The use of intravascular ultrasound imaging to improve use of inferior vena cava filters in a high-risk bariatric population

Efficacy and safety of pre-operative insertion of inferior vena cava filter in patients undergoing bariatric surgery: a systematic review

Prophylactic placement of inferior vena cava (IVC) filters prior to performing bariatric surgery is an intervention of unclear safety and efficacy with disagreement between current practice guidelines. To better characterize the risk and benefit of IVC filter insertion prior to bariatric surgery based on the current evidence. A systematic review of the literature of patients with prophylactic IVC filter insertion prior to bariatric surgery was performed and 32 studies were identified for inclusion into the review, of which none were randomized controlled trials. Meta-analysis was performed including the high-quality included studies. Seven high quality studies reported thrombotic events in patients undergoing bariatric surgery who had an IVCF and a control group which allowed for meta-analysis. The pooled odds ratio of venous thrombotic events in the IVC filter population versus the group without IVC filters was 1.57 (95%CI 0.89, 2.76). Among high quality studies 5 reported major bleeding with a rate of 0.76% and 6 reported on IVC filter complications with a rate of 0.67%. Overall no significant reduction in the rate of venous thrombosis was found with prophylactic IVC filter insertion. Use of IVC filters for prophylaxis remains a concern given the lack of clear efficacy in this setting and a small but present complication risk.

Intravascular Ultrasound for the Peripheral Vasculature-Current Applications and New Horizons

Intravascular ultrasound (IVUS) is a proven and rapidly developing imaging modality that can be used for a multitude of both diagnostic and interventional purposes. By allowing for superior intraluminal characterization, compared with angiography, IVUS has emerged as a technically valuable tool in interventional procedures such as transjugular intrahepatic portosystemic shunt/direct intrahepatic portosystemic shunt, venous interventions (May Thurner stenting, inferior vena cava filter placement, recanalization in the setting of chronic venous thrombosis/insufficiency), percutaneous fenestration in the setting of aortic dissection and angioplasty. Additional applications evaluating coronary arteries and plaque morphology have been described, but are outside the scope of this review. In addition to IVUS's merit as a pre- and intra-procedural guidance modality, there are also several advantages compared to the gold standard of angiography which include decreased need for iodinated contrast, decreased radiation exposure and decreased procedural times in certain cases. With current research, such as that aimed at supraharmonic imaging, further improvements in imaging depth, resolution and contrast to noise ratio are on the horizon.

Decision analysis of retrievable inferior vena cava filters in patients without pulmonary embolism

BACKGROUND

Retrievable filters are increasingly implanted for prophylaxis in patients without pulmonary embolism (PE) but who may be at transient risk. These devices are often not removed after the risk of PE has diminished. This study employs decision analysis to weigh the risks and benefits of retrievable filter use as a function of the filter's time in situ.

METHODS

Medical literature on patients with inferior vena cava (IVC) filters and a transient risk of PE were reviewed. Weights reflecting relative severity were assigned to each adverse event. The risk score was defined as weight × occurrence rate and combines the frequency and severity for each type of adverse event. The value function in the decision model combines the following risks: (1) risk in situ; (2) risk of removal, and (3) relative risk without filters. A decreasing net risk score represents a net expected benefit, and an increasing net risk score indicates the expected harm outweighs the expected benefit.

RESULTS

The net risk score reaches its minimum between day 29 and 54 postimplantation. This is consistent with an increasing net risk associated with continued use of retrievable IVC filters in patients with transient, reversible risk of PE. The results were insensitive to reasonable variations in the assessed weights and adverse event occurrence rates.

CONCLUSIONS

For patients with retrievable IVC filters in whom the transient risk of PE has passed, quantitative decision analysis suggests the benefit/risk profile begins to favor filter removal between 29 and 54 days after implantation.

Forensic Considerations in Bariatric Surgery Patients

Bariatric surgery is gaining in popularity in the United States and around the world as a treatment for morbid obesity. Patients seek surgery in order to lose weight and limit the long-term effects of insulin-resistant diabetes, heart disease and lung disease, including risk of sudden death. While gastric bypass in patients with morbid obesity can reduce the risk of diabetes and myocardial infarction to population levels, the risk of death remains increased. These patients may die suddenly and unexpectedly as a direct result of surgery, as an indirect result of surgery, or of end-organ damage wrought by years of obesity, completely unrelated to the surgery. Proper forensic pathologic assessment of these patients requires an understanding of the anatomic changes caused by bariatric surgery, the complications and the metabolic consequences of the different procedures. In order to better understand this subgroup of patients, a search of the peer-reviewed medical literature at the National Library of Medicine was conducted for articles using the keywords bariatric, surgery, gastric bypass, autopsy, review, toxicology, alcohol, drug, ethanol, absorption, elimination, litigation, forensic, and death. This review outlines the most common laparoscopic and open surgical procedures; the common immediate post-surgical complications that lead to morbidity and mortality; forensic toxicological considerations in bariatric patients; and the long-term complications and other causes that could lead to unexpected death in these patients.

The role of intravascular ultrasound in venous thromboembolism

Venous thromboembolism (VTE) remains a serious problem, and treatments surrounding this potentially life-threatening disease continue to evolve. Evidence-based guidelines purport the need for minimally invasive catheter-based procedures as part of the armamentarium to prevent and treat VTE. When the appropriate clinical scenarios arise, intravascular ultrasound (IVUS) becomes a necessary part of those procedures to provide alternative imaging that complements traditional venography. IVUS of the major axial veins provides a 360-degree two-dimensional gray scale ultrasound image of lumen and vessel wall structures. IVUS remains the criterion standard for venous imaging when contemplating catheter-based procedures from the common femoral vein to the inferior vena cava. Not only can precise location and size of these veins be determined by the IVUS probe from key landmarks and venous branches, but other important abnormalities can be visualized. These include external compression, acute and chronic thrombus, fibrosis, mural wall thickening, spurs, and trabeculations. Specific procedures that use IVUS include the treatment of venous obstruction and the placement of vena cava filters at the bedside. IVUS remains a vital part of accurately imaging the major axial veins when contemplating catheter-based procedures to prevent or treat VTE-related disorders.

Difficulties in managing the surgical patient who is morbidly obese

Managing patients who are morbidly obese in the intensive care unit is associated with a variety of problems uncommonly experienced with the those who are not morbidly obese. Clinicians experience a myriad of unique problems and circumstances, from the need for special beds and lifts to unusual and unknown volumes of distribution resulting in unclear drug dosing. This review examines several issues including sedation, invasive monitoring, venous thromboembolism prophylaxis, surgical infections, nutritional support, and other complications that may be of particular importance to the critically ill patient who is morbidly obese. In many cases, care is altered based on the complicating issues surrounding morbid obesity. In other cases, the presence of obesity suggests no alterations in our routine critical care delivery. A comprehensive review of the literature is undertaken, data are critically considered, and overall opinion is rendered based on the available peer-reviewed literature. In many cases, data are not available that address the specific patient population in question, so related papers (like gastric bypass data) are considered. Many issues do not have definitive answers based on randomized controlled trials, and much is left to treating clinician opinion and local practice patterns. Where good data exist, however, one should consider carefully and individually deviation from the evidence-based approach.