Assessment of an age-adjusted warfarin initiation protocol

Chinese stroke patients with atrial fibrillation used Robert's age-adjusted warfarin loading protocol obtained good INR results within therapeutic range

To assess whether Roberts' age-adjusted warfarin loading protocol is effective in Chinese patients and whether the SAMeTT2R2 score can predict international normalized ratio (INR) control. Roberts' protocol for warfarin titration was applied to patients with non-valvular atrial fibrillation (NVAF) complicated with ischemic stroke at the Department of Neurology between 2014 and 2019. Clinical and sociodemographic variables were recorded. A minimum of 1-year follow-up was used to calculate the time in therapeutic range (TTR) of the INR. A total of 94 acute ischemic stroke patients with NVAF were included in the study. Seventy-seven (81.9%) of the patients had attained stable INR (2.0-3.0) at the fifth dose, and 90.0% of the patients had achieved stable INR on the ninth day. Seventeen (18.1%) of the patients had an INR > 4 during dose-adjustment period. Patients with INR > 4 had significantly lower body weight (53.8 vs. 63.1 kg, P = 0.014), lower rate of achievement of stable INR (35.3% vs. 92.2%, P = 0.000), and lower rate of TTR ≥ 65% (23.5% vs. 70.1%, P = 0.001), but with no significant increase in bleeding risk. A total of 89 patients underwent long-term INR follow-up, of which 58 (65.2%) patients achieved TTR ≥ 65%. Patients with poor TTR had significantly lower body weight (56.3 vs. 63.7 kg, P = 0.020) and lower rate of stable INR achievement (64.5% vs. 89.7%, P = 0.002). All 94 patients had SAMeTT2R2 score ≥ 2. There was no linear association between SAMeTT2R2 score and the rate of TTR ≥ 65% (Ptrend = 0.095). Chinese ischemic stroke patients with NVAF on warfarin can safely and quickly achieve therapeutic INR using Roberts' age-adjusted protocol and can obtain a good TTR. Lower body weight may be a predictor of poor TTR and INR > 4. Patients who have not attained stable INR after adjusting the dose five times are at high risk for poor TTR. SAMeTT2R2 score may not predict TTR in Chinese ischemic stroke patients with NVAF.

Fibrinogen, Coagulation, and Ageing

The World Health Organization estimates that the world's population over 60 years of age will nearly double in the next 30 years. This change imposes increasing demands on health and social services with increased disease burden in older people, hereafter defined as people aged 60 years or more. An older population will have a greater incidence of cardiovascular disease partly due to higher levels of blood fibrinogen, increased levels of some coagulation factors, and increased platelet activity. These factors lead to a hypercoagulable state which can alter haemostasis, causing an imbalance in appropriate coagulation, which plays a crucial role in the development of cardiovascular diseases. These changes in haemostasis are not only affected by age but also by gender and the effects of hormones, or lack thereof in menopause for older females, ethnicity, other comorbidities, medication interactions, and overall health as we age. Another confounding factor is how we measure fibrinogen and coagulation through laboratory and point-of-care testing and how our decision-making on disease and treatment (including anticoagulation) is managed. It is known throughout life that in normal healthy individuals the levels of fibrinogen and coagulation factors change, however, reference intervals to guide diagnosis and management are based on only two life stages, paediatric, and adult ranges. There are no specific diagnostic guidelines based on reference intervals for an older population. How ageing relates to alterations in haemostasis and the impact of the disease will be discussed in this chapter. Along with the effect of anticoagulation, laboratory testing of fibrinogen and coagulation, future directions, and implications will be presented.

Comparison of Warfarin Initiation at 3 mg Versus 5 mg for Anticoagulation of Patients with Mechanical Mitral Valve Replacement Surgery: A Prospective Randomized Trial

Background

The increased warfarin sensitivity observed after mechanical mitral valve replacement (MVR) operations dictates clinical discretion in warfarin dose initiation. Evidence is still lacking with regard to anticoagulation management of MVR patients.

Objective

This study aimed to compare initiating warfarin at the recommended dosing regimen versus empirically lowered doses intended to account for the variation in warfarin sensitivity.

Methods

A prospective, single-blind, randomized, comparative study was conducted in postoperative MVR patients. Patients were randomly assigned to either the 5 mg group (n = 25) or the 3 mg group (n = 25) and were initiated on a 5 or 3 mg warfarin dose, respectively. Time to target international normalized ratio (INR), time in therapeutic range, occurrence of bleeding/thromboembolic events, and cost of bridging with enoxaparin were assessed for both groups.

Results

Target INR was achieved earlier in the 5 mg group than in the 3 mg group (p = 0.033), with a mean ± SD of 5.3 ± 2.0 and 6.6 ± 2.0, respectively (95% confidence interval of the mean difference 1.022–1.890). Bleeding events did not differ significantly between the two groups. The cost of enoxaparin consumption per patient was significantly higher in the 3 mg group versus the 5 mg group (p = 0.002).

Conclusions

The initiation of warfarin at a 5 mg dose in MVR patients was more efficacious than the 3 mg dose in terms of time to reach the target INR. Moreover, the cost of enoxaparin bridging was significantly reduced with a 5 mg warfarin initiation dose. Bleeding events were comparable.

ClinicalTrials.gov ID

NCT04235569, 22 January 2020.

AM Versus PM Postoperative Administration of Warfarin With a Mechanical Mitral Valve

Background: Currently, there are no guidelines regarding the optimal daily timing of inpatient warfarin administration. Objective: The purpose of this study was to determine whether dosing warfarin in the morning will have a significant impact on therapeutic international normalized ratio (INR) achievement compared with evening administration in mechanical mitral valve patients initiated on warfarin following cardiac surgery. Methods: This was a single-center, pre- and post-retrospective cohort conducted between 2014 and 2018. One-hundred fifty-four adult patients who underwent a mechanical mitral valve replacement or alternative cardiac surgery with a history of a mechanical mitral valve were enrolled. The primary outcome was achievement of therapeutic INR at any time point after initiation of warfarin. Pre-intervention administration timing was 6 pm and post-intervention timing was 10 am. Results: Baseline characteristics including age, sex, and race were similar between the 2 groups (P = NS for each characteristic). Therapeutic INR achievement was significantly improved at all time points following 10 am warfarin administration compared with 6 pm (hazard ratio = 1.69; P = .005). Mean time-to-therapeutic INR was 7.37 days in the post-intervention group and 8.39 days in the pre-intervention group (P = .073). There were no significant differences in INR >4, bleeding, or thrombotic complications between groups. Conclusion and Relevance: This retrospective analysis suggests that there may be a postoperative benefit in therapeutic INR achievement in mechanical valve patients when dosing warfarin in the morning compared with evening administration. Large-scale studies should be conducted to further elucidate the potential benefit across more heterogeneous populations.

Efficacy of protocol-based pharmacotherapy management on anticoagulation with warfarin for patients with cardiovascular surgery

WHAT IS KNOWN AND OBJECTIVE

Anticoagulation therapy with warfarin requires periodic monitoring of prothrombin time-international normalized ratio (PT-INR) and adequate dose adjustments based on the data to minimize the risk of bleeding and thromboembolic events. In our hospital, we have developed protocol-based pharmaceutical care, which we called protocol-based pharmacotherapy management (PBPM), for warfarin therapy. The protocol requires pharmacists to manage timing of blood sampling for measuring PT-INR and warfarin dosage determination based on an algorithm. This study evaluated the efficacy of PBPM in warfarin therapy by comparing to conventional pharmaceutical care.

METHODS

From October 2013 to June 2015, a total of 134 hospitalized patients who underwent cardiovascular surgeries received post-operative warfarin therapy. The early series of patients received warfarin therapy as the conventional care (control group, n=77), whereas the latter received warfarin therapy based on the PBPM (PBPM group, n=68). These patients formed the cohort of the present study and were retrospectively analysed.

RESULTS

The indications for warfarin included aortic valve replacement (n=56), mitral valve replacement (n=4), mitral valve plasty (n=22) and atrial fibrillation (n=29). There were no differences in patients' characteristics between both groups. The percentage time in therapeutic range in the first 10 days was significantly higher in the PBPM group (47.1%) than that in the control group (34.4%, P<.005). The average time to reach the steady state was significantly (P<.005) shorter in the PBPM group compared to the control group (7.3 vs 8.6 days).

WHAT IS NEW AND CONCLUSION

Warfarin therapy based on our novel PBPM was clinically safe and resulted in significantly better anticoagulation control compared to conventional care.

Implications of an inpatient warfarin dosing nomogram on safety outcomes post-discharge

Many hospitals have implemented warfarin dosing nomograms to improve patient safety. To our knowledge, no study has assessed the impact inpatient warfarin initiation has in both medical and surgical patients, on safety outcomes post discharge. To evaluate the impact of a suggested institutional nomogram for the initiation of warfarin, the primary endpoint was the incidence of bleeding throughout follow up. Secondary endpoints included the composite of INR changes ≥0.5/day and INR >4. Patients were followed for a period of 2 weeks post-discharge. The composite endpoint was evaluated for an effect on reaching therapeutic INR, time to reach therapeutic INR, and bleeding events throughout follow up. A single center retrospective study comparing the safety of adherence vs. non-adherence to a warfarin nomogram. A total of 206 patients were included, 73 patients in the nomogram adherence vs. 133 in the nonadherence arm. There was no difference in the proportion of patients who bled throughout the follow up period, adherence 9.6% vs. nonadherence to the nomogram 13.5%, p = 0.407. There was however a statistical difference in the mean total number of bleeding events, 0.096 (7/73) in the adherence vs. 0.158 (21/133) in the non-adherence arm, p = 0.022. There was also no difference in the composite endpoint, 19.2% in the adherence vs. 28.6% in the non-adherence arm p = 0.180. A positive correlation between the inpatient composite and risk of bleeding throughout follow up was noted. The findings of this study support adherence to the nomogram as opposed to non-adherence.

Comparing Usual Care With a Warfarin Initiation Protocol After Mechanical Heart Valve Replacement

BACKGROUND

The immediate postoperative warfarin sensitivity for patients receiving heart valve prostheses is increased. Established warfarin initiation protocols may lack clinical applicability, resulting in dosing based on clinical judgment.

OBJECTIVE

To compare current practice for warfarin initiation with a known warfarin initiation protocol, with doses proportionally reduced to account for the increased postoperative sensitivity.

METHODS

We compared the Mechanical Heart Valve Warfarin Initiation Protocol (Protocol group) with current practice (clinical judgment-Empirical group) for patients receiving mechanical heart valves in an observational before-and-after format. End points were the time to achieve a stable therapeutic international normalized ratio (INR), doses held in the first 6 days, and overanticoagulation in the first 6 days.

RESULTS

The Protocol group (n = 37) achieved a stable INR more rapidly than the Empirical group (n = 77; median times 5.1 and 8.7 days, respectively; P = 0.002). Multivariable analysis indicated that the Protocol group (hazard ratio [HR] = 2.22; P = 0.005) and men (HR = 1.76; P = 0.043) more rapidly achieved a stable therapeutic INR. Age, serum albumin, amiodarone, presence of severe heart failure, and surgery type had no impact. Protocol patients had fewer doses held (1.1% vs 10.1%, P < 0.001) and no difference in overanticoagulation (2.7% vs 9.1%, P = 0.27).

CONCLUSION

The Mechanical Heart Valve Warfarin Initiation Protocol provided a reliable approach to initiating warfarin in patients receiving mechanical aortic or mitral valves.

Analysis of the first therapeutic-target-achieving time of warfarin therapy and associated factors in patients with pulmonary embolism

The present study aimed to investigate the factors affecting the first therapeutic-target-achieving (TTA) time of warfarin therapy in patients with acute pulmonary embolism (PTE). Between January 2008 and June 2013, patients with PTE confirmed by transpulmonary arterial enhanced computed tomographic pulmonary angiography or pulmonary ventilation perfusion scanning were included in the present study. Data collected included demographic information, history of tobacco and alcohol intake, basic diseases (stable and unstable hypertension, diabetes, heart failure, cancer/cerebral infarction, old myocardial infarction and atrial fibrillation), liver and kidney function, the haemoglobin and platelet count of the blood, international normalized ratio monitoring, warfarin dosage adjustment and medication combinations. Dynamic changes in international normalized ratio, anticoagulant efficacy, and adverse events within 90 days were monitored and analyzed. Univariate analysis demonstrated that the following factors affect the first TTA time: Initial dose, body mass index (BMI), liver function, heart failure, and the administration of levofloxacin, cephalosporins, and blood circulation-activating drugs. Logistic regression analysis revealed that the following were independent factors of the first TTA time: Initial dose, BMI, liver function, heart failure and levofloxacin. Therefore, the results of the present study demonstrated that various factors may affect the first TTA time of warfarin therapy, including the initial dose, BMI, liver function, heart function and concomitant medication.

How to manage warfarin therapy

Long-term treatment with warfarin is recommended for patients with atrial fibrillation at risk of stroke and those with recurrent venous thrombosis or prosthetic heart valves. Patient education before commencing warfarin - regarding signs and symptoms of bleeding, the impact of diet, potential drug interactions and the actions to take if a dose is missed - is pivotal to successful use. Scoring systems such as the CHADS2 score are used to determine if patients with atrial fibrillation are suitable for warfarin treatment. To rapidly achieve stable anticoagulation, use an age-adjusted protocol for starting warfarin. Regular monitoring of the anticoagulant effect is required. Evidence suggests that patients who self-monitor using point-of-care testing have better outcomes than other patients.

Stroke prevention in atrial fibrillation in heart failure

Heart failure and atrial fibrillation are major problems of modern cardiology with important clinical, prognostic, and socioeconomic implications. The risks are high morbidity, impaired quality of life, poor outcome, and increased risk of stroke. Oral anticoagulation with vitamin K antagonists or novel licensed medicines should be considered unless contraindicated. Possible benefits of sinus rhythm maintenance are not entirely clear and need to be explored further. Relatively scarce data are available on stroke prevention in atrial fibrillation in heart failure with preserved ejection fraction; this requires further research.

Comparison of initial loading doses of 5 mg and 10 mg for warfarin therapy

CONTEXT: The question of what is the best loading dosage of warfarin when starting anticoagulant treatment has been under discussion for ten years. We were unable to find any comparative studies of these characteristics conducted here in Brazil. OBJECTIVE: To compare the safety and efficacy of two initial warfarin dosage regimens for anticoagulant treatment. METHODS: One-hundred and ten consecutive patients of both sexes, with indications for anticoagulation because of venous or arterial thromboembolism, were analyzed prospectively. During the first 3 days of treatment, these patients were given adequate heparin to keep aPTT (activated partial thromboplastin time) between 1.5 and 2.5, plus 5 mg of warfarin. From the fourth day onwards, their warfarin doses were adjusted using International Normalized Ratios (INR; target range: 2 to 3). This prospective cohort was compared with a historical series of 110 patients had been given 10 mg of warfarin on the first 2 days and 5 mg on the third day with adjustments based on INR thereafter. Outcomes analyzed were as follows: recurrence of thromboembolism, bleeding events and time taken to enter the therapeutic range. RESULTS: Efficacy, safety and length of hospital stay were similar in both samples. The sample that were given 10 mg entered the therapeutic range earlier (means: 4.5 days vs. 5.8 days), were on lower doses at discharge and had better therapeutic indicators at the first return appointment. CONCLUSIONS: The 10 mg dosage regimen took less time to attain the therapeutic range and was associated with lower warfarin doses at discharge and better INR at first out-patients follow-up visit.

Warfarin Dosing and Body Mass Index

Background: Warfarin is still the most commonly used anticoagulant for the treatment of venous thromboembolism and other hypercoagulable states. Warfarin metabolism is affected by multiple factors, including diet, medications, and individual patient characteristics. As both underdosing and overdosing can increase risks to patients, several studies have attempted to develop dosing protocols. However, few have investigated how patient weight and body mass index (BMI) affect warfarin dosing. Objective: The objective of this study was to determine the association between BMI and the total weekly dose (TWD) of warfarin. Methods: In this retrospective study, we identified patients taking warfarin who had an international normalized ratio (INR) within the therapeutic range to assess if there was a significant correlation between TWD, that is, maintenance warfarin dosing, and BMI in obese and nonobese patients. Results: A total of 831 patients were studied, with a BMI range between 13.4 and 63.1 kg/m2. We found that BMI is positively correlated with the total weekly warfarin dose. Our study showed that for each 1-point increase in BMI, the weekly warfarin dose increased by 0.69 mg. We found that the average warfarin weekly dose in this population can be estimated using the formula: 12.34 + 0.69 × BMI. Conclusion: There is an association between BMI and the TWD of warfarin. This could have dosing implications for both patients and prescribers, as patients with a high BMI will be expected to require higher doses of warfarin to maintain a therapeutic INR.

The Influence of NSAIDs on Coumarin Sensitivity in Patients with CYP2C9 Polymorphism After Total Hip Replacement Surgery

OBJECTIVE

To determine the influence of NSAIDs on the international normalized ratio (INR) in patients with cytochrome P450 (CYP)-2C9 enzyme variants starting acenocoumarol (an oral coumarin) therapy during the first 7 days after total hip replacement surgery.

METHODS

In this prospective study, an age-dependent protocol was used for the initiation of the acenocoumarol dose. Low-molecular-weight heparin was given for 5 days. The study included 100 patients undergoing total hip replacement surgery. After the inclusion of the last patient, polymerase chain reaction CYP2C9 mutation testing was performed for all patients. Drug-use evaluation of NSAIDs and other potential coumarin-drug interactions was also performed.

RESULTS

Eleven patients had an INR on 1 or more days >4.9. There were 52 patients who were using NSAIDs. Patients with a CYP2C9 mutation had a mean INR curve similar to patients without the mutation when NSAIDs were not coadministered. Within the group of patients heterozygous for a CYP2C9 mutation (n=30) only concomitant use of a NSAID resulted in an INR >4.9 (0% vs 38.9%, p<0.05).

CONCLUSION

In the group of patients with a CYP2C9 variant (*2 or *3 alleles), only concomitant use of a NSAID resulted in INRs >4.9. The cost effectiveness of CYP2C9 screening before elective surgery has yet to be determined.

Impact of Introducing Anticoagulation-Related Prescribing Guidelines in a Hospital Setting using Academic Detailing

AIM

Assess the impact of using academic detailing-assisted guideline roll-out on warfarin initiation, reversal of warfarin overanticoagulation, and uptake of deep vein thrombosis (DVT) prophylaxis across 4 metropolitan teaching hospitals.

METHODS

Baseline data were collected for 3 months prior to intervention. Prescribers were then informed about the guidelines, including feedback of current hospital performance and the basis for the guidelines. Post-intervention data were collected for 3 months after guideline implementation.

RESULTS

Uptake of DVT prophylaxis in medical patients increased from 52.8% to 67.0% (p=0.004). No impact on operative surgical patients was seen, possibly due to the high pre-existing rate of uptake (86.1% vs 84.1%, p=0.7). DVT prophylaxis rates in non-operative surgical patients were similar to medical patients, with similar, but non-significant improvements. The time to reach a stable therapeutic international normalized ratio (INR) after warfarin initiation was reduced (p=0.03) as were the number of INR's >4 in the first week of therapy (p=0.03). There were significant improvements in appropriate vitamin K use for warfarin overanticoagulation in patients with an INR above 6 (48% vs 74%, p=0.007), timely follow-up tests (49% vs 62%, p=0.009), and the proportion of next INR's being less than 4 (49% vs 61%, p=0.04).

CONCLUSIONS

The use of academic detailing to facilitate guideline roll-out had a positive impact on nearly all areas studied. The academic detailing process within the hospital setting was received enthusiastically by prescribers.

Clinical Outcomes of a Collaborative, Home-Based Postdischarge Warfarin Management Service

Background:

Warfarin remains a high-risk drug for adverse events, especially following discharge from the hospital. New approaches are needed to minimize the potential for adverse outcomes during this period.

Objective:

To evaluate the clinical outcomes of a collaborative, home-based postdischarge warfarin management service adapted from the Australian Home Medicines Review (HMR) program.

Methods:

In a prospective, nonrandomized controlled cohort study, patients discharged from the hospital and newly initiated on or continuing warfarin therapy received either usual care (UC) or a postdischarge service (PDS) of 2 or 3 home visits by a trained, HMR-accredited pharmacist in their first 8 to 10 days postdischarge. The PDS involved point-of-care international normalized ratio (INR) monitoring, warfarin education, and an HMR, in collaboration with the patient's general practitioner and community pharmacist. The primary outcome measure was the combined incidence of major and minor hemorrhagic events in the 90 days postdischarge. Secondary outcome measures included the incidences of thrombotic events, combined hemorrhagic and thombotic events, unplanned and warfarin-related hospital readmissions, death, INR control, and persistence with therapy al 8 and 90 days postdischarge.

Results:

The PDS (n = 129) was associated with statistically significantly decreased rates of combined major and minor hemorrhagic events to day 90 (5.3% vs 14.7%; p = 0.03) and day 8 (0.9% vs 7.2%; p = 0.01) compared with UC (n = 139). The rate of combined hemorrhagic and thrombotic events to day 90 also decreased (6.4% vs 19.0%; p = 0.008) and persistence with warfarin therapy improved (95.4% vs 83.6%; p = 0.004). No significant differences in readmission and death rates or INR control were demonstrated.

Conclusions:

This study demonstrated the ability of appropriately trained accredited pharmacists working within the Australian HMR framework to reduce adverse events and improve persistence In patients taking warfarin following hospital discharge. Widespread implementation of such a service has the potential to enhance medication safety along the continuum of care. KEY WORDS: adverse drug events, community pharmacy services, international normalized ratio, patient discharge, warfarin.

Development of a bayesian forecasting method for warfarin dose individualization

PURPOSE

The aim of this study was to develop a Bayesian dose individualization tool for warfarin. This was incorporated into the freely available software TCIWorks ( www.tciworks.info ) for use in the clinic.

METHODS

All pharmacokinetic and pharmacodynamic (PKPD) models for warfarin in the medical literature were identified and evaluated against two warfarin datasets. The model with the best external validity was used to develop an optimal design for Bayesian parameter control. The performance of this design was evaluated using simulation-estimation techniques. Finally, the model was implemented in TCIWorks.

RESULTS

A recently published warfarin KPD model was found to provide the best fit for the two external datasets. Optimal sampling days within the first 14 days of therapy were found to be days 3, 4, 5, 11, 12, 13 and 14. Simulations and parameter estimations suggested that the design will provide stable estimates of warfarin clearance and EC50. A single patient example showed the potential clinical utility of the method in TCIWorks.

CONCLUSIONS

A Bayesian dose individualization tool for warfarin was developed. Future research to assess the predictive performance of the tool in warfarin patients is required.

A role for pharmacists in community-based post-discharge warfarin management: protocol for the 'the role of community pharmacy in post hospital management of patients initiated on warfarin' study

BACKGROUND

Shorter periods of hospitalisation and increasing warfarin use have placed stress on community-based healthcare services to care for patients taking warfarin after hospital discharge, a high-risk period for these patients. A previous randomised controlled trial demonstrated that a post-discharge service of 4 home visits and point-of-care (POC) International Normalised Ratio (INR) testing by a trained pharmacist improved patients' outcomes. The current study aims to modify this previously trialled service model to implement and then evaluate a sustainable program to enable the smooth transition of patients taking warfarin from the hospital to community setting.

METHODS/DESIGN

The service will be trialled in 8 sites across 3 Australian states using a prospective, controlled cohort study design. Patients discharged from hospital taking warfarin will receive 2 or 3 home visits by a trained 'home medicines review (HMR)-accredited' pharmacist in their 8 to 10 days after hospital discharge. Visits will involve a HMR, comprehensive warfarin education, and POC INR monitoring in collaboration with patients' general practitioners (GPs) and community pharmacists. Patient outcomes will be compared to those in a control, or 'usual care', group. The primary outcome measure will be the proportion of patients experiencing a major bleeding event in the 90 days after discharge. Secondary outcome measures will include combined major bleeding and thromboembolic events, death, cessation of warfarin therapy, INR control at 8 days post-discharge and unplanned hospital readmissions from any cause. Stakeholder satisfaction will be assessed using structured postal questionnaire mailed to patients, GPs, community pharmacists and accredited pharmacists at the completion of their study involvement.

DISCUSSION

This study design incorporates several aspects of prior interventions that have been demonstrated to improve warfarin management, including POC INR testing, warfarin education and home visits by trained pharmacists. It faces several potential challenges, including the tight timeframe for patient follow-up in the post-discharge period. Its strengths lie in a strong multidisciplinary team and the utilisation of existing healthcare frameworks. It is hoped that this study will provide the evidence to support the national roll-out of the program as a new Australian professional community pharmacy service.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry Number 12608000334303.

Practical application of the 10-mg warfarin initiation nomogram

Initiation of warfarin therapy is a clinical challenge. A 10-mg warfarin initiation nomogram was recently validated in a randomized controlled trial. We sought to determine the efficacy and safety of this 10-mg warfarin initiation nomogram in 'real-life' daily practice. A retrospective cohort including all outpatients beginning concurrent treatment with warfarin and low-molecular-weight heparin over a 24-month period in our Thrombosis Unit was reviewed. Eight hundred and forty-one patients were included; of them, 640 (76.1%) were started on the nomogram. The nomogram was entirely followed in 324 patients (38.5%). The efficacy and safety profile was similar to that observed in the original clinical trial; 86% of patients managed according to the nomogram reached the international normalized ratio target of 2.0-3.0 within 5 days. Mean duration of low-molecular-weight heparin treatment was 6.0 +/- 1.9 days, and 3.7% of patients had an international normalized ratio of at least 5.0 in the first 4 weeks of treatment. The 10-mg nomogram effectively results in an early therapeutic international normalized ratio with a good safety profile in 'real-life' daily practice.

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.

Implementing anticoagulation management by pharmacists in the inpatient setting

PURPOSE

This article identifies approaches for implementing an inpatient anticoagulation program involving pharmacists; two successful inpatient anticoagulation programs previously reported in the literature are described with a discussion of steps to consider in developing or expanding such a service.

SUMMARY

Two institutions implemented pharmacist-managed anticoagulation services. One institution identified an undesirable incidence of medication-related adverse events occurring in hospitalized patients receiving anticoagulants. Pharmacists were asked to assist. Pharmacist activities included the selection of anticoagulants, patient education, verification of insurance coverage of the patient's anticoagulant, and coordination of follow-up. Physicians were available to assist. At the other institution, the department of pharmacy was asked by the orthopedic surgeons to manage warfarin for the prophylaxis against venous thromboembolism. The pharmacy department worked with the medical staff to gain approval of all policies, guidelines, and protocols to establish an anticoagulation service. Because of the success of the program, the pharmacy department expanded the service beyond warfarin. The steps to establishment of an anticoagulation service are described. The challenges facing such programs are discussed, including the potential anticoagulants in development that will create ongoing challenges in deciding which anticoagulation approach to use and in identifying patients for whom the newer agents may or may not be best suited.

CONCLUSION

Requirements for establishing a successful inpatient anticoagulation management program included defining the pharmacist's role in identifying patient needs, gaining support from other health care professionals, designing a program that addresses the needs of the patients, and managing unanticipated issues.

Warfarin induction at 5 mg daily is safe with a low risk of anticoagulant overdose: results of an audit of patients with deep vein thrombosis commencing warfarin

BACKGROUND

Conventionally warfarin therapy is initiated using a loading dose given over several days. Daily international normalised ratio (INR) monitoring is recommended to prevent overdose; however, with a large proportion of patients with deep vein thrombosis now receiving treatment out of hospital daily blood tests are inconvenient. We introduced a low-dose protocol for starting anticoagulant therapy that only required INR testing on days 4 and 6 and audited the results to assess safety and efficacy.

METHODS

Two-hundred and forty-eight patients with confirmed deep vein thrombosis were started on warfarin therapy at 5 mg daily for 3 days. INR measurements were taken at day 4 and day 6.

RESULTS

Of these patients, 21% had an INR within the therapeutic range on day 4 and 52% had a therapeutic INR on day 6. The risk of overdose was small with only one case with an INR above 4.0 on day 4 and nine cases on day 6. There were no reported cases of bleeding.

CONCLUSION

The low-dose protocol with infrequent testing is safe and convenient for outpatient management. However, our results suggest that patients on this protocol take between 6-10 days to achieve a stable INR.

Upsetting the apple cart: A community anticoagulation clinic survey of life event factors that undermine safe therapy

Anticoagulation therapy is a life-enhancing therapy for patients who are at risk for embolic events secondary to atrial fibrillation, valve replacement, and other comorbidities. Clinicians are motivated to decrease the amount of time that patients are either under- or over-anticoagulated, common conditions that decrease patient safety at either extreme. The primary purpose of this descriptive study was to examine the relationship between personal life event factors as measured by Norbeck's Life Events Questionnaire, core demographics such as age and income, and anticoagulation regulation. Although many factors affect anticoagulation therapy, the precise impact of life events, positive or negative, is unknown. The salient findings of this study (n = 202) showed a small, though statistically significant, inverse relationship (r = -0.184, P < .01) between negative life events and decreased time within therapeutic international normalized ratio. Total Life Event scores showed a statistically significant inverse relationship (r = -0.159, P < .05) to international normalized ratio time within therapeutic level. Lower income was inversely associated with higher negative Life Event scores (r = -0.192, P < .01). The findings demonstrate the need for strategies that address the potential impact of life events in conjunction with coexisting screening measures used in anticoagulation clinics. Implications for this study are limited by lack of methodology documenting concurrent social support factors and limitations of the research tool to reflect life event issues specific to outpatient seniors.

Factors Affecting the Maintenance Stable Warfarin Dosage in Hong Kong Chinese Patients

BACKGROUND

Multiple factors can affect the anticoagulation effect of warfarin. The objective of this study was to determine the relationship between different clinical factors and outcomes of warfarin therapy in Hong Kong Chinese patients.

METHODS

The study was conducted at the anticoagulation clinic of the Prince of Wales Hospital from 1 April to 31 December 2003. Clinical data collected included demographics, indications of warfarin, dietary vitamin K consumption, and drug-drug interactions. Blood samples were obtained for the genetic polymorphism analysis of CYP 2 C 9. Linear and multiple regression analysis were used for statistical analysis to determine the correlation between variables and the importance of various factors as the determinants of warfarin dosage requirement.

RESULTS

A total of 63 patients were recruited. The mean warfarin dosage was 3.30+/-2.23 mg/day. The warfarin dosage ranged from 0.75 to 12 mg/day. The mean age was 59+/-14 years old. Age, dietary vitamin K consumption, chronic heart failure, atrial fibrillation, hypertension, smoking and drinking status were found to be factors statistically significant affecting warfarin dosage. We detected no single nucleotide polymorphism in CYP 2 C 9 exon 4.

CONCLUSION

Age, dietary vitamin K consumption, warfarin indication for atrial fibrillation, co-morbid with CHF, smoking and drinking status were found to be the factors that affected the warfarin requirement in Hong Kong Chinese patients. However, the genetic polymorphism in exon 4 of CYP 2 C 9 may not be associated with the warfarin sensitivity in this patient population.

Evaluation of the First International Normalized Ratio after Acute Care Discharge to the Primary Care Environment

Purpose

To determine the percentage of patients who maintain a therapeutic INR (international normalized ratio) when presenting for their first INR follow-up in the primary care setting after hospital discharge.

Methods

Prospective observational trial enrolling patients newly initiated on warfarin.

Results

Data for 35 patients were collected. Fifty-one percent of patients were therapeutic at their first follow-up lab visit with 23% subtherapeutic and 26% supratherapeutic.

Conclusion

A low percentage of patients were therapeutic and more intervention is necessary in the immediate post-discharge time.

Relative impact of covariates in prescribing warfarin according to CYP2C9 genotype

Patients on warfarin anticoagulant therapy demonstrate wide variation in maintenance dose. Patients possessing variants (*2 and *3) of the cytochrome P450 2C9 gene require reduced maintenance doses compared to those having wild-type alleles (*1). Many other clinical factors have been shown to affect warfarin dose as well. To determine the relative impact of CYP2C9 genotype, age, gender, body surface area, concomitant medication, treatment indication and comorbidity, we conducted a retrospective cohort study in 453 patients managed by the anticoagulation service of a large, horizontally integrated, multispecialty group practice. In this largely Caucasian patient population, the CYP2C9 gene frequencies for *1/*1, *1/*2, *1/*3, *2/*2, *2/*3 and *3/*3 were 65.1%, 19.0%, 12.1%, 1.6%, 1.8% and 0.4%, respectively, approximating Hardy-Weinberg equilibrium. Mean maintenance doses for these genotypes were 36.5, 29.1, 23.5, 28.0, 18.1 and 5.5 mg/week, respectively. In univariate analyses, genotype alone accounted for 19.8% of the variability in maintenance dose. Age, body surface area and male gender accounted for 14.6%, 7.5% and 4.7%, respectively, while cardiac valve replacement as the indication for warfarin accounted for 5.4% of the variability. Collectively, these factors accounted for 33.7% of all dosing variability according to multiple regression. These results will help strengthen the mathematical models that are currently being developed for prospective gene-based warfarin dosing.

Comparison of a Frail-Friendly Nomogram with Physician-Adjusted Warfarin Dosage for Prophylaxis after Orthopaedic Surgery on a Geriatric Rehabilitation Unit

Warfarin dosing for thromboprophylaxis in post-operative patients is time-consuming. Warfarin-dosing nomograms can be used in post-operative arthroplasty patients, but warfarin requirements are lower in frail older people. We modified an existing post-arthroplasty nomogram to a frail-friendly version and evaluated its performance in a frail elderly post-orthopaedic surgery on a geriatric rehabilitation ward to determine if it would improve quality indicators for oral anticoagulation. On a geriatric rehabilitation unit, post-operative orthopaedic patients were assigned to either physician-adjusted warfarin dosing or the nursing-administered nomogram. The proportion of days within target INR values was significantly higher in the nomogram group (77%, 95% CI 74% to 81%) compared to the physician-adjusted group (53%, 95% CI 46% to 60%), with no major bleeding or thromboembolic complications. The number of warfarin-related telephone calls to physicians was significantly reduced by tenfold. Use of a frail-friendly nomogram improved quality and efficiency of patient care on a geriatric rehabilitation unit.

Initiating Warfarin Therapy: 5 mg versus 10 mg

OBJECTIVE

To review the literature investigating initial dosing of warfarin at 5 or 10 mg for treatment of acute venous thromboembolism.

DATA SOURCES

Articles were identified through searches of MEDLINE (1966–December 2003) using the key words warfarin, oral anticoagulation, warfarin dose, warfarin initiation, venous thromboembolism, and anticoagulation. Additional references were located through review of the bibliographies of the articles cited.

STUDY SELECTION AND DATA EXTRACTION

Studies of the initial dosing of warfarin at 5 or 10 mg were evaluated and relevant information was included, as were those that identified known factors that influence the maintenance dose of warfarin.

DATA SYNTHESIS

For the treatment of acute venous thromboembolism, warfarin dosing is often provider dependent. Until recently, studies suggested that 5 mg initiation was as effective as 10 mg, without increasing the risk of bleeding. However, the most recent study comparing a 5- versus 10-mg initial dosing nomogram supports an initial dose of 10 mg. These results should be interpreted with caution, however, since patients at high risk for bleeding were excluded from the study. Several patient-specific factors will affect the maintenance dose, guiding clinicians to start with lower (<5 mg) or higher (>5 mg) doses.

CONCLUSIONS

Although recent evidence supports a 10-mg initiation nomogram, clinicians should consider patient-specific factors prior to deciding an initial warfarin dose. If a 10-mg loading dose is utilized, strict compliance with the protocol is necessary.

Improving the outcomes of anticoagulation: an evaluation of home follow-up of warfarin initiation

OBJECTIVES

A number of studies have reported that the risk of bleeding associated with warfarin is highest early in the course of therapy. This study examined the effect of a programme focused on the transition of newly anticoagulated patients from hospital to the community.

DESIGN

Open-label randomized controlled trial.

SETTING

Home-based follow-up of patients discharged from acute care hospital in southern Tasmania, Australia.

SUBJECTS

A total of 128 patients initiated on warfarin in hospital and subsequently discharged to general practitioner (GP) care were enrolled in the study. Sixty were randomized to home monitoring (HM) and 68 received usual care (UC).

INTERVENTIONS

HM patients received a home-visit by the project pharmacist and point-of-care international normalized ratio (INR) testing on alternate days on 4 occasions, with the initial visit two days after discharge. The UC group was solely managed by the GP and only received a visit 8 days after discharge to determine anticoagulant control.

RESULTS

At discharge, 42% of the HM group and 45% of the UC group had a therapeutic INR. At day 8, 67% of the HM patients had a therapeutic INR, compared with 42% of UC patients (P < 0.002). In addition, 26% of UC patients had a high INR, compared with only 4% of HM patients. Bleeding events were assessed 3 months after discharge and occurred in 15% of HM patients, compared with 36% of the UC group (P < 0.01).

CONCLUSIONS

This programme improved the initiation of warfarin therapy and resulted in a significant decrease in haemorrhagic complications in the first 3 months of therapy.