A rigid barrier between the heart and sternum protects the heart and lungs against rupture during negative pressure wound therapy

<p>Abstract</p> <p>Objectives</p> <p>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.</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>After 24 hours of NPWT at -120 mmHg the area of epicardial petechial bleeding was 11.90 ± 1.10 cm²when no protective disc was used, and 1.15 ± 0.19 cm²when 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.</p> <p>Conclusion</p> <p>Inserting a rigid barrier between the heart and the sternum edges offers protection against heart rupture and lung injury during NPWT.</p

Effects on heart pumping function when using foam and gauze for negative pressure wound therapy of sternotomy wounds

<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>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.</p> <p>Conclusions</p> <p>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.</p

Pressure transduction and fluid evacuation during conventional negative pressure wound therapy of the open abdomen and NPWT using a protective disc over the intestines

<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Methods</p> <p>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.</p> <p>Results</p> <p>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.</p> <p>Conclusions</p> <p>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.</p

Wound contraction and macro-deformation during negative pressure therapy of sternotomy wounds

<p>Abstract</p> <p>Background</p> <p>Negative pressure wound therapy (NPWT) is believed to initiate granulation tissue formation via macro-deformation of the wound edge. However, only few studies have been performed to evaluate this hypothesis. The present study was performed to investigate the effects of NPWT on wound contraction and wound edge tissue deformation.</p> <p>Methods</p> <p>Six pigs underwent median sternotomy followed by magnetic resonance imaging in the transverse plane through the thorax and sternotomy wound during NPWT at 0, -75, -125 and -175 mmHg. The lateral width of the wound and anterior-posterior thickness of the wound edge was measured in the images.</p> <p>Results</p> <p>The sternotomy wound decreased in size following NPWT. The lateral width of the wound, at the level of the sternum bone, decreased from 39 ± 7 mm to 30 ± 6 mm at -125 mmHg (p = 0.0027). The greatest decrease in wound width occurred when switching from 0 to -75 mmHg. The level of negative pressure did not affect wound contraction (sternum bone: 32 ± 6 mm at -75 mmHg and 29 ± 6 mm at -175 mmHg, p = 0.0897). The decrease in lateral wound width during NPWT was greater in subcutaneous tissue (14 ± 2 mm) than in sternum bone (9 ± 2 mm), resulting in a ratio of 1.7 ± 0.3 (p = 0.0423), suggesting macro-deformation of the tissue. The anterior-posterior thicknesses of the soft tissue, at 0.5 and 2.5 cm laterally from the wound edge, were not affected by negative pressure.</p> <p>Conclusions</p> <p>NPWT contracts the wound and causes macro-deformation of the wound edge tissue. This shearing force in the tissue and at the wound-foam interface may be one of the mechanisms by which negative pressure delivery promotes granulation tissue formation and wound healing.</p

Ischemic heart disease induce upregulation of endothelin receptor mRNA in human coronary arteries

Endothelin has been implicated in the pathogenesis of ischemic heart disease and congestive heart failure. The aims were to quantify endothelin type A (ETA) and type B (ETB) receptor mRNA levels in human coronary arteries from patients with ischemic heart disease, congestive heart failure and controls using real-time polymerase chain reaction (real-time PCR). In addition, the suitability of organ culture as a model mimicking endothelin receptor changes in cardiovascular disease was evaluated by in vitro pharmacology and real-time PCR. Endothelin ETA and ETB receptor mRNA levels were significantly higher in arteries from patients with ischemic heart disease (0.23 +/- 0.04 and 0.35 +/- 0.06) as compared to congestive heart failure (0.09 +/- 0.02 and 0.07 +/- 0.01) and controls (0.08 +/- 0.02 and 0.08 +/- 0.01). After organ culture, the endothelin ETB receptor mRNA levels were elevated, and the sarafotoxin 6c-induced vasoconstriction was more efficacious. Increased endothelin receptor activity may contribute to the increased vascular tone and development of atherosclerotic disease in ischemic heart disease in man. (C) 2003 Elsevier B.V. All rights reserved

Clinical translation of a novel photoacoustic imaging system for examining the temporal artery

The objective was to provide a clinical setup for photoacoustic imaging (PAI) of the temporal artery in humans and to describe the challenges encountered and methods of overcoming them. The temporal artery was examined in 7 patients with suspect giant cell arteritis (GCA), both in vivo and ex vivo, and the results were compared to that of histology. To adapt PAI to human studies, the transducer was fixed to an adjustable arm to reduce motion artifacts and a stepping motor was developed to enable 3D scanning. Risks associated with the use of lasers, ultrasound, and electrical equipment were evaluated by measuring energy levels, and safety precautions were undertaken to prevent injury to the patients and staff. The PAI spectra obtained clearly delineated the artery wall, both in vivo and ex vivo, although the latter were of higher quality due to the lack of artifacts. The results could be compared to that of histology. The energy levels involved were found to be below limits given in regulatory standards. Eye protectors prevented irradiation of the patient&#x2019;s eyes, and visual function after the procedure was found not to be affected. The patients reported no discomfort during the investigations. PAI provides images of the temporal artery wall that may be used for the future diagnosis of GCA in humans. The technique could be further refined by addressing the specific problems of motion artefacts and interference from blood and other chromophores. This study paves the way for other clinical applications of PAI