Richard Ingemansson

Effects of vacuum‐assisted closure therapy on inguinal wound edge microvascular blood flow

Vacuum‐assisted closure (VAC) therapy has been shown to facilitate wound healing. Data on the mechanisms are scarce, although beneficial effects on blood flow and granulation tissue formation have been presented. In the current study, laser Doppler was used to measure microvascular blood flow to an inguinal wound in pigs during VAC therapy (− 50 to − 200 mmHg), including consideration of the different tissue types and the distance from the wound edge. VAC treatment induced an increase in microvascular blood flow a few centimeters from the wound edge. The increase in blood flow occurred closer to the wound edge in muscular as compared to subcutaneous tissue (1.5 cm and 3 cm, at − 75 mmHg). In the immediate proximity to the wound edge, blood flow was decreased. This hypoperfused zone was increased with decreasing pressure and was especially prominent in subcutaneous as compared to muscular tissue (0–1.9 cm vs. 0–1.0 cm, at − 100 mmHg). When VAC therapy was terminated, blood flow increased multifold, which may be due to reactive hyperemia. In conclusion, VAC therapy affects microvascular blood flow to the wound edge and may thereby promote wound healing. A low negative pressure during treatment may be beneficial, especially in soft tissue, to minimize possible ischemic effects. Intermittent VAC therapy may further increase blood flow.

Clinical transplantation of initially rejected donor lungs after reconditioning ex vivo.

BACKGROUND A major problem in clinical lung transplantation is the shortage of donor lungs. Only about 20% of donor lungs are accepted for transplantation. A method to evaluate and recondition lungs ex vivo has been tested on donor lungs that have been rejected for transplantation. METHODS The donor lungs were reconditioned ex vivo in an extracorporeal membrane oxygenation (ECMO) circuit with STEEN solution (Vitrolife AB, Kungsbacka, Sweden) mixed with erythrocytes. The hyperoncotic solution dehydrates edematous lung tissue. Functional evaluations were performed with deoxygenated perfusate by varying the inspired fraction of oxygen. After the reconditioning, the lungs were kept immersed at 8 degrees C in extracorporeal membrane oxygenation until transplantation was performed. RESULTS Six of nine initially rejected donor lungs were reconditioned to acceptable function, and in six recipients, double lung transplantation was performed. Three-month survival was 100%. One patient has since died due to sepsis after 95 days, and one due to rejection after 9 months. Four recipients are alive and well without any sign of bronchiolitis obliterans syndrome 24 months after the transplantation. CONCLUSIONS The result from the present study is promising, and we continue to transplant reconditioned lungs.

Deep sternal wound infection: a sternal-sparing technique with vacuum-assisted closure therapy.

BACKGROUND Vacuum-assisted closure therapy is a novel treatment employed to aid wound healing in different areas of the body and recently also in sternotomy wounds. Aggressive vacuum-assisted closure treatment of the sternum in postoperative deep wound infection enhances sternal preservation and the rate of possible rewiring. METHODS The records of 40 consecutive patients with deep sternal wound infection were reviewed. Sternal bone sparing was achieved by using layers of paraffin gauze (Jelonet; Smith and Nephew Medical, Hull, UK) at the bottom of the wound in order to cover and protect visible parts of the right ventricle, lung tissue, and grafts from the sternal edges. Two separate layers of polyurethane foam (KCI, Copenhagen, Denmark) were placed so as to fit between the sternal edges and subcutaneously. A continuous negative pressure of 125 mm Hg was applied and subsequent revision was made exclusively in nongranulation areas. RESULTS There were no deaths during the 90 days of follow-up. Three late deaths unrelated to the infection and three subcutaneous fistulas occurred during the total follow-up period (3 to 41 months). The median duration of the vacuum-assisted closure therapy was 10 days (range, 3 to 34). The series represents a total of 474 days with the vacuum-assisted closure device without serious adverse events. CONCLUSIONS In our opinion this modified vacuum-assisted closure therapy is a safe and reproducible option to bridge patients with postoperative deep sternal wound infection to complete healing. Reconstruction of the sternum was achieved in all patients without the use of muscle or omental flap surgery.

Wound edge microvascular blood flow during negative-pressure wound therapy: examining the effects of pressures from -10 to -175 mmHg.

Background: Negative-pressure wound therapy is believed to accelerate wound healing by altered wound edge microvascular blood flow. The current standard negative pressure is –125 mmHg. However, this pressure may cause pain and ischemia and often has to be reduced. The aim of the present study was to examine the blood flow effects of different levels of negative pressures (–10 to –175 mmHg). Methods: Wound edge microvascular blood flow was studied in a peripheral wound model in eight 70-kg pigs on application of negative-pressure wound therapy. Blood flow was examined, using laser Doppler velocimetry, in subcutaneous and muscle tissue at 0.5, 2.5, and 5 cm from the wound edge. Results: Blood flow changed gradually with increasing negative pressure until reaching a steady state. Blood flow decreased close to the wound edge (0.5 cm) and increased farther from the wound edge (2.5 cm). At 0.5 cm, blood flow decreased 15 percent at –10 mmHg, 64 percent at –45 mmHg, and 97 percent at –80 mmHg. At 2.5 cm, blood flow increased 6 percent at –10 mmHg, 32 percent at –45 mmHg, and 90 percent at –80 mmHg. Higher levels of negative pressure did not have additional blood flow effects (p > 0.30). No blood flow effects were seen 5 cm from the wound edge. Conclusions: Blood flow changes gradually when the negative pressure is increased. The levels of pressure for negative-pressure wound therapy may be tailored depending on the wound type and tissue composition, and this study implies that –80 mmHg has similar blood flow effects as the clinical standard, –125 mmHg.

Evidence-based recommendations for the use of Negative Pressure Wound Therapy in traumatic wounds and reconstructive surgery: Steps towards an international consensus

Negative pressure wound therapy (NPWT) has become widely adopted over the last 15 years and over 1000 peer reviewed publications are available describing its use. Despite this, there remains uncertainty regarding several aspects of usage. In order to respond to this gap a global expert panel was convened to develop evidence-based recommendations describing the use of NPWT. In this paper the results of the study of evidence in traumatic wounds (including soft tissue defects, open fractures and burns) and reconstructive procedures (including flaps and grafts) are reported. Evidence-based recommendations were obtained by a systematic review of the literature, grading of evidence, drafting of the recommendations by a global expert panel, followed by a formal consultative consensus development program in which 422 independent healthcare professionals were able to agree or disagree with the recommendations. The criteria for agreement were set at 80% approval. Evidence and recommendations were graded according to the SIGN (Scottish Intercollegiate Guidelines Network) classification system. Twelve recommendations were developed in total; 4 for soft tissue trauma and open fracture injuries, 1 for burn injuries, 3 for flaps and 4 for skin grafts. The present evidence base is strongest for the use of NPWT on skin grafts and weakest as a primary treatment for burns. In the consultative process, 11/12 of the proposed recommendations reached the 80% agreement threshold. The development of evidence-based recommendations for NPWT with direct validation from a large group of practicing clinicians offers a broader basis for consensus than work by an expert panel alone.

Safe lung preservation for twenty-four hours with perfadex

The function of six porcine left lung allografts was studied after pulmonary (140 mL/kg) and bronchial (50 mL/kg) artery perfusion with Perfadex (Kabi Pharmacia, Uppsala, Sweden) at room temperature, followed by 24-hour storage of the lungs in an atelectatic state in 6 degrees to 8 degrees C Perfadex, which is a low-potassium-dextran solution. Left lung transplantation was done followed by right pneumonectomy, thereby making all the animals 100% dependent for their survival on the transplanted lungs. The pigs (mean weight = 56 kg, range = 51 to 58 kg, n = 18; 6 donors, 6 recipients, and 6 sham operated) were ventilated with a volume-controlled ventilator (20 breaths/min, 500 mL tidal volume, 8 cm H2O positive end-expiratory pressure, inspired oxygen fraction = 0.5). All the transplanted animals were in good condition throughout the 24-hour observation period with arterial oxygen tensions around 25 kPa (188 mm Hg) and arterial carbon dioxide tensions around 5 kPa (38 mm Hg). The mean pulmonary arterial pressure was around 30 mm Hg, and the pulmonary vascular resistance around 500 dyn.s.cm-5; neither showed any tendency to change with time. After 24 hours the inspired oxygen fraction was increased to 1.0 and the arterial oxygen tension increased to 43.3 +/- 5 kPa (325 +/- 38 mm Hg) (mean +/- standard error of the mean; n = 6). A sham operation (bilateral thoracotomy, right pneumonectomy) was done in 6 pigs, which were followed up for 24 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence-based recommendations for negative pressure wound therapy: Treatment variables (pressure levels, wound filler and contact layer) - Steps towards an international consensus

Negative pressure wound therapy (NPWT) is becoming a commonplace treatment in many clinical settings. New devices and dressings are being introduced. Despite widespread adoption, there remains uncertainty regarding several aspects of NPWT use. To respond to these gaps, a global expert panel was convened to develop evidence-based recommendations describing the use of NPWT. In a previous communication, we have reviewed the evidence base for the use of NPWT within trauma and reconstructive surgery. In this communication, we present results of the assessment of evidence relating to the different NPWT treatment variables: different wound fillers (principally foam and gauze); when to use a wound contact layer; different pressure settings; and the impact of NPWT on bacterial bioburden. Evidence-based recommendations were obtained by a systematic review of the literature, grading of evidence and drafting of the recommendations by a global expert panel. Evidence and recommendations were graded according to the Scottish Intercollegiate Guidelines Network (SIGN) classification system. In general, there is relatively weak evidence on which to base recommendations for any one NPWT treatment variable over another. Overall, 14 recommendations were developed: five for the choice of wound filler and wound contact layer, four for choice of pressure setting and five for use of NPWT in infected wounds. With respect to bioburden, evidence suggests that reduction of bacteria in wounds is not a major mode of action of NPWT.

Negative‐pressure wound therapy using gauze or open‐cell polyurethane foam: Similar early effects on pressure transduction and tissue contraction in an experimental porcine wound model

Negative‐pressure wound therapy (NPWT), also known as topical negative‐pressure therapy, is widely used to manage wounds and accelerate healing. NPWT has so far been delivered mainly via open‐cell polyurethane foam, but increasing interest has been directed toward delivering NPWT via gauze. In the present study, the early effects of NPWT on pressure transduction and wound contraction were examined in wounds filled with either polyurethane foam or gauze. An experimental setup of a porcine wound model was used, in which the animals were anesthetized for 12–14 hours. Negative pressures between −50 and −175 mmHg were applied in −25 mmHg increments. Wound bed pressure was measured using a saline filled catheter sutured to the bottom of the wound. The contraction of the wound edges was also determined. The recordings were performed upon reaching steady state, which typically occurred within 1 minute. For both fillers, wound bed negative pressure increased linearly with delivered vacuum with little deviation from set pressure (correlation coefficient 0.99 in both cases). Similar tissue contraction was observed when using foam and gauze. The most prominent contraction was observed in the range of 0 to −50 mmHg with greater vacuum only producing minor further movement of the wound edge. In conclusion, the present experimental study shows that gauze and foam are equally effective at delivering negative pressure and creating mechanical deformation of the wound.

The Influence of Low and High Pressure Levels during Negative-Pressure Wound Therapy on Wound Contraction and Fluid Evacuation

Background: Negative-pressure wound therapy promotes healing by drainage of excessive fluid and debris and by mechanical deformation of the wound. The most commonly used negative pressure, −125 mmHg, may cause pain and ischemia, and the pressure often needs to be reduced. The aim of the present study was to examine wound contraction and fluid removal at different levels of negative pressure. Methods: Peripheral wounds were created in 70-kg pigs. The immediate effects of negative-pressure wound therapy (−10 to −175 mmHg) on wound contraction and fluid removal were studied in eight pigs. The long-term effects on wound contraction were studied in eight additional pigs during 72 hours of negative-pressure wound therapy at −75 mmHg. Results: Wound contraction and fluid removal increased gradually with increasing levels of negative pressure until reaching a steady state. Maximum wound contraction was observed at −75 mmHg. When negative-pressure wound therapy was discontinued, after 72 hours of therapy, the wound surface area was smaller than before therapy. Maximum wound fluid removal was observed at −125 mmHg. Conclusions: Negative-pressure wound therapy facilitates drainage of wound fluid and exudates and results in mechanical deformation of the wound edge tissue, which is known to stimulate granulation tissue formation. Maximum wound contraction is achieved already at −75 mmHg, and this may be a suitable pressure for most wounds. In wounds with large volumes of exudate, higher pressure levels may be needed for the initial treatment period.

Evidence-based recommendations for the use of negative pressure wound therapy in chronic wounds: Steps towards an international consensus

AIM Negative Pressure Wound Therapy (NPWT) has become widely adopted over the last 15 years and over 1000 peer-reviewed publications are available describing its use. Despite this, there remains uncertainty regarding several aspects of usage. In order to respond to this gap a global expert panel was convened to develop evidence-based recommendations describing the use of NPWT. In this communication the results of the study of evidence in chronic wounds including pressure ulcers, diabetic foot ulcers (DFU), venous leg ulcers (VLU), and ischaemic lower limb wounds are reported. METHODS Evidence-based recommendations were obtained by a systematic review of the literature, grading of evidence, drafting of the recommendations by a global expert panel followed by a formal consultative consensus development program in which 422 independent healthcare professionals were able to agree or disagree with the recommendations. The criteria for agreement were set at 80% agreement. Evidence and recommendations were graded according to the SIGN (Scottish Intercollegiate Guidelines Network) classification system. RESULTS The primary treatment goal of NPWT in most chronic wounds is to achieve wound closure (either by secondary intention or preparing the wound for surgical closure). Secondary goals commonly include: to reduce wound dimensions, and to improve the quality of the wound bed. Thirteen evidence based recommendations were developed in total to address these treatment goals; 4 for pressure ulcers, 4 for DFU, 3 for ischaemic lower limb wounds and 2 for VLU. CONCLUSION The present evidence base is strongest for the use of NPWT in non-ischaemic DFU and weakest in VLU. The development of evidence-based recommendations for NPWT with direct validation from a large group of practicing clinicians offers a broader basis for consensus than work by an expert panel alone.