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Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier disc (HeartShield™) has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up by the negative pressure and damaged by the sharp sternum bone edges. Seven patients treated with conventional NPWT and seven patients treated with NPWT with a protective barrier disc (HeartShield) were compared with regard to bacterial clearance and infection parameters including C-reactive protein levels and leucocyte counts. C-reactive protein levels and leucocyte counts dropped faster and bacterial clearance occurred earlier in the HeartShield® group compared with the conventional NPWT group. Negative biopsy cultures were shown after 3·1 ± 0·4 NPWT dressing changes in the HeartShield group, and after 5·4 ± 0·6 NPWT dressing changes in the conventional NPWT group (P < 0·001). All patients were followed up with clinical check-up after 3 months. None of the patients in the HeartShield group had any signs of reinfection such as deep sternal wound infection (DSWI) or sternal fistulas, whereas in the conventional NPWT group, two patients had signs of sternal fistulas that demanded hospitalisation. HeartShield hinders the right ventricle to come into contact with the sharp sternal edges during NPWT and thereby protects from heart damage. This study shows that using HeartShield is beneficial in treating patients with DSWI. Improved wound healing by HeartShield may be a result of the efficient drainage of wound effluents from the thoracic cavity., (© 2013 The Authors. International Wound Journal © 2013 Medicalhelplines.com Inc and John Wiley & Sons Ltd.)

This study aimed to compare the changes in microvascular blood flow in the small intestinal wall, wound contraction and fluid evacuation, using the established V.A.C. abdominal dressing (VAC dressing) and a new abdominal dressing, the ABThera open abdomen negative pressure therapy system (ABThera dressing), in negative pressure wound therapy (NPWT). Midline incisions were made in 12 pigs that were subjected to treatment with NPWT using the VAC or ABThera dressing. The microvascular blood flow in the intestinal wall was measured before and after the application of topical negative pressures of −50, −75 and −125mmHg using laser Doppler velocimetry. Wound contraction and fluid evacuation were also measured. Baseline blood flow was defined as 100% in all settings. The blood flow was significantly reduced to 64·6±6·7% (P <0·05) after the application of −50mmHg using the VAC dressing, and to 65·3±9·6% (P <0·05) after the application of −50mmHg using the ABThera dressing. The blood flow was significantly reduced to 39·6±6·7% (P <0·05) after the application of −125mmHg using VAC and to 40·5±6·2% (P <0·05) after the application of −125mmHg using ABThera. No significant difference in reduction in blood flow could be observed between the two groups. The ABThera system afforded significantly better fluid evacuation from the wound, better drainage of the abdomen and better wound contraction than the VAC dressing., (© 2013 The Authors. International Wound Journal © 2013 Medicalhelplines.com Inc and John Wiley & Sons Ltd.)

Objective: Right ventricular rupture, resulting in serious bleeding, is a life-threatening complication associated with negative-pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier between the heart and the sharp sternal edges has been successfully tested on pigs. In the present article, we demonstrate increased safety in NPWT through the use of the HeartShield device., Methods: Six patients were treated with a specially designed device in combination with NPWT. The device consists of a horizontally placed disk covered in foam. The back of the T-shaped device sticks up between the sternal edges and up above skin level. This part of the device is also covered in foam. Drainage is performed through two holes at the top of the device. The device and foam are changed every second to third day, and -120 mm Hg of continuous therapy is used. Six patients were treated with traditional NPWT, serving as control group., Results: No signs of calluslike formation were seen on the right ventricle in the group treated with the HeartShield device. In the conventional NPWT control group, all six patients had calluslike formation (>1 × 2 cm2) on the anterior part of the right ventricle. All patients in the HeartShield group had grade 1 epicardial petechial bleeding (<0.5 cm2) on the right ventricle. In the control group, one patient had grade 1 (<0.5 cm2), three patients had grade 2 (0.5-2.0 cm2), and two patients had grade 3 (>2.0 cm2) epicardial petechial bleeding on the right ventricle. No major bleeding or mortality was observed in either group during the course of the study., Conclusions: The use of the HeartShield device significantly minimizes the contact between the right ventricle and the sternal edges, thereby decreasing the risk for life-threatening complications due to bleeding.

Bacteria- and fungus-binding mesh binds with and inactivates bacteria and fungus, which makes it an interesting alternative, wound filler for negative pressure wound therapy (NPWT). This study was conducted to compare the performance of pathogen-binding mesh, foam and gauze as wound fillers in NPWT with regard to pressure transduction, fluid retention, wound contraction and microvascular blood flow. Wounds on the backs of 16 pigs were filled with pathogen-binding mesh, foam or gauze and treated with NPWT. The immediate effects of 0, -40, -60, -80 and -120 mmHg, on pressure transduction and blood flow were examined in eight pigs using laser Doppler velocimetry. Wound contraction and fluid retention were studied during 72 hours of NPWT at -80 and -120 mmHg in the other eight pigs. Pathogen-binding mesh, gauze and foam provide similar pressure transduction to the wound bed during NPWT. Blood flow was found to decrease 0.5 cm laterally from the wound edge and increase 2.5 cm from the wound edge, but was unaltered 5.0 cm from the wound edge. The increase in blood flow was similar with all wound fillers. The decrease in blood flow was more pronounced with foam than with gauze and pathogen-binding mesh. Similarly, wound contraction was more pronounced with foam, than with gauze and pathogen-binding mesh. Wound fluid retention was the same in foam and pathogen-binding mesh, while more fluid was retained in the wound when using gauze. The blood flow 0.5-5 cm from the wound edge and the contraction of the wound during NPWT were similar when using pathogen-binding mesh and gauze. Wound fluid was efficiently removed when using pathogen-binding mesh, which may explain previous findings that granulation tissue formation is more rapid under pathogen-binding mesh than under gauze. This, in combination with its pathogen-binding properties, makes this mesh an interesting wound filler for use in NPWT., (© 2012 The Authors. International Wound Journal © 2012 John Wiley & Sons Ltd and Medicalhelplines.com Inc.)

High closure rates of the open abdomen have been reported following negative pressure wound therapy (NPWT). However, the method has occasionally been associated with increased development of intestinal fistulae. We have previously shown that the application of NPWT to the open abdomen causes a decrease in microvascular blood flow in the small intestinal loop and the omentum adjacent to the visceral protective layer of the dressing. In this study we investigate whether the negative pressure affects only small intestinal loops lying directly below the dressing or if it also affects small intestinal loops that are not in direct contact with the dressing. Six pigs underwent midline incision and application of NPWT to the open abdomen. The microvascular blood flow was measured in four intestinal loops at different depths from the visceral protective layer, at two different locations: beneath the dressing and at the anterior abdominal wall, before and after the application of NPWT of -50, -70, -100, -120, -150 and -170 mmHg, using laser Doppler velocimetry. Negative pressures between -50 and -170 mmHg caused a significant decrease in the microvascular blood flow in the intestinal loops in direct contact with the visceral protective layer. A slight, but significant, decrease in blood flow was also seen in the intestinal loops lying beneath these loops. The decrease in microvascular blood flow increased with the amount of negative pressure applied. No difference in blood flow was seen in the intestinal loops lying deeper in the abdominal cavity. A decrease in blood flow was seen in the upper two intestinal loops located apically and anteriorly, but not in the lower two, indicating that this is a local effect and that pressure decreases with distance from the source. A long-term decrease in blood flow in the intestinal wall may induce ischaemia and secondary necrosis in the intestinal wall, which could promote the development of intestinal fistulae. We believe that NPWT of the open abdomen is a very effective treatment, but that it could be improved by gaining more knowledge on the mechanisms involved., (© 2012 The Authors. International Wound Journal © 2012 John Wiley & Sons Ltd and Medicalhelplines.com Inc.)

We have recently shown that negative pressure wound therapy (NPWT) induces a decrease in microvascular blood flow in the small intestinal loop close to the dressing. The effect of NPWT is thus thought to be local. In this study, we investigate whether the application of NPWT in laparostomy affects the haemodynamics. Midline incisions were made in six pigs followed by NPWT at -120 mmHg for 20 minutes. The cardiac output, mean systemic arterial pressure, mean pulmonary artery pressu re, central venous pressure, left atrial pressure and superior mesenteric artery blood flow were recorded. The blood flow in a small branch of the superior mesenteric artery was then recorded under NPWT between -50 and -175 mmHg. Cardiac output was not affected by NPWT [P = not significant (n.s.)]. Neither the mean arterial pressure nor the mean pulmonary artery pressure was affected by NPWT (P = n.s.). Negative pressures of -50, -75, -100 and -125 mmHg did not alter the blood flow in the small branch of the superior mesenteric artery (P = n.s.). After application of -150 mmHg, a significant decrease in blood flow was seen (P < 0·01), while the application of -175 mmHg resulted in only a slight decrease in blood flow (P = n.s.). The effect of NPWT in laparotomy seems to be local and to have no influence on central haemodynamics or the blood flow to the superior mesenteric artery., (© 2012 The Authors. International Wound Journal © 2012 John Wiley & Sons Ltd and Medicalhelplines.com Inc.)

Background: There are increasing reports of serious complications and deaths associated with negative pressure wound therapy (NPWT). Bleeding may occur when NPWT is applied to a wound with exposed blood vessels. Inserting a rigid disc in the wound may protect these structures. The authors examined the effects of rigid discs on wound bed tissue pressure and blood flow through a large blood vessel in the wound bed during NPWT., Methods: Wounds were created over the femoral artery in the groin of 8 pigs. Rigid discs were inserted. Wound bed pressures and arterial blood flow were measured during NPWT., Results: Pressure transduction to the wound bed was similar for control wounds and wounds with discs. Blood flow through the femoral artery decreased in control wounds. When a disc was inserted, the blood flow was restored., Conclusions: NPWT causes hypoperfusion in the wound bed tissue, presumably as a result of mechanical deformation. The insertion of a rigid barrier alleviates this effect and restores blood flow.

A devastating complication associated with negative-pressure wound therapy (NPWT) after cardiac surgical intervention is heart rupture resulting in serious bleeding. The benefit of a rigid barrier between the underlying organs and the sharp sternal edges has been demonstrated in pigs. In the present article, we present our first 6 patients with deep sternal wound infection treated with NPWT in combination with a protective device. The median duration of NPWT was 8 days (range, 6-14 days). No major bleeding or signs of organ damage were observed. The use of a protective device seems to decrease the risk of bleeding complications., (Copyright © 2013 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.)

There are increasing reports of deaths and serious complications associated with the use of negative pressure wound therapy (NPWT). Bleeding may occur in patients when NPWT is applied to a wound with exposed blood vessels or vascular grafts, possibly due to mechanical deformation and hypoperfusion of the vessel walls. Recent evidence suggests that using a rigid barrier disc to protect underlying tissue can prevent this mechanical deformation. The aim of this study was to examine the effect of rigid discs on the tissue exposed to negative pressure with regard to tissue pressure and microvascular blood flow. Peripheral wounds were created on the backs of eight pigs. The pressure and microvascular blood flow in the wound bed were measured when NPWT was applied. The wound was filled with foam, and rigid discs of different designs were inserted between the wound bed and the foam. The discs were created with or without channels (to accommodate exposed sensitive structures such as blood vessels and nerves), perforations, or a porous dressing that covered the underside of the discs (to facilitate pressure transduction and fluid evacuation). When comparing the results for pressure transduction to the wound bed, no significant differences were found using different discs covered with dressing, whereas pressure transduction was lower with bare discs. Microvascular blood flow in the wound bed decreased by 49 ± 7% when NPWT was applied to control wounds. The reduction in blood flow was less in the presence of a protective disc (e.g., -6 ± 5% for a dressing-covered, perforated disc, p = 0.006). In conclusion, NPWT causes hypoperfusion of superficial tissue in the wound bed. The insertion of a rigid barrier counteracts this effect. The placement of a rigid disc over exposed blood vessels or nerves may protect these structures from rupture and damage., (© 2012 by the Wound Healing Society.)

Higher closure rates of the open abdomen have been reported with negative pressure wound therapy (NPWT) than with other kinds of wound management. We have recently shown that NPWT decreases the blood flow in the intestinal wall, and that the blood flow could be restored by inserting a protective disc over the intestines. The aim of the present study was to investigate whether layers of Jelonet™ (Smith & Nephew) dressing (paraffin tulle gras dressing made from open weave gauze) over the intestines could protect the intestines from hypoperfusion. Midline incisions were made in ten pigs and were subjected to treatment with NPWT with and without four layers of Jelonet over the intestines. The microvascular blood flow was measured in the intestinal wall before and after the application of topical negative pressures of -50, -70 and -120 mmHg, using laser Doppler velocimetry. Baseline blood flow was defined as 100% in all settings. The blood flow was significantly reduced, to 61 ± 7% (P < 0·001), after the application of -50 mmHg using conventional NPWT, and to 62 ± 7% (P < 0·001) after the application of -50 mmHg with Jelonet dressings between the dressing and the intestines. The blood flow was significantly reduced, to 38 ± 5% (P < 0·001), after the application of -70 mmHg, and to 42 ± 6% (P < 0·001) after the application of -70 mmHg with Jelonet dressings. The blood flow was significantly reduced, to 34 ± 9% (P < 0·001), after the application of -120 mmHg, and to 38 ± 6% (P < 0·001) after the application of -120 mmHg with Jelonet dressings. The use of four layers of Jelonet over the intestines during NPWT did not prevent a decrease in microvascular blood flow in the intestinal wall., (© 2011 The Authors. © 2011 Blackwell Publishing Ltd and Medicalhelplines.com Inc.)

Background: Negative pressure wound therapy (NPWT) has gained acceptance among surgeons, for the treatment of open abdomen, since very high closure rates have been reported with this method, compared to other kinds of wound management for the open abdomen. However, the method has occasionally been associated with increased development of fistulae. We have previously shown that NPWT induces ischemia in the underlying small intestines close to the vacuum source, and that a protective disc placed between the intestines and the vacuum source prevents the induction of ischemia. In this study we compare pressure transduction and fluid evacuation of the open abdomen with conventional NPWT and NPWT with a protective disc., Methods: Six pigs underwent midline incision and the application of conventional NPWT and NPWT with a protective disc between the intestines and the vacuum source. The pressure transduction was measured centrally beneath the dressing, and at the anterior abdominal wall, before and after the application of topical negative pressures of -50, -70 and -120 mmHg. The drainage of fluid from the abdomen was measured, with and without the protective disc., Results: Abdominal drainage was significantly better (p < 0. 001) using NPWT with the protective disc at -120 mmHg (439 ± 25 ml vs. 239 ± 31 ml), at -70 mmHg (341 ± 27 ml vs. 166 ± 9 ml) and at -50 mmHg (350 ± 50 ml vs. 151 ± 21 ml) than with conventional NPWT. The pressure transduction was more even at all pressure levels using NPWT with the protective disc than with conventional NPWT., Conclusions: The drainage of the open abdomen was significantly more effective when using NWPT with the protective disc than with conventional NWPT. This is believed to be due to the more even and effective pressure transduction in the open abdomen using a protective disc in combination with NPWT.

Purpose: Higher closure rates of the open abdomen have been reported with negative pressure wound therapy (NPWT) compared with other wound therapy techniques. However, the method has occasionally been associated with increased development of intestinal fistulae. The present study measures microvascular blood flow in the intestinal wall and the omentum before and during NPWT., Methods: Six pigs underwent midline incision and application of NPWT to the open abdomen. The microvascular blood flow in the underlying intestinal loop wall and the omentum was recorded before and after the application of NPWT of -50, -70, -100, -120, -150, and -170 mmHg respectively, using laser Doppler velocimetry., Results: A significant decrease in microvascular blood flow was seen in the intestinal wall during application of all negative pressures levels. The blood flow was 2.7 (±0.2) Perfusion Units (PU) before and 2.0 (±0.2) PU (*p < 0.05) after application of -50 mmHg, and 3.6 (±0.6) PU before and 1.5 (±0.2) PU (**p < 0.01) after application of -170 mmHg., Conclusions: In the present study, we show that negative pressures between -50 and -170 mmHg induce a significant decrease in the microvascular blood flow in the intestinal wall. The decrease in blood flow increased with the amount of negative pressure applied. One can only speculate that a longstanding decreased blood flow in the intestinal wall may induce ischemia and secondary necrosis in the intestinal wall, which, theoretically, could promote the development of intestinal fistulae. We believe that NPWT of the open abdomen is a very effective treatment but could probably be improved.

Objectives: Blood flow changes in the intestines during conventional negative pressure wound therapy (NPWT), and NPWT using a protective disc over the intestines in laparostomy., Background: Higher closure rates of the open abdomen have been reported with NPWT compared with other kinds of wound management. However, the method has been associated with increased development of fistulae. We have compared the changes in blood flow in the intestinal wall using conventional NPWT and NWPT with a protective disc between the intestines and the vacuum source., Methods: Midline incisions were made in 10 pigs and either conventional NPWT or NPWT with a disc over the intestines was applied. The microvascular blood flow was measured in the intestinal wall before and after the application of topical negative pressures of -50, -70, and -120 mmHg, using laser Doppler velocimetry., Results: The blood flow was significantly decreased (by 24%) after the application of conventional NPWT at -50 mmHg, compared with a slight decrease (2%) after the application of NWPT with a protective disc (P < 0.05). The blood flow was significantly decreased (by 54%) after the application of conventional NPWT at -120 mmHg, compared with a slight decrease (17%) after application of NPWT using a protective disc (P < 0.001)., Conclusions: Inserting a disc between the intestines and the vacuum source in NPWT protects the intestines from ischemia. The decreased blood flow in the intestinal wall may induce ischemia, which could promote the development of intestinal fistulae.

Pain upon negative pressure wound therapy (NPWT) dressing removal has been reported and is believed to be associated with the observation that granulation tissue grows into foam. Wound tissue damage upon removal of the foam may cause the reported pain. Calcitonin gene-related peptide (CGRP) and substance P are neuropeptides that cause inflammation and signal pain and are known to be released when tissue trauma occurs. The aim of this controlled in vivo study was to compare the expression of CGRP and substance P in the wound bed in control wounds and following NPWT and foam or gauze dressing removal. Eight pigs with two wounds each were treated with open-pore structure polyurethane foam or AMD gauze and NPWT of 0 (control) or -80 mm Hg for 72 hours. Following removal of the wound filler, the expression of CGRP and substance P was measured, using arbitrary units, in sections of biopsies from the wound bed using immunofluorescence techniques. Substance P and CGRP were more abundant in the wound edge following the removal of foam than of gauze dressings and least abundant in control wounds. The immunofluorescence staining of the wound edge for CGRP was 52 ± 3 au after the removal of gauze and 97 ± 5 au after the removal of foam (P <0.001). For substance P, the staining was 55 ± 3 au after gauze removal and 95 ± 4 au after foam removal (P <0.001). CGRP and substance P staining was primarily located to nerves and leukocytes. The increase in CGRP and substance P immunofluorescence was especially prominent in the dermis but also was seen in subcutaneous and muscle tissue. Using gauze may be one way of reducing NPWT dressing change-related pain. New wound fillers designed to optimize granulation tissue formation and minimize pain issues presumably will be developed in the near future.

Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) following cardiac surgery. The use of a rigid disc has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up towards, and damaged by, the sharp sternum edges. The aim of the present study was to compare the wound fluid evacuation from the pericardium and the left pleura when using NPWT with such a disc between the sternal edges and the heart, and when using conventional NPWT. Six pigs underwent median sternotomy followed by NPWT at -120 mmHg, using foam, with or without a rigid plastic disc between the heart and the sternal edges. A 250 ml saline was infused into the pericardium, and the time required for fluid evacuation was measured. A 500 ml saline was infused into the left pleura and the time for fluid evacuation measured. The pericardium was effectively drained of 250 ml fluid in both cases [conventional NPWT: 24 ± 0·7 seconds, NPWT with the disc: 25 ± 1·1 seconds (n.s.)]. The left pleura was effectively drained when using NPWT with the disc, but was not drained at all when using conventional NPWT. The left pleura could be effectively drained of 500 ml fluid when a rigid perforated plastic disc was inserted between the sternal edges and the heart during NPWT. Significantly less drainage of the left pleura was possible when using conventional NPWT without the disc. The pericardium was equally good drained using NPWT with or without the disc., (© 2011 The Authors. © 2011 Blackwell Publishing Ltd and Medicalhelplines.com Inc.)

The use of a rigid disc as a barrier between the wound bed and the wound filler during negative pressure wound therapy (NPWT) has been suggested to prevent damage to exposed organs. However, it is important to determine that the effects of NPWT, such as wound contraction and fluid removal, are maintained during treatment despite the use of a barrier. This study was performed to examine the effect of NPWT on wound contraction and fluid evacuation in the presence of a rigid disc. Peripheral wounds were created on the backs of eight pigs. The wounds were filled with foam, and rigid discs of different designs were inserted between the wound bed and the foam. Wound contraction and fluid evacuation were measured after application of continuous NPWT at -80 mmHg. Wound contraction was similar in the presence and the absence of a rigid disc (84 ± 4% and 83 ± 3%, respectively, compared with baseline). Furthermore, the rigid disc did not affect wound fluid removal compared with ordinary NPWT (e.g. after 120 seconds, 71 ± 4 ml was removed in the presence and 73 ± 3 ml was removed in the absence of a disc). This study shows that a rigid barrier may be placed under the wound filler to protect exposed structures during NPWT without affecting wound contraction and fluid removal, which are two crucial features of NPWT., (© 2011 The Authors. © 2011 Blackwell Publishing Ltd and Medicalhelplines.com Inc.)

Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up and damaged by the sharp sternum bone edges. The aim of this study was to investigate the haemodynamic effects of placing a rigid barrier over the heart to protect it from rupture during NPWT. Eight pigs underwent median sternotomy followed by NPWT at --70 and --120 mmHg, using foam, with or without a rigid plastic disc between the heart and the sternal edges. The heart frequency, cardiac output, mean systemic arterial pressure, mean pulmonary artery pressure, central venous pressure and left atrial pressure were recorded. Cardiac output was not affected by NPWT, regardless of whether a rigid barrier was used. Heart frequency decreased during NPWT without a disc, and showed a tendency towards a decrease when using a rigid disc. The blood pressure decreased during NPWT without a disc, and showed only a tendency towards a decrease when a disc was inserted between the heart and the sternum. In conclusion, the results of this haemodynamic study show that a rigid disc can safely be placed over the heart during NPWT, to prevent heart rupture. The haemodynamic effects of NPWT in sternotomy wounds are slightly reduced by the presence of the rigid disc., (© 2011 The Authors. © 2011 Blackwell Publishing Ltd and Medicalhelplines.com Inc.)

Objectives: Right ventricular heart rupture is a devastating complication associated with negative pressure wound therapy (NPWT) in cardiac surgery. The use of a rigid barrier has been suggested to offer protection against this lethal complication, by preventing the heart from being drawn up and damaged by the sharp edges of the sternum. The aim of the present study was to investigate whether a rigid barrier protects the heart and lungs against injury during NPWT., Methods: Sixteen pigs underwent median sternotomy followed by NPWT at -120 mmHg for 24 hours, in the absence (eight pigs) or presence (eight pigs) of a rigid plastic disc between the heart and the sternal edges. The macroscopic appearance of the heart and lungs was inspected after 12 and 24 hours of NPWT., Results: After 24 hours of NPWT at -120 mmHg the area of epicardial petechial bleeding was 11.90 ± 1.10 cm² when no protective disc was used, and 1.15 ± 0.19 cm² when using the disc (p < 0.001). Heart rupture was observed in three of the eight animals treated with NPWT without the disc. Lung rupture was observed in two of the animals, and lung contusion and emphysema were seen in all animals treated with NPWT without the rigid disc. No injury to the heart or lungs was observed in the group of animals treated with NPWT using the rigid disc., Conclusion: Inserting a rigid barrier between the heart and the sternum edges offers protection against heart rupture and lung injury during NPWT.

Background: Higher closure rates of the open abdomen have been reported with negative pressure wound therapy (NPWT) than with other wound management techniques. However, the method has occasionally been associated with increased development of fistulae. We have previously shown that NPWT induces ischemia in the underlying small intestines close to the vacuum source, and that a protective disc placed between the intestines and the vacuum source prevents the induction of ischemia. In the present study we compare macroscopic changes after 12, 24, and 48 hours, using conventional NPWT and NPWT with a protective disc between the intestines and the vacuum source., Methods: Twelve pigs underwent midline incision. Six animals underwent conventional NPWT, while the other six pigs underwent NPWT with a protective disc inserted between the intestines and the vacuum source. Macroscopic changes were photographed and quantified after 12, 24, and 48 hours of NPWT., Results: The surface of the small intestines was red and mottled as a result of petechial bleeding in the intestinal wall in all cases. After 12, 24 and 48 hours of NPWT, the area of petechial bleeding was significantly larger when using conventional NPWT than when using NPWT with the protective disc (9.7 ± 1.0 cm(2) vs. 1.8 ± 0.2 cm(2), p < 0.001, 12 hours), (14.5 ± 0.9 cm(2) vs. 2.0 ± 0.2 cm(2), 24 hours) (17.0 ± 0.7 cm(2) vs. 2.5 ± 0.2 cm(2) with the disc, p < 0.001, 48 hours), Conclusions: The areas of petechial bleeding in the small intestinal wall were significantly larger following conventional NPWT after 12, 24 and 48 hours, than using NPWT with a protective disc between the intestines and the vacuum source. The protective disc protects the intestines, reducing the amount of petechial bleeding.

Background: Topical negative pressure (TNP) therapy is increasingly used in open abdomen management. It is not known to what extent this pressure propagates through the dressing to the bowel surface, potentially increasing the risk of bowel fistula formation. The present study in a porcine model was designed to evaluate pressure propagation., Methods: A commercially available TNP therapy system (ABThera/VAC) was applied in six pigs after laparotomy. Pressure sensors were placed in predetermined positions in the dressing and in the abdominal cavity and the pressure was registered at TNP settings of -50, -75, -100, -125, and -150 mmHg. Next, after infusing 200 ml of saline into the abdomen through a catheter, the amount of fluid drained through the system during 10 min of TNP therapy was registered. Finally, pressure was measured above and below eight layers of paraffin gauzes during TNP therapy., Results: Observed pressure within the outer two foams and the foam of the visceral protective layer correlated with preset TNP. The median pressure at the bowel surface was between -2 and -10 mmHg, regardless of preset TNP. Median fluid drainage was 95% of the infused fluid at -75 mmHg and 124% at -150 mmHg. Paraffin gauzes had a limited isolating effect, reducing the pressure by 13% in median., Conclusions: Negative pressure reaching the bowel surface during TNP therapy with the ABThera system is limited for all TNP levels. Reduced therapy pressure does not lead to reduced pressure at the bowel surface. The system drains the abdominal cavity completely of fluid. Paraffin gauzes are of limited value as a means of pressure isolation.

Background: There are increasing reports of deaths and serious complications associated with the use of negative pressure wound therapy (NPWT), of which right ventricular heart rupture is the most devastating. The use of a rigid barrier has been suggested to offer protection against this lethal complication by preventing the heart from being drawn up against the sharp edges of the sternum. The aim of the present study was to determine whether a rigid barrier can be safely inserted over the heart with regard to the sternum wound edge movement., Methods: Sternotomy wounds were created in eight pigs. The wounds were treated with NPWT at -40, -70, -120 and -170 mmHg in the presence and absence of a rigid barrier between the heart and the edges of the sternum. Wound contraction upon NPWT application, and wound distension under mechanical traction to draw apart the edges of the sternotomy were evaluated., Results: Wound contraction resulting from NPWT was similar with and without the rigid barrier. When mechanical traction was applied to a NPWT treated sternum wound, the sternal edges were pulled apart. Wound distension upon traction was similar in the presence and absence of a the rigid barrier during NPWT., Conclusions: A rigid barrier can safely be inserted between the heart and the edges of the sternum to protect the heart and lungs from rupture during NPWT. The sternum wound edge is stabilized equally well with as without the rigid barrier during NPWT., (© 2011 Lindstedt et al; licensee BioMed Central Ltd.)

The study was performed to compare the effects of negative-pressure wound therapy (NPWT) using gauze and foam on wound edge movement and the macroscopic appearance of the heart and lungs after NPWT. Sternotomy wounds were created in 6×70 kg pigs. Negative pressures of -40, -70, -120 and -160 mmHg were applied and the following were evaluated: wound contraction, distension and the macroscopic appearance of the heart and lungs after NPWT. Wound contraction was greater when using foam than gauze (3.5±0.3 cm and 1.3±0.2 cm, respectively, P<0.01). The application of traction to the lateral edges of the sternotomy resulted in greater wound distention with foam than with gauze (5.3±0.3 cm and 3.6±0.2 cm, respectively, P<0.001). After using foam, the surface of the heart was red and mottled, and lung emphysema and sometimes, lung rupture were observed. After using gauze, the organ surface had no markings. The study shows that foam allows greater wound contraction and distension than gauze. This movement of the wound edges may cause damage to the underlying organs. There is less damage to the heart and lungs when using gauze than foam.

Negative-pressure wound therapy (NPWT) has been used for the treatment of deep sternal wound infection (DSWI) with promising results. However, questions have been raised regarding the potential risk of right ventricle (RV) rupture during treatment. In the present study, we evaluate our clinical experience of NPWT focusing on RV rupture and major bleeding complications and its potentially negative impact on 30-day mortality during an 11-year period. Serious bleeding complications during NPWT were reviewed for 176 patients treated for DSWI between January 1999 and April 2010. The 30-day mortality following DSWI was 1.1% (2/176). Four patients (2.3%) suffered bleeding from the RV rupture during NPWT of the sternal wound (two spontaneous and two debridement related). Furthermore, two patients had debridement-related bleedings from the venous bypass grafts during wound dressing change. The very low 30-day mortality (1.1%) following DSWI supports the use of NPWT. Overall, even if major bleeding complications may occur, the risk of RV rupture seems to be outweighed by the benefit of superior infection control. However, surgical experience is recommended when debriding sternal wounds and we recommend the use of a wound dressing, such as paraffin gauze, in order to protect the RV from direct contact with the polyurethane foam.

Background: Negative pressure wound therapy (NPWT) has remarkable effects on the healing of poststernotomy mediastinitis. Foam is presently the material of choice for NPWT in this indication. There is now increasing interest in using gauze, as this has proven successful in the treatment of peripheral wounds. It is important to determine the effects of NPWT using gauze on heart pumping function before it can be used for deep sternotomy wounds. The aim was to examine the effects of NPWT when using gauze and foam on the heart pumping function during the treatment of a sternotomy wound., Methods: Eight pigs underwent median sternotomy followed by NPWT at -40, -70, -120 and -160 mmHg, using foam or gauze. The heart frequency, cardiac output, mean systemic arterial pressure, mean pulmonary artery pressure, central venous pressure and left atrial pressure were recorded., Results: Cardiac output was not affected by NPWT using gauze or foam. Heart frequency decreased during NPWT when using foam, but not gauze. Treatment with foam also lowered the central venous pressure and the left atrial pressure, while gauze had no such effects. Mean systemic arterial pressure, mean pulmonary artery pressure and systemic vascular resistance were not affected by NPWT. Similar haemodynamic effects were observed at all levels of negative pressure studied., Conclusions: NPWT using foam results in decreased heart frequency and lower right and left atrial filling pressures. The use of gauze in NPWT did not affect the haemodynamic parameters studied. Gauze may thus provide an alternative to foam for NPWT of sternotomy wounds.

Pressure transduction to the wound bed in negative pressure wound therapy (NPWT) is crucial in stimulating the biological effects ultimately resulting in wound healing. In clinical practice, either foam or gauze is used as wound filler. Furthermore, two different drainage techniques are frequently employed. One involves the connection of a non-perforated drainage tube to the top of the dressing, while the other involves the insertion of perforated drains into the dressing. The aim of this study was to examine the efficacy of these two different wound fillers and drainage systems on pressure transduction to the wound bed in a challenging wound (the sternotomy wound). Six pigs underwent median sternotomy. The wound was sealed for NPWT using different wound fillers (foam or gauze) and drainage techniques (see earlier). Pressures between 0 and -175 mmHg were applied and the pressure in the wound was measured using saline-filled catheters sutured to the bottom of the wound (over the anterior surface of the heart) and to the side of the wound (on the thoracic wall). The negative pressure on the wound bed increased linearly with the negative pressure delivered by the vacuum source. In a dry wound, the pressure transduction was similar when using the different wound fillers (foam and gauze) and drainage techniques. In a wet wound, pressure transduction was better when using a perforated drainage tube inserted into the wound filler than a non-perforated drainage tube connected to the top of the dressing (-116 ± 1 versus -73 ± 4 mmHg in the wound at a delivered pressure of -125 mmHg for foam, P < 0·01), regardless of the type of wound filler. Gauze and foam are equally effective at delivering negative pressure to the wound bed. Perforated drainage tubes inserted into the wound filler are more efficient than a non-perforated drainage tubes connected to the top of the dressing. The choice of drainage technique may be particularly important in wounds with a large volume of exudate., (© 2010 The Authors. Journal Compilation © 2010 Blackwell Publishing Ltd and Medicalhelplines.com Inc.)

Previous research has shown -125 mmHg to be the optimal negative pressure for creating an environment that promotes wound healing, and this has therefore been adopted as a standard pressure for patients with deep sternal wound infection. However, it has not yet been clearly shown that -125 mmHg is the optimal pressure from a haemodynamic point of view. Furthermore, there have been reports of cardiac rupture during -125 mmHg negative pressure therapy. We therefore studied the effects of a lower pressure: -75 mmHg. Twelve pigs were used. After median sternotomy, sealed negative pressure therapy of -75 mmHg was applied. Baseline measurements were made and continuous recording of the cardiac output, end-tidal CO(2) production, mean arterial pressure, mean pulmonary pressure (pulmonary artery pressure), systemic vascular resistance, pulmonary vascular resistance, left atrial pressure and central venous pressure was started. Six pigs served as controls. No statistically significant difference was observed in any of the haemodynamic parameters studied, compared with the controls. The present study shows that, with a suitable foam application technique, -75 mmHg can be applied without compromising the central haemodynamics.

Negative pressure wound therapy (NPWT) has been adopted as the first-line treatment for poststernotomy mediastinitis as a result of the excellent clinical outcome. The knowledge concerning the effects of NPWT on the cardiovascular system and homeostasis is still limited. The aim of the present study was to investigate whether the plasma levels of neurohormones change during NPWT. Six pigs underwent median sternotomy followed by NPWT at -125 mmHg. The plasma levels of noradrenaline, adrenaline, neuropeptide Y, substance P, vasoactive intestinal peptide (VIP), and calcitonin gene-related peptide (CGRP) were determined before (0 min) and 5, 20, 60 and 180 min after the application of NPWT. The results show a transient increase in the plasma levels of noradrenaline and adrenaline when NPWT was applied. The plasma level of the adrenergic co-transmitter neuropeptide Y was higher in NPWT--than in sham-treated pigs, after 180 min of negative pressure. After 180 min of NPWT there was an increase in the plasma levels of the sensory nerve transmitter substance P, while no such effect was observed for CGRP or VIP. In conclusion, the results suggest sympathetic nerve activation during NPWT. This may be the result of an increase in workload on the heart during the initial phase of NPWT.

Several studies have suggested that mediastinitis is a strong predictor for poor long-term survival after coronary artery bypass surgery (CABG). In those studies, several conventional wound-healing techniques were used. Previously, we have shown no difference in long-term survival between CABG patients with topical negative pressure (TNP)-treated mediastinitis and CABG patients without mediastinitis. The present study was designed to elucidate if TNP, applied over the myocardium, resulted in an increase of the total amount of coronary blood flow. Six pigs underwent median sternotomy. The coronary blood flow was measured, before and after the application of TNP (-50 mmHg), using coronary electromagnetic flow meter probes. Analyses were performed before left anterior descending artery (LAD) occlusion (normal myocardium) and after 20 minutes of LAD occlusion (ischaemic myocardium). Normal myocardium: 171.3 +/- 14.5 ml/minute before to 206.3 +/- 17.6 ml/minute after TNP application, P < 0.05. Ischaemic myocardium: 133.7 +/- 18.4 ml/minute before to 183.2 +/- 18.9 ml/minute after TNP application, P < 0.05. TNP of -50 mmHg applied over the LAD region induced a significant increase in the total coronary blood flow in both normal and ischaemic myocardium.

Objective: Topical negative pressure, commonly used in wound therapy, has been shown to increase blood flow and stimulate angiogenesis in subcutaneous tissue and skeletal muscle. In wound therapy, intermittent negative pressure is often preferred to continuous negative pressure as tissue exposed to intermittent therapy shows twice as much granulation tissue formation than that exposed to continuous pressure after 2 weeks of therapy. The present study was designed to elucidate the differences in microvascular blood flow in the left anterior descending artery area between continuous and intermittent myocardial topical negative pressure of -50 mmHg., Methods: Six pigs underwent median sternotomy. Laser Doppler probes were inserted horizontally into the heart muscle in the left anterior descending artery area at depths of approximately 5-6 mm. Measurements of microvascular blood flow were performed in normal myocardium and ischemic myocardium during 20 min of countinuous and intermittent topical negative pressure at -50 mmHg., Results: Both continuous and intermittent topical negative pressure of -50 mmHg significantly increased microvascular blood flow in the underlying myocardium: from 56.2 +/- 13.1 perfusion units (PU) before to 132.8 +/- 7.4 PU during countinuous topical negative pressure application (P < 0.05) and from 75.8 +/- 12.1 PU before to 153.6 +/- 4.7 PU during intermittent topical negative pressure application (P < 0.05)., Conclusion: No statistically significant difference was found between microvascular blood flow during 20 min of continuous and intermittent topical negative pressure at -50 mmHg in this porcine model.

Background: Topical negative pressure (TNP), widely used in wound therapy, is known to stimulate wound edge blood flow, granulation tissue formation, angiogenesis, and revascularization. We have previously shown that application of a TNP of -50 mmHg to the myocardium significantly increases microvascular blood flow in the underlying tissue. We have also shown that a myocardial TNP levels between -75 mmHg and -150 mmHg do not induce microvascular blood flow changes in the underlying myocardium. The present study was designed to elucidate the difference between -25 mmHg and -50 mmHg TNP on microvascular flow in normal and ischemic myocardium., Methods: Six pigs underwent median sternotomy. The microvascular blood flow in the myocardium was recorded before and after the application of TNP using laser Doppler flowmetry. Analyses were performed before left anterior descending artery (LAD) occlusion (normal myocardium), and after 20 minutes of LAD occlusion (ischemic myocardium)., Results: A TNP of -25 mmHg significantly increased microvascular blood flow in both normal (from 263.3 +/- 62.8 PU before, to 380.0 +/- 80.6 PU after TNP application, * p = 0.03) and ischemic myocardium (from 58.8 +/- 17.7 PU before, to 85.8 +/- 20.9 PU after TNP application, * p = 0.04). A TNP of -50 mmHg also significantly increased microvascular blood flow in both normal (from 174.2 +/- 20.8 PU before, to 240.0 +/- 34.4 PU after TNP application, * p = 0.02) and ischemic myocardium (from 44.5 +/- 14.0 PU before, to 106.2 +/- 26.6 PU after TNP application, ** p = 0.01)., Conclusion: Topical negative pressure of -25 mmHg and -50 mmHg both induced a significant increase in microvascular blood flow in normal and in ischemic myocardium. The increase in microvascular blood flow was larger when using -25 mmHg on normal myocardium, and was larger when using -50 mmHg on ischemic myocardium; however these differences were not statistically significant.

Background: We have previously shown that a myocardial topical negative pressure (TNP) of -50 mmHg significantly increases microvascular blood flow in the underlying myocardium in normal, ischemic, and reperfused porcine myocardium. The present study was designed to elucidate the effect of different TNP levels between -50 and -150 mmHg on microvascular flow in normal and ischemic myocardium., Materials and Methods: Seven pigs underwent median sternotomy. The microvascular blood flow in the myocardium was recorded, before and after the application of TNP, using laser Doppler velocimetry. Analyses were performed before left anterior descending artery (LAD) occlusion (normal myocardium) and after 20 min of LAD occlusion (ischemic myocardium)., Results: A TNP of -50 mmHg significantly increased microvascular blood flow in both normal (from 320.0+/-56.1 PU before TNP application to 435.7+/-65.5 PU after TNP application, P=.028) and ischemic myocardium (from 110.0+/-36.7 PU before TNP application to 194.3+/-56.2 PU after TNP application, P=.012). TNP between -75 and -150 mmHg showed no significant increase in microvascular blood flow in normal or ischemic myocardium., Conclusions: Of pressures between -50 and -150 mmHg, a TNP of -50 mmHg seems to be the most effective negative pressure concerning significant increase in microvascular blood flow in both normal and ischemic myocardium.

Background: Topical negative pressure (TNP), commonly used in wound therapy, has been shown to increase blood flow and stimulate angiogenesis in skeletal muscle. We have previously shown that a myocardial TNP of -50 mmHg significantly increases microvascular blood flow in the myocardium. When TPN is used in wound therapy (on skeletal and subcutaneous tissue) a zone of relative hypoperfusion is seen close to the wound edge. Hypoperfusion induced by TNP is thought to depend on tissue density, distance from the negative pressure source, and the amount negative pressure applied. When applying TNP to the myocardium, a significant, long-standing zone of hypoperfusion could theoretically cause ischemia, and negative effects on the myocardium. The current study was designed to elucidate whether hypoperfusion was produced during myocardial TNP., Methods: Six pigs underwent median sternotomy. Laser Doppler probes were inserted horizontally into the heart muscle in the LAD area, at depths of approximately, 1-2 mm. The microvascular blood flow was measured before and after the application of a TNP. Analyses were performed before left anterior descending artery (LAD) occlusion (normal myocardium) and after 20 minutes of LAD occlusion (ischemic myocardium)., Results: A TNP of -50 mmHg induced a significant increase in microvascular blood flow in normal myocardium (**p = 0.01), while -125 mmHg did not significantly alter the microvascular blood flow. In ischemic myocardium a TNP of -50 mmHg induced a significant increase in microvascular blood flow (*p = 0.04), while -125 mmHg did not significantly alter the microvascular blood flow., Conclusion: No hypoperfusion could be observed in the epicardium in neither normal nor ischemic myocardium during myocardial TNP.