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Bariatric surgery and bleeding

EPT more accurate for bariatric surgery anticoagulant dosage

Although anticoagulants are given before surgery and during hospitalisation to reduce VTE, the optimal dose, timing and the duration of the treatment for obese patients has yet to be determined

Endogenous thrombin potential (ETP), which measures the enzyme in blood plasma that causes blood to clot and bleeding risk, provides a more accurate assessment of the best dosage for various anticoagulants, according to researchers from Rutgers Ernest Mario School of Pharmacy. The results revealed that 80 percent of patients receiving enoxaparin had minor bleeding during surgery, which correlated with the ETP measurement.

Although anticoagulants are given before surgery and during hospitalisation to reduce venous thromboembolism (VTE) risk, the optimal dose, timing and the duration of the treatment for obese patients has yet to be determined. The paper, ‘Anticoagulant activity of enoxaparin and unfractionated heparin for venous thromboembolism prophylaxis in obese patients undergoing sleeve gastrectomy’, published in the journal Surgery for Obesity and Related Diseases, sought to:

  • Evaluate the attainment of anti-Xa goal levels in sleeve gastrectomy patients managed with the institution standard VTE chemoprophylaxis
  • Analyse discordance between anti-Xa and TGA in terms of adequacy of anticoagulation; and
  • Evaluate the correlation of various measures of body composition with coagulation parameters.

"There is no requirement for drug manufacturers to perform research studies in obese individuals, which means there are no standard recommendations," said Dr Luigi Brunetti from the Rutgers and the lead investigator on the study, and in collaboration with Dr Leonid Kagan (also from Rutgers) and Dr Ragui Sadek at Advanced Surgical and Bariatrics of New Jersey. "We do not know which methods perform best in preventing blood clots without risk of bleeding in cases of extreme body weight."

Dr Luigi Brunetti (left) Dr Leonid Kagan (Credit: Rutgers Ernest Mario School of Pharmacy)

In the study, patients received either subcutaneous enoxaparin (which lowers the activity of clotting proteins in the blood) or unfractionated heparin (UFH, which works with a natural protein in the body to block clot formation). Standard institutional practice is to administer the first anticoagulant dose two to three hours prior to surgery. The subcutaneous injection is administered in the side or back of the upper arm to avoid administration close to the site of surgery. Enoxaparin 40mg (Lovenox, Sanofi-Aventis) was administered subcutaneously every 12 hours. UFH (heparin sodium, Hospira) was administered subcutaneously every eight hours depending on body weight. Patients weighing more than or equal to 120kg received 7500 units, while others received 5000 units.

Outcomes

In total 60 patients were enrolled, with 16 receiving enoxaparin and 44 receiving UFH. Baseline demographics were similar between groups with the exception of BMI and weight, which were significantly higher in the UFH group. The enoxaparin group achieved the anti-Xa target for prophylaxis significantly more frequently than the UFH group (93.8 % vs. 4.5%, respectively; p<0.0001).

"Currently, most physicians prescribe 40 milligrams of enoxaparin twice daily, and some are advocating for even higher doses for patients with extreme obesity," added Brunetti. "That dosage is ill-advised based on our study, which found that patients who received that dose experienced minor bleeding. I suspect a higher dosage would result in more minor bleeding and perhaps major bleeding as well. ETP can potentially help physicians better understand the right dosage, so obese patients will see benefits without being harmed."

Furthermore, the target ETP reduction from baseline was more frequently obtained in the enoxaparin group vs. UFH (50% versus 27.7%, respectively; p=0.12). ETP and anti-Xa were concordant in 68.3% of cases (based on the goal definitions used). No patients were readmitted with a VTE within 30 days of hospital discharge. Major bleeding during surgery occurred in one patient in the enoxaparin group. Minor bleeding was significantly more common in the enoxaparin group (87.5% versus 27.3%, respectively; p<0.0001).

“High dose enoxaparin achieves target anti-Xa and ETP more frequently than high dose UFH prophylaxis at the expense of greater rates of minor bleeding. Change in ETP is correlated to several body composition measures, in particular basal metabolic rate, in patients receiving enoxaparin,” the authors concluded. “Further study is needed to determine if ETP guided therapy is a more appropriate measure of coagulation status and better correlated to patient outcomes. Ultimately, a randomised controlled trial is necessary to identify which prophylaxis regimen provides the greatest benefit-to-risk ratio and whether monitoring coagulation parameters provides any clinical utility.”

To access this paper, please click here

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