6 Factors Impacting Thromboembolism after Bariatric Body-Contouring Surgery
Abstract
Venous thromboembolism (VTE) is the most deadly complication of body contouring after massive weight loss (MWL). VTE includes the spectrum of disease ranging from deep venous thrombosis (DVT) to pulmonary embolism (PE). Perioperative measures that can be taken to prevent VTE are stratified according to patient risk. Signs and symptoms of DVT and PE after body-contouring surgery are discussed, in addition to work-up and treatment.
Introduction
Prevalence of Deep Venous Thrombosis/Pulmonary Embolism
The overall incidence of deep venous thrombosis (DVT) in the United States is 84 to 150 per 100,000 per year, or 250,000 cases per year. One million patients are tested annually in the United States for suspicion of DVT, and approximately 25% have the diagnosis confirmed.1–3
The incidence of pulmonary embolism (PE) in the United States has a wide reported range, from 125,000 to 400,000 cases per year, causing 200,000 deaths per year.4,5 PE is the third most common direct cause of death in the United States6,7 PE causes approximately 5% of all perioperative deaths.8 In a landmark multicenter study, the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED), 60 to 70% of all autopsied hospital patients were found to have one or more pulmonary emboli present, 70% of which were undiagnosed prior to death.9
Surgery presents an important risk factor for venous thromboembolism (VTE). Orthopedic surgery is associated with one of the highest rates of PE and DVT, even with prophylaxis. Elective hip replacement has an incidence of PE of 2 to 3%, and hip fracture fixation, 4 to 7%.10 Aggregate general surgery procedures, including cancer resections, have a reported PE incidence of 0.1 to 0.8%, rising to 3.5% in bariatric patients, even with prophylaxis.11 The bariatric surgery literature has shown a VTE risk of 0.2 to 1% after gastric bypass surgery.12
The rate of VTE in plastic surgery procedures ranges from 1 to 10% depending on the procedure.13 PE is the major cause of death following liposuction, accounting for 23% of all deaths. In a prospective series of office-based surgical procedures, 63.6% of postoperative deaths were secondary to VTE.13 Abdominoplasty alone has a lower risk of VTE compared with procedures combining abdominoplasty with other excisional procedures, 4.7% versus 5.5%.14 Belt lipectomy procedures present the highest risk of VTE in plastic surgery, with Hatef et al14 reporting a 7.7% risk of DVT in their series, and Aly et al15 reporting a rate of 9.4% incidence of PE in their series.
Onset and Progression of Deep Venous Thrombosis
Approximately 50% of DVTs associated with surgery start intraoperatively, most beginning in the calf: 50% of these spontaneously resolve, and prophylaxis facilitates lysis of the remainder with prevention of formation of new DVTs.13
Approximately 25% of untreated symptomatic calf DVTs extend to the proximal veins within 1 week of presentation. In a study investigating patients with symptomatic DVT, 88% had above-the-knee involvement, and 12% had only below-the-knee involvement.16 Although below-the-knee DVT can embolize without proximal involvement, it is most often above-the-knee DVTs that embolize and cause pulmonary complications. Proximal DVT results in PE 50% of the time.17 The majority of patients with symptomatic proximal DVT and without chest symptoms have PE on a lung scan. The highest risk period for postoperative fatal PE occurs 3 to 7 days after surgery.13
The recurrence rate of DVT alone following treatment approaches 10% in patients with risk factors for DVT and is much lower (3%) in patients without risk factors.18 Although less than 10% of DVT patients develop severe post-phlebitic leg syndrome, a debilitating constellation of symptoms including edema, pain, leg ulcers, and skin induration similar to patients with venous insufficiency, up to 35% of patients may show milder symptoms.19,20 Therapy is only modestly successful, consisting of long-term use of sequential compression devices (SCDs) and surgical venous reconstruction and/or thrombectomy.21
Onset and Progression of Pulmonary Embolism
Pulmonary emboli, if diagnosed and treated early, carry a mortality rate of 2 to 8%. Even with aggressive treatment, 10% of PE patients have recurrent PE, and the death rate in this group approaches 45%.22 The caveat to these statistics is that many patients have subclinical DVT and PE with few if any symptoms, and they often improve spontaneously. The true incidence and prevalence of these diseases are therefore difficult to determine.
Roughly 10% of patients with acute PE die within 30 to 120 minutes of embolization, usually before medical help is available.23 The presence of shock at presentation increases the associated mortality.18 Of those obtaining prompt medical care, 2 to 8% of patients who survive initially will die despite treatment.1 For effective therapy, aggressive early treatment is required.
Of those who survive the acute stages of PE, approximately 5% continue to have significant right-sided heart failure after 1 year, a disabling and often lethal disease.24
Risk Factors of Venous Thromboembolism
Virchow described the triad of factors leading to VTE: venous stasis, vascular injury, and hypercoagulability13 ( Table 6.1 ). Body-contouring surgery involves many of these factors, including vessel injury with trauma to superficial veins, general anesthesia with a decrease in peripheral vascular resistance, intraoperative positioning decreasing venous return, and decreased ability for postoperative ambulation with stasis.14
Other important risk factors associated with VTE are prolonged airline travel of more than 8 hours and elevated estrogen levels.12 Estrogen may come from exogenous sources, including oral contraceptive pills (OCPs) and hormone replacement therapy (HRT); there is a three- to sixfold increase in the risk of VTE with OCP and a two- to fourfold increase in risk with HRT.13 Hormonal therapy with estrogens should be discontinued at least 1 week before the planned surgical procedure.
Hypercoagulability leads to VTE and occurs secondary to genetic or acquired coagulation disorders. Common inherited disorders include factor V Leiden; prothrombin 20210A; and deficiencies of protein C, protein S, and antithrombin III. Factor V Leiden is present in 4 to 6% of Caucasians.13 Acquired disorders leading to hypercoagulability are induced by medications or by disease, including antiphospholipid antibody syndrome, hyperhomocysteinemia, and cancer.13
Obesity is a risk factor for VTE.17 Reports show that obesity is associated with a relative risk factor of 2.5 for DVT and 2.1 for PE.25–27 A body mass index (BMI) >30 kg/m2 presents an increased risk for DVT in excisional body-contouring surgery at 6.9%.14
One of the greatest risk factors for VTE is a personal history of VTE4,12,25,27–29 ( Table 6.2 ). This information must be specifically elicited during the initial meeting with the patient, and surgical prophylaxis must be planned accordingly ( Fig. 6.1 ).
Risk Stratification
Individuals who are candidates for plastic surgery may be stratified according to their risk of DVT/PE into low-, moderate-, or high-risk categories. The American College of Chest Physicians (ACCP) presents a risk stratification with low-, moderate-, and high-risk categories, based on surgical complexity and duration, with associated risk factors and limits to mobility. Risk stratification then helps determine the VTE risk and the suggested thromboprophylaxis. In this way, low-risk patients undergoing minor surgery require no specific thromboprophylaxis; moderate-risk patients, including most surgical patients, should get chemoprophylaxis or mechanical prophylaxis alone if there is a high bleeding risk; and high-risk patients should get therapeutic dosing of anticoagulant therapy.12
Due to the lack of plastic surgery–specific thromboprophylactic guidelines and risk stratification by the ACCP, several risk assessment models have been developed for this patient population. In 2004, Davison et al4 reviewed the Caprini risk assessment model and made modifications specific to plastic surgery patients. The risk assessment model comprises three steps ( Table 6.2 ). The first step exposes the patient’s risk factors. The second step assesses the pre-disposing risk factors. The scores from the first and second steps are added to assign a patient to one of four risk groups: low, moderate, high, and highest.
Each risk group in the Davison-Caprini risk assessment model has associated recommendations for VTE prophylaxis ( Table 6.2 ). Low-risk groups require proper surgical positioning and early ambulation. It is recommended that the moderate-risk group receive proper positioning and early postoperative ambulation, as well as elastic stockings and intermittent pneumatic compression devices. The high-risk group receives similar prophylaxis to the moderate-risk group, with consideration of low molecular weight heparin (LMWH) administration based on bleeding risk. The highest-risk group should have proper operating room positioning, early ambulation, mechanical devices such as intermittent pneumatic compression or venous foot pumps, anticoagulant therapy with LMWH, and consideration of warfarin therapy postoperatively.4
A retrospective study evaluating 360 body-contouring patients from the University of Texas Southwestern Medical Center evaluated the Davison-Caprini risk assessment tool. The data showed that this risk assessment model is useful in assigning thromboembolic risk to plastic surgery patients. Of the 19 VTE events identified in their patients, 89.5% (17 of 19) were placed in the highest risk groups, and the remainder (2 of 19) were stratified to the high-risk group. The authors of the study suggest further revision to the Davison-Caprini risk assessment model to include circumferential abdominoplasty, BMI 30 kg/m2, and HRT as important VTE risk factors. These factors may be used to more specifically stratify plastic surgery patients into VTE risk categories.14
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7 The Anatomy and Chronology of Body Sculpting: Areas Requiring Correction and Timing of Procedures
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