Post-sternotomy mediastinitis (PSM): Facing a difficult-to-treat serious infection (1998-2016)

Abstract

Background: PSM is uncommon but one of the most feared complication of cardiac surgery, with high mortality and cost of treatment. Our objective is to describe the clinical characteristics, microbiology, medical and surgical management and the results of PSM in a single cardiovascular reference center. Methods & Materials: Retrospective analysis of consecutive episodes of PSM registered in the institutional database. Categorical variables were compared using Chi-square or Fischer exact tests; continuous variables with Student's t was used as applicable. IBM® SPSS Statistics program version 21 was used. Results: From November/1998 to December/2016, 182 (1.78%) PSM episodes in 10.233 cardiothoracic surgeries performed (57% CABG, 18% valve replacement and 22% CABG + valve replacement; 72% programmed) were included. Mean age: 65 yo (SD + 11,96). Male: 131 (72%). BMI: 28.83 (SD + 4.91). Comorbidities: DBT 43%, previous MI 33%, smokers 50%, CHF 19%, previous cardiac surgery 8.8%, bilateral internal thoracic artery grafting 29%. Clinical picture: fever 70%, pain 46.7%, erythema 33.5%, sternal click 13%, purulent discharge 69.2%, wound dehiscence 16%, sepsis 30%. Most frequent combined clinical signs/symptoms were: fever + purulent discharge (11%). Most PSM turned up during the 2nd week after surgery (median time: 11 d). Diagnostic methods: subxiphoid aspiration was positive in 121/134 (90.3%); blood cultures 107/161 (66.45%). Microbiology: GPC 122 (60.7%; S. aureus 41.7%, CNS 13.9%, Enterococcus spp 3.8%, SVG 1.3%), GNB 78 (42.9%; K. pneumonia 23%, P. aeruginosa 21%, E. coli 18%), polimicrobial 33 (18.1%), Candida spp 7 (1.3%), negative cultures 1.1%. Surgical treatment: 159/180 (88%) pts underwent open debridement; in 157 surgical treatment was completed with primary sternal closure in the early 72 hs from the diagnosis of PSM. Complications: infective endocarditis 1.6%, sternal osteomyelitis 23%, in-hospital mortality: 17%. Outcome: cure and improvement 145 (80.6%); relapse 2/180 (1.1%) requiring second debridement. Conclusion: PSM is an unusual but very complex and frequently subtle disease that requires a high index of suspicion to be identified. It demands combined medical and surgical approach in order to decrease the mortality. Wound (subxiphoid) aspiration is an extremely easy way to perform rapid diagnosis, yielding high microbiology performance. Immediate debridement, drainage and primary sternal closure could be an interesting approach.