In plastic reconstructive surgery the use of prophylactic antibiotics is considered for wounds in which tissue trauma can not exactly be delineated as in gun shot wounds, bites, contusions; for extensive surgery lasting more than three hours in the oral area, with opening of the maxillary sinuses; when large foreign bodies are implanted; if there is massive intraoperative contamination and for patients with reduced antibacterial defence mechanisms. A principal factor leading to infection is reduced tissue oxygenation, which can be reversed by the use of benzopyrones as experimentally demonstrated.