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VTE prophylaxis

IVC filters do not reduce VTE events during bariatric surgery

Prescribing higher doses of thrombolytic drugs does not seem to reduce the rates of bleeding

There is ‘no evidence’ that using inferior vena cava (IVC) filters helps to prevent venous thromboembolism (VTE) during bariatric surgery, a literature review has reported. The systematic review and meta-analysis, published in JAMA Surgery, noted a trend toward higher DVT (deep vein thrombosis) rates and mortality in patients receiving filters.

"Overall, our findings support the use of 'standard' doses of pharmacotherapy as prophylaxis for patients undergoing bariatric surgery, consistent with current American College of Chest Physicians guidelines, which do not distinguish between patients undergoing bariatric surgery and those undergoing other types of abdominal surgery," the authors conclude. "We found no evidence to support filter placement as prophylaxis in patients undergoing bariatric surgery, with a trend toward higher DVT (deep vein thrombosis) rates and higher mortality in patients receiving filters."

The researchers from The Johns Hopkins University, Baltimore, also found that prescribing higher doses of thrombolytic drugs does not seem to reduce the rates of bleeding.

As prophylaxis to prevent VTE is currently recommended for patients undergoing abdominal surgery, study lead Dr Daniel J Brotman and colleagues wanted to assess the comparative effectiveness and safety of pharmacologic and mechanical strategies to prevent VTE in patients undergoing bariatric surgery.

Daniel Brotman

They identified 13 studies in their review; eight studies of pharmacologic strategies and five studies of filter placement. They found no randomised clinical trials addressing the comparative effectiveness of different interventions to prevent VTE among patients undergoing bariatric surgery so all the studies were observational in nature.

The filters that were used varied according to physician and practice preference. They included these retrievable filters: Gunther Tulip, Bard Recovery, OptEase, Cook Celect, and Bard G2, and nonretrievable filters such as the Greenfield Stainless Steel, Simon Nitinol, and TrapEase.

There was insufficient evidence supporting the hypothesis that filters reduce the risk of pulmonary embolism, with a point estimate suggesting increased rates with filters (pooled relative risk [RR], 1.21; 95% CI, 0.57-2.56). There was low-grade evidence that filters are associated with higher mortality (pooled RR, 4.30; 95% CI, 1.60-11.54) and higher deep vein thrombosis rates (2.94; 1.35-6.38).

The authors found only one study that included the filter retrieval rate: 92%. Also, filter use was sometimes accompanied by drug therapy, such as enoxaparin, heparin, or warfarin.

"If you're undergoing minimally invasive bariatric surgery, receive standard doses of blood thinners and get up and about as soon as possible after your operation, the chances of getting a blood clot are low," he added. "And the evidence suggests that use of filters may do more harm than good. If filters helped, we could find no evidence of that. The data suggest more patients are harmed than benefit from these devices."

He said the risk of fatal blood clots in bariatric surgery patients is less than 1%. One reason may be that the operation is becoming less invasive, allowing patients to get up and walk around sooner after surgery.

One study suggested that low-molecular-weight heparin is more efficacious than unfractionated heparin in preventing VTE (0.25% vs. 0.68%, p<.001), with no significant difference in bleeding. One study suggested that prolonged therapy (after discharge) with enoxaparin sodium may prevent VTE better than inpatient treatment only.

The various dosing regimens of enoxaparin ranged from 30mg once daily to 60mg twice daily. Overall, the results were not strong enough to recommend augmented dosing of enoxaparin, no matter the patient's weight. There was, however, a trend for more bleeding with higher doses of the drug.

"I was a bit surprised by this, since we do use higher doses of blood thinning medications in larger patients when we're treating clots, so one would think that larger patients would also require higher doses of these medications to prevent clots," said Brotman. "But if this was the case, we could not detect it."

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