[Use of mezlocillin in open heart surgery (author's transl)].

Concentrations of mezlocillin in serum and heart tissue were studied in 29 patients undergoing open heart surgery. The antibiotic agent was administered three times as a bolus injection of 2 grams each: after induction of anaesthesia, after initiation of extracorporeal bypass (ECC) and shortly after discontinuation of ECC. Serum levels were measured in 25 patients from samples drawn 30 minutes after the bolus injection and subsequently biologic assays were carried out by the agar diffusion method. The mean initial values during the three phases of surgery were 119.2, 170.6 and 236.0 micrograms/ml, respectively; at 60 minutes the values were 61.3, 100.8 and 101.9 micrograms/ml. Calculation of the exponential curve enabled a mathematical comparison of the half-life of the substance during the pre-ECC, ECC and post-ECC periods. The most rapid elimination was found to occur prior to initiation of ECC, the slowest during ECC, while in the post-ECC period the elimination was similar to, but somewhat slower than that of, the pre-ECC period. The concentration, measured in the tissue of eleven aortic valves, averaged 35.96 (range 8.4 to 63.4) micrograms/ml. The mean concentration found in papillary muscles of the left ventricle, resected at the time of mitral valve replacement in six patients, was 31.54% (range 17.7 to 58.33) micrograms/ml. Mean tissue concentration found in five resected mitral valves was 43.77 (range 27.33 to 71.5) micrograms/ml. The findings indicate that mezlocillin, administered as described, will reach serum and tissue concentrations at all periods of open heart surgery well above those of the minimum inhibitory concentration of most clinically relevant bacteria.