Current recommendations for warfarin therapy. Use and monitoring

Effect of chamomile intake on blood coagulation tests in healthy volunteers: a randomized, placebo-controlled, crossover trial

BACKGROUND

Chamomile is consumed worldwide for enjoyment and its potentially desirable properties. Widespread patient resource websites, however, discourage preoperative chamomile intake, lest bleeding could worsen. This precaution, though, stems largely from indirect evidence in one case report. To evaluate if chamomile ingestion impacts coagulation assays via coumarin-like substances, we designed a randomized, placebo-controlled, crossover study.

MATERIALS AND METHODS

Healthy volunteers were randomized to three interventions in a cross-over-design spanning 5 weeks per subject. Interventions included 7-day consumption of chamomile tea (3 tea bags × 3 times daily = 9 tea bags daily), a chamomile extract capsule (3 times daily), or a placebo capsule (3 times daily). A 7-day washout period elapsed between intervention periods. The primary outcome was the change in prothrombin time (PT) before vs. after each intervention. Secondary outcomes included changes in the international normalized ratio (INR), activated partial thromboplastin time (aPTT), thrombin time (TT), reptilase time (RT), and fibrinogen (FG) surrounding each intervention.

RESULTS

All 12 enrolled subjects were randomized and completed the study. The primary outcome of PT change (mean ± SD) was similar across interventions (chamomile tea =  - 0.2 ± 0.4 s, extract capsule =  - 0.2 ± 0.4 s, and placebo capsule = 0.1 ± 0.5 s; p = 0.34). INR change was 0 s (p = 0.07) for each intervention. The aPTT, TT, RT, and FG, did not change significantly across interventions (p = 0.8, p = 0.08, p = 0.8, and p = 0.2 respectively).

CONCLUSIONS

Chamomile intake by tea or capsule does not prolong PT. These findings challenge the notion to avoid perioperative chamomile intake in patients not taking warfarin.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT05006378; Principal Investigator: Jonathon Schwartz, M.D.; Registered August 16, 2021.

From Ink Pens to Computers: A Personal Look Back at Landmark Changes during 5 Decades as a Clinical Laboratory Scientist in U.S. Hemostasis Laboratories

In 2023, Seminars in Thrombosis and Hemostasis will be celebrating its 50^th anniversary, and similarly this will also mark my 5^th decade of working in, or association with, laboratories that perform hemostasis testing. My career started at a large military medical center, but I also worked at several other facilities, including military dispensaries, community hospitals, and a large academic institution. The difference between each type of hemostasis laboratory was as expected, with larger facilities having better instrumentation and more prolific test menus. However, whether one worked in a large academic center, or a small rural hospital, regulatory changes affected every clinical laboratory to the same degree. Advances in technology also eventually affected every hemostasis laboratory, but these salient changes were more likely to occur earlier at the larger institutions. As Seminars in Thrombosis and Hemostasis celebrates its 50^th anniversary, that milestone triggered recollection about those salient events that occurred during my own career in hemostasis testing. As such, I describe (my impression) the top ten landmark changes that altered laboratory practice at the facilities where I worked during the past 5 decades.

Development of an Institutional Periprocedural Management Guideline for Oral Anticoagulants

Patients on oral anticoagulation commonly undergo surgery or other invasive procedures. Periprocedural management of oral anticoagulants involves a careful balance of the thromboembolic risk and bleeding risk. To standardize clinical practice at our institution, we developed a guideline for periprocedural management for patients taking oral anticoagulants that incorporates published data and expert opinion. In this article, we present our clinical practice guideline as a decision support tool to aid clinicians in developing a consistent strategy for managing periprocedural anticoagulation and for safely bridging anticoagulation in patients who require it.

Aortic thrombosis in dogs: presentation, therapy, and outcome in 26 cases

OBJECTIVES

The pathogenesis and presentation of aortic thrombosis (AT) in dogs is not well characterized and an effective antithrombotic therapy for AT in dogs has not been identified. Our goal is to report the clinical presentation and results of therapies in dogs with AT.

ANIMALS

Twenty-six client-owned dogs.

METHODS

Retrospective review of medical records of dogs diagnosed with AT between 2003 and 2010.

RESULTS

Twenty-six dogs had an apparent primary mural aortic thrombus. None had structural heart disease at diagnosis. Twenty dogs were ambulatory with varying degrees of pelvic limb dysfunction. Duration of ambulatory dysfunction was 7.8 weeks (range 1 day-52 weeks). A majority of dogs (58%) had no concurrent conditions at diagnosis. Fourteen dogs were treated with a standard warfarin protocol for a median period of 22.9 months (range 0.5-53 months). Ambulatory function improved in all dogs treated with warfarin. Time until clinical improvement was 13.9 days (range 2-49 days). Dogs treated with warfarin did not become non-ambulatory, die or undergo euthanasia related to AT, or have a known serious hemorrhagic event.

CONCLUSIONS

The pathogenesis of AT in dogs is distinct from that of aortic thromboembolism (ATE) in cats. Aortic thrombosis in dogs is more likely to involve local thrombosis in the distal aorta with embolization to the arteries of the pelvic limb resulting in chronic progressive ambulatory dysfunction. Chronic warfarin administration is well-tolerated and appears to be an effective short-term and long-term therapy for dogs with AT.

Home prothrombin time monitoring: a literature analysis

The anticoagulant activity of warfarin sodium is monitored by the prothrombin time (PT) using the international normalized ratio (INR). Standard oral anticoagulant therapy monitoring requires frequent patient visits to physicians' offices and/or laboratories to optimize warfarin dosage. Home PT monitoring by patients can increase testing frequency and may thus decrease complications associated with oral anticoagulant therapy. Clinical studies suggest that home PT monitoring is more effective than uncoordinated management and is as effective as care through specialized anticoagulation clinics for keeping INRs within a therapeutic range. There are accurate and reliable instruments available, but paramount to the success of home PT monitoring is sound patient selection, appropriate patient training, and consistent quality control.

Warfarin therapy in older adults: managing treatment in the primary care setting

Oral anticoagulant therapy with war farin is commonly used to prevent thromboembolic events in patients at risk. The degree of anticoagulation is variable among individuals and is influenced by many factors; therefore, patients must be monitored frequently to assess for potential adverse effects related to treatment. Individuals older than age 65 are at particular risk for thromboembolic events as well as anticoag ulant-related complications. Because of these factors, elderly individuals pose a unique challenge in maintain ing anticoagulant control. The purpose of this article is to revisit the role of warfarin therapy for elderly individ uals in the primary care setting and to provide nurse practitioners with the information necessary to prescribe and monitor this medication appropriately. This article provides indications for warfarin therapy and also identifies potential barriers to effective management with specific implications for the older population.

Vascular thrombohemorrhagic disorders: hereditary and acquired

This review has summarized the more important diseases that may be accompanied by or lead to a disorder of hemostasis or thrombosis via alterations of the vasculature. It is to be stressed that the vascular component of hemostasis is often overlooked by clinicians caring for patients with disorders of hemostasis and thrombosis. It should be appreciated that the vasculature is intricately related to the coagulation protein system and to platelets when involved in thrombohemorrhagic diatheses. Although many vascular disorders may lead to hemorrhage or thrombosis, it must be appreciated that often it is impossible to discern between a primary vascular defect/damage and a defect that has been induced by platelet activation/dysfunction or procoagulant abnormalities.

Warfarin toxicity in the emergency department: recommendations for management

OBJECTIVE

To examine patients who presented to a hospital emergency department with evidence of warfarin toxicity, and to review the available published literature to determine what guidelines are available for management of this problem.

METHOD

A retrospective analysis of all adult patients who presented to The Geelong Hospital Emergency Department between 1 January 1996 and 30 June 1998 with international normalized ratio > 6 due to warfarin toxicity.

RESULTS

A total of 84 patients with international normalized ratio > 6 were included in the study. The average age was 68.3 years. Fifty-three per cent were women. The international normalized ratio was between 6 and 10 in 33 patients (39%), and greater than 10 in 51 patients (61%). Major bleeding occurred in 16.7% of patients, minor bleeding in 17.8%. Sixty-five per cent had no bleeding. Seven patients died, four of those with bleeding. Patients with an international normalized ratio > 10 were more likely to receive fresh frozen plasma (77.6% vs 28.6%; P < 0.001) and in greater amounts (3.0 units vs 0.8 units; P < 0.001) than those with an international normalized ratio of 6-10. There were also more episodes of major bleeding, although not significant. Patients with major bleeding were older (mean 75.4 years vs 67.5 years; P = 0.04), more likely to be admitted (P = 0.046), were more often given fresh frozen plasma (P = 0.003) and in greater amounts (3.28 units vs 2.0 units; P = 0.02).

CONCLUSION

Warfarin toxicity is a common problem, and variation in management is not surprising considering the lack of consensus in the literature on this topic. Current recommendations are summarized and a simple flowchart for management of this problem is provided.

Management and dosing of warfarin therapy

When initiating warfarin therapy, clinicians should avoid loading doses that can raise the International Normalized Ratio (INR) excessively; instead, warfarin should be initiated with a 5-mg dose (or 2 to 4 mg in the very elderly). With a 5-mg initial dose, the INR will not rise appreciably in the first 24 hours, except in rare patients who will ultimately require a very small daily dose (0.5 to 2.0 mg). Adjusting a steady-state warfarin dose depends on the measured INR values and clinical factors: the dose does not need to be adjusted for a single INR that is slightly out of range, and most changes should alter the total weekly dose by 5% to 20%. The INR should be monitored frequently (eg, 2 to 4 times per week) immediately after initiation of warfarin; subsequently, the interval between INR tests can be lengthened gradually (up to a maximum of 4 to 6 weeks) in patients with stable INR values. Patients who have an elevated INR will need more frequent testing and may also require vitamin K1. For example, a nonbleeding patient with an INR of 9 can be given low-dose vitamin K1 (eg, 2.5 mg phytonadione, by mouth). Patients who have an excessive INR with clinically important bleeding require clotting factors (eg, fresh-frozen plasma) as well as vitamin K1.