RESUMO
Background : Risk factors for surgical site infection (SSI) are thought to include poorly controlled diabetes mellitus, dialysis, and a long operating time, but patients without risk factors can also develop infection. Therefore, it is possible that SSI could be prevented by routinely using the precautions against SSI developed for high-risk patients. We investigated the route and pathogenetic mechanism of mediastinitis, which is the most frequent SSI after cardiac surgery. We hypothesized that mediastinitis occurred when the deep sternal marrow was contaminated by skin bacteria. Based on this hypothesis, we investigated the efficacy of various intraoperative prophylactic methods for preventing mediastinitis. Methods : We evaluated 658 patients undergoing cardiac surgery at our institution between April 2011 and July 2016. They were classified into two groups. Group C comprised 406 patients who received standard insertion of a sternal retractor after sternotomy. Group S was 252 patients in whom a retractor was inserted after covering the sternal marrow with oxidized cellulose hemostats and belt-like thin towels, with surplus parts of the towels being used to fill subcutaneous dead space at the superior and inferior margins of the midline wound. We investigated the following 10 risk factors for mediastinitis: diabetes (HbA1c≥7.5), renal failure (Cr≥2), smoking, obesity (BMI≥30), reoperation, urgent/emergency operation, intubation in the preoperative period, long operating time (≥8 h), reopening the chest for hemostasis, and coronary artery bypass grafting (CABG). Factors associated with mediastinitis were determined using univariate modeling analysis followed by multi-variate logistic regression analysis. Results : Mediastinitis occurred in 13 patients (2.0%). The significant risk factor for mediastinitis were urgent/emergency operation and CABG, but 1 patient had no risk factors. A univariate analysis showed statistical significance in CABG, presence of maneuver covering the sternal marrow, JapanSCORE-II in mortality and deep sternum infection (DSI). Reopening the chest for hemostasis, CABG, aortic aneurysm, plural risk factors, and JapanSCORE-II in DSI were identified as a risk factor by multiple logistic regression, not all factors showed a significant difference. Mediastinitis only occurred in group C, and it was significantly less frequent in group S with additional precautions against infection including propensity score matching analysis (p<0.05). Conclusion : When the bone marrow of the transected sternum was covered tightly to protect it from contamination by skin bacteria during cardiac surgery, the frequency of postoperative mediastinitis was significantly reduced.
RESUMO
The indications of steroid therapy for inflammatory abdominal aortic aneurysm (IAAA) is controversial. We here report a rare case whose persistent postoperative high fever and duodenal obstruction due to adhesion to the residual aortic wall were successfully treated by steroid. A 73-year-old man was referred to our hospital because of abdominal pain and a pulsating mass in his umbilical region. CT scan showed a remarkably dilated infrarenal abdominal aorta (10cm in diameter) with a mantle sign. Preoperatively C-reactive protein (CRP) was high, however temperature was normal. We replaced the aneurysm with a bifurcated prosthetic graft (18×9mm collagen impregnated knitted Dacron) by laparotomy on April 10, 2001. The aneurysm showed a thick and fibrous surface tightly adhering to the jejunum, sigmoid colon and ureters. We tried to minimize surgical injury to perianeurysmal fibrotic tissue. However the right ureter was injured and repaired using a double-J catheter. Histopathological examination revealed lymphoplasmocystic infiltration in the wall of the aorta, which was compatible with IAAA. From the 10th postoperative day high fever (38 to 39°C) persisted and CT revealed perigraft seroma with air density. Graft infection was suspected and the perigraft fluid was drained by puncture. However cultures of the serous fluid was negative. Moreover, approximately 1, 500ml gastric juice was drained per day via a nasogastric tube. Therefore we suspected postoperative inflammatory reactions to the impregnated Dacron graft and/or inflammation of the residual aortic wall. This patient was given 20mg prednisolone intravenously 18 days after the operation and the dose of steroid was then tapered. This therapy had an obvious effect on the recovery of the general condition. Body temperature and CRP was normal when he was discharged 46 days after surgery. The patient had no complaints and the thickness of the residual aortic wall around the graft was found to have decreased one year after the operation on follow up CT.