Reply

Abstract

Sir:FigureWe thank Dr. Charles Yuen Yung Loh for his thoughtful comments provided in response to our article evaluating the incidence of venous thromboembolism in microsurgical breast reconstruction. He underscores the importance of the dosage and timing of administration of low-molecular-weight heparin, and its link to postoperative hematoma. As highlighted in our prospective cohort study, the incidence rates of major bleeding with the initiation of dalteparin for thromboprophylaxis 6 hours after surgery were similar to those reported in the general surgery and orthopedic surgery patient populations.1–3 The dose of dalteparin used in our study (5000 units) for thromboprophylaxis is equivalent to 40 mg of enoxaparin. With such a dose, we have not observed the high rates of postoperative bleeding reported by Dr. Loh, which prompted his group to reduce the dose to 20 mg. Venous thromboembolism prophylaxis guidelines in the United States and in the United Kingdom do not discriminate between different low-molecular-weight heparin agents. Three low-molecular-weight heparin agents are currently available in the United States: enoxaparin, dalteparin, and tinzaparin. According to the U.S. Food and Drug Administration, both enoxaparin and dalteparin are approved agents for thromboprophylaxis in patients undergoing abdominal surgery. This indication may possibly be extrapolated to women undergoing microsurgical autologous breast reconstruction using the abdominal donor site. However, there is a paucity of evidence comparing the efficacy and safety of enoxaparin versus dalteparin in the plastic surgery literature. To our knowledge, no study has compared differences in dosage and timing of administration between agents following microsurgical breast reconstruction. Of note, Bergqvist et al. found higher rates of perioperative hemorrhage when the first dose of low-molecular-weight heparin was administered 2 hours preoperatively.4 Furthermore, Turpie et al. found a 70 percent reduction in the risk of venous thromboembolism without excessive bleeding when the first dose of enoxaparin was given 12 to 24 hours postoperatively following hip replacement.2 Thus, plastic surgeons must still rely on the literature in other areas or on personal experience, as opposed to empirical evidence, to base their clinical decisions regarding the choice of agent, dosage, and timing of administration. Ultimately, decisions with respect to thromboprophylaxis in microsurgical breast reconstruction should be guided by considerations such as drug availability in a given institution, cost, ease of administration, and patient comfort, in addition to the clinically relevant outcomes of thromboprophylaxis. A multicenter prospective trial powered to detect differences in venous thromboembolism events with different regimens of low-molecular-weight heparin prophylaxis, controlling for various dosages and timing of administration in women undergoing microsurgical breast reconstruction, would be welcome. Such a trial would be able to highlight significant increases in the incidence of major bleeding associated with various low-molecular-weight heparin agents, variable doses, and frequency of administration. Such evidence could provide definitive information in a population where bleeding can have devastating consequences. Valerie Lemaine, M.D., M.P.H. Division of Plastic Surgery, Mayo Clinic, Rochester, Minn. Joseph J. Disa, M.D. Plastic and Reconstructive Surgery, Memorial Sloan-Kettering Cancer Center, New York, N.Y. DISCLOSURE The authors have no financial interest to declare in relation to the content of this communication.