Reassessment of venous thromboembolism and bleeding risk in medical patients receiving VTE prophylaxis

RATIONALE, AIMS, AND OBJECTIVES

The majority of hospitalized nonsurgical medical patients receive pharmacological prophylaxis for venous thromboembolism (VTE), and reassessment of changes in thrombosis and bleeding risk factors during hospital admission may represent an opportunity to discontinue unnecessary or unsafe therapy. The use of validated, clinically derived risk assessment models (RAMs) represents a shift towards an individualized, patient-centred approach to VTE prophylaxis. We are interested in using these tools to assess whether risk categories for VTE and bleeding change during admission and to assess whether such changes result in discontinuation of prophylaxis. Our primary objective was to determine whether VTE and bleed risk categories changed during the course of admission to warrant discontinuation of VTE prophylaxis, using the International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) VTE and Bleed RAMs, respectively. Secondary objectives were to determine the number of patients whose risk categorizations for VTE and bleeding warranted discontinuation of VTE prophylaxis and to survey whether prophylaxis was continued or discontinued.

METHODS

A retrospective review was undertaken for a cross-sectional, randomly selected sample of patients who received VTE prophylaxis while admitted to medical wards in a collection of regional hospitals.

RESULTS

Of the 351 medical records reviewed, only eight patients (2.3%) changed their VTE risk category and six (1.7%) changed their bleed risk category to warrant discontinuation of VTE prophylaxis. Ninety patients (26%) were at high risk of VTE and low risk of bleed throughout admission, warranting continued VTE prophylaxis. The majority of patients remained at low risk of VTE throughout admission but remained on VTE prophylaxis until discharge.

CONCLUSIONS

Risk categories for VTE and bleeding for medical patients did not appreciably change throughout hospital admission. Use of VTE RAMs at admission and prior to initiation of therapy should reduce unnecessary prophylaxis in the majority of medical patients who are at low risk of VTE.

Assessment of venous thromboembolism risk and initiation of appropriate prophylaxis in psychiatric patients

Introduction

Venous thromboembolism (VTE) prophylaxis is not included among the measures for the Inpatient Psychiatric Facilities Quality Reporting Program. Evidence suggests that antipsychotic agents may be an independent risk factor for the development of VTE; therefore, development of a VTE risk stratification tool would improve the quality and safety of care for the psychiatric inpatient population. This study aims to develop clinically relevant criteria to assess VTE risk upon admission to an inpatient psychiatric hospital.

Methods

This retrospective, single-center cohort study enrolled patients in 2 cohorts from an inpatient psychiatric hospital. Patients in cohort I with new-onset VTE diagnosis during admission were identified through international classification of diseases 9 and 10 coding. Cohort II consisted of a random sample of 100 patients in a 3-month period. The percentage meeting criteria for prophylaxis in each cohort was assessed utilizing both the Padua Prediction Score and a modified score.

Results

In cohorts I and II, 66.7% and 14% of patients, respectively, met criteria for VTE prophylaxis utilizing the modified Padua Prediction Score. One patient received VTE prophylaxis in each cohort, and the median time to VTE diagnosis in cohort I was 42 days. In cohort I, the rate of VTE was 0.08% based on estimated discharges in the 26-month period. This is less than the annual rate of 1% to 2.4% for nursing homes or postacute rehabilitation facilities.

Discussion

We recommend the implementation of clinical decision support to prompt individualized reassessment of VTE risk when length of stay exceeds 30 days.

Derivation of a risk assessment model for hospital-acquired venous thrombosis: the NAVAL score

Venous thrombosis (VT) is a preventable cause of death in hospitalized patients. The main strategy to decrease VT incidence is timely thromboprophylaxis in at-risk patients. We sought to evaluate the reliability of risk assessment model (RAM) data, the incremental usefulness of additional variables and the modelling of an adjusted score (the NAVAL score). We used the RAM proposed by Caprini for initial assessment. A 5 % systematic sample of data was independently reviewed for reliability. We evaluated the incremental usefulness of six variables for VT during the score modelling by logistic regression. We then assessed the NAVAL score for calibration, reclassification and discrimination performances. We observed 11,091 patients with 37 (0.3 %) VT events. Using the Caprini RAM, high-risk and moderate-risk patients were respectively associated with a 17.4 (95 % confidence interval [CI] 6.1-49.9) and 4.2 (95 % CI 1.6-11.0) increased VT risk compared with low-risk patients. Four independent variables were selected for the NAVAL score: "Age", "Admission clinic", "History of previous VT event" and "History of thrombophilia". The area under the receiver-operating-characteristic curve for the NAVAL score was 0.72 (95 % CI 0.63-0.81). The Net Reclassification Index (NRI) for the NAVAL score compared with the Caprini RAM was -0.1 (95 % CI -0.3 to 0.1; p = 0.28). We conclude that the NAVAL score is a simplified tool for the stratification of VT risk in hospitalized patients. With only four variables, it demonstrated good performance and discrimination, but requires external validation before clinical application. We also confirm that the Caprini RAM can effectively stratify VT risk in hospitalized patients in our population.

Current state of medical thromboprophylaxis in Australia

BACKGROUND

Australia has two published national guidelines for general medical thromboprophylaxis (MT), but the two differ in detail and the basis for patient selection remains uncertain. Several aspects of current guidelines are controversial, as is the proposed design of a dedicated prescribing box in the National Inpatient Medication Chart.

AIM

To discuss and comment on the current standing of medical thromboprophylaxis in Australia.

METHOD

We have marshalled literature known to us from our previous published research, and have applied this knowledge to discuss shortcomings, which, in our opinion, exist in current medical thromboprophylaxis practice, and to suggest solutions.

CONCLUSION

Australian guidelines are flawed because they are based on unsuitable evidence (incidence of subclinical thrombotic disease) and define eligibility broadly, such that about 80 per cent of patients are considered eligible. They urge that prescribers should "consider" prophylaxis without supplying an adequate basis for doing so. They do not provide grounds for assessing the balance between hazard (in the form of major bleeds) and benefit (thrombotic events avoided). Other clinical factors promoting unnecessary use of medical thromboprophylaxis include the use of age as a risk factor and proposed inclusion of a new DVT prophylaxis section in the National Inpatient Medication Chart (NIMC), which implicitly discourages non-prescription of prophylaxis.

Potent anticoagulant aptamer directed against factor IXa blocks macromolecular substrate interaction

An aptamer targeting factor IXa has been evaluated in animal models and several clinical studies as a potential antithombotic therapy. We elucidate the molecular mechanism by which this aptamer acts as an anticoagulant. The aptamer binds tightly to factor IXa and prolongs the clotting time of human plasma. The aptamer completely blocks factor IXa activation of factor X regardless of the presence of factor VIIIa. However, the aptamer does not completely block small synthetic substrate cleavage, although it does slow the rate of cleavage. These data are consistent with the aptamer binding to the catalytic domain of factor IXa in such a way as to block an extended substrate-binding site. Therefore, unlike small molecule inhibitors, aptamers appear to be able to bind surfaces surrounding an active site and thereby sterically interfere with enzyme activity. Thus, aptamers may be useful agents to probe and block substrate-binding sites outside of the active site of an enzyme.

[Thromboprophylaxis: medical recommendations and hospital programs]

Venous thromboembolism (VTE) is the most preventable cause of death in hospitalized patients. Hospital-related VTE is associated with more than half of the VTE burden in a community, either in-hospital or after discharge. Selective thromboprophylaxis is recommended for patients at risk. Patient selection for thromboprophylaxis requires proper VTE risk stratification. VTE stratification may be achieved by either risk assessment models (RAM) or by models based on patient's illness and associated risk factors. Whatever the model, a thromboprophylatic recommendation should be formulated for each VTE risk category. VTE thromboprophylaxis may include general measures, mechanic compression procedures, pharmacological intervention or a combined approach. After many decades of consensus statements, a large proportion of at risk patients (20% to 75%) still does not receive proper thromboprophylaxis. This study aims to alert to the relevance of thromboprophylaxis and to suggest hospital thromboprophylatic strategies in a Brazilian setting.

Primary prophylaxis of venous thromboembolism in children

Venous thromboembolism (VTE) is rare in children and young adolescents, and occurs predominantly in those with congenital heart disease in whom guidelines exist for VTE prophylaxis. For other paediatric patients, the rarity of the event makes writing an evidence-based clinical practice guideline difficult because each of the known risk factors contributes only a small increase in risk. Thrombophilia screening is controversial because few results assist with prediction of likely thrombosis and may not alter recommendations for prophylaxis. Recent publications highlight the importance of non-pharmacological prevention of VTE in children and adolescents undergoing surgery and the importance of liaison among surgeon, anaesthetist and haematologist. This annotation was written with the aim of collating current evidence for VTE prophylaxis and emphasising the need for further research in vulnerable subgroups.