Commentary: Negative pressure wound therapy: Not so negative!

Central MessageApart from reduced perfusion and tissue hypoxia, several other factors influence occurrence of wound infections. Benefits of NPWT on sternotomy wounds are not limited to improving perfusion alone.See Article page 256. Apart from reduced perfusion and tissue hypoxia, several other factors influence occurrence of wound infections. Benefits of NPWT on sternotomy wounds are not limited to improving perfusion alone. See Article page 256. Near-infrared spectroscopy to assess the parasternal tissue oxygen saturation after coronary artery bypass grafting has not been previously reported. In this elegant study, Jenkins and colleagues evaluated the effect of negative-pressure wound therapy (NPWT) and left internal thoracic artery (LITA) harvesting on tissue oxygen saturation in diabetic patients, and its correlation with sternal wound infections.1Jenkins S. Komber M. Mattam M. Briffa N. Negative pressurewound therapy in patients with diabetes undergoing left internal thoracic artery harvest: a randomized control trial.J Thorac Cardiovasc Surg. 2024; 167: 256-268Abstract Full Text Full Text PDF Scopus (1) Google Scholar The study confirmed a reduction in the parasternal tissue oxygen saturation on the fifth day that returned to preoperative levels 6 weeks after internal thoracic artery harvesting, in both NPWT and standard dressing groups. The effect of NPWT on tissue perfusion and oxygen levels has been a subject of debate and controversy.2Kairinos N. Voogd A.M. Botha P.H. Kotze T. Kahn D. Hudson D.A. et al.Negative-pressure wound therapy II: negative-pressure wound therapy and increased perfusion. Just an illusion?.Plast Reconstr Surg. 2009; 123: 601-612Crossref PubMed Scopus (131) Google Scholar,3Sogorski A. Lehnhardt M. Goertz O. Harati K. Kapalschinski N. Hirsch T. et al.Improvement of local microcirculation through intermittent negative pressure wound therapy (NPWT).J Tissue Viability. 2018; 27: 267-273Crossref PubMed Scopus (19) Google Scholar One of the proposed theories is that although the oxygen saturation remains constant, NPWT leads to an increase in blood velocity, with a resultant increase in total available oxygen to the tissues.3Sogorski A. Lehnhardt M. Goertz O. Harati K. Kapalschinski N. Hirsch T. et al.Improvement of local microcirculation through intermittent negative pressure wound therapy (NPWT).J Tissue Viability. 2018; 27: 267-273Crossref PubMed Scopus (19) Google Scholar The combined effects of LITA harvest and NPWT has been previously studied in a porcine model. This study reported a reduction of blood flow in the left parasternal region after LITA harvest with a significant improvement in perfusion after application of NPWT. The study proposed that NPWT creates a pressure gradient at the application site compared with the surrounding tissues that results in increased blood flow to the wound.4Petzina R. Gustafsson L. Mokhtari A. Ingemansson R. Malmsjö M. Effect of vacuum-assisted closure on blood flow in the peristernal thoracic wall after internal mammary artery harvesting.Eur J Cardiothorac Surg. 2006; 30: 85-89Crossref PubMed Scopus (69) Google Scholar NPWT in this study did not show any increase in wound edge oxygenation compared with standard dressings. In this context, it has to be noted that despite the trial being well planned and conducted, there was a considerable decrease in power of the study because of early discharge in some and failure to return for 6-week follow-up in others. This led to an incomplete data set in 30% (24/80) patients, which was far greater than the anticipated 7.5%. Three patients were reexplored and should have been excluded from the study in keeping with the protocol and might have further affected the observations. The study also showed no correlation between wound edge oxygenation and occurrence of sternal wound infections. Rather than being a negative finding, this observation is of considerable importance aligned with the knowledge that etiology of wound infections is multifactorial, with reduced perfusion and tissue hypoxia being one of the determinants. The benefit of NPWT is not limited to improved perfusion alone. In closed sternotomy wounds, NPWT has been hypothesized to exert beneficial effects by extracting exudates, barrier function against bacterial contamination, and by reducing lateral stress on the skin edges after skin closure with sutures or staples.5Singh D. Chopra K. Sabino J. Brown E. Practical things you should know about wound healing and vacuum-assisted closure management.Plast Reconstr Surg. 2020; 145: 839e-854eCrossref PubMed Scopus (23) Google Scholar Clinical corroboration of beneficial effects of NPWT over conventional surgical dressings has also been obtained in observational as well as randomized settings.6Rashed A. Csiszar M. Beledi A. Gombocz K. The impact of incisional negative pressure wound therapy on the wound healing process after midline sternotomy.Int Wound J. 2021; 18: 95-102Crossref PubMed Scopus (9) Google Scholar, 7Suelo-Calanao R.L. Thomson R. Read M. Matheson E. Isaac E. Chaudhry M. et al.The impact of closed incision negative pressure therapy on prevention of median sternotomy infection for high risk cases: a single centre retrospective study.J Cardiothorac Surg. 2020; 15: 222Crossref PubMed Scopus (14) Google Scholar, 8Witt-Majchrzak A. Żelazny P. Snarska J. Preliminary outcome of treatment of postoperative primarily closed sternotomy wounds treated using negative pressure wound therapy.Pol Przegl Chir. 2015; 86: 456-465Crossref PubMed Scopus (32) Google Scholar, 9Philip B. McCluskey P. Hinchion J. Experience using closed incision negative pressure wound therapy in sternotomy patients.J Wound Care. 2017; 26: 491-495Crossref PubMed Scopus (5) Google Scholar The benefit has been most apparent in obese patients (mean body mass index of 37)10Grauhan O. Navasardyan A. Hofmann M. Müller P. Stein J. Hetzer R. Prevention of poststernotomy wound infections in obese patients by negative pressure wound therapy.J Thorac Cardiovasc Surg. 2013; 145: 1387-1392Abstract Full Text Full Text PDF PubMed Scopus (132) Google Scholar and in patients with multiple risk factors for developing wound complications.7Suelo-Calanao R.L. Thomson R. Read M. Matheson E. Isaac E. Chaudhry M. et al.The impact of closed incision negative pressure therapy on prevention of median sternotomy infection for high risk cases: a single centre retrospective study.J Cardiothorac Surg. 2020; 15: 222Crossref PubMed Scopus (14) Google Scholar The study provides valuable information on parasternal tissue oxygenation after internal thoracic artery harvest in diabetic patients with or without NPWT. Besides filling an important knowledge gap that existed in this area of cardiac surgery the study also provides a base on which larger studies in the future could be built and the authors must be congratulated for their efforts. Negative pressure wound therapy in patients with diabetes undergoing left internal thoracic artery harvest: A randomized control trialThe Journal of Thoracic and Cardiovascular SurgeryVol. 167Issue 1PreviewPatients with diabetes undergoing CABG are at risk of wound infection. Incisional negative pressure wound therapy has been shown to be effective in decreasing incidence of infection in high-risk wounds. Near infrared spectroscopy (NIRS) can be used to assess wound oxygenation and low values can predict infection. Full-Text PDF