Reconsidering the Role of Routine Anticoagulation for Venous Thromboembolism Prevention in Plastic Surgery

T oday, many plastic surgeons prescribe routine anticoagulation (“chemoprophylaxis”) in an effort to reduce venous thromboembolism (VTE) risk in plastic surgery patients. Anticoagulation has an appeal because it seems to make sense. However, its efficacy and safety have been challenged. New oral factor Xa inhibitors such as rivaroxaban (Xarelto; Janssen Pharmaceuticals, Titusville, NJ) and apixaban (Eliquis; Bristol-Myers Squibb, NewYork, NY) are often prescribed because they do not require injections. However, oral anticoagulants have not been shown to be effective in reducing VTE risk in plastic surgery patients. Dini et al terminated their prospective randomized study of chemoprophylaxis because of an alarming rate of hematomas in abdominoplasty patients who received rivaroxaban. Patronella discontinued using rivaroxaban after experiencing a 2.8% hematoma rate. Hunstad et al reported 3 hematomas requiring evacuation among 132 patients (2.3%), excluding 2 hematomas that were evacuated before the patients received rivaroxaban. By contrast, in my own study of 167 consecutive abdominoplasties treated with no chemoprophylaxis, there were no hematomas. Both the series reported by Hunstad et al and my own identified 1 known VTE (0.76% and 0.60%, respectively). Although its use is approved in patients undergoing knee or hip replacement, rivaroxaban is not approved by the US Food and Drug Administration (FDA) for deep venous thrombosis prophylaxis in plastic surgery. In a recently published study, Sarhaddi et al conclude that fondaparinux reduces the risk of VTE without increasing the risk of bleeding. In a retrospective chart review, the authors compared 2 historical groups of abdominoplasty patients. The first group treated between 2008 and 2011 (n = 233) did not receive chemoprophylaxis. The second group treated between 2011 and 2014 (n = 259) were prescribed fondaparinux. There were 5 VTEs in the untreated group and zero in the treated group. A χ test determined a significant difference (P = 0.02). However, the study is limited by a small study population. Group sizes of just over 200 patients are small when examining a complication that typically occurs at a rate of less than 1%. A limitation of a retrospective study design is that it allows the investigator to choose the time periods for the study, inviting selection bias. Moreover, a traditional χ test loses reliability when the cell sizes are fewer than 5. Some statisticians use a Yates correction when the expected frequency is fewer than 10. (In the study by Sarhaddi et al, 2 of the 4 group sizes were 0 and 5.) This correction is recommended to reduce the risk of a type I statistical error (ie, concluding that a real difference exists when it does not). When a Yates correction is used, the P value becomes 0.055. The Yates correction is not universally accepted, and some statisticians believe it may be too rigorous, but this issue underscores the weakness of the comparison. In the study by Sarhaddi et al, several of the VTEswere diagnosed at time points well beyond the 1-week period of anticoagulation. It is not clear that anticoagulation that stops 1 week after surgery will prevent VTEs that develop later. A therapeutic benefit is unlikely. Deep venous thromboses that develop after plastic surgery take 5 weeks on average to resolve with treatment. Another limitation of this study is the fact that the true rate of deep venous thromboses is unknown because Doppler ultrasound screeningwas not done. Clinical signs of VTE are notoriously unreliable. Shaikh et al were surprised to find that none of their 36 “highest risk” patients with Caprini scores of greater than 10 developed a VTE. A 2016 meta-analysis by Pannucci et al found that chemoprophylaxis did not significantly reduce VTEs in plastic surgery patients with Caprini scores of greater than 8. Moreover, the bleeding risk was increased. Pannucci et al recommend against adding routine chemoprophylaxis to intermittent pneumatic compression for VTE prophylaxis in non–risk-stratified plastic surgery patients. Other investigators have reported VTEs despite anticoagulation. Hatef et al reported a 5% incidence of VTE after abdominoplasty despite administering enoxaparin in high-risk patients, plus an increased risk of bleeding. Jeong et al reported 19 VTEs among 574 plastic surgery patients who received chemoprophylaxis (3.3%) versus only 5 VTEs among 1024 patients who did not receive chemoprophylaxis (0.5%). This difference, favoring the untreated patients, is highly significant (P < 0.00001).