Weight-adjusted tinzaparin provides safe thromboprophylaxis after bariatric surgery

Extended thromboprophylaxis with weight-adjusted tinzaparin appeared safe and effective for patients following bariatric surgery, according to results of a single-center retrospective cohort study.

Patients experienced few incidences of venous thromboembolism and major bleeding.

“Bariatric surgery is an effective intervention for producing sustained weight reduction in obese patients and, currently, is the second most common surgical procedure performed in North America,” Eric K. Tseng, MD, hematologist at St. Joseph’s Hospital and McMaster University in Ontario, and colleagues wrote. “Patients undergoing bariatric surgery are at moderate to high risk for VTE, which comprises deep vein thrombosis and pulmonary embolism, due to associated risk factors that include obesity, perioperative venous stasis and hypercoagulability.”

The optimal strategy for postsurgery VTE prophylaxis remains uncertain.

“An issue relevant to bariatric surgery is whether to use a weight-adjusted dose of low-molecular-weight heparin prophylaxis instead of a fixed, low-dose low-molecular-weight heparin regimen, which may result in an inadequate anticoagulant effect,” the researchers wrote. “In a meta-analysis of 19 observational studies, it was concluded that the incidence of major bleeding appeared to increase using weight-adjusted doses of heparin with no advantage for VTE reduction. ... Meanwhile, a prospective study with tinzaparin demonstrated that anti-Xa activity is independent of body weight when weight-based dosing is used in obese patients, suggesting that weight-based dosing is appropriate.”

Tseng and colleagues assessed 1,212 consecutive patients (median age, 45 years; median weight, 130 kg) undergoing bariatric surgery from July 2009 to December 2012. Patients received weight-adjusted tinzaparin (Innohep, LEO Pharma) in doses ranging from 4,500 IU to 14,000 IU daily for 10 days after surgery (1 to 3 days inpatient treatment, 7 to 9 days outpatient).

Most patients (98.8%) underwent gastric bypass (78.3%) or sleeve gastrectomy (20.5%).

Researchers collected safety data on 1,212 in-hospital only patients and on 819 patients with 30 days of follow-up.

Among patients with 30-days of follow-up, four patients (0.5%) experienced VTE, including three with PE and one case of superior mesenteric vein thrombosis. Thirteen patients (1.6%) experienced major bleeding.

Among the full study population, researchers observed three patients (0.2%) with VTE — all of which were PE within 1 to 5 days following surgery — and 22 patients (1.8%) with major bleeding.

Researchers measured trough antifactor Xa activity in a subset of 187 patients after a median 6 days of tinzaparin treatment. All these patients had antifactor Xa levels of 0.4 IU/mL or less, with 74.8% having undetectable activity (< 0.10 IU/mL).

“These findings suggest that 10 days of weight-adjusted tinzaparin is a safe strategy [for] VTE prophylaxis after bariatric surgery,” the researchers wrote.

“Our findings also support the premise that extended prophylaxis beyond the in-hospital period appears to be safe and feasible,” they added. “Most VTE events after bariatric procedures occur after discharge from hospital, providing the rationale for extended duration prophylaxis, especially as patients are now discharged within 48 hours (often the same day) after bariatric surgery.”

Researchers cited no control group and lack of data on VTE risk factors as potential limitations of the study.

“In conclusion, this study provides evidence for the safety of extended thromboprophylaxis with weight-adjusted tinzaparin after bariatric surgery,” the researchers wrote. “The dosing protocol used in this real-world study demonstrates low rates of VTE and major bleeding. Given the moderate to high risk of postoperative VTE in this surgical population, this approach should be considered in bariatric centers for routine thromboprophylaxis.” – by Cassie Homer

Disclosures: Tseng reports research grants from Pfizer and personal fees from LEO Pharma. Please see the study for all other authors’ relevant financial disclosures.