Weight loss following bariatric surgery was evaluated by various methods. Total weight loss compared to the patient's weight before surgery, decrease in BMI, weight loss according to standard weight and BMI, loss of excess weight relative to standard weight (EWL) based on age and height, or loss in excess BMI based on BMI 25 kh/m2 (EBMIL) are some of these assessment methods (21). The rate of weight loss (% EWL), which has been popularly used recently, showed a success target of 50 and above in the first 1–2 years (22). In our study, % EWL and % EBMIL achieved in the first 3 months were calculated as 40.6 kg/m2 and 45.5 kg/m2 respectively, and no study in the literature has interpreted weight loss in the first 3 months. The previously published data focused on the 1-year results.
By virtue of heomeostasis there exists a delicate balance between coagulation and fibrinolysis in the vascular system and the disruption of this balance leads to pathological events. The increase in obesity in coronary heart diseases, peripheral vascular diseases, stroke, arterial and venous thrombosis (23) shows that this balance increases in favor of coagulation. Various clinical and epidemiological studies argue that there is a strong link between obesity and thrombosis (24, 25).
Increased fat mass in obesity is not only an increased fat tissue energy store, but also an increase in the secretion of a metabolically active fat cell and an increased autocrine, paracrine and endocrine effect with it. Leptin secreted from fat cell, adeponectin, resistin, plasminogen activator inhibitor – 1 (PAI – 1), tissue factor (TF), tumor necrosis factor alpha (TNF – α), transforming growth factor beta (TGF – β) and interleukin – 6 (IL – 6) all play an active role in thrombosis. (18). Increasing leptin in obese causes an increase in insulin resistance and increases the incidence of stroke and myocardial infarction (26). Hyperfibrinogenemia found especially in obese women increases the risk of developing coronary and peripheral artery diseases, stroke and venous thrombosis. Increased fibrinogen indicates the risk of developing arterial and venous thrombosis with fibrin formation, platelet aggregation, deterioration of blood viscosity, and atherosclerosis (26).
In recent years, many studies have been carried out especially on TF, Factor VII and PAI – 1. PAI – 1, a serine protease inhibitor and one of the most important coagulating agents providing the balance against the fibrinolytic system, has been shown to have a significant effect on the increase in morbidly obese patients and in the increase in thrombotic events in obesity (27). Along with it, an increase is detected in FVII, thrombin, thrombin-antithrombin complex (TAT) and TF activities, which have a significant role in thrombotic events (26, 27).
There are different and sometimes contradictory studies in the literature on the role of thrombocyte in obesity. The most important risk factors for increased venous thromboembolism in obese patients are inflammation, decreased fibrinolysis and increased thrombin formation, as well as increased platelet activation (17).
A significant improvement has been detected in morbid obese patients in hematological changes in blood flow, such as increased blood and plasma viscosity (27). Morbid obese patients, with either low-calorie diet (28) or weight loss after bariatric surgery operations had improvement in increased erythrocyte aggregation that appears in morbid obesity and impairs blood flow, and an improvement in the impaired lipid profile in hyperlipidemia have also had been found (24). Weight loss associated with obesity surgery and thromboembolic mediators such as PAI – 1 and TF reduction, chronic inflammation, metabolic changes, and provides improvement in platelet dysfunction (28). In the literature, long-term weight loss achieved by bariatric surgery and thromboembolic events that improve with it show that obesity is a thrombosis risk factor that can change and improve (18).
Lupoli et al. (29) reported improvement in impaired fibrinolytic activity in patients after bariatric surgery. In this study, while they recorded a 20% decrease in PAI – 1 in the first months, they found a 10% decrease in t-PA. However, decreases were found in FVII, Protein C and S (29). These factors were related to vitamin K. The rapidly decreasing fat mass with weight loss may also be the cause of the fat-soluble vitamin K deficiency, and it also explains the increased bleeding risk in the early period (29). The decrease in PAI – 1 was found to be between 75–80% at 12 months in other studies. In this study by Ferrer et al., it was determined that the platelet volume, not the platelet count, changed in the postoperative 12th month. However, a significant PT, CT prolongation and fibrinogen change were also noted (30).
Pulmonary embolism (1%) and deep vein thrombosis of obesity surgery of surgery and deep vein thrombosis (DVT) (1%) is a significant cause of mortality (31). In a comprehensive 8-year review of 4293 patients at the Cleveland Clinic by Jamal et al., they found that laparoscopic bariatric surgery and/or postoperative prophylactic anticoagulant therapy did not change the risk of DVT. This risk is average diagnostic time post-operative was 24th day. In the study, they showed that the conversion, increased age and high BMI increased this risk (31). In the study of Carmody et al. although routine heparin prophylaxis does not reduce this rate, the authors recommend more aggressive prophylaxis (32).
As we stated in our study, patients were discharged with a multivitamin supplement that did not contain vitamin K in the post-operative period. The significant decrease in fibrinogen and platelet in the 1st month we recorded may be associated with an increase in consumptive coagulopathy and accompanying enhanced micro-embolic events. Prolongation in PT and aPTT and elevation in INR may suggest that intrinsic and extrinsic coagulation pathways are affected. These changes may have resulted from the decrease of coagulation factors that depend on hemostasis parameters. The increase in D – Dimer in the 3rd month compared to the 1st month may be due to the partial decrease in consumption.
When these results are evaluated together, in the middle and long term of bariatric surgery, improvement and improvement in hypercoagulopathy, but in the short term, an increase in bleeding diathesis due to some factor deficiencies and an increase in thromboembolic events due to various post-operative reasons are detected.
According to the different data we recorded in our study and obtained from the literature, bleeding diathesis is also important along with thromboembolic events in the first months of bariatric surgery. The increase in the PT, aPTT and INR values in the first and third months compared to the pre-operative values, which we stated in the results of our study, was thought to indicate the bleeding diathesis occurring in this period. At the same time, considering the increase in D – Dimer values and the subsequent regression in the third month, the risk of early bleeding and simultaneous thromboembolism can be considered in these patients. Therefore, it is important to carry out close follow-up and laboratory screenings regularly in the first months (33). Particular attention should be paid to bleeding that may occur in the stapler line after surgery. It may be recommended to use low-molecular weight heparin (LMWH) for a long time in the early post-operative period together with vitamin support (34, 35).
The main limitation of the study could be attributed comorbidities. Some of the patients included in the study used antihypertensive and antidiabetic drugs. It is not known whether these drugs will have a different effect on bleeding and coagulation parameters.
The strength of this study could be ealborated as: the study was performed at a designated time interval, in a single center, with the same devices. The patients were followed up closely in the preoperative and postoperative period. Individuals with fibrinolytic, antithrombotic, anticoagulant use, previous deep vein thrombosis (DVT) or thromboembolic surgery were excluded from the study.