Obesity has traditionally been considered an increased risk factor for the development of VTE, which is preventable [7]. However, a meta-analysis of more than 5,500 patients, undergoing bariatric surgery failed to demonstrate any indisputable correlation between the presence of obesity and a higher incidence of postoperative DVT [8]. Actually, there are several VTE risk factors including poor glycemic control, dyslipidemia, inflammation, oxidative stress, endothelial dysfunction and impaired venous return that may intensify the risk of VTE in morbid obese patients[2]. Therefore, in the present study, in addition to patients with history of VTE, we excluded patients with higher risks including older age, super obesity (BMI>50), inflammatory related disease, cardiovascular disease and uncontrolled diabetes (FBS>180).
Although , the American Society for Metabolic and Bariatric Surgery acknowledges the importance of early ambulation and sequential compression device use and recommends the use of chemoprophylaxis in all bariatric surgery patients unless contraindicated [9], the ideal method of prophylaxis for VTE in bariatric surgery has yet to be elucidated. There is no generally accepted guidance regarding the type, dose, or duration of prophylactic method in bariatric surgery [10]. The present retrospective study with 12 months follow up and controlled confounders by excluding and matching between groups, showed no greater effect of chemical prophylaxis in VTE prevention.
Although pharmacologic prophylaxis against postoperative DVT is more used in bariatric surgery [11], its use may increase the incidence of hemorrhagic, cost, hospital stay and allergic complications associated with the use of chemical agents [12–15]. In a recent systematic review and meta-analysis of 19 studies by using a standardized definition of hemorrhage, indicated that there was 2% incidence of bleeding complications. They concluded that the incidence of major bleeding seems to increase using weight-adjusted doses of heparin with no advantage in terms of VTE reduction [16]. Therefore, it indicated that bleeding complications associated with chemoprophylaxis, are an important problem, which have to be considered for pharmacologic agent prescription in VTE prophylaxis.
To the best of our knowledge, only 3 studies have investigated the efficacy of mechanical prophylaxis in VTE prevention of patients underwent bariatric surgery. Frantzides et al. studied 1692 patients undergoing laparoscopic Roux-en-Y gastric bypass. This study compared the using of twice daily routine enoxaparin and using of only mechanical methods including SCD and early ambulation in the patients. They found that there was no difference in incidence of DVT and PE in the two groups but the incidence of intraluminal bleeding was higher in group who had used anticoagulant than the group who only was on mechanical prophylaxis [17]. Another study, which was done on 957 patients without a history of VTE who underwent a laparoscopic Roux-en-Y gastric bypass reported that the use of mechanical prophylaxis with SCDs, early ambulation, and short operative times were as effective as chemical prophylaxis in the prevention of VTE. They reported that incidence of DVT and PE was 0.31 and 0.10%, respectively, on postoperative day 30 and the bleeding complication rate was 0.73% [18]. Gonzalez et al investigated the rate of DVT in morbid obese patients underwent laparoscopic Roux-en-Y gastric bypass when a pneumatic compression stocking is used as the only prophylaxis against DVT instead of anticoagulants. In addition, Patients were encouraged to be mobilized on the evening of the operation. The incidence of DVT was as low as 0.8% [8]. Likewise, in agreement with our results, these previous studies indicated that mechanical prophylaxis, early ambulation and hydration made not only the incidence of VTE lower postoperative, but also the bleeding rates significantly lower than chemical prophylaxis. It is worth noting that the incidence of DVT and PE in our study is well within the range reported by the previous studies, which used mechanical or chemical or both. This shows both the efficacy and benefit of the mechanical measures that we used. The possible explanation is that in the present study firstly, we avoided hemoconcenteration by intravenously hydration pre and post operation. Secondly, we used LCS for at least 2 months post operation, which avoids placing the knee in acute angulation, preventing venous pooling in the lower extremities. Third, we enforced patient for early ambulation after surgery. It has to be noted that early ambulation is the most important factor in the prevention of VTE [18]. Forth, although in our procedure we put the patients on Liyod davis position and short operating times, which might have beneficial effect on reducing the risk of VTE, because pneumoperitoneum and the reverse trendelenberg position used in laparoscopic gastric bypass can increase the risk of VTE by lowering venous return to the heart.
Furthermore, Bhattacharya et al. in a web-based survey investigated the DVT prophylaxis measures amongst 11 surgeons from high-volume centers in Asia in patients undergoing bariatric surgery. In this published systematic review, it has been indicated that the VTE incidence reported by Asian surgeons ranged from 0% to 0.2% [5]. This incidence is considerably lower than what is reported in Western literature that ranged from 0.5 and 2% [19, 20]. Therefore, according to Bhattacharya study, bariatric surgery can be safely performed without pharmacologic VTE prophylaxis in Asian morbid obese patients. Therefore, the variations in VTE prophylaxis have to be considered because of its effect on postoperative complication such as VTE and bleeding. Actually, an individualized prophylaxis regimen that balances efficacy and safety is suggested for each patient, based on various risk factors.
The most important strength of this study among the few studies, which assess mechanical prophylaxis in VTE prevention in morbid obese patients underwent bariatric surgery, is that this is the first study, which compares VTE incidence rate after excluding the high-risk patients and matching them between groups.
This study has also some limitations. Firstly, the weakest point of this study is an inadequate sample size for a complication with as low an incidence as less than 1% the sample size of 300 odd patients in each group is definitely insufficient to draw a solid conclusion as the study is not adequately powered. Secondly, we did not use PCD as a mechanical device for PTE prevention. Therefore, we suggest using PCD for ideal VTE mechanical prophylaxis in future studies. Moreover, we only evaluate clinically evident VTE, however it would be more valuable if we had performed Duplex and multi-slice computed tomographic scan for all patients to recognize also subclinical cases of VTE. Furthermore, we did not measure active clotting times and factor X levels, which are the coagulation biomarkers.