STERNAL WOUND-INFECTION IN CARDIAC-SURGER Y - ANALYSIS OF 1,000 OPERATIONS

BACKGROUND: Sternal wound infection (SWI) is the most important compli cation in cardiac surgery. The aim of this study was to describe the f requency and clinical and microbiological features of this complicatio n. METHODS: All the cases of SWI which were observed in the authors' h ospital in the first 1,000 cardiac surgery operations performed with e xtracorporeal circulation were retrospectively reviewed, The cases wer e identified through the Infectious Diseases and Cardiac Surgery Depar tment files and were classified according to the depth of the infectio n. During the study period neither the prophylaxis against infection n or the surgical techniques were modified. RESULTS: Forty-three patient s (4.3%) presented SWI. Fourteen were superficial infections and 29 we re deep infections of which 9 were classified as osteomyelitis and 20 as mediastinitis. A progressive decrease was observed in the proportio n of SWI over time parallel to an increase in the number of operations performed. Staphylococcus aureus was the agent most frequently isolat ed (60.4%). Gram-positive aerobic cocci were found in 66.7% of the tot al number of isolations, being most frequent in the deep infections (8 3.3% of the isolations). The gramnegative aerobic bacilli were isolate d more frequently in the superficial infections than in the deep infec tions (57.8% v.s. 16.7% of the isolations, respectively p < 0.01). In patients with SWI the predictive value of the positive blood cultures for the diagnosis of mediastinitis was 83.3%, with a sensitivity of 50 % and specificity of 91.3%. Three patients with deep infection develop ed chronic complications and another three died (mortality by mediasti nitis 15.0%). The mean postoperative stay was 52 days for the patients with deep infection and 39 days for those with superficial infection (p = NS). CONCLUSIONS: The percentage of surgical wound infection duri ng the study period showed a trend to a decrease parallel with an incr ease in the number of operations. The gram-positive bacteria were resp onsible for most of the SWI. Although the depth of SWI is difficult to clinically predict, the presence of bacteremia suggests the existence of mediastinitis. Despite their lesser clinical importance, the super ficial infections carry a long postoperative stay.