacy anticoagulation service on the outcomes of anticoagulation therapy

CONTEXT

A growing body of reports has documented the ability of anticoagulation management services to help patients receiving warfarin therapy achieve better outcomes compared to the care provided by their personal physicians (ie, usual care).

OBJECTIVE

To compare clinical outcomes associated with anticoagulation therapy provided by a clinical pharmacy anticoagulation service (CPAS) to usual care.

DESIGN

Retrospective, observational cohort study, 6 months in duration.

SETTING

Large nonprofit, group-model health maintenance organization.

PATIENTS

A total of 6,645 patients receiving warfarin therapy were included in the final analyses (intervention group, 3,323 patients; control group, 3,322 patients).

INTERVENTION

Anticoagulation therapy for patients in the intervention group was managed by a centralized, telephonic CPAS. Therapy for patients in the control group was managed in the usual manner by their personal physicians.

MAIN OUTCOME MEASURES

The primary outcome was the occurrence of anticoagulation therapy-related complications. A secondary outcome was the proportion of time spent in the target international normalized ratio (INR) range for each patient. Cox proportional hazards regression analyses were used to examine the risk of complications in relation to the study group.

RESULTS

Patients in the CPAS were 39% less likely to experience an anticoagulation therapy-related complication than were patients in the control group (hazard ratio, 0.61; 95% confidence interval, 0.42 to 0.88). The number of patients needed to treat to prevent an anticoagulation therapy complication was 52. Additional analyses revealed that improved outcomes associated with CPAS were mediated largely through improved therapeutic INR control. Patients in the CPAS group spent 63.5% of study period days within their target INR range compared to 55.2% in the control group (p < 0.001).

CONCLUSIONS

A centralized, telephonic, pharmacist-managed anticoagulation monitoring service reduced the risk of anticoagulation therapy-related complications compared to that with usual care. The cumulative evidence supporting the superior care associated with implementing a pharmacist-managed anticoagulation monitoring service was sufficient to recommend widespread implementation.

Reduction in Warfarin Adverse Events Requiring Patient Hospitalization After Implementation of a Pharmacist-Managed Anticoagulation Service

STUDY OBJECTIVE

To compare adverse events related to anticoagulation in patients assigned to a pharmacist-managed anticoagulation service versus those receiving usual care.

DESIGN

Retrospective cohort analysis.

SETTING

Three hundred-bed community hospital.

PATIENTS

Four hundred twenty patients referred for anticoagulation management.

MEASUREMENTS AND MAIN RESULTS

Primary outcomes were the number of adverse events requiring patient hospitalization and the number of patients experiencing such events. Secondary outcomes were the median length of hospital stay/admission and the total number of hospital days. The total numbers of adverse events requiring hospitalization were three for the pharmacist-managed group and 14 for the usual care group (p=0.0153). The number of patients experiencing an adverse event requiring hospitalization was also lower for the pharmacist-managed group than for the usual care group (3 vs 10, p = 0.0962). The median length of hospital stay associated with each adverse event was not significantly different between the two groups; however, the total number of hospital days accrued was higher in the usual care group.

CONCLUSION

At 6 months after discontinuation of the pharmacist-managed anticoagulation service, the frequency of adverse events increased significantly, resulting in both an increased number of hospitalizations and an increased number of hospital days accrued. This coordinated anticoagulation program using a pharmacist reduced warfarin-related complications.

Monitoring oral anticoagulant therapy by telephone communication

The number of patients who need supervision during oral anticoagulant treatment is growing constantly. We have presently enrolled 156 patients who were referred to our anticoagulant clinic and who were taking sodium warfarin with target International Normalized Ratios (INR) of low (2-3), intermediate (2.5-3.5) and high (3-4) range. Patients performed the tests in laboratories situated in locations at their convenience and received further instructions from a specialist via telephone communication. A total of 8758 prothrombin times (5214, 1947 and 1597 tests for individuals in the low, intermediate and high range, respectively) were performed over the period of 3.16 +/- 2.6 years (range, 6 months-9.5 years) and reported to the specialist. It was found that in the aforementioned three groups of intensity 63.3, 57.0 and 47.7% of the INRs were within the target range, the respective percentages for the expanded (+/- 0.5) target INR being 92.8, 87.8 and 78.5%. The INTERDAY software was used to calculate the number and proportion of days within the target INR range, the respective results being 71.0, 64.0 and 51.6% and 96.2, 93.2, 86.4% for the expanded range. The number and percentage of bleeding and embolic complications' referrals to the emergency room and hospitalizations were similar to those reported for anticoagulant clinics in which patients have to actually pay a personal visit in order to receive instructions. Our study is significant in that it documents that trans-telephonic communication is feasible safe and cost-effective and that the clinical results are at least as good as those obtained by traditional consultation.

Thyroid, hemostasis and thrombosis

The aim of this paper is to briefly review some practical aspects of the relationship between thyroid function and several disorders of the hemostatic system in terms of bleeding and thrombosis. Thrombocytopenia, acquired hemophilia, hypercoagulability, cardioembolism and other biochemical coagulative and fibrinolytic abnormalities have been described in the past years both in hyper- and hypothyroidism. Since most of hyper- and hypothyroid conditions are the consequence of autoimmune thyroid disease (1), either deranged immune function, altered circulating thyroid hormone concentration, or both may concur in the pathogenesis of hemostatic disorders of potential crucial clinical impact. These aspects will be outlined and discussed in an attempt to give answers to some questions, often arising in the clinical approach.

The pharmacology and management of the vitamin K antagonists: the Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy

This article concerning the pharmacokinetics and pharmacodynamics of vitamin K antagonists (VKAs) is part of the Seventh American College of Chest Physicians Conference on Antithrombotic and Thrombolytic Therapy: Evidence-Based Guidelines. The article describes the antithrombotic effect of VKAs, the monitoring of anticoagulation intensity, the clinical applications of VKA therapy, and the optimal therapeutic range of VKAs, and provides specific management recommendations. Grade 1 recommendations are strong, and indicate that the benefits do, or do not, outweigh the risks, burdens, and costs. Grade 2 suggests that individual patient's values may lead to different choices (for a full understanding of the grading see Guyatt et al, CHEST 2004; 126:179S-187S). Among the key recommendations in this article are the following: for dosing of VKAs, we suggest the initiation of oral anticoagulation therapy with doses between 5 and 10 mg for the first 1 or 2 days for most individuals, with subsequent dosing based on the international normalized ratio (INR) response (Grade 2B). In the elderly and in other patient subgroups with an elevated bleeding risk, we suggest a starting dose at < or = 5 mg (Grade 2C). We recommend basing subsequent doses after the initial two or three doses on the results of INR monitoring (Grade 1C). The article also includes several specific recommendations for the management of patients with INRs above the therapeutic range and for patients requiring invasive procedures. For example, in patients with mild to moderately elevated INRs without major bleeding, we suggest that when vitamin K is to be given it be administered orally rather than subcutaneously (Grade 1A). For the management of patients with a low risk of thromboembolism, we suggest stopping warfarin therapy approximately 4 days before they undergo surgery (Grade 2C). For patients with a high risk of thromboembolism, we suggest stopping warfarin therapy approximately 4 days before surgery, to allow the INR to return to normal, and beginning therapy with full-dose unfractionated heparin or full-dose low-molecular-weight heparin as the INR falls (Grade 2C). In patients undergoing dental procedures, we suggest the use of tranexamic acid mouthwash (Grade 2B) or epsilon amino caproic acid mouthwash without interrupting anticoagulant therapy (Grade 2B) if there is a concern for local bleeding. For most patients who have a lupus inhibitor, we suggest a therapeutic target INR of 2.5 (range, 2.0 to 3.0) [Grade 2B]. In patients with recurrent thromboembolic events with a therapeutic INR or other additional risk factors, we suggest a target INR of 3.0 (range, 2.5 to 3.5) [Grade 2C]. As models of anticoagulation monitoring and management, we recommend that clinicians incorporate patient education, systematic INR testing, tracking, and follow-up, and good communication with patients concerning results and dosing decisions (Grade 1C+).

Frequency and Causes of Overanticoagulation and Underanticoagulation in Patients Treated with Warfarin

STUDY OBJECTIVE

To determine the frequency and the specific causes of over- and underanticoagulation in patients who receive warfarin therapy and are managed in an anticoagulation clinic.

DESIGN

Retrospective medical record review.

SETTING

University-affiliated anticoagulation clinic.

SUBJECTS

One thousand twenty patients (mean age 60.2 yrs [range 17-84 yrs]) receiving warfarin therapy during a 1-year index period.

MEASUREMENTS AND MAIN RESULTS

Of 12,897 international normalized ratios (INRs) evaluated, 6642 (51.5%) were within range and 8525 (66.1%) were within 0.2 INR units of range. Among 2881 out-of-range INRs below 2.0, the most common cause of underanticoagulation was indeterminate (856, 29.7%). Response to previous change in dosage (16.4%), noncompliance or dosing errors (16.3%), and initiation of therapy (15.6%) were other common causes of underanticoagulation. Changes in drugs, medical condition, dietary vitamin K intake, alcohol use, and activity level, in combination, accounted for only 15.1% of INRs below 2.0. Among 603 out-of-range INRs greater than 4.0, the most common cause of overanticoagulation was indeterminate (43.0%). Changes in medical condition (15.9%), response to a previous change in warfarin dosage (11.4%), and interactions with prescription drugs (7.3%) were other common causes of overanticoagulation. In combination, noncompliance or dosing errors, initiation of therapy, and change in dietary vitamin K intake accounted for only 15.4% of INR values above 4.0.

CONCLUSION

Out-of-range INRs are encountered frequently during warfarin therapy as a result of changes in numerous factors. Despite extensive evaluation of potential causes of over- and underanticoagulation, a specific cause commonly cannot be determined.