Manual slow firing mode of Signia™ Stapling System can achieve less staple line bleeding from pulmonary artery

Introduction

Background

According to the 2021 annual report from The Japanese Association for Thoracic Surgery, anatomical lung resection—including lobectomy and segmentectomy for primary malignant pulmonary tumors—accounts for approximately 80% of all procedures, with 70% being performed by video-assisted thoracic surgery (VATS) (1). Vascular dissection is an important technique in anatomical lung resection. Bleeding from the pulmonary artery (PA) is the primary cause of conversion to open thoracotomy during the VATS approach (2,3). With the increasing use of VATS, vascular staplers and energy devices are being predominantly used for PA dissection. Staplers allow for easy and safe vascular dissection in a short time, even using VATS; stapling devices continue to evolve (4). Adverse events during PA dissection have been reported in 0.44–1.2% of cases (3,5-7). Although most staple line (SL) bleeding does not develop into severe problems, bleeding/oozing from arterial stumps should be avoided because it leads to increased blood loss, obscuring surgical area, prolonging operative time, and adds to surgical stress (8,9). Moreover, a previous report advocated that minor bleeding could result in a serious complication if inadequate measures are taken (10).

Rationale and knowledge gap

The manual slow firing mode (MSFM) is the stapling mode of the Signia™ Stapling System (Covidien, Mansfield, MA, USA) (11). Signia™’s conventional normal mode (NM) is called an adaptive Firing™ technology, which detects the thickness and pressure of a clamped object and automatically adjusts the stapling speed in three stages: standard (fast), medium, and slow. In contrast, MSFM performs “continuous” slow-speed stapling during the firing process.

B-shaped staple formation and reduced tissue damage are especially important factors for safe stapling (12,13) and to achieve this, the usefulness of continuous slow-speed stapling has been reported in a few studies (13,14). Slow-speed stapling for the stomach with the Endo GIA™ endoscopic linear stapler (Covidien, Mans field, MA, USA) indicated reliable staple formation with less serosal laceration (13). In thoracic surgery, MSFM has also been reported to be more advantageous than NM for secure staple formation during tracheal resection (14). However, few reports exist on the efficacy of MSFM in treating PA.

Objective

Our study aimed to evaluate whether MSFM could reduce SL bleeding during PA dissection by preventing staple malformation and tissue damage. To achieve this, we evaluated the efficacy of MSFM for PA dissection by comparing bleeding from the PA stumps with conventional NM using a uniform surgical procedure. We present this article in accordance with the STROBE reporting checklist (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-549/rc).

Methods

Study design and patient selection

We retrospectively reviewed the records of consecutive patients who underwent anatomical lung resection of segmentectomy, lobectomy, or bilobectomy at our institute between November 2020 and November 2024. We included patients who underwent PA dissection using the Signia™ Small Diameter Reload (SDR) COVIDIEN’s novel vascular stapler (Figure 1). The SDR vascular cartridge lineup includes gray 30-mm, white 30-mm, and white 45-mm options. However, this study included only cases using the gray 30-mm cartridge. PA dissection was classified as conventional NM or MSFM, and the presence of SL bleeding in each mode was evaluated.

Figure 1 Flow chart.

SL bleeding is typically divided into two categories: (I) bleeding/oozing that can be managed by no intervention or performing compression alone and (II) bleeding that necessitates additional interventions, such as the application of a fibrin sealant patch, clipping, ligation, or manual suturing regardless of clamping use. However, the latter situation has become rare with the evolution of vascular staplers (3,5-7). On the other hand, more advanced stapling technology that minimizes oozing should be explored. Therefore, we focused on the degree of bleeding/oozing (I) and have subclassified it into two sub-categories based on previous reports (7,15): (i) bleeding/oozing from the PA proximal stump that persisted for ≥15 s without intervention or required compression for >5 s and (ii) extremely minimal oozing. In this study, we defined SL bleeding as (i) and (II). Hemostatic Likert score 1 was defined as no bleeding at tissue site after initially blotting the SL (7,15). We often apply a brief cotton swab compression to remove the initial small amount of oozing to correctly evaluate the SL. However, due to the retrospective nature of the study, the brief compression time was not uniform; hence, we defined specific compression time as that of 5 s. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Institutional Review Board of Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital (approval No. 3426). The requirement for informed consent was waived owing to the retrospective observational nature of the study.

MSFM technique

When fully clamped on the PA and in firing mode, pressing the safety button and double-clicking either of the lower lateral buttons twice activates the slower speed setting (Figure 2). The Signia™ has three-speed settings: standard (fast), medium, and slow, with staple closure times of 2.8, 5, and 10 s, respectively, when using a 30-mm cartridge. An audible tone confirmed the speed selection, with the three sequential tones denoting continuous slow-speed operation. The surgeon maintains downward pressure on the toggle to initiate firing. Using MSFM with a 30-mm cartridge ensures uniform stapling over 10 s (11).

Figure 2 How to do MSFM. After clamping the pulmonary artery and setting fire modes through pressing the safety button (arrow), either side of the lower lateral buttons (arrowhead) is double-clicked twice to adjust a slow speed setting. The three sequential tones reflect the MSFM. MSFM, manual slow firing mode.

Surgical procedure

All surgical procedures were performed by M.S., T.I., R.S., and K.N. (with years from graduation of 12 years as a doctor and board-certified member of the Japanese Association for Chest Surgery; 8 years as a doctor; 19 years as a doctor and board-certified member of the Japanese Association for Chest Surgery; and 32 years as a doctor and board-certified member of the Japanese Association for Chest Surgery, respectively). Most of the operation, KN participated as a first assistant or an operator. We adopted a hybrid VATS approach for anatomical lung resection. Hybrid VATS was performed under both direct and thoracoscopic vision through a 1–2-cm port (at the 7th or 8th intercostal space along the middle axially line) and a muscle-sparing mini-thoracotomy (incision, 5–8 cm in the fourth, fifth, or sixth intercostal space at the anterior or posterior axillary line) (16,17). A rib retractor or wound protector (Multi-flap gate; Sumitomo Bakelite, Tokyo, Japan or Alexis^® Wound Retractor; Applied Medical, Rancho Santa Margarita, California, USA) was adjusted at the surgeon’s discretion. Open thoracotomy was sometimes performed depending on the degree of adhesion and tumor status, in accordance with the VATS procedure. In all cases, a scope was used as the light source to record the procedure.

The pulmonary hilum was exposed to visualize the PA branches. The PA branches were sufficiently isolated from the distal side to the main PA within the vascular sheath, the outer adventitia. The PA branch was encircled using absorbable suture thread. Small-size PAs were divided by a stapler or energy device with proximal side ligation at the surgeon’s choice. On the other hand, all large-size PAs were divided by a stapler. The stapler was usually inserted through the camera port, and sometimes through a thoracotomy with no tension. Before stapling, tension at the root of PA was reconfirmed using scope vision, and stapling was performed. Whether NM or MSFM should be used depends on the choice of treatment by the surgeon. During firing, all surgeons checked PA tension through scope vision or direct vision through thoracotomy. After de-clumping the stapler, bleeding from the PA stump was assessed. The bleeding did not stop naturally, and the bleeding point was compressed using a cotton swab (Naruke Thoraco Cotton, Kenzmedico Co., Ltd., Saitama, Japan). In cases of uncontrollable bleeding due to cotton swab compression, a fibrin sealant patch (TachoSil; Takeda Austria GmbH, Linz, Austria) was used. If massive bleeding could not be controlled by these procedures, complete hemostasis of the clipping, suturing, and clumping of the main PA was performed.

Variables and post-stapling bleedings

Data, including age at surgery, sex, laterality, approach, surgical procedure, and pathology, were collected from the patient’s medical records. The presence of SL bleeding in the MSFM and NM groups was evaluated according to the operation records and the surgical video-assisted system. In clinical settings, we occasionally encounter cases wherein two or more PA branches with different roots are simultaneously dissected using a single cartridge (Figure 3A,3B). In these cases, we separately assessed the SL bleeding data of each PA individually. Stapling closure time was measured using a surgical video-assisted system.

Figure 3 A case of left lower lobectomy. Two branches of A6a (arrow) and A6b+c (arrowhead) entered to main pulmonary artery (A). We divided these branches simultaneously with a single gray cartridge (B). The bleeding information was recorded individually.

PA diameters were assessed using high-resolution computed tomography with a 1-mm slice thickness. The largest PA branch diameter was measured. In addition, a previous report found that the PA as small as 7 mm could be safely divided using either a staler or LigaSure energy device (Covidien, Mansfield, MA, USA) (18). Therefore, we defined the size of PA as follows: small PA, PA branch <7 mm, which could be divided using either stapler or energy device; and large PA (≥7 mm), for which stapler use was recommended. We also evaluated SL-bleeding data according to PA size.

Statistical analysis

Categorical variables are expressed as numbers (percentages) and compared using Pearson’s chi-squared test or Fisher’s exact test, as appropriate. Continuous variables are expressed as medians (range) and were compared using the Mann-Whitney U test. All tests were two-sided, and statistical significance was set at P<0.05. All statistical analyses were performed using GraphPad Prism 10 software (GraphPad Software, San Diego, CA, USA).

Results

Clinical characteristics

Of the 433 anatomical lung resections performed during the study period, 82 consecutive patients were included. The patients’ baseline characteristics are presented in Table 1. Seventy-seven patients underwent VATS, while five patients underwent open thoracotomy. Lobectomy and segmentectomy were performed in 43 (including two cases of bilobectomy) and 39 patients, respectively.

Table 2 reveals the characteristics of all divided PAs and their surgical outcomes. In total, a hundred and seventy-one PAs were divided using a gray 30-mm cartridge of Signia™. Of these, 84 and 87 arteries were divided using NM and MSFM, respectively. The mean diameter of the resected PAs with NM and MSFM were 6.6 (range, 2.1–14.1) and 6.3 (range, 2.3–14.2) mm, respectively (P=0.59).

In the NM group, all PAs were dissected at fast-speed. MSFM needed a significantly longer stapling closure time of 10.4 (range, 9.5–11.4) s than NM of 3.0 (range, 2.5–3.7) s (P<0.001). However, the incidence of SL bleeding in the MSFM group (10/87, 11.5%) was lower than that in the NM group (22/84, 26.2%) (P=0.01). Among all transected PAs, only one case of NM required a fibrinogen-combined tissue-sealing sheet. Severe events, such as rupture, stapling failure, or delayed postoperative bleeding, were not encountered in either mode.

SL bleeding according to PA diameter

We evaluated SL bleeding according to PA sizes. In the NM group, 47 small PAs (<7 mm) and 37 large PAs (>7 mm) were divided using NM. In contrast, 49 small and 38 large PAs were divided by MSFM (Table 3). For small PAs, no significant difference was observed in the SL bleeding rate between the NM and MSFM groups [9/47 (19.1%) vs. 5/49 (10.2%), P=0.26]. However, among large PAs, the SL bleeding rate was significantly lower in the MSFM group than in the NM group [13/37 (35.1%) vs. 5/38 (13.2%), P=0.03].

SL bleeding to simultaneous multiple PA branch division by a single cartridge

With NM, two and three PA branches were simultaneously divided using a single cartridge in 20 and 3 cases, respectively; resulting in a total of 49 arteries divided arteries. In contrast, with MSFM, two PA branches were simultaneously divided in 10 cases, resulting in a total of 20 divided PAs (Table 4). The SL bleeding rate for multiple simultaneous PA branch divisions is shown in Figure S1. No significant difference was observed in SL bleeding between the NM and MSFM groups (22.4% vs. 20.0%; P>0.99).

Discussion

The PA is a vessel within a low-pressure circulation system, consisting of three layers: a thin inner intima, a media with a particularly rich elastic fiber, and an outer adventitia (19). The PA wall is very thin and fragile, requiring a delicate surgical technique during dissection. Unexpected PA injury is the main reason for conversion from VATS to open thoracotomy and can lead to fatal hemorrhage within moments; thus, safe PA dissection is important for anatomic lung resection (2,3). Our study found that MSFM using Signia™ can significantly decrease SL bleeding from the PA compared with conventional NM. To our best knowledge, evidence supporting the use of MSFM for PA dissection remains limited.

A bleeding occurs for PAs, in at least 4.2% of cases after PA stapling (7). A previous study revealed bleeding rates of 24.6% (15/61 cases) and 16.0% (4/25 cases) for the right apical anterior truncus of the PA when divided using a three-row gray cartridge with powered and manual staplers, respectively (8). In this study, we used the Signia™ SDR gray 30-mm cartridge. Although the SDR is a novel two-row vascular stapler, the similar hemostatic capacity was reported comparable to that of a conventional three-row stapler (7). Regarding SL bleeding, previous studies included various types of dissected arteries, staplers, and definitions, making direct comparisons of the post-stapling bleeding rate difficult (3,5-8). For accurately assessing post-stapling bleeding, standardizing PA branch isolation and maneuverability of stapler is important. Currently, VATS includes various approaches such as hybrid, multiport, and uniportal techniques. Stressful conditions during stapling, such as twisting and lifting, result in disrupting SL integrity (6). To address this, the risk of vascular stress is particularly high using uniportal VATS due to its limited maneuverability (10,20). Our procedure ensures sufficient dissection of the arteries within the vessel sheath to the periphery, insertion of a stapler with no resistance, and stressless stapling. In addition, the stapling closure time of MSFM was significantly longer than that of NM. Paying more attention to the traction of the PAs during firing is needed. These procedures can be safely performed through hybrid VATS in all cases (16,17). Furthermore, the powered stapling system of Signia™ and narrow-profile of SDR makes this easier. Thus, in this study, both the surgical procedure and main operator were standardized between NM and MSFM, reducing potential bias caused by the surgical technique; our findings purely reflected the real stapler performance. The SL bleeding rate of 26.2% using NM in our study is not too high compared with that in previous reports (8). Moreover, MSFM resulted in significant reduction of SL bleeding from 26.2% to 11.5% in the NM group. Among all dissected PAs, only one divided by NM required a fibrin sealant patch for hemostasis. No cases of non-acceptable SL bleeding that required additional intervention were observed in each mode. These findings are also consistent with those in previous reports (3,5-7).

Several factors are associated with SL bleeding, with staple malformations being an important factor. Appropriate B-type staple formation is important for safe stapling (12-14), which involves PA dissection. Empirically, slow-speed stapling is favorable for thick, hard tissues; thus, Signia™ NM automatically adjusts the stapling speed to slow when stapling such tissues (11). Moreover, “continuous” slow-speed stapling was more advantageous for staple formation than normal firing for stomach and tracheal resections (13,14). However, the usefulness of continuous slow-speed stapling for thin tissues, such as the PA, remains unassessed. In NM, all PAs were divided rapidly owing to their thin nature. Given the mechanism of creating a B-shaped staple from the originally U-shaped staple, we expected that MSFM would be more feasible for correct staple formation than fast-speed stapling. In addition, in stomach resection, continuous slow-speed stapling gradually deforms the tissue and makes it relatively thin, which is also advantageous for tissue laceration (13). However, since the PA is a thin tissue; we considered less tissue deformation present during stapling, regardless of the stapling mode, making the effect of laceration negligible. However, continuous slow-speed stapling may contribute to the capture of thin inner intima and prevent vessel damage. Directly examining the shape of the staples in the PA stump in situ and performing a pathological evaluation of each dissected PAs is challenging. Therefore, an in vitro examination is needed to further investigate these effects.

Appropriate cartridge selection is another factor related to the prevention of SL bleeding. The mean wall thickness of normal pulmonary arteries with a mean diameter of 2.1 mm has been reported to be 0.162 mm (21). According to the manufacturer’s instructions, the recommended tissue thickness of gray and white cartridges of SDR was 0.75–1.0 mm and 1.0–1.5 mm, respectively (11). Given that the artery wall was further compressed after clamping, we believe that the gray cartridge provides the most stable option for PA dissection. However, a previous retrospective study revealed that adverse events of PA dissection were not significantly different between these two cartridges (5). Hence, a prospective comparative study is needed because of the lack of evidence.

In the present study, MSFM had no significant effect on SL bleeding in small PAs. Because the SDR is a two-row stapler, we encountered a very small number of staplers left in the small vessel stumps (Figure 4). We suggest that this condition resulted in bleeding from the edge of the SL regardless of the stapling mode. For small-vessel dissection, we can also use an energy device, which shows a postoperative hemorrhage rate of 0.3%; this finding is also a good surgical option (18). However, we cannot divide large vessels (≥7 mm) using energy devices alone, making safe stapling favorable. In the present study, we found that MSFM was more effective in preventing SL bleeding than NM in large vessels, from 35.1% to 13.2%, a finding that we suggest to be highly desirable for thoracic surgeons.

Figure 4 A case of firing for small vessels. Only one stapler stayed in row.

Although we occasionally encountered this situation, we needed to dissect multiple PA branches with different roots using a single staple cartridge, which has rarely been reported. In the present study, MSFM did not improve SL bleeding with simultaneous PA branch dissection compared with NM. One possible explanation is that the root of one vessel could be pulled toward the other vessel during stapling, which induced the tension of the artery (Figure S1). In this study, the number of MSFM cases was small; thus, further studies are required to validate these findings.

This study has some limitations. First, this was a retrospective single-center study. Second, our definition of SL bleeding, requiring compression for ≥5 s, was subject to the surgeon’s choice. However, since the main operator and surgical procedure are the same for NM and MSFM, we consider the bias to be negligible. Third, previous studies have suggested that pre-compression time before firing was associated with secure stapling (22,23). In this study, pre-compression time was not integrated. However, given the thin nature of the PA wall, we suggest that the influence of pre-compression is small.

Conclusions

Compared with NM, MSFM could reduce SL bleeding from large-diameter PAs. An additional surgical procedure in MSFM is the simple button operation. Although this technique requires a longer closure time, the technique is an effective surgical approach, which is expected to reduce hemostasis time and blood loss due to reduced bleeding.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-549/rc

Data Sharing Statement: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-549/dss

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-549/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-549/coif). All authors have not received any kind of financial support from Covidien. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. This study was approved by the Institutional Review Board of Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital (approval No. 3426). The requirement for informed consent was waived owing to the retrospective observational nature of the study.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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