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Larger doses of LMWH needed for DVT Prevention in Surgery for Obesity (Bariatric Surgery)?

Henry I. Bussey, Pharm.D., FCCP, FAHA
March 2004

Although this article is not on a new report, ClotCare would like to thank Matt Young, Pharm.D. of the Eastern Idaho Regional Medical Center for bringing this information to our attention.

Patients who undergo surgery for obesity are at significant risk for thromboembolic complications. Although low molecular weight heparins (LMWH) have been used for DVT prevention for quite some time, there continues to be controversy as to whether the dose needs to be adjusted in obese patients. In this case series of 481 patients, the first 92 patients received the "standard" enoxaparin (Lovenox) regimen of 30 mg every 12 hours. The subsequent 389 patients received a larger dose of 40mg every twelve hours. The two groups were similar in terms of body mass index, age, gender, and history of prior DVT (3.2% in the lower dose group and 3.9% in the higher dose group). Other DVT preventive measures were used in both groups (early ambulation, graduated compression stockings, and intermittent pneumatic compression devices) and the mean time in surgery was longer in the lower dose group (213 min. vs. 175 min.). The incidence of post-operative DVTs was 5.4% (5 of 98 patients) in the low dose group and 0.6% (2 of 389 patients) in the high dose group (p < 0.01). One patient in each group required treatment for bleeding.

Although this was not a randomized controlled trial, and it is possible that the longer time in surgery may have increased the risk of DVT in the low dose group, the results suggest that a higher dose of LMWH may be superior to the usual regimen in preventing DVT in bariatric surgery patients.


Scholten DJ, Hoedema RM, Scholten SE. A comparison of two different prophylactic dose regimens of low molecular weight heparin in bariatric surgery. Obesity Surgery 2002; 12(1):19-24.

Related Study

ClotCare would like to thank Richard H. Parrish II, PhD, RPh of Shenandoah University for bringing this related study to our attention and for providing the summary below.

This randomized, prospective trial of 60 consecutive obese patients undergoing Roux-en-Y gastric bypass (RYGB) studied the effect of two doses of nadroparin as prophylaxis for post-operative venous thromboembolism. Patients were randomized to receive either 0.6 mL (5,700 IU) or 1.0 mL (9,500 IU) of nadroparin started pre-operatively and then given once daily post-operatively until discharge. The authors found no statistically significant differences between the two groups in any of the measured coagulation parameters either preoperatively or at days 1, 3, and 5 postoperatively. No thrombotic events were observed pre- or post-operatively, and no patient developed meta-thrombotic syndrome at the 3 and 6 months follow-up. No hemorrhagic events occurred in patients given the lower dose compared with two major bleeding episodes in those given the higher dose. They concluded that 0.6 mL (5,700 IU) of nadroparin once daily is safe, well-tolerated, and as effective in prophylaxis of venous thromboembolism as the higher dose of 1 mL (9,500 IU) in morbidly obese patients.

ClotCare Editor's Note

Nadroparin is not available in the U.S. Many surgeons may be reluctant to initiate anticoagulation pre-operatively as was done in this study. One should not presume that the dosing regimens used in this study would have the same safety and efficacy if started post-operatively.


Kalfarentzos F, Stavropoulou F, Yarmenitis S, Kehagias I, Karamesini M, Dimitrakopoulos A et al. Prophylaxis of venous thromboembolism using two different doses of low-molecular-weight heparin (nadroparin) in bariatric surgery: a prospective randomized trial. Obes Surg 2001;11(6):670-6.

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Friday, June 14, 2024