Questions You Should Know about Hemostatic Stapler Supplier

The introduction of both new surgical devices and reengineered existing devices leads to modifications in the way traditional tasks are carried out and allows for the development of new surgical techniques. Each new device has benefits and limitations in regards to tissue interactions that, if known, allow for optimal use. However, most surgeons are unaware of these attributes and, therefore, new device introduction creates a &#;knowledge gap&#; that is potentially dangerous. The goal of this review is to present a framework for the study of device&#; tissue interactions and to initiate the process of &#;filling in&#; the knowledge gap via the available literature. Surgical staplers, which are continually being developed, are the focus of this piece. The integrity of the staple line, which depends on adequate tissue compression, is the primary factor in creating a stable anastomosis. This review focuses on published studies that evaluated the creation of stable anastomoses in bariatric, thoracic, and colorectal procedures. Understanding how staplers interact with target tissues is key to improving patient outcomes. It is clear from this review that each tissue type presents unique challenges. The thickness of each tissue varies as do the intrinsic biomechanical properties that determine the ideal compressive force and prefiring compression time for each tissue type. The correct staple height will vary depending on these tissue-specific properties and the tissue pathology. These studies reinforce the universal theme that compression, staple height, tissue thickness, tissue compressibility, and tissue type must all be considered by the surgeon prior to choosing a stapler and cartridge. The surgeon&#;s experience, therefore, is a critical factor. Educational programs need to be established to inform and update surgeons on the characteristics of each stapler. It is hoped that the framework presented in this review will facilitate this process.

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The objective of this review is to emphasize the framework for the study of device&#;tissue interactions and to initiate the process of &#;filling in&#; this framework with data from the available literature concerning surgical staplers. Examples of studies that describe surgical stapler&#;tissue interaction in bariatric, colorectal, and thoracic procedures are mentioned and referenced in this paper; however, an in-depth discussion of these topics that takes into consideration all published studies is beyond the scope of this review. In addition, more detailed information regarding individual staplers and their evolution, as well as the difference between the products of different manufacturers, can be obtained from the various companies and the literature.

Although these questions appear to be straightforward (see Table 2 ), to date, there are little to no published scientific data regarding the various tissue and device interactions and thus no definitive answers to these questions. Developing a deeper foundation to solve these issues will require a collective effort to gather, collate, and organize the available data. This effort will also require widespread collaboration between physicians, scientists, and engineers from both clinical practice and the medical device industry. Ideally, a systematic research program and subsequent educational programs would help to fill the educational gap that exists for most practicing surgeons and, very importantly, in surgical training. 4

The first consideration in this simple framework pertains to the specific type of device used. Surgeons must know the basic unit used by the device (eg, staple in a stapler), the desired outcome (eg, create an anastomotic staple line), and the type of device that will perform the function (eg, stapler). The second consideration is the relevant properties of the tissue that affect its interaction with the device. Finally, the biomechanical interaction between tissue and device must be considered. An example of potential research questions regarding these device&#;tissue interactions for staplers is shown in Table 2 .

The surgical stapler is an example of a device that is commonly used during surgical procedures and, at the same time, is in an almost constant state of developmental evolution. Although these devices are highly versatile and efficient, there have been well-documented incidences of staple line leaks leading to postoperative complications that often resulted from issues not attributable to ischemia. 2 Of these, technical errors can play a significant role, potentially increasing the risk of bleeding, transfusions, and unplanned proximal diversions, particularly in gastrointestinal procedures. 1 , 3 Many surgeons are not aware of the tissue handling characteristics and limitations of new or reengineered staplers, and thus there is a knowledge gap that can impact the clinical outcome of operations. To improve surgeons&#; understanding of staplers and stapler&#;tissue interactions with the goal being to optimize the clinical outcome and fill this knowledge gap, a framework is needed within which the existing literature can be reviewed and the available data gathered and made accessible ( Table 1 ).

An unintended consequence of these rapid technological advances is the production of a collective &#;knowledge gap&#; in surgeons&#; understanding of how devices interact with tissue. In many cases, surgeons may not understand either the scientific/clinical basis for the optimal use of these devices or how to optimally take advantage of unique intricacies inherent to a particular device. Consequently, surgeons may often fall back on their own experience, exercise their own judgment, or rely on anecdotal evidence, which may translate into suboptimal patient outcomes, even if the devices themselves function correctly. 1

Technological advances across numerous scientific disciplines have produced many unique surgical devices and instruments that are used during surgery. Both the ongoing introduction of new devices and continuing technical improvements in existing devices are changing the way surgeons perform traditional tasks and enabling them to develop new surgical techniques with the goal of improving patient outcomes.

When trying to decrease anastomotic leak rates for instance, Çakabay et al emphasized the importance of meticulous technique and suggested a protocol-driven approach. 35 Additional studies also support the concept that a surgeon&#;s experience with a given device is a key determinant in patient outcomes. A review of operative reports and web-based charts for colon and rectal resections at Brigham and Women&#;s Hospital (Boston) found that 19% of these procedures featured a technical error involving the stapling device. 1 Errors included (but were not limited to) surgeon misfiring, incomplete anastomosis (inadequate donuts, staple line defects, or primary device failure), and were associated with a significantly (P<0.03) increased risk of gastrointestinal bleeding, transfusions, and unplanned proximal diversions. Similarly, a review published over two decades ago of anastomoses made during esophageal resections at the Royal Victoria Hospital (Belfast) concluded that although stapling devices brought uniformity to the creation of anastomoses, they &#;cannot compensate for deficiencies in surgical technique&#; and further commented that advances in technology &#;cannot overcome deficiencies in technique such as indelicate handling of the tissues, tension on anastomoses, ischemic anastomoses, and the attempted salvage of unsatisfactory anastomoses rather than takedown and construction of a second anastomosis&#;. 36

As shown, many device-associated variables, such as stapler diameter, staple size, tissue location, and compression time as well as tissue variables (ie, tissue thickness and compressibility), can affect the integrity of the staple line and patient outcomes. However, all these factors must be considered in the context of perhaps the most relevant variable: the experience and surgical technique of the surgeon.

Similar, albeit less formal, efforts have been undertaken for surgical stapling. McColl et al created a multiple-choice test to assess general surgery residents&#; knowledge on the purpose and function of linear, circular, and laparoscopic staplers. 34 The test was administered both before and after a 40-minute didactic teaching lecture delivered through a collaborative effort between an attending general surgeon and industry representative with comprehensive knowledge of stapling devices. Mean test scores significantly increased from 53% (pretest) to 77% (posttest), (P<0.05). In this small group (n=26), this study again identifies a significant gap in existing stapling knowledge and showed the feasibility and value of industry&#;surgeon collaboration to develop an effective educational program for clinicians.

Formal testing has recently revealed that there are knowledge gaps in many surgeons&#; understanding of the safe use of many commonly used medical devices. Such deficiencies have led to the creation of educational programs. For instance, The Society of Gastrointestinal and Endoscopic Surgeons has begun to fill this gap for energy devices with a well-developed online curricula, a textbook (Fundamental Use of Surgical Energy&#;), and a validated examination based on content derived from the collaboration of health care professionals and representatives from industry. 32 , 33

In addition to the magnitude of the compressive force, compression time is another important variable. Using a linear stapler, Nakayama et al showed in stomach tissue that there was a relationship between the amount of time a tissue was compressed and optimal (defined as a well formed closed staple) staple formation. 30 Increasing precompression times both decreased staple height and increased optimal staple formation rate. In a separate study, Nakamura et al reported that prolonged perifiring compression with a linear stapler effectively prevented pancreatic fistula formation and reduced the length of stay following laparoscopic distal pancreatectomy. 31 It is important to note that while compression is a key factor in maintaining staple line integrity, excessive compression must be avoided to prevent ischemia and tissue destruction. 2

Numerous studies performed with various tissue types (gastric, 28 colorectal, 1 and pancreatic 29 ) provide data that demonstrate the importance of a surgeon&#;s familiarity with tissue thickness and compressibility in order to optimize stapler&#;tissue interaction. The most robust papers examining the relationship between outcomes and compression come from the bariatric literature, where the results obtained with staples of different lengths have been compared. Three studies which collectively assessed more than 4,000 patients came to the same conclusion; namely, that more compression is advantageous and that a smaller staple height was associated with a lower incidence of hemorrhage and stenosis/stricture. 24 , 26 , 27 The largest of these studies also noted a trend toward a decreased leak rate in the shorter staple subgroup. 24

The mechanical properties of tissues are also influenced by inherent patient differences including specific tissue location, accessibility, comorbidities, prior medications/therapy, and the pathological condition of the tissue. Differences in the profile for each patient in regards to this list of variables not only influence the tissue thickness but also its compressibility. For example, the changes in thickness associated with irradiation may alter the inherent compressibility of the tissue. As the tissue becomes less compressible, an increased amount of pressure needs to be applied by the stapler to the tissue to ensure that the desired closed staple height is obtained. All stapler reloads are indicated for a specific closed staple height; the tissue is also compressed to the same height. Surgeons must be aware that the choice of staple cartridge (staple height) will determine the amount of compression imparted upon the tissue when the stapler is closed and fired.

There are published data concerning device&#;tissue interactions that demonstrate the importance of the biomechanical factors and variables mentioned above, including compression. As early as the s, Astafiev&#;s experiments with stapling devices of his era demonstrated that &#;The defined values of isolated organ walls cannot serve as initial data for estimation of suturing gap range in instruments, for they do not include the tissue turgor that depends on blood filling, tissue fluid pressure, and other factors.&#; 23 Consequently, each tissue type must be appropriately compressed before suturing or stapling to achieve the optimal amount of perfusion and homeostasis for healing. More recent studies lend further support to the concept that increased compression is associated with desirable outcomes: lower leak rates, 24 increased intraluminal pressure, 25 improved hemostasis, 24 and minimized wound contraction, potentially leading to decreased stricture rates. 24 , 26 , 27

It is important to realize that the principles of tissue biomechanics that are important for stapling also apply to hand sewn anastomoses. 22 One of the critical biomechanical variables to consider when joining two tissues together is the degree of compression applied. The optimal amount of compression for a particular tissue will largely depend on the tissue&#;s mechanical properties. The biphasic nature of human tissue, its inherent compressibility, and differences in thickness all work together to produce a viscoelastic response when tissue is placed under a compressive force. Consequently, tissue properties will change over time as the tissue is compressed, resulting in changes such as tissue elongation and stress relaxation. 2 In addition to the impact of tissue thickness on compression, the inherent elasticity of the tissue in question is also an important variable. 2 The force and duration of compression ideally will result in optimal tissue compression and elongation such that the staple line will be hemostatic and well perfused without the development of tissue shearing. 2

The unique properties of the different types of tissues in the body have a major impact on the choice of a stapler and staple height. Different tissues in the body vary in thickness, and dimensions may change based on sex, age, organ/system/anatomical structure, age, location within an organ, preoperative therapies, intraoperative medications, and the disease state. Furthermore, tissue has a biphasic nature due to having both liquid and solid properties, and different tissue types have inherently different ratios of liquid and solid components as well as air components. In addition to these intrinsic mechanical tissue properties that help to differentiate tissue, intrinsic biochemical properties such as the protein content and metabolic profile are also differentiating factors. Moreover, the extrinsic blood supply will also vary by tissue type and contributes further to differentiation. The compressive load necessary to form a stable anastomosis will depend on these inherent tissue properties, as well as the current physical condition of the tissues to be joined, and is of paramount importance for achieving adequate perfusion and healing as well as to limit ischemia/tissue destruction. Optimal stapling of any tissue requires an adequate tissue compression time (to decrease the fluid in the tissue) to allow elongation of the tissue being compressed, smooth firing of the instrument, and consistent staple line formation; this need must be balanced against the risk of increased tissue tearing and excessive tensile strength. 2

An example of how the choice of a particular stapler might affect surgical outcomes can be seen if the circular end to end anastomotic stapler is considered. These devices come in different diameter sizes to accommodate the variety of bowel lumen diameters encountered clinically. The effect of circular stapler lumen diameter (not staple size) on outcomes is still a matter of debate. Our literature search found 17 publications addressing this topic; 5 &#; 21 however, many of the outcomes measures considered (hemorrhage, leak, weight loss) were not significant or did not show consistent trends from study to study. For example, Kim et al reported that use of a 25 mm diameter circular stapler was a risk factor for gastric stasis during the early postoperative period (eg, 6 months) when compared to results obtained with a 29 mm diameter circular stapler. However, the 29 mm stapler was found to be a risk factor for bile reflux, gastritis, and esophagitis in the late postoperative period (eg, 12 months). 5 Of note, prior studies did not show significance in regards to these or similar outcomes measures. The only exception to this lack of concordance is that there was a consistent trend across 12 studies towards increased stenosis and stricture with a smaller lumen stapler. Thus, the clinical data are often very difficult to interpret; the ideal stapler type may vary based on which outcome measure is assessed (stenosis versus bile reflux).

Staples in surgical staplers are made available in various sizes and heights ( Table 3 ) so that the surgeon can choose the one that provides appropriate homeostasis/tissue apposition without significant ischemia or tissue destruction. 2 If the closed staple height is too high, then it may inadequately appose the tissues and result in leakage, bleeding, and/or dehiscence. Conversely, if the staple height selected is too low, then ischemia, serosal shearing, or &#;cheese wiring&#; may result, potentially leading to leakage or frank necrosis. There are at least three staple heights for most linear staplers. Presently, it is our experience that staple selection is largely based on anecdotal evidence and the practices of attending surgeons passed down from teacher to student at each institution.

Note: Presence of unacceptable forms can compromise integrity and strength of the staple line resulting in an increased rate of leaks and bleeding. Reprinted from Am J Surg. Akiyoshi T, Ueno M, Fukunaga Y, et al. Incidence of and risk factors for anastomotic leakage after laparoscopic anterior resection with intracorporeal rectal transection and double-stapling technique anastomosis for rectal cancer. ;202(3):259&#;264. Copyright © , with permission from Elsevier. 60

Most modern staplers bend each staple into a B-shape staple form, which helps to secure the tissue in place. However, malformed staples can occur because staple leg bending depends on a number of tissue/stapler characteristics including tissue thickness, tissue viscosity, staple height, and other staple properties (thickness, bending characteristics, type of metal, etc). Staples are designed to form consistently, and staples that are not forming as intended should be investigated. Figure 1 provides examples of acceptable and unacceptable staple forms, as determined by a staple manufacturer (note that staplers should always be used in accordance with published indications and contraindications).

While the modern surgical stapler can be traced back to the work of Humer Hültl in the early s, today&#;s instruments are markedly different, largely due to the work of innovators such as von Petz and Ravitch. 3 Unlike the original devices, modern staplers are most often single-use instruments (advantageous from the viewpoint of sterility). Also, staplers have been developed for use in either open or minimally invasive procedures.

We focused primarily on studies that reported data from relatively smaller patient populations because these studies typically disclosed the specific devices used during the surgical procedure, whereas larger patient studies often did not report this information as they generally focused on the surgical techniques.

A search of the medical literature using MEDLINE ® , EMBASE&#;, and the Knovel ® Technology Database was conducted for the period of January &#;November to identify published articles and electronic book chapters related to surgical device&#;tissue interactions, surgical staplers, and the use of surgical staplers in thoracic, bariatric, and colorectal surgical procedures. The full articles were retrieved and manually filtered in order to identify relevant articles. Additional references were identified from the reference lists of the filtered articles.

Specialty specific device&#;tissue interaction considerations

Bariatric surgery

Staple line integrity is a major priority in bariatric surgery. Leaking staple lines and hemorrhage are associated with considerable morbidity and, in some cases, mortality. The overall incidence of bariatric surgical complications is reported to be <10% and the incidence of postoperative bleeding about 3%.37 The incidence of potentially life-threatening, permanently disabling, or fatal complications varies depending on the particular procedure done; for gastric bypass surgery, sleeve gastrectomy, and adjustable gastric band, the rate of these types of complications are 3.6% versus 2.2% versus 0.9%, respectively (P<0.001 for all).38

When considering device&#;tissue interactions in the field of bariatric surgery, a strong familiarity and understanding of the stomach is of critical importance. The stomach is an example of an organ whose tissue thickness varies considerably from location to location; this characteristic will influence the performance of staplers. Mean stomach wall thickness measurements range from 1.6 to 3.1 mm (maximum values range from 2.2 to 4.5 mm), with thickness typically increasing as one moves from the esophageal gastric junction to the pylorus. Moreover, thickness is reduced along the axis of the stomach and toward the greater curvature versus the lesser curvature.28

The varying tissue thickness of the stomach mandates that the surgeon carefully consider the specific location of the planned staple line, as this will influence the choice of staple size.28 For example, use of a staple that is &#;too small&#; in the prepyloric region of the stomach can lead to excessive tissue compression or inadequate staple formation. This could ultimately lead to tearing of the tissue or even staple line failure. Thus, it may not be surprising that, in the authors&#; experience, most surgeons use staples with longer leg heights when stapling on the distal stomach as compared to the more proximal stomach.

The importance of choosing the most appropriate staple size was demonstrated in a retrospective study of patients who had laparoscopic Roux-en-Y gastric bypass surgery. Patients who had an anastomosis constructed with a circular stapler (Covidien EEA ; 25 mm diameter anvil; Mansfield, MA, USA) that fired staples having a 3.5 mm open staple height had a significantly lower rate of stricture requiring dilatation than those in whom a circular stapler (Covidien EEA25; 25 mm diameter anvil) firing staples with 4.8 mm open staple height was utilized (6.1% versus 15%, P=0.01). Of note, the rate of leakage and abscess formation for the small and large staple anastomoses was similar.26 A larger study comparing a series of 1,074 patients who had undergone Roux-en-Y gastric bypass using a circular stapler (Covidien DST Series EEA; 25 mm diameter anvil) that fired staples with a 3.5 mm open staple height with another series of 2,606 patients treated using a circular stapler (Covidien Premium Plus CEEA; 25 mm diameter anvil) firing staples with a 4.8 mm open staple height noted significantly lower rates of hemorrhage (0.37% versus 2.45%, P<0.001) and insignificantly lower rates of leak and stenosis for the smaller staple size group.24 It is important to note that these results demonstrate an association between staple size and outcome; however, since the studies were not randomized and because the tissue thickness in each case is unknown, it is not possible to attribute the improved results to the use of the smaller staple height. It should be mentioned that the main difference between the circular staplers on the market presently is that the Covidien EEA has a fixed open staple height of 3.5 mm (closed staple height 1.5 mm) or 4.8 mm (closed staple height 2.0 mm) whereas the Ethicon CDH (Ethicon Inc., Somerville, NJ, USA) has a variable staple height range (ie, open staple height of 5.5 mm with a gap setting that can be adjusted to control for a closed staple height from 1.0 to 2.5 mm). The abovementioned studies emphasize the importance of understanding the relationship of tissue compression with closed staple height.

Colorectal surgery

In colorectal surgery, anastomotic leakage (reported incidence varying from 0 to as high as 30%39) is a major issue due to the increased risk of associated complications, the potential need for additional operative procedures, extended hospital stays, and increased morbidity and mortality rates. Anastomotic leakage rates vary from the colon to the rectum, with much higher rates in the rectum. Anastomotic leaks may affect long-term outcomes and have been associated with an increased prevalence of locoregional recurrence in cancer patients40,41 and poor functional results in patients undergoing low anterior resection.42

As in bariatric surgery, tissue thickness is an important consideration in colorectal cases. The normal uncompressed thickness of the small intestine wall typically measures between 1 and 2 mm (distended lumen), whereas the colon wall may be up to 3 mm thick (distended).43 Bowel wall thickening can occur in pathological situations. Mild thickening of <2 mm may occur from infectious enterocolitis, ulcerative colitis, Crohn&#;s disease, radiation injury, ischemia, diverticulitis, edema, or submucosal hemorrhage. More marked thickening of >2 mm can result from adenocarcinoma, gastrointestinal stromal tumor, metastases, lymphoma, severe colitis, severe diverticulitis, or systemic lupus erythematosus.43 As observed for other tissues, understanding how these conditions can influence properties such as tissue thickness and compressibility is paramount if the surgeon is to select the most appropriate anastomotic method (staple versus hand sewn), and if a stapled anastomosis is to be constructed, the best stapler (linear versus circular) and staple height to obtain the best possible surgical outcome.

Anastomosis following rectal resection presents the surgeon with the additional technical challenge of rejoining the bowel deep in the pelvis, where access is difficult because of the bony confines. Further, linear transection of the distal rectum to remove the specimen is also quite challenging, especially in the narrow, deep male pelvis. When using laparoscopic methods, two or more staple firings may be required to transect the rectum. Further, because it is difficult to place the linear staplers at right angles to the axis of the rectum in the deep pelvis, the staple line may be long and oblique; at least one author suggests that this issue may increase the risk of anastomotic leak.44

Curved or radial staplers have been developed as an alternative to the standard straight, linear stapler to facilitate division of the distal rectum. These staplers have gently arched end effectors, and the final result is a curved staple line. The slightly rounded stapler head has a narrower profile than a standard linear stapler of the same length, and this feature facilitates placement of the device into the deep pelvis, while preserving staple line length. This type of stapler lays down three rows of staples and transects the rectum between the second and third staple rows. This obviates the need to manually divide the rectum with a scalpel after using a standard transverse stapler (eg, Ethicon PROXIMATE® TX or Covidien DST Series&#; TA type). Mari et al integrated the use of a curved stapler into their procedure for laparoscopic lower anterior rectal resections,45 and they reported no intraoperative or postoperative bleeding and only two leaks among the 45 patients in the series.

A patient&#;s comorbidities can influence tissue properties and should be taken into consideration. For instance, it is well known that diabetes mellitus can change the microvascular properties of the tissue and that corticosteroid use is associated with a higher rate of anastomotic leaks. If the thickness of the bowel is impacted by these comorbidities, then the surgeon should recognize this fact and make the selection of staple height and technique (hand sewn versus stapled) with this in mind. However, it is not clear if, and how, specific comorbidities affect tissue compressibility or elasticity. Presently, surgeons may choose to proximally divert the higher risk patient with multiple comorbidities after constructing an anastomosis in order to lower the chance of a symptomatic leak forming. Although there are no supportive data or guidelines presently, it seems reasonable to take comorbidities into account when attempting to predict a given device tissue interaction.

Other risk factors for anastomotic leakage after laparoscopic intracorporeal colorectal anastomosis (Table 4) have been published. Kim et al reviewed patients over a 2-year period who had undergone laparoscopic sigmoidectomy and anterior resection using a double-stapling technique for distal sigmoid and rectal cancers.15 In this series, they found that repeated applications of linear staplers to transect the rectum distally was a significant risk factor (P=0.04) for anastomotic leakage. Furthermore, in a univariate analysis, the use of circular staplers with large diameters (ie, 31 and 33 mm) was associated with a significantly higher rate of anastomotic leakage after laparoscopic rectal transection versus results with the smaller diameter staplers (P=0.022). The authors speculated that a larger diameter circular stapler may cause the distal remnant rectum to be more distended and, consequently, make the rectal wall thinner and decrease blood supply to the stapled anastomosis.

Table 4.

Univariate and multivariate analyses for factors potentially contributing to anastomotic leakage after laparoscopic colorectal anastomosis

Characteristic Number of anastomotic leakage/total patients % Univariate analysis Multivariate analysis* P-value Hazard ratio 95% CI P-value Age, years 0.996 &#;&#;60 7/123 5.7 1.00 &#; &#;>60 10/147 6.8 1.34 0.44&#;4.05 0.606 Sex 0.209 &#;Female 4/105 3.8 1.00 &#; &#;Male 13/165 7.9 1.84 0.50&#;6.81 0.364 BMI, kg/m2 0.572 &#;&#;25 11/204 5.4 1.00 &#; &#;>25 6/66 9.1 1.62 0.51&#;5.14 0.413 Previous laparotomy 1.000 &#;No 15/234 6.4 1.00 &#; &#;Yes 2/36 5.6 1.52 0.28&#;8.39 0.631 ASA score 0.655 &#;1 14/198 7.1 &#;2 3/69 4.3 &#;3 0/3 0 Tumor location 0.021 &#;Sigmoid colon 5/165 3.0 1.00 &#; &#;Upper rectum 5/47 10.6 3.27 0.81&#;13.16 0.095 &#;Middle/lower rectum 7/58 12.1 5.44 1.44&#;20.66 0.013 Tumor, cm 0.202 &#;&#;3 10/112 8.9 1.00 &#; &#;>3 7/158 4.4 0.70 0.22&#;2.21 0.538 Operation time, min 0.025 &#;&#;200 3/119 2.5 1.00 &#; &#;>200 14/151 9.3 1.45 0.32&#;6.61 0.632 Length of 1st cartridge, mm 1.000 &#;60 13/202 6.4 1.00 &#; &#;45 4/68 5.9 0.88 0.21&#;3.74 0.858 Number of stapler firings 0.04 &#;1 1/92 1.1 1.00 &#; &#;2 13/146 8.9 6.69 0.80&#;56.01 0.080 &#;&#;3 3/32 9.4 6.60 0.52&#;84.11 0.146 Diameter of circular stapler, mm 0.022 &#;25, 29 3/123 2.4 1.00 &#; &#;31, 33 14/147 9.5 3.73 0.77&#;18.19 0.104 Stage 1.000 &#;I&#;II 10/153 6.5 1.00 &#; &#;III&#;IV 7/117 6.0 1.04 0.35&#;3.08 0.949 Open in a new tab

To emphasize the importance of proper surgical training and experience in achieving good surgical outcomes, Detry et al published a review of 1,000 consecutive colorectal anastomoses performed by a single surgical team between and and suggested that stapled anastomoses were safe and reliable if the staplers were properly utilized and the steps of the procedure standardized.46 Several authors report that procedural innovation and a fundamental understanding of surgical stapling devices are important in achieving good patient outcomes.45,47

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Thoracic surgery

Vital structures, such as the pulmonary arteries, bronchi, and the vagus nerve and its branches, must be considered when using staplers in the chest.

Similar to colorectal and gastric tissues, lung tissue also varies in thickness and compressibility. The inherent air content of the lungs make them even more variable in thickness than many other tissues. Difference in tissue properties also extend to the biochemical makeup of lung tissue. For instance, it is known that lung tissue has a natural elasticity due to its higher proportion of elastin. This affects the tissue&#;s properties and likely changes it viscoelastic behavior and, consequently, the ideal compression time and degree of compression.

To this end, the location of the lesion within the lung must be taken into account. For example, if stapling is performed in the periphery of the lung, where there is more air than solid or liquid components, then adequate compression requires less pressure and a shorter prefiring compression time. In contrast, the more centrally located lung tissue contains more fluid (blood) and solid components (bronchial cartilage). Consequently, longer compression times and taller staples are required to obtain a well formed staple line and to maintain staple line integrity.48

Another variable is the pathological state of tissue, ie, diseased or normal. Increases in thoracic tissue thickness are observed for a number of pathological conditions including lung carcinoma, pulmonary fibrosis, and asbestosis. Conditions such as emphysema and tuberculosis can also affect tissue and outcomes. For example, emphysematic tissue is often characterized as containing less protein, which can make it more difficult to achieve aerostasis.49 In fact, Hunt and Aye showed that patients with emphysema are at the highest risk of air leak.50 Furthermore, because of destruction of connective tissue and increased compliance, there may be an increased risk of tissue tearing adjacent to staple lines,51 which may delay healing after surgery.52

The development of a bronchopleural fistula is a major complication associated with thoracic surgery. Although the incidence of these fistulas after pneumonectomy is reported to be lower after stapling (2.0%&#;5.2%) versus hand suturing (6.6%&#;18.2%),53 techniques to further reduce the rate of fistula formation would, if successful, improve patient outcomes. Aoki et al noted that when fistulas develop after stapling the main bronchus, the specific site of the fistula is the stump&#;s center; they hypothesized that there was increased tension in the membranous part of the bronchus in this location due to compression by the stapler.53 They conducted a small study in patients undergoing pneumonectomy wherein the conventional procedure was modified by folding both sides of the cartilaginous wall while stapling, thereby reducing the tension, and then not covering the stump afterwards. None of the patients developed a fistula although a larger study is required to confirm these results.

The introduction of video-assisted thoracic surgery (VATS) methods over the past 20 years has greatly changed thoracic surgery. VATS methods allow for minimally invasive treatment of benign and malignant pulmonary lesions, lung volume reduction surgery, decortication, mediastinal mass removal, evacuation of fluid or infectious tissue from the pleural cavity, and diaphragmatic plication. Compared with open procedures, the benefits of VATS include shorter hospital stays and less postoperative pain, morbidity, narcotics usage, and scarring.54&#;57 Unfortunately, there are minimal published data specific to device&#;tissue interactions in this area. What is clear, however, is that technique still matters.

A review of all thoracoscopic procedures performed by Gossot et al over a 1-year period was conducted to determine the rate of adverse events related to the use of an endostapler during VATS.58 Both a database and recorded videotapes of the procedures were evaluated. Their review of 434 staple firings carried out on 130 patients showed that some adverse events were attributed to surgical errors; however, others were attributed to the stapling device, ie, oozing (13 cases), active hemorrhages on staple line (five cases), partial or total disruption of the staple line (13 cases versus one case), and technical device malfunctions (two cases).58 They determined that 34 out of 434 (7.6%) stapler firings resulted in a minor or major problem; this incidence is higher than that noted in patients undergoing similar open thoracic operations. In 12 cases, no specific action was required, whereas in 22 cases the resulting problem mandated repair. They speculated that there were three reasons for the increased incidence of stapler-associated problems in VATS versus open lung resection: 1) indecision in choosing between the 3.5 and 4.5 mm staple height due to difficulty in appreciating both the thickness and resistance of lung tissue in the minimally invasive setting, 2) the relatively small jaw opening of endostapler can make loading of the tissue difficult and may create friction and lead to tearing of the tissue, and 3) difficulty in precisely positioning the stapler tip may result in excessive traction being placed on the tissue.58 A key message was that adverse events were attributable to both surgical errors as well as device-related errors. Training and educational programs should help to reduce the incidence of surgical errors, whereas improvements by manufacturers in staple design would help reduce device errors and complications.

Of the identified cases, there were 491 patients in each group (982 total) after matching. The observed incidence proportion of hemostasis-related complications during the surgical admission was lower in the GST group as compared with the SIG group (3 events/491 [0.61%] vs 11 events/491 [2.24%]; odds ratio [SIG=reference] = 0.28, 95% CI=0.13&#;0.60, P=0.). Differences between the GST and SIG groups were not statistically significant for leak, total hospital costs, LOS, OR time, and all-cause inpatient readmission at 30, 60, and 90 days.

Using the Premier Healthcare Database of US hospital discharge records, we selected patients undergoing inpatient sleeve gastrectomy with dates of surgical admission between March 1, (SIG launch), and December 31, . Outcomes measured during the surgical admission included in-hospital hemostasis-related complications (bleeding/transfusion; primary outcome), leak, total hospital costs, length of stay (LOS), and operating room time; 30-, 60-, and 90-day all-cause inpatient readmissions were also examined. We used 1:1 cardinality matching to balance the GST and SIG groups on numerous patient and hospital/provider characteristics, allowing a maximum standardized mean difference (SMD) &#;0.05 for all matching covariates. Generalized estimating equations (GEE) accounting for hospital-level clustering were used to compare the study outcomes between the GST and SIG groups.

A recent study from Japan, presented a case series that showed potential benefits of lower bleeding at the vascular stump in pulmonary artery transection associated with the use of Ethicon&#;s ECHELON FLEX&#; Powered Vascular Stapler as compared with Medtronic&#;s iDrive TM powered stapler. 9 However, no other comparative assessment between powered staplers is available to the best of our knowledge at the time of this writing. Therefore, we conducted this retrospective study to assess the comparative real-world risk of hemostasis-related complications and other outcomes associated with the use of the powered staplers GST and SIG among patients undergoing laparoscopic sleeve gastrectomy for obesity.

Currently, two powered stapling systems are predominantly used in clinical practice, Ethicon&#;s GST and Medtronic&#;s Signia&#; Stapling System (SIG). GST, launched in , has reload surfaces with proprietary pocket extensions to stabilize and hold in place tissue for the deployment of staples with uniform height. SIG, launched in , combines a Medtronic powered stapler handle and other components (such as linear adapter, power shell, stapler insertion guide, manual retraction tool etc.) representing a redesign from the original Endo-GIA TM iDrive TM powered stapler, while maintaining same original stapler reloads with Tri-Staple&#; technology. Though both staplers deliver battery-powered deployment of the staples and the knife, each technology has adopted a different design approach in achieving similar goals of stapling and transection. Ethicon&#;s GST stabilizes and controls tissue movement through multi-stage compression, gripping surface technology, and surgeon-controlled power. 6 In contrast, Medtronic&#;s SIG design promotes tissue movement through a single-stage adaptive compression at one of three pre-set device-controlled firing speeds, and a stepped cartridge surface. 7 , 8 As such, interest exists in the potential difference in outcomes, if any, related to the utilization of these two latest powered stapling technologies. However, owing to disproportionate market penetration and limited availability of data on competing powered staplers, the majority of the evidence available on the latest stapling innovation has been related to Ethicon&#;s technology.

Previous studies have associated powered staplers with a lower risk of hemostasis-related complications (eg, bleeding, transfusion) and lower overall hospital costs when compared with manual staplers in laparoscopic bariatric surgery and video-assisted thoracoscopic (VATS) lobectomy in the United States. 2 , 3 Additionally, the incorporation of gripping surface technology (GST) in Ethicon&#;s ECHELON FLEX&#; GST system (GST) has been associated with a lower need for staple line interventions such as endoclip placement, cauterization, and oversewing, in comparison with Ethicon&#;s powered stapler with standard reloads, among patients undergoing laparoscopic sleeve gastrectomy. 4 Similar findings have also been reported for VATS lobectomy in Korea, where GST was reported to be associated with lower hemostasis-related complications and lower overall hospital costs as compared with Ethicon&#;s manual staplers using reloads without GST. 5

Surgical staplers are widely used to perform excision of stomach tissue during laparoscopic sleeve gastrectomy, the most common surgical treatment for obesity in the US. 1 Innovation in surgical stapling technology has evolved from manual to power-operated staplers. In contrast with manual staplers, powered staplers use battery power to drive the knife blade and staples, thus eliminating the variable grip force of the surgeon.

In addition to the primary analyses, two post hoc sensitivity analyses were conducted. First, an analysis of key study findings was conducted wherein the GST and SIG groups were compared to one another within a hospital that contributed a substantive volume of cases included in both groups. This analysis was conducted as a means by which to examine whether the main study findings would be consistent when holding constant any unmeasured between-group differences driven by hospital/provider-level factors. Second, a confirmatory analysis of the primary outcome findings was conducted in the larger, pre-matching study sample using multivariable regression adjusting for all variables used for matching in the primary analyses.

Full details on the statistical analyses are available in the Statistical Appendix. Briefly, the GST and SIG groups were matched at a 1:1 ratio to establish comparison groups that were closely matched to one another in terms of all above-mentioned patient demographics, patient clinical characteristics, and hospital/provider characteristics. 14 , 15 After matching, univariable regression accounting for hospital-level statistical &#;clustering&#; was used to test for statistically significant differences in outcomes between the SIG and GST groups. A p-value of 0.05 was used as the threshold for statistical significance.

Study covariates were measured using records from the surgical admission. Patient demographics included age, sex, marital status, race, payer type, and year of surgical admission. Clinical characteristics included body mass index (BMI, reported in kg/m 2 ), the Charlson Comorbidity Index Score, and the Elixhauser comorbidity index, 12 , 13 accounting for comorbidities including: congestive heart failure, cardiac arrhythmia, valvular disease, pulmonary circulation disorders, peripheral vascular disorders, hypertension uncomplicated, hypertension complicated, paralysis, other neurological disorders, chronic pulmonary disease, diabetes uncomplicated, diabetes complicated, hypothyroidism, renal failure, liver disease (including nonalcoholic steatohepatitis), peptic ulcer disease excluding bleeding, human immunodeficiency virus, lymphoma, metastatic cancer, solid tumor without metastasis, rheumatoid arthritis/collagen, coagulopathy, deficiency anemia, alcohol abuse, drug abuse, psychoses, and depression. Hospital/provider characteristics included urban vs rural hospital, teaching vs non-teaching hospital, hospital US Census Division, hospital bed size category, annual laparoscopic sleeve gastrectomy volume, and surgical specialty of the physician performing the procedure. No other data regarding the existence of, or details about, the bariatric program at each contributing hospital were available in the database.

Total hospital costs were standardized to US Dollars based on the Medical Care component of the Consumer Price Index. In the Premier Healthcare Database, hospital costs are reported directly by the hospitals from which data are sourced in this database. Costs are determined based on each hospital&#;s own charge master. Analysis of operating room time was limited to patients with operating room times falling between 30 minutes and 24 hours. Analyses of all-cause hospital readmissions were limited to patients in Institutions that continued to contribute data to the Premier Healthcare Database through or beyond the readmission identification time period of interest (30, 60, or 90 days after the surgical admission).

This study&#;s primary outcome was in-hospital hemostasis-related complications, defined as a composite of either a diagnosis related to hemorrhage and/or acute hemorrhagic anemia, or a procedure code for blood product transfusion recorded during the surgical admission (see Supplemental Appendix 1 for specific diagnosis and procedure codes). As the timing of such bleeding-related events are not specifically determinable in the database, the primary endpoint captures all relevant bleeding related codes recorded intra- and post-operatively during the hospital stay. Secondary outcomes included leak, total hospital costs for the surgical admission from the hospital perspective (ie the cost of the surgical admission to the hospital &#; rather than charges to the payer/patient or reimbursement from the payer/patient), hospital length of stay, operating room time, and 30-, 60-, and 90-day all-cause inpatient readmission to the same hospital in which the surgical admission occurred.

Patients were classified as having either GST or SIG used during laparoscopic sleeve gastrectomy based on records in each hospital&#;s charge master, which is a comprehensive administrative record of billable procedures, equipment fees, supplies, devices, drugs, imaging services, and room and board, among other items. These records were searched for various combinations of model numbers and stapler names specific to each system. The list of charge master descriptions identified by the initial search was reviewed by two separate authors to ensure accuracy. Ultimately, two mutually exclusive groups were established: the GST group and the SIG group.

Patients selected for the study underwent elective inpatient laparoscopic sleeve gastrectomy as a procedure intended for the treatment of obesity between March 1, (SIG launch) and December 31, (latest data available at the time the study was conducted). The first observed inpatient admission meeting these criteria was designated the &#;surgical admission.&#; Patients were also required to be at least 21 years of age as of the day of surgical admission. To avoid confounding by surgical approach, patients were excluded from the analysis if they had a procedure code indicative of robotic assistance or a hospital charge master record for a robotic supply. Patients were also excluded if they had a point of origin or admission from another institution, or had zero or negative total hospital costs, room and board, or supply costs.

Study data were extracted from the Premier Healthcare Database ® (PHD), which is a population-based hospital research database that contains administrative records routinely contributed by several hundred US hospitals that are members of the Premier healthcare performance improvement alliance, representing approximately 25% of annual US inpatient discharges. 10 This database includes discharge-level information on patient demographics, diagnoses, procedures, medical supplies, costs, and hospital and provider characteristics. The PHD has been widely used for epidemiologic and economic research, forming the basis of over 600 peer-reviewed publications since . This study was conducted under an exemption from Institutional Review Board oversight for US-based studies using de-identified healthcare records, as dictated by Title 45 Code of Federal Regulations (45 CFR 46.101(b)(4)). International Classification of Diseases, 10th Revision, Clinical Modification and Procedure Classification System (ICD-10-CM/ICD-10-PCS) diagnosis and procedure codes used to query the database for patient selection, measurement of outcomes, and measurement of covariates, are provided in Supplemental Appendix 1 .

In the confirmatory analysis of the primary outcome findings, conducted in the larger pre-matching study sample (N=) using multivariable analyses, findings were nearly identical to the primary analyses. In the total pre-matching sample of patients, the multivariable-adjusted odds ratio of hemostasis-related complications associated with the use of GST (SIG = reference) was: 0.25, 95% CI = 0.14&#;0.45, P<0.. The multivariable-adjusted risk of hemostasis-related complications was 2.51% for SIG and 0.67% for GST, equating to a mean incremental difference of 1.84%, 95% CI = 0.62%-3.06%, P=0.003. In terms of the nature of the complications, 28/34 (82.4%) events in the GST group and 9/14 (64.3%) events in the SIG group involved diagnoses of acute posthemorrhagic anemia; 6/34 (17.6%) events in the GST group and 2/14 (14.3%) events in the SIG group involved diagnoses of postprocedural hemorrhage following digestive system procedure; 6/34 (17.6%) events in the GST group and 4/14 (28.6%) events in the SIG group were transfusion.

After matching, one non-teaching urban hospital with 300&#;399 beds contributed a substantive volume of both the GST (N=116) and SIG (N=157); we therefore conducted a post hoc unadjusted analysis of the risk of hemostasis-related complications, total hospital costs, length of stay, and operating room time within this hospital &#; as a means by which to examine whether the findings would be consistent when holding constant any unmeasured between-group differences driven by hospital/provider-level factors. The trend for hemostasis-related complications was consistent with that of the primary analyses, with the incidence proportion of patients with hemostasis-related complications being 0.86% (1 patient) for GST and 2.55% (4 patients) for SIG, and mean total hospital costs, length of stay, and operating room time being not substantively different from the primary analysis within this hospital setting (total hospital costs GST: $ vs SIG: $11,247; LOS, GST: 1.5 days vs SIG 1.8 days; OR time. GST: 107 mins vs SIG 113 mins).

Tables 5 and 6 show the results of the analyses of secondary outcomes. Regarding surgical admissions, the differences between the GST and SIG groups were not statistically significant for mean total hospital costs ($10,666 for GST vs $11,562 for SIG, P=0.184), mean length of stay (1.6 for GST vs 1.7 days for SIG, P=0.), mean operating room time (116.5 for GST vs 116.7 minutes for SIG, P=0.), and the incidence proportions of all-cause hospital readmissions within 30 (2.2% for GST vs 2.1% for SIG, P=0.), 60 (3.2% for GST vs 2.9% for SIG, P=0.), and 90 (3.6% for GST vs 3.2% for SIG, P=0.) days after discharge. No surrogate diagnoses for leak were observed in either the GST or SIG groups.

Notes: *There were 11 patients with hemostasis-related complications in the SIG group and 3 patients with hemostasis-related complications in the GST group (see Table 4 for component diagnoses); the risk difference between the SIG group and GST group was 1.63% (95% CI, 0.15&#;3.11%, P=0.031); the Generalized Estimating Equations-based odds ratio (SIG = reference) accounting for hospital-level clustering via an exchangeable correlation matrix and robust standard errors was 0.28 (95% CI, 0.13&#;0.60, P=0.).

Figure 2 shows the results to the analyses of the primary outcome of in-hospital hemostasis-related complications during the surgical admission. The incidence proportion of hemostasis-related complications was lower in the GST group as compared with the SIG group: 3 patients/491 [0.61%] for GST vs 11 patients/491 [2.24%] for SIG; GEE-based odds ratio [SIG = reference]=0.28, 95% CI=0.13&#;0.60, P=0.; the risk difference between the SIG group and the GST group was 1.63% (95% CI, 0.15%-3.11%, P=0.031). This composite data includes &#;acute posthemorrhagic anemia&#; in 2 of 3 events in the GST group and 8 of 11 events in the SIG group; &#;postprocedural hemorrhage following digestive system procedure&#; (2 events in the SIG group) and &#;transfusion&#; (1 event in the GST group and 3 in the SIG group) (see Table 4 ).

Before matching, there were 903 patients in the SIG group and in the GST group. Between-group differences were substantial for many matching covariates ( Figure 1 ). After 1:1 matching, 491 patients from the SIG group were matched to 491 patients in the GST group, coming from a total of 40 individual hospitals. All post-match standardized mean differences were <|0.05|, indicating excellent matching covariate balance between the study comparison groups. The median patient age was 42 years and 84% were female. The three most common comorbidities were hypertension (53%), depression (24%), and chronic pulmonary disease (19%). Nearly one-third of patients had a BMI between 40 and 44.9. The majority (57%) of the procedures were performed in hospitals in the Southern region of the US. Tables 1 , 2 , and 3 provide additional information on post-match patient demographics, patient clinical characteristics, and hospital/provider characteristics, respectively.

Discussion

To our knowledge, based on literature review, this study reports the first comparative effectiveness assessment between two leading powered stapling systems, Ethicon&#;s ECHELON FLEX&#; GST system and Medtronic&#;s Signia&#; Stapling System. We found that use of GST was associated with a lower risk of in-hospital hemostasis-related complications as compared with the SIG.

The lower in-hospital hemostasis-related complications associated with Ethicon&#;s powered staplers is consistent with previously published findings in both bariatric and thoracic procedures.2,3,5,8 However, while these earlier publications could not characterize such differences beyond the potential impact of powered firing (as they compared powered to manual stapling technologies), this analysis suggests that, potentially, there are additional differences between the stapling platforms that drive hemostasis-related complications. From an innovation perspective, although certain components of SIG are newer, the TriStapleTM cartridge reload remains the same as in Medtronic&#;s older manual stapling technology &#; potentially offering similar tissue effects as observed in the earlier studies. Although the current data lack the necessary clinical granularity to be able to ascribe causal factors to the differences between outcomes using the two study groups, the different design approach in achieving similar goals of stapling and transection may provide some initial hypotheses. Whereas GST stabilizes and controls tissue movement through a multi-stage compression, gripping surface technology, and surgeon-controlled power, SIG promotes tissue movement through a single-stage compression, a stepped cartridge and device-controlled power, thus potentially having different tissue effects intra- and postoperatively.

Among patients in the GST group, mean total hospital costs were $10,647 for patients without hemostasis-related complications and $13,691 for patients with hemostasis-related complications. This difference was more pronounced for the SIG group, with mean total hospital costs being $11,308 for patients without hemostasis-related complications and $22,623 for patients with hemostasis-related complications. There are, however, several factors such as unreported blood transfusion, return to the OR for washouts, prolonged LOS, and others that may drive the cost of managing hemostasis-related complications, many of which could not be accounted for in this analysis.

Differences between the GST and SIG groups were not statistically significant for mean total hospital costs, mean length of stay, and mean operating room time in the surgical admission, as well as all-cause patient readmission at 30, 60, and 90 days after discharge. Although the GST and SIG groups exhibited no statistically significant differences on total hospital costs for the surgical admission, there was nearly a $ between-group difference in the magnitude of mean total hospital costs for the surgical admissions ($10,666 for GST vs $11,562 for SIG). A difference of similar magnitude was also observed between the two groups with respect to median total hospital costs ($ for GST vs $10,487 for SIG). Precise explanation of the drivers of this difference would require more detailed hospital cost data. To address the potential of GEE models to introduce type 2 errors (false negatives) in the presence of unbalanced clusters, we conducted a sensitivity analysis using the Cochran-Mantel-Haenszel test &#; an alternative form of non-parametric cluster-adjusted statistical significance testing to test for differences in median total hospital costs between the GST and SIG groups. In this sensitivity analysis, differences in median costs between the two groups was statistically significant (p<0.001).

This study has several limitations. First, SIG has been on the market for a shorter period of time (launched in ) in comparison with GST (available since ). Consequently, the sample size available for the SIG was small before matching. Furthermore, the sample sizes for groups are not reflective of the national volume of procedures performed with these devices. During the 22-month study period, assuming the Premier Healthcare Database represented approximately 25% of all bariatric cases performed in the US, (264,000 sleeve gastrectomy cases during this period), the total powered stapling cases available for analysis represented about 2% of the available cases.16 After matching, that number dropped down to about 0.4%. As the SIG and GST groups differed substantially on many matching covariates, the post-match SIG sample size was further diminished, leading to an overall sample size of 982 patients (491 in each group) and small numbers of patients with hemostasis-related complications (3 in the GST group and 11 in the SIG group). However, in the confirmatory sensitivity analysis based on the larger, pre-matches sample of cases, the study findings were nearly identical 2.51% for SIG and 0.67% for GST, equating to a mean incremental difference of 1.84%, 95% CI = 0.62%-3.06%, P=0.003. Ultimately, there is presently no data source available that can account for a larger proportion of US bariatric surgery volume to address the present study&#;s research question.

Second, the identification of GST and SIG was based upon the hospital charge master, which may be subject to misclassification. However, the charge master descriptions used to identify the surgical stapler groups in the present analysis were specific and differentiated from one another and most hospitals used only either GST or SIG. In addition, ICD-10-PCS codes do not differentiate between primary vs revision sleeve gastrectomy procedures and hence could not be controlled for in the analysis; however, the selection of the first observed procedure within the database reduced the likelihood of selecting revision procedures within the study period in both study groups.

Third, the study database also restricts our ability to identify and account for several variables which might influence the risk of bleeding: 1) staple line interventions such as over-sewing or imbrication, glues, and buttress; 2) energy devices used to divide the greater curvature vessels; and 3) anticoagulants used to prevent venous thromboembolism. Staple line buttress, including the type and manner in which it is used by the surgeon has been associated with a decreased risk of bleeding in sleeve gastrectomy.17 Energy devices used to divide the great curve vessels come in many forms, such as ultrasonic and advanced bipolar, and are manufactured or reprocessed by many different companies. The standardization or control for these devices was not able to be examined in this study. Furthermore, the technique and skill level of the surgeon using the devices was not able to be assessed in the present study, which may impact proper vessel sealing. Improperly sealed vessels are at risk for rupture when the patient emerges from anesthesia or during hypertensive episodes that occur with extubation. Anticoagulant use was also not accounted for in this study. We do not know if or when anticoagulation for prevention of VTE was utilized, what drug was used and in what dose and frequency. The use of perioperative VTE prophylaxis, especially given before surgery, can affect the risk of hemostasis-related complications. Furthermore, this study is unable to fully assess the risk of bleeding from other common and known sources such as injury to the liver or spleen, mesentery, or abdominal wall. However, there is no reason to believe that such unmeasured variability is likely to differ by choice of the stapler.

Fourth, as noted in the methods section, there is no specific diagnosis code for leak in the ICD-10-CM taxonomy and therefore we used surrogate diagnoses to identify leak; however, we observed no records for such diagnoses. Future analyses based on data sources that can more accurately identify leak are needed.

Finally, as is common with all non-randomized studies, causal linkages cannot be established by the present study. Results of the present study&#;s sensitivity analyses demonstrate consistency of findings when holding constant any unmeasured between-group differences driven by hospital/provider-level factors, and in the larger, more variable pre-matching sample. Nevertheless, future randomized trials comparing these platforms, and/or further repeated observational studies are needed to confirm the present study&#;s findings. Until such data are available, the similarity in findings related to hemostasis-related outcomes associated with the use of Ethicon&#;s ECHELON powered staplers seen in previous observational studies appears to offer face validity to the results of the current analysis.2,3,5

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