Penetration of cephapirin and cephalothin into the right atrial appendage and pericardial fluid of patients undergoing open-heart surgery.

To prevent infection in 27 patients who underwent coronary artery bypass or cardiac valve replacement surgery, each patient received a single 2-g dose of either cephalothin or cephapirin intravenously before the operation (prior to opening of the chest cavity). Samples of the right atrial appendage, pericardial fluid, and serum were obtained at various intervals after injection of the antibiotic and were assayed for cephalosporin concentrations. Cephapirin consistently reached higher levels than cephalothin in the right atrial appendage and pericardial fluid; both cephalosporins, however, reach concentrations in these sites well above their minimal inhibitory concentrations (MICs) for penicillin-resistant staphylococci. Of particular interest was the brevity of the period (about 100 min) during which levels of both antibiotics were maintained above the MIC in the right atrial appendage. This finding emphasizes the need for administration of these antibiotics shortly before surgery.