Cephalosporins in surgery. Prophylaxis and therapy.

Prophylactic antibiotics in surgery are intended to prevent morbidity and mortality, as well as to reduce the duration and cost of hospitalisation. The indications for prophylaxis, and its effectiveness, should be evaluated with these criteria in mind. The basis for antibiotic prophylaxis in surgery is either provision of an effective concentration of antibiotic in the tissue site at the time of potential contamination, or (primarily in the case of colorectal surgery) to reduce the inoculum of potentially contaminating bacteria. Cephalosporins are the antibiotics most widely used for prophylaxis in surgery, and have clearly been shown to reduce postoperative morbidity in vaginal hysterectomy, resection of head and neck cancers, vascular grafting, total joint replacement, repair of hip fractures, and high risk gastroduodenal surgery. They are probably also useful in cardiac surgery, abdominal hysterectomy, caesarean section, and colorectal surgery. For orthopaedic, cardiac, gynaecological, and gastroduodenal procedures it is important to select an antibiotic with proven clinical activity against Gram-positive organisms. For head and neck surgery, the spectrum of activity should also include oral anaerobes and Enterobacteriaceae. For biliary surgery an antibiotic effective against both Gram-positive and Gram-negative organisms may offer at least theoretical advantages, while for appendicectomy a cephamycin represents the most appropriate choice. In colorectal procedures, activity against B. fragilis is the major consideration in selecting an antibiotic for systemic prophylaxis. When intra-abdominal sepsis occurs following surgery, a potentially wide range of bacteria may be implicated, but in practice such infections are due to a small number of species, with B. fragilis most commonly implicated. The most useful cephalosporins in this setting are those active against both aerobic Gram-negative bacteria and anaerobes, especially B. fragilis. In practice, an aminoglycoside is often administered concomitantly. Importantly, prompt surgical treatment is the cornerstone of management of abdominal sepsis, and empirical antibiotic therapy should be adjusted as needed when culture and sensitivity tests become available.