Initiation of warfarin therapy in elderly medical inpatients: a safe and accurate regimen

Prevention and treatment of venous thromboembolism in older people

The incidence of deep vein thrombosis (DVT) and pulmonary embolism (PE), collectively called venous thromboembolism (VTE), increases with age and has been reported to be higher in males. The annual incidence rates per 1000 for DVT and PE are 1.3 and 1.8, respectively, for people aged between 65 and 69 years, rising to 2.8 and 3.1, respectively, in those aged between 85 and 89 years. Older people are about eight times more likely to develop VTE in hospitals, nursing homes or other chronic care facilities than younger adults. About 1.7% develop PE within one year of treatment for DVT, whilst the one year recurrence rate for PE was 8.0%. About 3% of patients with DVT and 21% of those with PE die in hospital. One year mortality with DVT is 21% and that with PE is 39%.

Delivery of Optimized Anticoagulant Therapy: Consensus Statement from the Anticoagulation Forum

Objective:

To provide recommendations, policies, and procedures pertaining to the provision of optimized anticoagulation therapy designed to achieve desired clinical endpoints while minimizing the risk of anticoagulant-related adverse outcomes (principally bleeding and thrombosis).

Study Selection and Data Extraction:

Due to this document's scope, the medical literature was searched using a variety of strategies. When possible, recommendations are supported by available evidence; however, because this paper deals with processes and systems of care, high-quality evidence (eg, controlled trials) is unavailable. In these cases, recommendations represent the consensus opinion of all authors who constitute the Board of Directors of The Anticoagulation Forum, an organization dedicated to optimizing anticoagulation care. The Board is composed of physicians, pharmacists, and nurses with demonstrated expertise and significant collective experience in the management of patients receiving anticoagulation therapy.

Data Synthesis:

Recommendations for delivering optimized anticoagulation therapy were developed collaboratively by the authors and are summarized in 9 key areas: (I) Qualifications of Personnel, (II) Supervision, (III) Care Management and Coordination, (IV) Documentation. (V) Patient Education, (VI) Patient Selection and Assessment, (VII) Laboratory Monitoring, (VIII) Initiation and Stabilization of Warfarin Therapy, and (IX) Maintenance of Therapy. Recommendations are intended to inform the development of care systems containing elements with demonstrated benefit in improvement of anticoagulation therapy outcomes. Recommendations for delivering optimized anticoagulation therapy are intended to apply to all clinicians involved in the care of outpatients receiving anticoagulation therapy, regardless of the structure and setting in which that care is delivered.

Conclusions:

Anticoagulation therapy, although potentially life-saving, has inherent risks. Whether a patient is managed in a solo practice or a specialized anticoagulation management service, a systematic approach to the key elements outlined herein will reduce the likelihood of adverse events. The need for continued research to validate optimal practices for managing anticoagulation therapy is acknowledged.

Warfarin: what are the clinical implications of an out-of-range-therapeutic international normalized ratio?

Warfarin is a commonly used oral anticoagulant, and has well-established clinical efficacy. However, it has a narrow therapeutic window, and a mode-of-action affected by inter-individual differences and environmental factors. The effectiveness and safety of warfarin are closely related to maintenance of the international normalized ratio (INR) within therapeutic range. A supra-therapeutic INR puts patients at risk of bleeding, whereas a sub-therapeutic INR may not protect against thromboembolic complications. Research suggests a lack of anticoagulation control during warfarin therapy in different settings. Careful monitoring of the INR is essential, especially in geriatric or cancer populations who are at an increased risk of major hemorrhage. Warfarin is an effective treatment but optimization of the risk-benefit ratio is crucial in order to maximize efficacy and safety. Here, we will assess the extent to which INRs are an issue in the management of warfarin therapy, and the effect INRs may have on clinical outcomes.

A Pilot Study Comparing Two Methods for Warfarin Management in Hospitalized Patients

Background:

The potential for medication errors in a hospital setting has led to a change from daily order writing to scheduled dosing. It has also been hypothesized that scheduled dosing may decrease the pharmacists' workload in a community teaching hospital.

Objective:

To evaluate the impact that scheduled warfarin dosing would have on patient safety for a pharmacist-run anticoagulation service.

Methods:

Two methods for managing warfarin in a pharmacist-run anticoagulation service were compared. A retrospective chart review was conducted on a random sample of 80 inpatients who received warfarin either from January 2006 through December 2006 (control/daily dosing group) or from January 2007 through March 2007 (scheduled dosing group). Patients not managed by pharmacists or with a target international normalized ratio (INR) range other than 2 to 3 were excluded.

Results:

A total of 35 patients met inclusion criteria; 20 patients were in the daily order (control) group and 15 were in the scheduled dosing group. A total of 7 doses were omitted in the daily dosing group, compared with none in the scheduled dosing group. Of the 7, 4 were omissions in administration and 3 were order omissions. In the control group, the dose was changed 47 times (36%) compared with 23 times (28%) in the scheduled dosing group. In the daily dosing group, 28 (22%) INRs were within the therapeutic range and 97 (78%) were in the nontherapeutic range. In the scheduled dosing group, 24 (25%) INRs were within the therapeutic range and 72 (75%) were in the nontherapeutic range.

Conclusions:

Scheduled dosing eliminated omission-type medication errors and was more efficient than daily dosing. The process change decreased pharmacist workload without having a negative impact on patient care.

Genetic-based dosing in orthopedic patients beginning warfarin therapy

High variability in drug response and a narrow therapeutic index complicate warfarin therapy initiation. No existing algorithm provides recommendations on refining the initial warfarin dose based on genetic variables, clinical data, and international normalized ratio (INR) values. Our goal was to develop such an algorithm. We studied 92 patients undergoing primary or revision total hip or knee replacement. From each patient we collected a blood sample, clinical variables, current medications, and preoperative and postoperative laboratory values. We genotyped for polymorphisms in the cytochrome P450 (CYP) 2C9 and vitamin K epoxide reductase (VKORC1) genes. Using stepwise regression, we developed a model for refining the warfarin dose after the third warfarin dose. The algorithm explained four fifths of the variability in therapeutic dose (R(2)(adj) of 79%). Significant (P > .05) predictors were INR value after 3 doses (47% reduction per 0.25-unit rise), first warfarin dose (+7% per 1 mg), CYP2C9*3 and CYP2C9*2 genotype (-38% and -17% per allele), estimated blood loss (interacting with INR(3)), smoking status (+20% in current smokers), and VKORC1 (-11% per copy of haplotype A). If validated, this model should provide a safer, more effective process for initiating warfarin therapy.

The risks of warfarin use in the elderly

The use of warfarin in the elderly, particularly for stroke prevention in chronic atrial fibrillation, is steadily increasing. Although the benefits of warfarin are greatest in the elderly, so are the risk of adverse outcomes and the difficulties of anticoagulant management. Clinical systems need to improve to counter this therapeutic dilemma, as warfarin is likely to remain the only widely available oral anticoagulant for the foreseeable future. Aspects that require attention are: the careful selection of patients in whom treatment with warfarin is appropriate; initiating therapy in a low dose (e.g., 2.5-5 mg/day); thorough education of patients and carers; close monitoring, especially with any change in the patient's regular drug therapy; involving patients more in the management of their warfarin therapy (self-monitoring/management in suitable patients); and ongoing review of the appropriateness of therapy as circumstances change.

Warfarin pharmacology, clinical management, and evaluation of hemorrhagic risk for the elderly

Elderly patients as a group may present more of a challenge in managing warfarin therapy because of alterations in pharmacokinetics from other medications, diet, and disease; pharmacodynamic changes; increased risk for hemorrhage; and difficulty in monitoring. The elderly, however, may derive the most benefit from warfarin therapy for certain indications, such as the prevention of stroke in atrial fibrillation or recurrent events following deep venous thrombosis. Warfarin can be managed as effectively as in other populations with careful attention to these issues.

Therapy Insight: how changes in renal function with increasing age affect cardiovascular drug prescribing

Age is well recognized as a powerful prognostic factor in the setting of cardiovascular disease. With the aging of the US population, it is projected that more than 50 million people will be aged over 65 years by the year 2020. This growing elderly population has increased rates of morbidity and mortality owing to cardiovascular disease; however, proven therapies for prevention and treatment are often underused in older patients, largely because physicians perceive them as being frail and have limited understanding of age-related unique adverse and therapeutic effects. Advancing age is associated with a number of physiologic and pathophysiologic changes that impact the toxic effects, efficacy and dosing of many medications. Decreases in lean muscle mass affect the volume of distribution, and reductions in hepatic function affect the metabolism of many medications. Age-related reductions in renal function might have the most profound impact on the safety profile and dosing of medications in elderly patients. The strong association between renal and cardiovascular disease makes recognition of renal dysfunction and appropriate dose adjustment particularly important in elderly patients with cardiovascular disease. This article reviews current approaches to the estimation of renal function, and unique considerations related to prescribing medication for elderly patients with concomitant renal and cardiovascular disease.

Haemorrhagic Complications of Vitamin K Antagonists in the Elderly

In patients >75 years of age, the two main indications for oral anticoagulant therapy with vitamin K antagonists (VKAs) are treatment of venous thromboembolic disease and prevention of systemic embolism in patients with nonvalvular atrial fibrillation. In both indications, a target International Normalized Ratio of 2.5 (range 2.0-3.0) is recommended. Bleeding is the adverse effect feared by physicians that most limits the use of VKAs in older frail patients. In this paper, we discuss (i) the risk of VKA-related bleeding with advancing age; (ii) the severity of bleeding complications and particularly the risk of intracranial haemorrhage in older patients; (iii) the risk factors for bleeding related to patient characteristics; and (iv) the risk factors or determinants for bleeding related to treatment variables (warfarin induction and maintenance administration, instability of anticoagulation, poor compliance and patient's education level, and concomitant use of drugs). Avoiding over-anticoagulation and/or reducing periods of overdosing in the course of oral anticoagulant treatment with tailored monitoring may help to minimise the risk of bleeding in older patients.

[Use of anticoagulant treatments in the elderly]

PURPOSE

The frequency of pathologies requiring anticoagulant treatment (thromboembolic disease, atrial fibrillation) is particularly high in people above 75. The risk of haemorrhagic complications is also highest in this population of patients.Therefore, the assessment of the risk/benefit ratio of an anticoagulant treatment may overestimate the haemorrhagic risk and lead to the under-using of anticoagulant treatment in such pathologies as atrial fibrillation. CURRENT KNOWLEDGE AND KEY-POINTS: However, the use of "classical" anticoagulant treatments such as non-fractionated heparin, low-molecular-weight heparin, and above all, antivitamin K requires special precautions. Several hemorrhagic risk factors are well known and should be spotted out. Finally, the risk/benefit ratio of an anticoagulant treatment in the elderly patients must rely on a comprehensive geriatric assessment.

PROSPECTS AND PROJECTS

In the era of "new anticoagulant treatments", and particularly of per-os antithrombin, it may seem anachronous to issue a statement over the use of "classical anticoagulant treatments", but in the present state of knowledge, the evaluation of these new molecules is not sufficient in the elderly population of patients.