Improving the quality of anticoagulation of patients with atrial fibrillation in managed care organizations: results of the managing anticoagulation services trial

Frequency of Concurrent Use of Warfarin with Potentially Interacting Drugs

STUDY OBJECTIVE

To determine the rates of concomitant use of drugs known to interact with warfarin by increasing the prothrombin time expressed as the international normalized ratio (INR), decreasing the INR, or increasing bleeding risk without apparent changes in INR in a cohort of patients receiving long-term warfarin therapy.

DESIGN

Retrospective, longitudinal cohort study.

SETTING

Large pharmacy benefits manager database.

PATIENTS

A total of 134,833 patients who were prescribed long-term warfarin from June 1, 1999-May 31, 2000.

MEASUREMENTS AND MAIN RESULTS

Longitudinal pharmacy claims from the pharmacy benefits manager database were reviewed to identify coprescription of warfarin and drugs associated with significant interactions with warfarin. Of the 134,833 patients receiving long-term warfarin therapy, 109,998 (81.6%) were prescribed a concurrent prescription for at least one potentially interacting drug, including 87,346 (64.8%) who were prescribed one or more concomitant drugs associated with interactions known to increase the INR. Acetaminophen-containing products, prescribed for 22.7% of patients receiving concomitant prescriptions, and thyroid hormones, prescribed for 17.5%, were the most commonly prescribed concurrent drugs associated with an increased INR response. The most frequently prescribed interacting agents associated with a decreased INR response were trazodone (2.2%) and carbamazepine (1.1%). The most commonly prescribed agents independently associated with increased bleeding risk were cyclooxygenase-2 inhibitors.

CONCLUSION

Many patients receiving warfarin therapy are treated with concomitant drugs that may interact with the warfarin. The high percentage of patients taking drugs that may increase INR or bleeding risk is a reminder that bleeding events are a likely adverse outcome of combining drugs that interact with warfarin. Careful warfarin management is necessary to avoid adverse events associated with drug interactions.

Warfarin Anticoagulation and Outcomes in Patients With Atrial Fibrillation

OBJECTIVE

To examine the relationship between international normalized ratio (INR) and outcomes (major bleeding events and strokes) in patients with atrial fibrillation (AF) receiving anticoagulation with warfarin.

METHODS

A systematic review and metaanalysis of studies published in the English language between January 1, 1985, and October 30, 2002, was performed. MEDLINE (PubMed), Current Contents, and relevant reference lists were searched. Studies enrolling patients with nonvalvular AF receiving warfarin anticoagulation were eligible for inclusion if they reported stroke and/or major bleeding events in relation to INR, or time spent in therapeutic range. The risk of bleeds in overanticoagulated patients (INR > 3) and the risk of strokes in underanticoagulated patients (INR < 2) were assessed.

RESULTS

Twenty-one studies (6,248 patients) met all inclusion criteria. Of the 21 studies, a target conventional INR of 2 to 3 was used in 9 studies. An INR < 2, compared with an INR > or = 2, was associated with an odds ratio (OR) for ischemic events of 5.07 (95% confidence interval [CI], 2.92 to 8.80). An INR > 3, compared with an INR < or = 3, was associated with an OR for bleeding events of 3.21 (95% CI, 1.24 to 8.28). On average, in the four studies with a target INR range of 2 to 3, patients with AF receiving warfarin spent 61% of time within, 13% of time above, and 26% below the therapeutic range.

CONCLUSION

Available evidence indicates that in patients with nonvalvular AF, the risk of ischemic stroke with insufficient warfarin anticoagulation (INR < 2), and the risk of bleeding events with overanticoagulation (INR > 3) are significantly higher relative to patients with AF maintained within the recommended INR of 2 to 3. However, the published data are sparse, heterogeneous, and primarily reported from clinical trials. More studies evaluating clinical outcomes in relation to INR are needed, especially in a real-world setting.

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+).

Hemorrhagic Complications of Anticoagulant Treatment

This chapter about hemorrhagic complications of anticoagulant treatment is part of the seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy: Evidence Based Guidelines. Bleeding is the major complication of anticoagulant therapy. The criteria for defining the severity of bleeding varies considerably between studies, accounting in part for the variation in the rates of bleeding reported. The major determinants of vitamin K antagonist-induced bleeding are the intensity of the anticoagulant effect, underlying patient characteristics, and the length of therapy. There is good evidence that vitamin K antagonist therapy, targeted international normalized ratio (INR) of 2.5 (range, 2.0 to 3.0), is associated with a lower risk of bleeding than therapy targeted at an INR > 3.0. The risk of bleeding associated with IV unfractionated heparin (UFH) in patients with acute venous thromboembolism (VTE) is < 3% in recent trials. This bleeding risk may increase with increasing heparin dosages and age (> 70 years). Low molecular weight heparin (LMWH) is associated with less major bleeding compared with UFH in acute VTE. UFH and LMWH are not associated with an increase in major bleeding in ischemic coronary syndromes, but are associated with an increase in major bleeding in ischemic stroke. Information on bleeding associated with the newer generation of antithrombotic agents has begun to emerge. In terms of treatment decision making for anticoagulant therapy, bleeding risk cannot be considered alone, ie, the potential decrease in thromboembolism must be balanced against the potential increased bleeding risk.

Ventilation of patients with acute lung injury and acute respiratory distress syndrome: has new evidence changed clinical practice?

OBJECTIVES

A recent randomized trial of mechanical ventilation in acute lung injury (ALI)/adult respiratory distress syndrome (ARDS) demonstrated a 22% relative reduction in mortality rate using 6 mL/kg predicted body weight tidal volume vs. 12 mL/kg predicted body weight tidal volume. We determined whether publication of these findings changed clinical practice.

DESIGN

Retrospective cohort, 12 months before (Pre) and 12 months after publication (Post) of a randomized trial supporting the use of a 6 mL/kg predicted body weight tidal volume strategy.

SETTING

Three tertiary care hospitals in northern New England.

PATIENTS

From a sample of 943 patients receiving prolonged mechanical ventilation between 1998 and 1999 (Pre) and between 2000 and 2001 (Post), 300 patients meeting the American-European Consensus Conference definition of ALI or ARDS were selected for analysis.

INTERVENTIONS

The tidal volume, tidal volume/kg predicted body weight, and proportion receiving tidal volume/kg > or =6 mL/kg and < or =12 mL/kg predicted body weight were recorded at noon the first day after the diagnosis of ALI or ARDS was established.

MEASUREMENTS AND MAIN RESULTS

Pre and Post mean tidal volume (+/- sd) size and tidal volume size/kg predicted body weight were 759 +/- 158 mL (median 750 mL) vs. 639 +/- 138 mL (median 600 mL, p <.001) and 12.3 +/- 2.7 mL/kg (median 11.7 mL/kg) vs. 10.6 +/- 2.4 mL/kg (median 10.7 mL/kg, p <.001) respectively. Pre and Post plateau pressures and peak airway pressures were similar.

CONCLUSION

Publication of a trial demonstrating large mortality reductions using small tidal volume was associated with significant reductions in tidal volume delivered to patients with ALI/ARDS. However, wide variation in practice persists, and the proportion of patients receiving tidal volumes within recommended limits (< or =8 mL/kg) remains modest.

The increasing need for anticoagulant therapy to prevent stroke in patients with atrial fibrillation

Ischemic stroke, a major complication of atrial fibrillation (AF), is believed to result from atrial thrombus formation caused by ineffective atrial contraction. Oral anticoagulant therapy effectively reduces the risk of ischemic stroke in patients with AF; this therapy is recommended for patients with any frequency or duration of AF and other risk factors for stroke, such as increased age (>75 years), hypertension, prior stroke, left ventricular dysfunction, diabetes, or heart failure. Recently published data comparing rate-control and rhythm-control strategies in AF emphasized the importance of maintaining an international normalized ratio higher than 2.0 during warfarin therapy and the need for continuing anticoagulant therapy to prevent stroke in high-risk patients, even if the strategy is rhythm control. Hemorrhagic complications can be minimized by stringent control of the international normalized ratio (particularly in elderly patients) and appropriate therapy for comorbidities such as hypertension, gastric ulcer, and early-stage cancers. Undertreatment of patients with AF is a continuing problem, particularly in the elderly population. Patients perceived as likely to be noncompliant, such as the functionally impaired, are less likely to receive warfarin therapy. However, stroke prevention with anticoagulants is cost-effective and improves quality of life, despite the challenges of maintaining appropriate anticoagulation with monitoring and warfarin dose titration. New medications in development with more predictable dosing and fewer drug-drug interactions may reduce the complexities of achieving optimal anticoagulation and increase the practicality of long-term anticoagulant therapy for patients with AF at risk of stroke.

Implications for Nursing Care of Patients With Atrial Fibrillation

Atrial fibrillation is the most common sustained cardiac dysrhythmia treated in North America and Europe. As such, it is one of the current epidemics in cardiovascular disease. Findings from the AFFIRM (Atrial Fibrillation Follow-up: Investigation of Rhythm Management) and RACE (RAte Control versus Electrical cardioversion for persistent atrial fibrillation) clinical trials are presented and the current evidence for the management of atrial fibrillation using anticoagulation, rate-control, and rhythm-control strategies is outlined. Implications for nurses are discussed including physiologic and psychosocial interventions.

Anticoagulation for atrial fibrillation

For over two decades, valuable insights have been accumulated from epidemiologic studies and randomized trials about the risks for and prevention of AF-related stroke. AF substantially raises the risk of stroke, most likely through an atrio-embolic mechanism. Warfarin and other members of its class of oral anticoagulants targeted at an INR of 2.5 can abrogate the risk of stroke attributable to AF effectively and fairly safely. High-quality management of anticoagulation can be achieved in usual clinical care. These insights have important implications for the care of individual patients and more generally for public health. Future research is needed to specify the risk of stroke and hemorrhage among patients with AF better, particularly among older individuals, to optimize use of antithrombotic agents, and to define the role of recently developed antithrombotic drugs and invasive nondrug approaches.

Physician compliance with outpatient oral anticoagulant guidelines in Auvergne, France

OBJECTIVE

Oral anticoagulants (OA) are commonly used, but they can lead to severe bleeding. We studied the indications and monitoring of OA in patients treated by general practitioners.

DESIGN

Retrospective cross-sectional study.

SETTING

Primary care.

PATIENTS

Four hundred thirty-eight randomly selected patients of a population of 2,452 patients treated with OA were studied.

INTERVENTIONS

We compared the indications for OA as reported by general practitioners with indications as defined according to recent guidelines.

MAIN RESULTS

Twenty-five percent of patients should not have been treated with OA. Inappropriate indications (13% of patients) were atrial fibrillation without risk factor (3.9%), prior uncomplicated myocardial infarction (2.7%), peripheral arterial disease (2.7%), superficial thrombophlebitis (2.3%), and atherothrombotic ischemic stroke (1.6%). For 12% of patients, the duration of OA was too long (venous thromboembolism without permanent risk factor in 10%). Frequency of International Normalized Ratio (INR) measurement was insufficient for 14% of patients and target INR was not achieved in 31%.

CONCLUSIONS

Our study demonstrated that clinicians' adherence to recommendations regarding indications for OA and management of this treatment should be improved. Implementation of anticoagulation clinics is probably needed.

Incidence and preventability of adverse drug events among older persons in the ambulatory setting

CONTEXT

Adverse drug events, especially those that may be preventable, are among the most serious concerns about medication use in older persons cared for in the ambulatory clinical setting.

OBJECTIVE

To assess the incidence and preventability of adverse drug events among older persons in the ambulatory clinical setting.

DESIGN, SETTING, AND PATIENTS

Cohort study of all Medicare enrollees (30 397 person-years of observation) cared for by a multispecialty group practice during a 12-month study period (July 1, 1999, through June 30, 2000), in which possible drug-related incidents occurring in the ambulatory clinical setting were detected using multiple methods, including reports from health care providers; review of hospital discharge summaries; review of emergency department notes; computer-generated signals; automated free-text review of electronic clinic notes; and review of administrative incident reports concerning medication errors.

MAIN OUTCOME MEASURES

Number of adverse drug events, severity of the events (classified as significant, serious, life-threatening, or fatal), and whether the events were preventable.

RESULTS

There were 1523 identified adverse drug events, of which 27.6% (421) were considered preventable. The overall rate of adverse drug events was 50.1 per 1000 person-years, with a rate of 13.8 preventable adverse drug events per 1000 person-years. Of the adverse drug events, 578 (38.0%) were categorized as serious, life-threatening, or fatal; 244 (42.2%) of these more severe events were deemed preventable compared with 177 (18.7%) of the 945 significant adverse drug events. Errors associated with preventable adverse drug events occurred most often at the stages of prescribing (n = 246, 58.4%) and monitoring (n = 256, 60.8%), and errors involving patient adherence (n = 89, 21.1%) also were common. Cardiovascular medications (24.5%), followed by diuretics (22.1%), nonopioid analgesics (15.4%), hypoglycemics (10.9%), and anticoagulants (10.2%) were the most common medication categories associated with preventable adverse drug events. Electrolyte/renal (26.6%), gastrointestinal tract (21.1%), hemorrhagic (15.9%), metabolic/endocrine (13.8%), and neuropsychiatric (8.6%) events were the most common types of preventable adverse drug events.

CONCLUSIONS

Adverse drug events are common and often preventable among older persons in the ambulatory clinical setting. More serious adverse drug events are more likely to be preventable. Prevention strategies should target the prescribing and monitoring stages of pharmaceutical care. Interventions focused on improving patient adherence with prescribed regimens and monitoring of prescribed medications also may be beneficial.

Which approach to anticoagulation management is best? Illustration of an interactive mathematical model to support informed decision making

BACKGROUND

Among patients with atrial fibrillation or mechanical heart valves, determining the best approach to oral anticoagulation largely depends on comparing the costs of anticoagulation management with the costs of events (thromboembolism and bleeding) averted. The Anticoagulation Management Event/Cost Model (ACME) is an interactive mathematical model intended to help clarify these trade-offs.

METHODS

The ACME is a series of linked, nested spreadsheets. At the least detailed level, the user specifies the percentage of patients falling into various management strategies (no anticoagulation, usual physician care, anticoagulation service, patient self-testing/self-management), and the ACME estimates event rates and costs. At more detailed levels the ACME performs a series of weighted average calculations combining, for example, utilization times unit price. Cost categories are divided into event-related and management-related costs (costs of management, testing, and medication).

RESULTS

Regardless of how anticoagulation is subsequently managed, perhaps the greatest benefit is obtained by moving patients who are not currently receiving anticoagulation onto warfarin. Additional benefits can be obtained by eliminating outliers (extremely high or extremely low anticoagulation levels). If changing to a more intensive approach also serves to reduce the tendency for physicians to prescribe anticoagulate below the optimal range, additional savings can be anticipated. The cost calculation typically involves a trade-off between increased up-front costs of anticoagulation management versus greater down-line savings associated with a decreased number of events. To assess the quality of anticoagulation within a given organization, it is critical to know the distribution of clotting levels for the population under anticoagulation.

CONCLUSIONS

Interactive mathematical models, if sufficiently well documented, can be helpful in clarifying decisions regarding costs and benefits of various methods of anticoagulation.

Physician attitudes concerning anticoagulation services in the long-term care setting

OBJECTIVES

There is little experience in the use of specialized anticoagulation services in the long-term care setting. Even less is known about physician attitudes regarding these services. To examine this issue, we surveyed physicians caring for nursing home residents in a sample of long-term care facilities located in Connecticut.

METHODS

We surveyed physicians providing care to nursing home residents of a convenience sample of 21 Connecticut nursing homes. (These facilities had participated in a quality assessment and improvement project on preventing strokes in nursing home residents with atrial fibrillation.) Physicians were requested to complete a structured questionnaire about the challenges to managing nursing home residents on warfarin therapy and preferences concerning the use of an anticoagulation service to manage warfarin therapy in this setting.

RESULTS

A total of 245 physicians were asked to participate in the survey, and 114 (47%) responded between November 5, 1999 and January 14, 2000. Of the 114 physicians who returned the survey, 91 reported that they currently cared for residents in long-term care facilities and thus completed the questionnaire. The majority of respondents agreed or strongly agreed that an anticoagulation service would reduce the workload on physicians, increase the costs of care for nursing home residents on warfarin, and increase the percent of time that nursing home residents on warfarin are maintained in the target therapeutic range. Most physicians disagreed or strongly disagreed with statements suggesting an anticoagulation service would decrease the costs of care for nursing home residents on warfarin, reduce the liability of the prescribing physician, interfere with their ability to care for patients on warfarin therapy, and reduce the risk of warfarin-related bleeding. Forty-five percent of respondents agreed with a statement that an anticoagulation service would intrude on physician decision-making. Only about half (53%) of the respondents indicated that they would or might utilize an anticoagulation service for managing their long-term care patients on warfarin.

CONCLUSIONS

Use of a specialized anticoagulation service to manage warfarin therapy is a systems-level approach with the potential to improve the effectiveness and safety of this treatment. Physician skepticism regarding the usefulness of anticoagulation services will only be overcome by subjecting this approach to rigorous evaluation and by assuring physicians of their ongoing involvement in decision-making regarding warfarin therapy in their patients.