Effect of protein binding on the penetration of nonmetabolized cephalosporins into atrial appendage and pericardial fluids in open-heart surgical patients

At various times before surgery, 33 patients undergoing coronary artery bypass or cardiac valve replacement surgery received a single 2.0-g dose of either cefazolin or cephradine. Simultaneous single serum, atrial appendage, and pericardial fluid samples were obtained from the patients at various times and analyzed for drug content. Compared with cephradine, cefazolin yielded higher total serum, atrial appendage, and pericardial fluid levels. Unbound (free) levels of cephradine in serum and pericardial fluid were, however, higher than those of cefazolin. It remains uncertain whether the higher and more prolonged total levels of cefazolin in the right atrial appendage and in serum, or the higher free levels of cephradine in pericardial fluid and in serum, provide either one with a therapeutic advantage.