Surgical Forum Abstracts
CONCLUSIONS: The MWT enhances healing mainly through increased wound deformation, cell proliferation and angiogenesis. These effects seem to be triggered during the early phase of application rather than by continuous stimulation.
Mortality reduction in the treatment of deep sternal wound infection after cardiac surgery Evan Matros, MD, MMSc, Lauren Bayer, PA-C, Jennifer Neuwalder, BA, Sary Aranki, MD, Lawrence Cohn, MD, FACS, Dennis Orgill, MD, PhD Brigham and Women’s Hospital, Boston, MA INTRODUCTION: Deep sternal wound infection (DSWI) is a major complication of open-heart procedures with a reported incidence of 0.2-7% and associated 30-day mortality of 7-35%. We performed a contemporary analysis of risk factors, morbidity and mortality rates in a large series from our institution. METHODS: Retrospective review of 179 consecutive cases of DSWI treated by a single plastic surgeon from 1992-2001. Cases were matched with non-infected controls by age, procedure, and year of surgery. Demographic and surgical characteristics were recorded prospectively. Univariate and multivariate analyses were performed to identify risk factors for development of DSWI. RESULTS: DSWIs were treated in 240 of 14,550 open-heart operations during the study period (1.6%); of these, 179 cases were treated by a single surgeon. Risk factors for development of DSWI included obesity, female gender, aspirin, and diabetes. Multivariate regression showed diabetes, bypass time, aspirin, female gender, smoking and obesity to be independent risk factors for DSWI. Patients were treated with debridement, flap closure and/or sternal rewiring. Rates of Methicillin-resistant Staph. aureus increased from 15 to 58% during the study period. Length of stay associated with DSWI was significantly longer compared with controls. Thirty-day perioperative mortality was 5% for those with DSWI compared to 1% for controls. One-year mortality rate associated with DSWI was 11%. CONCLUSIONS: Early diagnosis and improved surgical technique have led to the lowest reported mortality rate in a large series of patients with DSWI. As rates of diabetes and obesity increase, efforts should focus on ways to decrease morbidity associated with DSWI.
Oxidative stress and hypoxia inducible factor-1 alpha regulation Edward I Chang, MD, Eric I Chang, MD, Shang A Loh, MD, Michael G Galvez, BA, Geoffrey C Gurtner, MD, FACS Stanford University, Stanford, CA INTRODUCTION: Advanced age is known to impair neovascularization that is regulated in part by HIF-1-alpha. Oxidative stressinduced cellular damage has been a proposed mechanism for aging. This study aims to evaluate the effects of oxidative stress on HIF-1alpha expression and regulation. METHODS: Fibroblasts isolated from young/aged mice and humans (n⫽6) were assessed for HIF-1-alpha and PHD1-3. Murine
J Am Coll Surg
embryonic fibroblasts (MEFs) were subjected to oxidative stress and analyzed for HIF-1-alpha, PHD1-3, FIH, SDF, and VEGF by Western blot and real-time PCR (rtPCR). HIF-1-alpha binding was evaluated using a hypoxia response element luciferase reporter. Young/ aged murine ischemic flaps were assessed for HIF-1-alpha, and preliminary rescue experiments were performed with manganese superoxide dismutase (MnSOD). RESULTS: Aged murine fibroblasts exhibited significantly reduced ability to upregulate HIF-1-alpha in response to hypoxia with an associated increase in PHD1-3 compared to young controls. MEFs exposed to oxidative stress demonstrated an elevation in total HIF1-alpha protein, but exhibited a paradoxical impairment in HIF-1alpha function (82.1% ⫾4.2%, p⬍0.005). RtPCR confirmed reduced SDF and VEGF levels (35.2%, p⬍0.05 and 21.4%, p⬍0.005 respectively) following oxidative stress. No difference was noted in PHD1-3 or FIH. Aged human fibroblasts also demonstrated increased baseline HIF-1-alpha levels with a blunted response to hypoxia compared to controls. Only aged flaps necrosed which correlated with decreased HIF-1-alpha levels, and MnSOD rescues the aged phenotype. CONCLUSIONS: Impaired wound healing and neovascularization in aging appears to result from two distinct mechanisms: increased PHD degradation of HIF-1-alpha and direct impairment of HIF-1alpha from oxidative stress.
Regulation of the unfolded protein response in keloid fibroblasts Paris D Butler, MD, Zhen Wang, MD, Albert Koong, MD, PhD, Michael T Longaker, MD, MBA, FACS, George P Yang, MD, PhD, FACS Stanford University, Stanford, CA INTRODUCTION: Keloids are a common form of pathologic wound healing, and represent a major burden to our health care system. We have previously demonstrated that increased response to cellular stresses results in production of more pro-fibrotic factors in keloid cells and are looking for a common mechanism linking these cellular responses. Since keloid fibroblasts (KFs) are known to be secretory cells, we hypothesized that the unfolded protein response (UPR) could be deranged in KFs leading to increased activation of these cellular stress pathways. METHODS: Normal fibroblasts (NF) and KFs were exposed to two known inducers of the UPR. Cells were treated with 4g/ml of tunicamycin for 6, 12, or 24 hr or hypoxia (2% O2) for 24 or 48 hr, and total protein was harvested. UPR activation was measured by immunoblotting with specific antibody for the activated Xbp-1 protein. RESULTS: There is increased activation of Xbp-1 in KFs compared to NFs following exposure to hypoxia. In contrast, exposure to tunicamycin leads to a divergent response where NFs have increased activation of Xbp-1 compared to NFs. CONCLUSIONS: NFs and KFs have differences in UPR activation. In addition, we have found that NFs and KFs have divergent re-