Mediastinitis after heart surgery on systemic normothermia (years 1995-2000) versus moderate hypothermia (years 1987-1994)

Objective: To demonstrate the influence of systemic temperature during cardio pulmonary by-pass (CBP) on the occurrence of mediastinitis. Material and methods: Over the period 1995-2000, 4495 operations were performed through the median sternotomy on CPB and systemic normothermia. During the previous period 1987-1994, 3656 operations were performed on systemic moderate hypothermia. Cold crystalloid cardioplegia and antibiotic prophylaxis were used routinely. The wound re-closure was done 3 to 6 weeks after primary operation, only when wound swab cultures were negative. Results: After normothermic versus hypothermic CPB respectively: mediastinitis occurred in 8 (0.18% of all operations) versus 22 (0.6%; p<0.001) and was the cause of 2 deaths (0.04% of all; mortality rate 25%) versus 6 (0.16%; p<0.001; mortality rate 27%; NS). Neither frequency of early resternotomy for bleeding (3.5% and 4% respectively), nor superficial wound infection in dehisced sternotomy cases (43% versus 48%) differed significantly. Mediastinitis after operations on moderate systemic hypothermia was 3.3 times more frequent (p<0.001) than after those on normothermia, and 4 times more frequent (p<0.001) was the cause of death. Conclusions: Normothermic CPB significantly lowers the frequency of postoperative mediastinitis (and also death from it) in comparison with hypothermic one, however does not diminish mortality rate in the patients with mediastinitis. Deep and superficial infection rates were irrelevant to early resternotomy. Early rethoracotomy and superficial wound infection were irrelevant to CPB temperature. The patients after hypothermic CPB are significantly more prone to mediastinitis, which we consider to be secondary endogenous infection occurring in cases of severe weakened immunity and heavy respiratory insufficiency. (Clin. Exp. Med. Lett. 2005; 46(4):57-61)

Keywords: mediastinitis, surgery site infection, moderate hypothermia, normothermia, CPB