Suppurative mediastinitis after open-heart surgery: a case-control study covering a seven-year period in Santander, Spain.

Suppurative mediastinitis developed in 34 (0.9%) of 3,645 patients who underwent median sternotomy at the Hospital Marqués de Valdecilla in Santander, Spain, from 1985 through 1991. These cases were analyzed in a case-control study designed to identify risk factors for poststernotomy mediastinitis. The significant risk factors were (1) preoperative factors: heavy cigarette smoking and history of endocarditis; (2) intraoperative factors: emergency surgery, prolonged duration of surgery, prolonged bypass pump time, ventricular failure, and tearing of the aortic or femoral artery; and (3) postoperative factors: reoperation, prolonged mechanical ventilation, prolonged stay in the intensive-care unit, and tracheostomy. All patients had abnormal sternal wounds (i.e., signs of wound infection or serous discharge). Twelve patients were bacteremic. Thirty-eight organisms were recovered from 31 patients with mediastinitis; 23 of the isolates were gram-positive and 15 were gram-negative. The infections were treated with extensive debridement and appropriate antibiotics. Mortality was 35%. Chronic sternal osteomyelitis was documented in two cases.