IJCS | Volume 31, Nº2, March / April 2018

165 Table 1 – Characterization of the study patients Variables Total (n = 65) Controls (n = 52) Cases (n = 13) p-value Gender, n (%) 0.526* Female 24 (36.9) 18 (34.6) 6 (46.2) Male 41 (63.1) 34 (65.4) 7 (53.8) Age, years 58.8 ± 10.3 58.1 ± 10.4 61.6 ± 9.8 0.265† Obesity, n (%) 13 (20) 11 (21.2) 2 (15.4) 1.000* Number of pre-surgical risk factors 4 ± 2 3 ± 3 4 ± 1 0.056‡ Use of prophylactic antibiotics, n (%) Cefuroxime 44 (67.7) 39 (75) 5 (38.5) 0.019* Vancomycin 44 (67.7) 36 (69.2) 8 (61.5) 0.742* Cefazolin 15 (23.1) 9 (17.3) 6 (46.2) 0.059* Previous catheterization§ 61 (93.8) 49 (94.2) 12 (92.3) 1.000* LVEF, % 60 ± 19.3 60 ± 16 54 ± 29 0.300‡ Type of surgery, n (%) CABG 51 (78.5) 40 (76.9) 11 (84.6) 0.717* Valve replacement 17 (27.4) 12 (24.5) 5 (38.5) 0.319* Mitral 7 (11.3) 4 (8.2) 3 (23.1) 0.153* Aortic 6 (9.7) 4 (8.2) 2 (15.4) 0.597* Double replacement 4 (6.5) 4 (8.2) - 0.571* Valve replacement reoperation§ 3 (4.8) 3 (6) - 1.000* Mitral 2 (3.2) 2 (4) - 1.000* Double replacement 1(1.6) 1 (2) - 1.000* CABG + valve replacement 6 (9.7) 3 (6.1) 3 (23.1) 0.100* Post-surgical hospitalization time, days 13 ± 15 12 ± 4.8 40 ± 21 <0.001‡ Extracorporeal circulation time§, minutes 80 ± 40.3 77.5 ± 43.5 82 ± 18.3 0.770‡ Post-surgical creatinine, mg/dL 0.86 ± 0.36 0.80 ± 0.32 1.13 ± 2.12 0.004‡ Death, n (%) 6 (9.2) 3 (5.8) 3 (23.1) 0.089* Tests for p values: * Fisher exact test; † Student’s t test for independent samples; and ‡Wilcoxon Mann-Whitney test; § the variable has missing data. LVEF: left ventricular ejection fraction; CABG: coronary artery bypass grafting. diagnosed with mediastinitis. The median creatinine level observed after surgery was 0.86 mg/dL (± 0.36), and it was significantly higher in the mediastinitis group. Death occurred in 9.2% of the patients and in 23.1% of those who had post-sternotomy mediastinitis. No differences were observed in relation to gender and age, which confirms the pairing effectiveness. Agreatermedian number of pre-surgical risk factorswere observed among those with a diagnosis of mediastinitis, in addition to a higher proportion of patients who were submitted to CABG. The most common microorganism found in the bacteriological diagnosis of patients with mediastinitis was Staphylococcus aureus (30.7%) and there was a high occurrence of Gram-negative bacteria (GNB) (46.2%) (Table 2). Pinto et al. Factors Associated with Post-Sternotomy Mediastinitis Int J Cardiovasc Sci. 2018;31(2)163-172 Original Article