ORLANDO – The latest American Society of Hematology guideline on venous thromboembolism (VTE) tackles 30 key questions regarding prophylaxis in hospitalized patients undergoing surgery, according to the chair of the guideline panel, who highlighted 9 of those questions during a special session at the society’s annual meeting.
The clinical practice guideline, published just about a week before the annual meeting of the American Society of Hematology, focuses mainly on pharmacologic prophylaxis in specific surgical settings, said David R. Anderson, MD, dean of the faculty of medicine of Dalhousie University, Halifax, N.S.
“Our guidelines focused upon clinically important symptomatic outcomes, with less emphasis being placed on asymptomatic deep vein thrombosis detected by screening tests,” Dr. Anderson said.
At the special education session, Dr. Anderson highlighted several specific recommendations on prophylaxis in surgical patients.
Pharmacologic prophylaxis is not recommended for patients experiencing major trauma deemed to be at high risk of bleeding. Its use does reduce risk of symptomatic pulmonary embolism (PE) and deep vein thrombosis (DVT) by about 10 events per 1,000 patients treated; however, Dr. Anderson said, the panel’s opinion was that this benefit was outweighed by increased risk of major bleeding, at 24 events per 1,000 patients treated.
“We do recommend, however that this risk of bleeding must be reevaluated over the course of recovery of patients, and this may change the decision around this intervention over time,” Dr. Anderson told attendees at the special session.
That’s because pharmacologic prophylaxis is recommended in surgical patients at low to moderate risk of bleeding. In this scenario, the incremental risk of major bleeding (14 events per 1,000 patients treated) is outweighed by the benefit of the reduction of symptomatic VTE events, according to Dr. Anderson.
When pharmacologic prophylaxis is used, the panel recommends combined prophylaxis – mechanical prophylaxis in addition to pharmacologic prophylaxis – especially in those patients at high or very high risk of VTE. Evidence shows that the combination approach significantly reduces risk of PE, and strongly suggests it may also reduce risk of symptomatic proximal DVT, Dr. Anderson said.
In surgical patients not receiving pharmacologic prophylaxis, mechanical prophylaxis is recommended over no mechanical prophylaxis, he added. Moreover, in those patients receiving mechanical prophylaxis, the ASH panel recommends use of intermittent compression devices over graduated compression stockings.
The panel comes out against prophylactic inferior vena cava (IVC) filter insertion in the guidelines. Dr. Anderson said that the “small reduction” in PE risk seen in observational studies is outweighed by increased risk of DVT, and a resulting trend for increased mortality, associated with insertion of the devices.
“We did not consider other risks of IVC filters such as filter embolization or perforation, which again would be complications that would support our recommendation against routine use of these devices in patients undergoing major surgery,” he said.
In terms of the type of pharmacologic prophylaxis to use, the panel said low-molecular-weight heparin or unfractionated heparin would be reasonable choices in this setting. Available data do not demonstrate any significant differences between these choices for major clinical outcomes, Dr. Anderson added.
The guideline also addresses duration of pharmacologic prophylaxis, stating that extended prophylaxis – of at least 3 weeks – is favored over short-term prophylaxis, or up to 2 weeks of treatment. The extended approach significantly reduces risk of symptomatic PE and proximal DVT, though most of the supporting data come from studies of major joint arthroplasty and major general surgical procedures for patients with cancer. “We need more studies in other clinical areas to examine this particular question,” Dr. Anderson said.
The guideline on prophylaxis in surgical patients was published in Blood Advances (2019 Dec 3;3:3898-944). Six other ASH VTE guidelines, all published in 2018, covered prophylaxis in medical patients, diagnosis, VTE in pregnancy, optimal anticoagulation, heparin-induced thrombocytopenia, and pediatric considerations. The guidelines are available on the ASH website.
Dr. Anderson reported having no relevant conflicts of interest.
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