Venous thromboembolism (VTE) refers to inappropriate blood clots in the veins. VTE encompassing deep vein thrombosis (DVT) in which clots are formed in the deep veins of the body; and pulmonary embolism (PE), which occurs when a clot breaks and enters the arteries of the lungs.1 The incidence of VTE in the United States is 900,000 people annually, and the incidence of mortality is 60,000-100,000 each year.2 Risk factors for VTE include male gender, higher BMI, obesity hypoventilation syndrome, pulmonary hypertension, older ages, prolonged immobility, multiple traumas, malignancy, major surgery, personal history of VTE, operation time and the type of bariatric surgery.3

Obesity, a public health issue, increases the risk of other diseases, such as diabetes mellitus, malignancies, gastrointestinal disorders, depression, atherosclerotic cardiovascular diseases, hypertension, and VTE.4 VTE is a growing public health problem and patients with obesity have a moderate to high risk for pulmonary embolism, this fact has been studied since 1997.5

The prevalence of obesity has tripled in the last three decades and surgical methods have been explored to reduce obesity in a patient.6 Based on World Obesity Atlas 2022 prediction, one billion people will be living with obesity including 1 in 5 women and 1 in 7 men by 2030.7 Bariatric surgery has evolved in the United States and worldwide over the past two decades and reduces the risk of potentially life-threatening weight-related health problems. Most bariatric surgeries include Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG)8 . However, bariatric surgery is not free from complications and is associated with 0.1% - 1.1 mortality.9,10 However bariatric surgery is categorized in minimally invasive surgery, but it has a series of post operative complications including dumping syndrome, anastomic leakages, malnutrition, VTE, bowel obstruction, and sepsis.11 Among these complications, VTE is a major cause of postdischarge mortality after bariatric surgery.12 The overall 30-day incidence of postdischarge VTE following bariatric surgery was 0.29%.13 Although the amount of VTE after bariatric surgery is not very high, still is the major cause of postdischarge mortality, as well as the increasing prevalence of obesity and subsequently bariatric surgeries have seen a significant increase in VTE complications.

VTE is a preventable disease, and thromboprophylaxis is the main strategy to reduce VTE-induced mortality after bariatric surgery.14 Enoxaparin, which is sold inder the brand name Lovenox®, is used to treat and prevent deep vein thrombosis and embolism during pregnancy and following certain types of surgery such as SG, and RYGB. In addition, Rivaroxaban is under the brand of XARELTO®, and is usually prescribed for treatment and prevention of blood clots. It may prevent other clinical conditions such as the risk of ischemic strokes, as well as deep vein thrombosis (DVT), and embolic events.15 The main aim of this study is to evaluate the efficiency of thromboprophylaxis on VTE, including Enoxaparin and Rivaroxaban, in 1000 patients following sleeve gastrectomy surgery. To the best of our knowledge, this is the first study on evaluation of thromboprophylaxis medicine outcomes among laparoscopic sleeve gastrectomy patients in this large scale population.

In total, 1,000 patients underwent laparoscopic sleeve gastrectomy surgery between Apr 2017 and Jan 2021. All of subjects completed at least 3 months of follow-up. Patient’s characteristics are presented in Table 1. The mean age of all patients was 44.5 years old (standard deviation±3.3 yr) and most were under the age of 50. There were more females (61%) than males (39%). The median body weight was 127.6 kg. The mean BMI of subjects was 48.4±3.65 and the BMIs of 16.4% of patients were ≥55 kg/m2. The median follow-up time was 3 months. The age and sex of patients when they underwent bariatric surgery are illustrated in Table 1. The mean ASA score of patients was 2.1 (standard deviation 0.7) and EOSS grade was stage 2.3 (standard deviation 1.1). Fig. 1 presents more details on the strategies we considered in this study with summary of results from the target groups undergoing bariatric surgery whom were evaluated for VTE complications.

Fig. 1.

The schematic plan and strategies of this study including medicine treatment strategy immediately after laparoscopic sleeve gastrectomy as well as the strategy of medicine treatment after VTE diagnosis.

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The cumulative incidence of symptomatic postoperative VTE at 3 months was 1/1000 patients or 0.001%. The only VTE case observed was a 44-year-old male with BMI 46.2 kg/m2, with no history of VTE (and no family history of VTE) or smoking who received Rivaroxaban same as other patients in group 2. Patient had no history of steroid/immunosuppressant use in his life. This case was diagnosed 23 days after hospital discharge and laboratory variables included serum creatinine (0.92 mg/dL), albumin (4.10 g/dL), hematocrit (40.95%), and platelet count (265.32 109/L) for the patient after VTE diagnosis. Details regarding this patient are demonstrated in Table 2. At the 3-month follow up period of all other patients underwent bariatric surgery and received Enoxaparin or Rivaroxaban, there was no reported VTE-related mortality.

Bariatric surgery has a series of complications such as VTE, which is the major cause of post-discharge mortality following bariatric surgery.12 Increased age, weight, male gender, and having the history of VTE are the main risk factors for postoperative VTE.18 Although the rate of VTE after bariatric surgery is not very high, with increasing the rate of obesity and the need for bariatric surgery as an effective approach to reducing weight, VTE remains an important preventable complication in the populations.12,19

Since patients with obesity undergoing bariatric surgery are at risk of thromboembolic complications18 and based on the guidelines issued by the American College of Chest Physicians that recommends the use of thromboprophylaxis for bariatric surgery patients.20 In our study of patients undergoing bariatric surgery, all patients received thromboprophylaxis with each Enoxaparin or Rivaroxaban postoperatively and up until discharge from hospital for VTE prophylaxis.

All patients in this study received a fixed dose of Enoxaparin 2.5 mg twice daily or Rivaroxaban 10 mg once daily with or without food. The incidence of VTE at 3 months after bariatric surgery was 0.001%. The only male subject diagnosed with VTE was 44 years old with no history of VTE, smoking, documented venous insufficiency or varicose veins but he had history of pulmonary thromboendarterectomy (PTE). After VTE diagnosis, the patient received 15 mg of Rivaroxaban twice daily with food for three weeks, then 20 mg of Rivaroxaban prescribed once daily with food. Overall laboratory tests demonstrated normal levels of creatinine (0.92 mg/dL), albumin (4.10 g/dL), hematocrit (40.95%), and platelet count (265.32 109/L) even after VTE diagnosis. More information on clinical background of this patient is presented in table 2. The ASA score for all patients involved in this survey was ASA II which is considered a morbidly obese condition and is defined as mild systemic disease. On the other side, EOSS scoring analysis revealed that the target group in this study had 2.3 EOSS score. EOSS stage 2 indicated that patient has established obesity-related comorbidities requiring medical intervention. The mortality rate was zero at the 3-month follow-up period which is mainly due to the low population of this study. Therefore, we have approved that thromboprophylaxis might be effective in preventing VTE in patient undergoing bariatric surgery. However, further studies with large population, long-term follow-up and considering more clinical evaluations are needed to strongly confirm this relationship and efficacy of those thromboprophylaxis medicines on VTE complications after bariatric surgery. In this study we tried to focus on single-ethnicity target group, and its population-based nature, and with single-center surgical team performances, with follow-up of patients in the community. Furthermore, researchers can continue this survey on patients with higher scores of ASA and EOSS which consists of individuals with higher risks of post-operative complications.

In addition, in this study, the VTE was observed 23 days after discharging the patient from the hospital with laboratory variables including serum creatinine (0.92 mg/dL), albumin (4.10 g/dL), hematocrit (40.95%), and platelet count (265.32 109/L) after VTE diagnosis. This result is consistent with the findings reported across several published studies reporting that most VTE events occurred in bariatric surgery patients within 3 months after discharging from the hospital.21–27 Therefore, treatment with thromboprophylaxis with follow-up of patients at least for 3 months after hospital discharge is essential and should be considered for patients following bariatric surgery.

VTE is a preventable complication that has a risk of mortality after bariatric surgery. However, treatment of thromboprophylaxis with Enoxaparin and Rivaroxaban might be an effective strategy after bariatric surgery with a low incidence of severe bleeding complications. The only patient diagnosed with VTE, had no history of VTE, smoking, varicose vein, and family history of VTE, but he had history of PTE. This information can be taken into account during and after bariatric surgery.

Conception and design: TA; Administrative support: TA; Collection and assembly of data: BB, JO; Data analysis and interpretation: BB, JO; Manuscript writing: All authors; Final approval of manuscript: All authors.

This is a self-funded study.