Postoperative mediastinitis: a comparison of two electrocautery techniques on presternal soft tissues

Postoperative mediastinitis remains a serious surgical problem, complicating 0.4% to 5% of all cases. In an experiment designed to address this problem, 36 mongrel dogs underwent a median sternotomy incision. In group I (n = 18) all layers to the sternum were opened by a scalpel, and electrocautery was used only for pinpoint hemostasis. In group II (n = 18) the skin was opened by a scalpel and the remaining layers to the sternum were opened by electrocautery. Total kilojoules of electrical energy delivered to the tissues was 9.4 +/- 5.7 for group I and 44.1 +/- 7.0 for group II (p less than 0.001). Each group was randomly divided into three subgroups (n = 6): Ia and IIa were noninoculated controls; Ib and IIb were inoculated just before skin closure; Ic and IIc were inoculated and given one preoperative dose of cefonicid. The inoculum contained Staphylococcus intermedius in a 0.5 ml suspension of 10(8) organisms. Each animal was observed and the wounds were scored daily until death or until all survivors were put to death on the eighth postoperative day. Pleural fluid was cultured at autopsy. Ten dogs died of mediastinitis (four in IIa and six in IIb), but none from group I (p less than 0.01). Positive cultures from pleural fluid in matching subgroups (n = 6) occurred as follows: one in Ia and five in IIa (p less than 0.05); one in Ib and six in IIb (p less than 0.01); zero in Ic and two in IIc. We conclude that pinpoint hemostasis on the soft tissues of the sternotomy incision significantly reduces the severity and frequency of penetrating mediastinitis.