Penetration of penicillins into cardiac valves and auricles of patients undergoing open-heart surgery.

Prophylactic use of antibiotics in open-heart surgery for insertion of prosthetic valves is common, because of the serious consequences of postoperative staphylococcal infections, most notably prosthetic valve endocarditis. To ensure effective antibiotic cover during surgery, the penetration of cloxacillin and benzylpenicillin into the heart muscle and valves was studied intraoperatively. Both antibiotics were given intravenously (respective initial doses 2 g and 6 g) at induction of anesthesia to ten patients undergoing replacement of aortic or mitral valve, and the same doses were repeated after 4 hours. Serial serum samples and tissue samples from the right atrial auricle and the excised heart valve were analyzed for antibiotic concentrations. The mean serum concentrations of cloxacillin were 204 +/- 93 mg/l 10 min after the initial dose and less than or equal to 26 mg/l 30 min before the second dose. The corresponding values for benzylpenicillin were 323 +/- 145 and 43 +/- 24 mg/l. The cloxacillin concentrations in the auricle just before the start of extracorporeal circulation ranged from 4.5 to 80 mg/kg and (later) in the excised heart valves they were 8.5 to 45 mg/kg. The benzylpenicillin range was 16 to 153 mg/kg in auricle and 13 to 87 mg/kg in valve tissue. The authors conclude that the employed doses of the penicillins are adequate cover against the staphylococci which may be implicated in postoperative infections.