FAQ

A:Which type of materials should be chosen for the intraperitoneal cavity, retroperitoneal cavity, and superficial incisions separately?
polyvinyl alcohol foam is recommended to be used in intraperitoneal and retroperitoneal cavities, while polyurethane or polyvinyl alcohol foam is recommended for superficial incisions and external areas of sutured incisions.(Grade C).The materials and equipment required for VSD include foam,drainage tubes, transparent adhesive films, and negative pressure sources.Among them, the porous sponge-like foam materials are in contact with tissues, such as the wound surface, and the pores are connected to each other. There are two types of materials (1)polyvinyl alcohol(PVA),which has a small pore size of 0.06-0.27 mm in diameter and a high tensile strength (522.4 kPa)and is tough, and (2)polyurethane (PU), which has larger pores with a diameter of 0.4-0.6 mm that allows easy penetration for granulation, has low tensile strength (111.1 kPa) and is fragile . Retention of PU foam debris in the wound has been observed to affect healing.
In actual application, the surface of the foam material must be covered with a semipermeable membrane. After the generation of negative pressure, the foam is fixed with surrounding tissues to form a complete seal. Considering the effect of negative pressure on the intestinal blood supply, typically the negative pressure intensity applied on the abdomen is lower than that on the ex-tremities when using VSD technique. The value can be set at -125 mmHg to -300 mmHg(-17 kPa to -40 kPa) for skin outside the incision, extra peritoneal wounds, or within body cavity, while for temporary peritoneal closure and intra-abdominal application, the pressure should be adjusted to -50 mmHgto _175 mmHg (-6.7 to -23.3 kPa). Although there is no high-level evidence in evidence-based medicine, a lower negative pressure value, such as -50 mmHg to -80 mmHg, is recommended for patients with intestinal repair or anastomosis.

A: For abdominal incisions with a primarysuture which have a high risk of infection, prophylactic use of VSDis recommended to help reduce the onset of incision infection(Grade B).
A total of articles discussed prophylactic VSD(VSD) for abdominal incisions with primary suture, of which 6 were RCTs and 29 were observational studies,In 2016, the WHO issued a procedure based on evidence-based evidence for the prevention of intraoperative and post operative surgical site infections(SSls)in Lancet Infectious Diseases and proposed the application of prophylactic NPWT for stage I sutured incisions with a high risk of infection (conditional recommendation, low quality). A total of 20 articles were reviewed, including 6RCTs and 14 observational studies. Compared with traditional wound dressings, prophylactic NPWT(NPWT) reduces the risk of SSIs in closed wounds, Subgroup analysis of different surgical procedures revealed that use of VSD reduced the risk of SSls inabdominal and cardiac surgeries but had no effect in orthopedic ortraumatic surgeries. In subgroups with different incision categories(clean-contaminated incisions and clean incisions), VSD showed significant differences in reducing the incidence of SSls. By using a cost-effectiveness analysis, Chopra et al. compared closed-incision VSD therapy with standard dressings after abdominal incision closure in high-risk patients: 829 abdominal wall surgeries(260 closed-incision VSDs and 569 standard dressings)were included, and the results showed that closed-incision VSD saved 1546.52 US dollars compared with standard dressing, suggesting that closed-incision VSD was a cost-effective method when the SSl rate was greater than 16.39%. An international multidisciplinary consensus recommendation published in 2017 reviewed 100 articles published from 2000 to 2015 that compared traditional wound dressings with closed-incision negative pressure therapy. The results supported the use of VSD for sutured incisions in patients with a high risk of SSl and can reduce the incidence of SSI.
In subgroup analyses of different surgical types, four observa-tional studies of abdominal wall reconstructive surgery showed that pVSD reduced the incidence of SSls,whereas one observational study showed that pVSD had no apparent advantages in reducing the incidence of SSls. Additionally, six observational studies of colorectal surgery showed that pVSD reduced the incidence of SSls. one observational study of pan-creatoduodenectomy showed that pVSD reduced the incidence of SSls, and one RCT of ulcerative colitis ileostomy reversal showed that pVSD did not reduce the incidence of SSls.A total of six RCTs investigated multiple abdominal surgeries, among which three showed that pVSD reduced the incidence of SSls, two showed that pVSD did not reduce the incidence of SSls, and one showed that VSD reduced the incidence of SSls, but the differences were not significant,Eleven observational studies of abdominal surgeries, including pediatric contaminated surgery.gynecological malignancy surgery, cesarean section surgery, and liver transplantation surgery, also showed that pVSD reduced the incidence of incision infections. One RCT showed that pVSD reduced postoperative pain and the need for anes-thetics, however, although the incidence of SSls decreased, the difference was not significant.
Regarding the level of contamination in subgroups with different incision categories, one observational study showed that pVSD reduced the incidence of SSls in contaminated incisions, whereas another observational study showed that pVSD did not reduce the incidence of SSls in contaminated incisions.6l A total of twenty studies were included in the clean-contaminated surgery group, of which 13 observational studies showed that pVSD reduced the incidence of SSls for clean-contaminated incisions, three RCTs showed that pVSD reduced the incidence SSls, and another three RCTs showed that pVSD did not have apparent advantages in reducing infection incidences.
The high-risk factors for the onset of SSls include vascular dis-orders due to peripheral soft tissue injuries, hemorrhage or hematoma, necrotic tissue, intraoperative contamination, a long surgical time, and obesity, diabetes as well as smoking.

A: The use of VSD in severely contaminated/ infected abdominal surgical sites is recommended, which can
prevent/treat infections, quicken stage II closure of the incision, and shorten hospital stay (Grade B).
A total of 26 articles were included, of which 3 were RCTs and 23 were observational studies and case series.
One RCT consisting of 81 cases of severely contaminated incisions showed that 27 cases were closed in stage I, 29 cases had delayed closure, and 25 cases were applied VSD. The incision infection rates were 37%, 17%, and 0.2%, respectively. In two observational studies, VSD was used for an early deep incision infection after abdominal wall hernia tension-free repair. Among the 33 cases treated with suture removal and VSD, had mesh removal and the other 24 did not; all wounds healed within 4 weeks.
In the analysis of the effects and feasibility of VSD in severely contaminated/infected abdominal surgical sites, one RCT showed that VSD was safe in an open abdomen (OA) after severe intra-abdominal infection and improved the quality of life of patients,20 whereas the RCT by Roberts et al. on secondary abdominal cav
ity abscess following damage control surgery suggested that VSD reduced systemic inflammatory responses. Another RCT by Kirk-patrick et al.71 showed that VSD did not accelerate pus drainage or
reduce systemic inflammatory markers.
Multiple observational studies on the use of VSD for retroperitoneal space infections with different causes have shown that VSD can control early local infection, keep the abscess clean, promote collapse of the abscess, shorten healing time, reduce local complications, and reduce VSD-related complications.Tao et al. confirmed that VSD prevented sub-gingival infection after hepatectomy. In the study of 39 patients with severe intra-abdominal
infection conducted by Pliakos et al., VSD effectively reduced mortality but could not reduce the systemic bacterial burden or prevent the incidence of hospital-acquired infections. Another two observational studies showed that application of VSD during severe abdominal infection drained the pus and promoted the reduction of the abscess cavity; thus, granulation of the wound was fresh, and formation of a residual abscess was avoided.
Regarding the mechanism of action of indwelling VSD at the site of abdominal surgery, it is suggested that VSD could actively induce complete drainage, enlarge the drainage area and drainage range, prevent clogging, accelerate tissue swelling subsidence, and eliminate dead space effectively.In addition, VSD promoted blood circulation, reduced tissue edema, inhibited bacterial growth, and applied a local mechanical pull to promote shrinkage of the wound surface or wound cavity. Takei et al. suggested that the mechanism of action might be that the continuous vacuum negative pressure actively removed water, exudate, and residual pus from the edema tissue, induced cell proliferation & matrix synthesis, and accelerated healing. Additional observational and experimental studies suggested that the mechanism was the acceleration of blood perfusion, promotion of vascularization, and
improvement of local circulation and that negative pressure indirectly decreased the hydrostatic pressure of local tissue edema, reduced leakage, and accelerated regression of the edema.The hypoxic state caused by continuous negative pressure due to VSD also inhibited bacterial proliferation and eliminated bacterial colonization and the bacterial growth medium.
When VSD is used for the prevention and treatment of infections associated with abdominal surgical sites, the foam material should be in the lower or central part of the abscess; thus, the abdominal wall incision should be made in the nearest area to drain the foaming, and local bleeding and excessive growth of granulation tissue into the foam should be prevented. The foam materials and the drainage tube are firmly fixed by the suture to prevent exposure of the side hole of the drainage tube outside of the sponge, which can cause focal necrosis of the intestinal wall. In general, the foam materials should be removed or replaced every days; after more than 9 days, granulation tissue may grow into the foam, resulting in bleeding and difficulty in removing the foam.

A: VSD is recommended as the preferred method for temporary abdominal closure (TAC) and intra-abdominal volume increment under the conditions such as severe abdominal trauma, infection, and liver transplantation (Grade B).
This topic included 20 related articles: one RCT,93 and 19 were retrospective studies.
For patients with severe abdominal trauma or severe intra-abdominal infection received intraperitoneal procedures, such as hemorrhage and contamination control, primary suture of the abdominal wall may result in serious consequences, such as unplanned secondary surgery, ACS, severe intra-abdominal infection, and multiple organ failure, and thus has a high failure rate. TAC technology is needed for these patients. TAC can significantly increase the abdominal cavity volume and reduce abdominal pressure, avoid extra-vasation of intraperitoneal fluid, reconstruct abdominal wall barriers, protect intra-abdominal organs, prevent infection, and reduce the incidence of gastrointestinal fistulae.
TAC can be used in the following situations: (1) peritonitis, necrotizing fasciitis, and purulent abdominal infection; (2) abdominal trauma, damage control laparotomy, and abdominal wall damage; (3) mesenteric ischemia and situations when bowel circulation is difficult to determine due to various causes; (4) primary or secondary abdominal hypertension or ACS; and (5) liver transplantation. Ideally, TAC should be able to keep the abdominal cavity in a closed state, protect the internal organs of the abdominal cavity, avoid exogenous contamination or mechanical injury, drain the exudate from the abdominal cavity, expand the volume of the abdominal cavity to reduce the intra-abdominal pressure and prevent or treat ACS, and protect the integrity of the fascia to facilitate definitive abdominal closure in the future. Various TAC methods are available, including simple skin closure (jacket clamp or suture), suturing plastic and other materials to the skin, suture of artificial mesh to the fascia, and VSD-assisted closure.
The application of VSD-assisted TAC has become the mainstream method. The VSD system (ABCIra set, KCI, USA) meets most of the requirements of an ideal TAC. The surgical method is as follows: after completion of the intraperitoneal surgical operation, the greater omentum is placed under the incision to cover the intestine, lined with a thin film to help prevent adhesion between the intestinal tract and the abdominal wall, and then VSD foam is sutured to the abdominal fascia or skin to seal the abdomen incision. The film covers the entire wound and maintains a sealed environment. The drainage tube is connected to a vacuum suction device, and the pressure is adjusted to 60 kPa to 80 kPa. Generally, drainage can be continued for 5-7 days.
Negative pressure drainage prevents the accumulation of exudates and inflammatory mediators in the abdominal cavity. Continuous negative pressure drainage ensures timely transfer of intra-abdominal fluids that are rich in digestive fluids to outside of the body, thereby reducing systemic toxin reactions and creating a good local environment for recovery of the damaged pancreas. This approach minimizes the corrosive effects of harmful liquids on intestinal and abdominal wall tissues, facilitates debridement of necrotic tissue in pancreatitis, prevents or reduces open of the abdominal fascia tissue by acting alone or in combination with sustained traction of the fascia to significantly increase the rate of delayed closure of the fascia and reduce the occurrence of abdominal wall hernias, reduces hospital-acquired wound infections, and facilitates post-operative care.
In one retrospective study of TAC with 58 patients, VSD was applied in 27 patients, other treatments were applied in the rest 31 patients. The results showed that VSD was superior to other methods regarding the length of the abdominal opening, the frequency of dressing changes, re-exploration rate, the success rate of abdominal incision closure, and enteroatmospheric fistula. A prospective study conducted by Perez et al.100 showed that VSD after abdominal infection and intra-abdominal hypertension shortened the recovery time and increased the success rate of abdominal closure.
A study of VSD in 24 patients after liver transplantation showed that early fascial closure time can be shortened to a median of 5.5 days (1e12 days).56 The use of VSD can reduce the incidence of complications and mortality in liver transplantation patients undergoing TAC.49,56,101 One observational study by Plaudis et al.showed that the intra-abdominal pressure was effectively reduced with the use of VSD in patients with ACS caused by pancreatitis or multiple injuries. A case report of an open abdomen due to acute pancreatitis showed that VSD (ABThera kit, KCI, USA) helped aspirate large amounts of exudate in the abdominal cavity and facilitated infection management.
After TAC, the abdomen should be directly closed when patient's general condition improves, intra-abdominal inflammatory edema subsides, intra-abdominal infection is controlled within 1-2 weeks, intestinal edema is absorbed, and intra-abdominal pressure is < 12 mmHg; if the intra-abdominal pressure remains >12 mmHg after 1e2 weeks or abdominal wall defects are evident, the abdomen closure should be performed by skin grafting after formation of granulation tissue under the foam material and generate planned abdominal hernia, followed by definitive abdominal wall reconstruction in 6e12 months.102,103 VSD can increase the closure rate of the fascia layer to 70%e90% at the first stage. A systematic review of OAs which included 112 articles found that the rates of
early fascial layer closure were in a descending order of 74.6%, 48%, 35%, and 27% with the use of VSD plus active abdominal wall closure, VSD alone, negative pressure pack, and Bogota bag respectively.21 A retrospective study by Sibajaet et al.on 48 patients with severe intra-abdominal infections using VSD-assisted OA revealed a higher rate of early fascial closure, shortened ICU length of stay, decreased mortality, and reduced rates of associated complications. If the abdomen cannot be closed early, a series of complications may occur, including enteroatmospheric fistula, abdominal cavity infection, abdominal bleeding, and abdominal wall hernia. The most complicated complication is an enteroatmospheric fistula, which has an incidence of 5%e75%.105 Different TAC techniques have different rates of postoperative complications. One RCT showed that VSD-assisted TAC did not
cause intestinal fistulas,93 and a review suggested that VSD was better than the Bogota bag and Barker techniques in reducing complications and infection rates.

A: Application of VSD after inflammation, injury or surgery in the intraabdominal organs, such as the liver,
biliary tract, pancreas, and duodenum, can facilitate adequate drainage, prevent and control infections, and promote wound healing (Grade C).
Eleven studies on VSD application in intraperitoneal organ inflammation, injury and surgical treatment were included, one RCTand 10 observational studies.
One RCT showed an increase in granulocyte membrane fluidity and an increased survival rate in patients with severe pancreatitis undergoing necrotizing tissue debridement and VSD (p < 0.041).
One observational study reported the effects of laparoscopic VSD on the treatment of 8 patients with severe pancreatitis for which the gastrocolic ligament was cut and 4cm×15cm foam was placed in the lesser sac on the pancreatic surface. The foam was replaced 4-7 times after surgery; the average drainage within 48 h was
600 mL/d and decreased gradually every day, and the cure rate was significantly improved.
A case study showed that compared with conventional staged hepatectomy, foam materials placed between open liver lobes and application of VSD technique in gallbladder cancer patients with liver metastases who underwent liver segmentation and portal vein ligation in staged hepatectomy increased the volume of the remaining liver to 117% of the original (increased significantly on the left lateral side) and facilitated wound healing.47 An observa
tional study of liver transplantation combined with VSD showed that VSD application reduced the incidence of wound infection.49
The studied of VSD application in pancreatic duodenal injury by Huo et al.46,53,81 showed that VSD had good treatment effects on severe injuries of the common bile duct, duodenum, and pancreas and reduced complications and the infection rate. Moreover, VSD drainage could be safely and effectively passed through the jejunostomy fistula back to the gastrointestinal tract.
For patients with severe pancreatitis or pancreatic injury, VSD can improve the drainage efficiency and has good treatment effects in early pancreas damage without self-digestion; however, pancreatitis patients with self-digestion can have floccular necrotic tissue clogging the foam, and thus, the foam needs to be repeatedly
changed. In addition, the colon often has clogged foam due to mucus or feces, and thus, VSD is not suitable for colonic injury. Intraperitoneal placement should follow the principle of taking the shortest route out of the body; the appropriate length and width should be trimmed according to the need, and at least 1 cm of material should be retained outside the body to facilitate observation of the negative pressure effect. To avoid damage to the intestine, contact between the foam material and the intestinal suture should be avoided or minimized. A reliable method is to shorten the foam material so that approximately 1 cm is present between the foam material and the anastomosis, or the greater omentum should be placed between the foam and the intestine. Negative pressure and drainage effects, such as elasticity and collapse of the foam material exposed on the body surface, should be closely monitored. The effective drainage time of the foam material is 4-7 days; this time frame can be shortened or extended depending on the properties of the drainage materials. If blockage occurs, the foam material should be replaced, especially in patients with severe pancreatitis. Intra-abdominal irrigation is not recommended because irrigation is not synchronized with drainage and thus immediate detection of drainage defects due to foam or catheter blockage is almost impossible; moreover, the flushing fluid may enter the large abdominal cavity after the blockage, resulting in contamination or spread infection. In therapeutic applications, irrigation can be considered with drainage area limitations.107 After drainage for 48e72 h, the drainage tube patency and drainage of the irrigation fluid should be ensured; normal saline is recommended for irrigation.

A: VSD facilitates adequate drainage, controls infections, and promotes wound healing in the treatment of enterocutaneous, enteroatmospheric, and pancreatic fistulas (Grade B).
A total of 22 studies were included, one RCT,110 one systematic review,111 and 20 observational studies.
Intestinal fistulas include enterocutaneous fistulas (ECFs) and enteroatmospheric fistulas (EAFs). In intestinal fistulas, VSD can be used as the fistula mouth or surrounding wound drainage to reduce fistula exudates, control secondary infection, and improve healing. In the subgroup study of therapeutic VSD and pVSD, two observational studies showed that therapeutic VSD minimized erosion of the surrounding tissue by the digestive juice, avoided secondary infection, and promoted intestinal fistula closure. Polyvinyl alcohol white foam and the intubation vacuum suction method are recommended.79,99 There have been reports on the use of polyurethane black foam for the treatment of acute intestinal fistulas, with direct sealing, full coverage, and continuous drainage of the suction cups. Five observational studies showed that the application of polyurethane black foam reduced fistula exudate, improved wound healing, and facilitated intestinal fistula closure. VSD can be used as a temporary preoperative measure in chronic intestinal fistulas to isolate wounds and bowel fistulas with polyurethane foam dressings. One RCT showed that VSD increased the natural closure rate of fistulas.110 A case-controlled study applied VSD in 16 cases of intestinal fistula and found that VSD accelerated the healing of intestinal fistulas compared with traditional methods (8 cases). Eight observational studies have shown that VSD can
control fistula exudates, improve wound healing, and increase the success rate of intestinal fistula repair.111e118
In one observational study, 12 cases of high intestinal fistula were treated with VSD. In the end, all patients had spontaneous healing, with an average healing time of 45.3 days.119 Magalini et al. reported that the use of negative pressure closure and drainage successfully promoted self-healing for three cases of duodenal fistula and avoided reoperation. Pepe et al. reported the successful cure of four cases of intestinal fistula using negative pressure closure. Boulanger et al. reported that a case of small intestinal fistula successfully healed following negative pressure closure. Another case report showed that the use of negative pressure closure and drainage in the incision wounds of three cases of multiple intestinal fistulas facilitated control of the intestinal fistulas and promoted proliferation of granulation tissue on the wound surface, thereby creating conditions for the definitive digestive tract and abdominal wall reconstruction. One observational study suggested that additional studies were needed to assess the role of VSD.
One systematic review of the literature retrospectively included 10 articles with a total of 151 ECF patients and showed that over 58 (12-90) days, the average healing rate of VSD was 64.6% (7.7%-100%).111 In Bobkiewicz et al.'s observational study, 16 ECF patients undergoing VSD therapy and another 8 undergoing routine treatment were compared. The results showed that the frequency of dressing changes, healing times, treatment costs, and times required for the body temperature to return to normal, onset times of enteral nutrition, and incidences of secondary related complications were significantly lower in the VSD group than in the control group. A controlled study by Boulanger et al. investigated 18 cases of enteroatmospheric fistula undergoing continuous irrigation and negative pressure drainage using a self-made doublelumen drainage tube and 20 cases of ECF undergoing wound filling using a self-made drainage dressing or VSD at the fistula opening. The results showed that wound filling using the self-made drainage dressings or VSD at the fistula opening shortened the time for ECF wound healing, reduced the frequency of dressing changes, and shortened the hospitalization period.
Treatment of an open abdomen with an enteroatmospheric fistula is very tricky. VSD has been reported to have many advantages for the treatment of enteroatmospheric fistulas. Regarding the study of isolation techniques for enteroatmo-spheric fistulas, four observational studies showed that VAC could be combined with a "ring"/"silo", tire ring, or pacifier method to isolate wounds and intestinal fistulas.5
VSD is not recommended for the prevention and treatment of colonic fistulas because the colon secretes mucus, which can block the foam material and result in ineffective drainage.

A: Use of VSD technique for the treatment of intra-abdominal and extraperitoneal abscesses facilitates adequate drainage, controls infection, and promotes wound healing (Grade C).
A total of 6 observational studies were included.
The effects and feasibility of VSD for severe intra-abdominal infections and abdominal abscesses caused by severe pancreatitis or perforation of the gastrointestinal tract were analyzed. Wond berg et al. suggested that VSD was safe for an OA in cases of severe intra-abdominal infection and improved patient quality of life. Ruiz-Lopez et al found that VSD after abdominal infection and/or abdominal hypertension shortened the recovery time and increased the success rate of abdominal closure. Additionally, Kirkpatrick et al.71 showed that VSD did not accelerate pus drainage nor reduce systemic inflammatory markers.
Regarding the effect of VSD in complex conditions with different pathogenic factors, an observational study of VSD for postperforation abscesses in diverticulitis proved that VSD reduced the mortality and permanent rate of intestinal ostomy. Another observational study of pancreatic abscesses by Olejniket et al.showed that VSD reduced mortality and other complications. A retrospective study of VSD in intraperitoneal abscesses with multiple causes showed that the incidence of VSD-related complications and the rate of abdominal closure in stage I were increased. However, the benefits for other subgroups need to be further investigated.

A: VSD can be used for the treatment of abdominal wounds, wound cavities, and defects with various causes and can facilitate adequate drainage, control infections, promote granulation tissue hyperplasia and wound healing, and shorten the repair time (Grade C).
A total of 14 articles were included, of which 12 were observational studies and 2 were animal experimental
studies.
VSD can be used for the treatment of abdominal wall defects with different causes. Infection-induced abdominal wall defects can be treated with negative pressure drainage; one observational study of abdominal wall infections, necrotizing fasciitis, and abdominal wall defects caused by abdominal wall liposuction showed that the use of VSD promoted necrotic tissue drainage, controlled infection, promoted granulation, and facilitated early reconstruction of the impaired abdominal wall. Traumatic abdominal wall defects can be treated with negative pressure
drainage; two animal experiments investigated abdominal wall defects caused by explosion and showed that application of VSD in early TAC effectively protected the exposed organs, prevented the need for an intestinal fistula, reduced the incidence of wound and abdominal infection, shortened the preoperative preparation time,
reduced the number of dressing changes, and facilitated early closure of the abdominal cavity.
Several key technical points should be considered for the use of VSD for abdominal wall defects. Chen et al.133 suggested direct coverage of VSD dressings on the surface of the intestinal tract and immediate skin grafting after granulation formation. While Aydin et al. supported indirect contact with the intestinal tract and recommended the use of greater omentum or synthetic materials (such as silica gel mesh) to fence out the intestine and dressings. After then negative pressure drainage was applied to promote granulation. One observational study concluded that direct contact of the dressing with the intestinal tract had the risk of causing an intestinal fistula.130 With respect to negative pressure in abdominal wall defects, six observational studies recommend that the negative pressure should be at the range of 70-100 mmHg.
VSD is performed in the repair stage of abdominal wall defects. Three observational studies have shown that VSD can be used in combination with defect repair using synthetic materials (absorbable or non-absorbable) or flap transfer and skin graft during the repair and reconstruction of abdominal wall defects, which can increase the survival rate and shorten the healing time.

A: Direct contact of VSD foams with blood vessels should be avoided. The use of spacers with self-tissue or artificial materials is recommended and close observation of drainage traits is nonnegligible (Grade C).
A total of 8 observational studies were included.Although PU material has a large pore size and the potential to injured blood vessels and causes hemorrhage, vascular complications caused by VSD are rare in clinical practice. Bleeding often results from bleeding from fresh granulation tissue, but delayed hemorrhage due to vascular wall erosion after vascular injury is fairly common. Bleeding after VSD is mainly due to the two situations: coagulation dysfunction and placement of VSD devices directly on the exposed heart or blood vessels, especially blood
vessels after anastomosis, from which the suction may block thinwalled blood vessels and cause bleeding.137 An observational study has shown that multiple hemorrhages occur after VSD treatment in patients with proximal vascular anastomosis. To prevent such bleeding, an artificial barrier should be placed between the drainage surface and the foam to avoid affecting contraction of the wound and suction of exudates. Severe bleeding of the aorta after application of VSD to the sternotomy incision was observed in some cases, indicating that scattered
fragments at the wound should be removed before applying negative pressure. One study has also found that VSD device blockage might cause active bleeding. A retrospective study on 16 patients with deep spinal infection showed two cases of bleeding associated with continuous negative pressure after surgery.

A: When using VSD, the risk of intestinal injury should be monitored (Grade B).
A total of 19 articles involving VSD-related secondary intestinal injury after abdominal surgery were included, of which 2 were RCTs and 17 were retrospective studies.
Whether the use of VSD after abdominal surgery can lead to secondary intestinal injury and increase the incidence of intestinal fistulas is controversial. At present, an increasing number of studies have confirmed that the use of VSD does not increase the incidence of intestinal fistulas.
For patients who had no intestinal fistula before surgery, the incidence of intestinal fistula was 1.6%e37% after VSD-assisted TAC. In the prospective studies, two RCTs compared the incidence of intestinal fistulas in TAC surgeries using VSD and absorbable mesh fixed on the abdominal fascia and found no significant differences. Among the five observational studies, Plaudis et al. applied VSD for the treatment of ACS and
peritonitis in 22 patients, of whom three had intestinal fistulas. Navsari et al.148 treated 20 abdominal trauma patients with VSD after surgery, of whom one occurred secondary intestinal fistula and one had intestinal necrosis. Rao et al. applied VSD in 29 patients after abdominal surgery and met 6 cases of intestinal fistulas.
However, in a prospective observational study of 578 patients undergoing abdominal surgery, Carlson et al.found that the use of VSD did not increase the incidence of intestinal fistulas or intestinal insufficiency;sample matching in this study included a total of 187 pairs of patients and the analysis showed the same conclusions. In a prospective study examining clinical outcomes associated with a negative pressure wound therapy system and Barker's vacuumpacking technique performed by Cheatham et al.,153 280 patients
undergoing abdominal surgery were included; 178 were treated with VSD, of which 13 had gastrointestinal ischemic necrosis, 7 intestinal fistulas, and 5 intestinal obstruction. Among the 102
patients treated with Barker's vacuum-packing technique, 3 had gastrointestinal ischemic necrosis, 4 intestinal fistulas, and none intestinal obstruction. The outcomes of using VSD and Barker's vacuum-packing technique were not significantly different. Kleif et al. found that the use of VSD together with mesh-foilmediated closure reduced the incidence of intestinal fistulas. In a retrospective study of 108 patients undergoing surgical treatment for severe diffuse peritonitis, Mutafchiyski et al.146 found that the incidences of intestinal fistulas in the groups treated with VSD assisted TAC and mesh-foil laparostomy were respectively 8% and 19%, but without statistical significance. In another two studies by Bee et al.and Carlson et al.,incidence of intestinal fistulas after VSD was higher than that of the mesh-foil group, but the difference was not significant.
Five observational studies have shown that OA negative pressure wound treatment does not increase the incidence of intestinal fistulas. Shaikh et al. observed 42 cases of VSD treatment for abdominal incision dehiscence and OA over 5 years. The results showed that the VSD technique was safe and had no
direct correlation with the incidence of intestinal fistulas. In a retrospective study performed by Fieger etal.,patients with open abdomen underwent VSD therapy, 16 had intestinal fistulas. Similarly, Bjorck et al. € 98 showed there's no difference in the incidence of intestinal fistulas between the group using VSD and the group using mesh-mediated fascial traction for TAC after abdominal surgery. A retrospective study performed by Mintziras et al.of 43 patients with secondary peritonitis treated with VSD post-operatively, 16 developed intestinal fistulas and the receiver operating characteristic curve (ROC) analysis found that VSD treatment
significantly reduced the incidence of intestinal fistulas when the application duration was less than 13 days. In a double-center retrospective study of 81 patients undergoing laparotomy performed by Acosta et al.,1 the results showed no correlation between intestinal fistula formation and VSD therapy. Additionally, a retrospective study by Montori et al. showed no difference in the incidence of intestinal fistulas between the use of VSD and the modified Barker negative pressure package after abdominal surgery.
Mechanisms of intestinal injury secondary to abdominal VSD include the following. (1) Injury accompanied by abdominal or systemic pathological changes, including peritonitis & diverticulitis,85 mesenteric ischemia, arterial blood lactate greater than intestinal blood supply insufficiency, pancreatic necrosis, and diverticulitis.34,145,154 (2) Injury caused by decreased blood flow to the intestine due to negative pressure. Two observational studies showed that a negative pressure value of 17 kPa ( 125 mmHg) had excellent drainage effects and caused little damage to the small intestine.8,17 One observational study showed that a negative pressure of 6.7 kPa to 22.6 kPa ( 50 mmHg to 170 mmHg) significantly reduced the intestinal microvascular blood flow and the reduction amount was positively correlated with the negative pressure values.Two observational studies showed that 10.6 kPa ( 80 mmHg) was the optimal negative pressure for blood perfusion and cell growth23,24; however, the setting of negative pressure value needs to be further investigated. (3) The injury caused by direct stimulation of foam materials, which is associated with an excessive long application of VSD and frequent replacement.55 Two observational studies have shown that trimming the foam to approximately 1 cm from the anastomosis, placing the greater omentum between the foam and the intestine, applying hydrocolloid Ag dressing, and open hole dressing (such as Vaseline gauze, plastic films, or Bogota bag) can reduce spotty intestinal hemorrhagic lesions.

A: During the application of VSD, the occurrence of peritoneal adhesions should be monitored. When
applying VSD-assisted TAC, placement of a plastic film between the intestine and the abdominal wall helps reduce adhesions and improve early closure of the fascia (Grade C).
A total of 9 articles were included, with eight retrospective studies and one expert consensus.168
Intestinal adhesion is a common complication after abdominal surgery, with an incidence of up to 90%.169e173
Peritoneal adhesion mainly refers to abnormal adhesion between the intestinal tracts, between the intestine and the peritoneum, or between the intestine and the intra-abdominal organs.Pathological factors, such as peritoneal inflammation, mechanical injury, tissue ischemia, and foreign body implantation, can cause damage to the peritoneal surface, leading to the occurrence of peritoneal adhesions.The impact of the intraperitoneal application of VSD on the formation of peritoneal adhesions has not been established. One observational studies by Magalini et al. suggested that the use of VSD to enhance drainage of gastrointestinal fistulas could reduce the extent and scope of intestinal adhesion and facilitate subsequent surgery.
In OA surgeries for the treatment of diseases such as ACS, the use of VSD-assisted TAC technology can effectively reduce the intraabdominal pressure but cannot avoid the formation of adhesions. Intestinal adhesions and fascia retraction could occur with prolonged length of the abdominal opening; if the abdominal wall cannot be closed early, skin grafting must be performed on top of the granulation tissue, to form a planned abdominal hernia.Consensus on the open abdomen in trauma 2016 recommended the use of a layer of polypropylene
plastic film between the VSD and the intra-abdominal organs to reduce the incidence of intestinal adhesion, thus facilitating fascial closure and reducing the occurrence of related complications.