Optional vena cava filters for patients with high thromboembolic risk: questions to be answered

Detailed assessment of benefits and risks of retrievable inferior vena cava filters on patients with complicated injuries: the da Vinci multicentre randomised controlled trial study protocol

INTRODUCTION

Retrievable inferior vena cava (IVC) filters have been increasingly used in patients with major trauma who have contraindications to anticoagulant prophylaxis as a primary prophylactic measure against venous thromboembolism (VTE). The benefits, risks and cost-effectiveness of such strategy are uncertain.

METHODS AND ANALYSIS

Patients with major trauma, defined by an estimated Injury Severity Score >15, who have contraindications to anticoagulant VTE prophylaxis within 72 hours of hospitalisation to the study centre will be eligible for this randomised multicentre controlled trial. After obtaining consent from patients, or the persons responsible for the patients, study patients are randomly allocated to either control or IVC filter, within 72 hours of trauma admission, in a 1:1 ratio by permuted blocks stratified by study centre. The primary outcomes are (1) the composite endpoint of (A) pulmonary embolism (PE) as demonstrated by CT pulmonary angiography, high probability ventilation/perfusion scan, transoesophageal echocardiography (by showing clots within pulmonary arterial trunk), pulmonary angiography or postmortem examination during the same hospitalisation or 90-day after trauma whichever is earlier and (B) hospital mortality; and (2) the total cost of treatment including the costs of an IVC filter, total number of CT and ultrasound scans required, length of intensive care unit and hospital stay, procedures and drugs required to treat PE or complications related to the IVC filters. The study started in June 2015 and the final enrolment target is 240 patients. No interim analysis is planned; incidence of fatal PE is used as safety stopping rule for the trial.

ETHICS AND DISSEMINATION

Ethics approval was obtained in all four participating centres in Australia. Results of the main trial and each of the secondary endpoints will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ACTRN12614000963628; Pre-results.

Vena cava interruption

Anticoagulation has been proven to be effective in preventing and treating deep vein thrombosis and pulmonary embolus. However, many critically ill patients are unable to receive anticoagulation or suffer recurrent venous thromboembolism despite adequate treatment. This article examines the use of vena cava filters in the critically ill. Indications for, techniques, and complications of vena cava filter insertion are reviewed. The importance of vena cava filters with the option to be retrieved and bedside insertion in the intensive care unit is emphasized.

Incidence and risk factors for fatal pulmonary embolism after major trauma: a nested cohort study

BACKGROUND

Venous thromboembolism is common after major trauma. Strategies to prevent fatal pulmonary embolism (PE) are widely utilized, but the incidence and risk factors for fatal PE are poorly understood.

METHODS

Using linked data from the intensive care unit, trauma registry, Western Australian Death Registry, and post-mortem reports, the incidence and risk factors for fatal PE in a consecutive cohort of major trauma patients, admitted between 1994 and 2002, were assessed. Non-linear relationships between continuous predictors and risk of fatal PE were modelled by logistic regression.

RESULTS

Of the 971 consecutive trauma patients considered in the study, 134 (13.8%) died after their injuries. Fatal PE accounted for 11.9% of all deaths despite unfractionated heparin prophylaxis being used in 44% of these patients. Fatal PE occurred in those who were older (mean age 51- vs 37-yr-old, P=0.01), with more co-morbidities (Charlson's co-morbidity index 1.1 vs 0.2, P=0.01), had a larger BMI (31.8 vs 24.5, P=0.01), and less severe head and systemic injuries when compared with those who died of other causes. Sites of injuries were not significantly related to the risk of fatal PE. Fatal PE occurred much later than deaths from other causes (median 18 vs 2 days, P=0.01), and the estimated attributable mortality of PE was 49% (95% confidence interval 36-62%).

CONCLUSIONS

Fatal PE appeared to be a potential preventable cause of late mortality after major trauma. Severity of injuries, co-morbidity, and BMI were important risk factors for fatal PE after major trauma.

Crux vena cava filter

Inferior vena cava filters are widely accepted for pulmonary embolic prophylaxis in high-risk patients with contraindications to anticoagulation. While long-term complications have been associated with permanent filters, retrievable filters are now available and have resulted in the rapid expansion of this technology. Nonetheless, complications are still reported with optional filters. Furthermore, device tilting and thrombus load may prevent retrieval in up to 30% of patients, thereby eliminating the benefits of this technology. The Crux vena cava filter is a novel, self-centering, low-profile filter that is designed for ease of delivery, retrievability and improved efficacy while limiting fatigue-related device complications. This device has been proven safe and user-friendly in an ovine model and has recently been implanted in human subjects.

Evaluation of wall motion and dynamic geometry of the inferior vena cava using intravascular ultrasound: implications for future device design

PURPOSE

To use intravascular ultrasound (IVUS) to define the wall motion of the inferior vena cava (IVC) during normal respiratory cycles and evaluate its dynamic geometry during Valsalva maneuvers.

METHODS

Between September 2005 and October 2006, 10 patients who were having IVC filters placed underwent IVUS prior to filter implantation. With the anesthetized patient in a supine position, a 10-second IVUS recording of IVC motion below the renal veins was made during both normal respiratory cycles and Valsalva maneuvers. Diameters (n = 100 measurements) were measured from the epicenter of the lumen in both a long and short axis. Changes in diameters were evaluated using a Student t test for paired data; variations in IVC wall motion circumference of the vessel were compared using an analysis of variance for repeated measurements. Intra-/interobserver variability was analyzed with Bland-Altman plots.

RESULTS

The mean IVC diameter was 14.3+/-4.1 mm in the short axis and 23.2+/-3.5 mm in the long axis. There was significant variation in infrarenal IVC wall movement about the circumference, with 1.4+/-0.2 mm (range 0.6-1.8) displacement in the short axis and 1.0+/-0.2 mm (range 0.2-1.4) displacement in the long axis during the normal respiratory cycle (p = 0.04). In the short axis, the IVC diameter significantly increased with Valsalva from 14.3+/-4.1 to 19.6+/-1.2 mm (p = 0.0001); in the long axis, the diameter increased from 23.2+/-3.5 to 24+/-1.2 mm (p = 0.02). With Valsalva, there was a significantly greater change in the short axis (30.9%+/-4.8%) compared to the long axis (3.4%+/-2.2%; p = 0.0001). There were no significant differences in the interobserver and intraobserver measurements.

CONCLUSION

In the supine position, the IVC is elliptical and deforms anisotropically during the normal respiratory cycle. The greatest displacement (36%) is in the short axis during a Valsalva maneuver. These profound changes within the venous system will require intracaval devices to have active fixation to prevent migration. Devices should be designed to accommodate these changes to prevent fatigue failure.

Imaging of the Vena Cava in the Intensive Care Unit Prior to Vena Cava Filter Insertion: Carbon Dioxide as an Alternative to Iodinated Contrast

This study evaluates the safety and effectiveness of carbon dioxide (CO2) as a contrast agent in patients in the intensive care unit undergoing vena cava filter (VCF) insertion. We prospectively evaluated patients in the intensive care unit undergoing bedside VCF insertion using CO2 cavagraphy. Blood pressure, pulse rate, mixed venous oxygen saturation, and intracranial pressure were monitored before, during, and after the CO2 injection. Fifty patients in the intensive care unit (mean age 48.2 ± 16.5 years) were included in the study. Five patients had decreases in blood pressure, which resolved without intervention. Two patients required iodinated contrast as a result of inadequate CO2 imaging. All patients had successful insertion of VCF. The use of CO2 as a contrast agent is a safe and highly effective alternative for vena cava imaging and can be considered the first-line contrast agent for all critically ill patients requiring VCF placement.

Long-Term Retrievability of IVC Filters: Should We Abandon Permanent Devices?

Thromboembolic disease produces a considerable disease burden, with death from pulmonary embolism in the UK alone estimated at 30,000-40,000 per year. Whilst it is unproven whether filters actually improve longevity, the morbidity and mortality associated with thromboembolic disease in the presence of contraindications to anticoagulation is high. Thus complications associated with filter insertion, and whilst they remain in situ, must be balanced against the alternatives. Permanent filters remain in situ for the remainder of the patient's life and any complications from the filters are of significant concern. Filters that are not permanent are therefore attractive in these circumstances. Retrievable filters, to avoid or decrease long-term filter complications, appear to be a significant advance in the prevention of pulmonary embolism. In this review, we discuss the safety and effectiveness of both permanent and retrievable filters as well as the retrievability of retrievable inferior vena cava (IVC) filters, to explore whether the use of permanent IVC filters can be abandoned in favor of retrievable filters. Currently four types of retrievable filters are available: the Recovery filter (Bard Peripheral Vascular, Tempe, AZ, USA), the Günther Tulip filter (Cook, Bloomington, IN, USA), the OptEase Filter (Cordis, Roden, The Netherlands), and the ALN filter (ALN Implants Chirurgicaux, Ghisonaccia, France). Efficacy and safety data for retrievable filters are as yet based on small series, with a total number of fewer than 1,000 insertions, and follow-up is mostly short term. Current long-term data are poor and insufficient to warrant the long-term implantation of these devices into humans. The case of fractured wire from a Recovery filter that migrated to the heart causing pericardial tamponade requiring open heart surgery is a reminder that any new endovascular device remaining in situ in the long term may produce unexpected problems. We should also bear in mind that the data on permanent filters are much more robust, with reports on over 9,500 cases with follow-up of up to 8 years. The original implantation time of 10-14 days has been extended to more than 100 days as the mean implantation time with some of the filter types. Follow-up (preferably prospective) is necessary for all retrievable filters, whether or not they are retrieved. Until these data become available we should restrict ourselves to the present indications of permanent and retrievable filters. If long-term follow-up data on larger numbers of cases confirm the initial data that retrievable filters are as safe and effective as permanent filters, the use of the retrievable filters is likely to expand.

Venous thromboembolism in trauma: an update for the intensive care unit practitioner

Venous thromboembolism (VTE) in trauma patients is a capricious problem that continues to plague trauma surgeons and critical care physicians alike. Pharmacologic preventions of VTE with anticoagulants are often contraindicated in the trauma patient because of risk of bleeding diathesis. Mechanical prophylaxis in the form of venous compression boots often cannot be placed because of external fixators, swelling, and so forth. Providing effective VTE prophylaxis, while at the same time providing definitive care for the trauma patient, can be a nightmare. This review will first discuss the incidence and prevalence of VTE, as well as investigate the condition's diagnosis and treatment. Solutions to frequently encountered clinical dilemmas in managing VTE in trauma patients are considered in the form of frequently asked questions. Diagnostic techniques such as magnetic resonance venography, D-dimer, and various computed tomography methods are evaluated. Recent literature on preventive pharmacologic therapies is explored. The authors also consider whether vena cava filters prevent pulmonary embolism in trauma patients.

Vena cava filters in spinal cord injuries: evolving technology

BACKGROUND

Asymptomatic deep venous thrombosis (DVT) has been reported in 60% to 100% of persons with spinal cord injury (SCI). Several guidelines have been published detailing recommended venous thromboembolism (VTE) prophylaxis after acute SCI. Low-molecular-weight heparin, intermittent pneumatic compression (IPC) devices, and/or graduated compression stockings are recommended. Vena cava filters (VCFs) are recommended for secondary prophylaxis in certain situations.

OBJECTIVE

To clarify the use of vena cava filters in patients with SCI.

METHODS

Literature review.

RESULTS

Prophylactic use of vena cava filters has expanded in trauma patients, including individuals with SCI. Filter placement effectively prevents pulmonary emboli and has a low complication rate. Indications include pulmonary embolus while on anticoagulant therapy, presence of pulmonary embolus and contraindication for anticoagulation, and documented free-floating ileofemoral thrombus. VCFs should be considered in patients with complete motor paralysis caused by lesions in the high cervical cord (C2 and C3), with poor cardiopulmonary reserve, or with thrombus in the inferior vena cava despite anticoagulant prophylaxis. Three optional retrievable filters that are approved for use are discussed.

CONCLUSION

Retrievable VCFs are a safe, feasible option for secondary prophylaxis of VTE in patients with SCI. Objective criteria for temporary and permanent placement need to be defined.