VANCOMYCIN TISSUE PENETRATION IN CARDIAC PATIENTS

Vancomycin penetration into heart tissues (valves, myocardium, auricle s and pericardium) and mediastinal tissues (fat and sternal bone) afte r two regimens of administration was evaluated in a prospective, rando mized study. Twenty adult patients undergoing mitral or aortic valve r eplacement were included in the study and divided into two groups of t en patients each : Group 1 patients were administered a 15 mg/kg intra venous dose of vancomycin over 90 min upon anesthesia. Group 2 patient s received the same dose followed by a second 7.5 mg/kg intravenous do se of vancomycin over 30 min at time of initiation of the cardiopulmon ary bypass. In both groups further vancomycin administrations (10 mg/k g) were performed on hour 8, 16 and 24. Plasma and tissue vancomycin c oncentrations were assayed by fluorescence polarization immunoassay. A t different times of the surgical procedures (thorax opening and closu re, period of cardiopulmonary bypass) 67 to 100% of the patients in gr oup 1 had vancomycin concentrations in the studied tissues above the M IC 90 for Staphylococcus aureus (1 mug/g) and Staphylococcus epidermid is (2 mug/g). In group 2, for the same periods and the same tissues, 7 2 to 100% of patients had adequate vancomycin concentrations. In group 1 patients, mean ratios of vancomycin tissue concentrations/MIC 90 we re 6 +/- 2 to 20 +/- 4 for Staphylococcus aureus (MIC 90 : 1 mug/g) an d 3 +/- 1 to 10 +/- 4 for Staphylococcus epidermidis (MIC 90 : 2 mug/g ). In group 2 patients, mean ratios were 8 +/- 3 to 20 +/- 4 for Staph ylococcus aureus and 4 +/- 1 to 10 +/- 3 for Staphylococcus epidermidi s. The use of a second dose of vancomycin in group 2 significantly inc reased plasma concentrations (P>0.05). At the end of surgery, group 2 patients had higher vancomycin levels in pericardium, sternal bone and thoracic wall fat, but the difference did not reach the level of sign ificance. In conclusion, a similar and satisfactory penetration of van comycin was observed in both groups in cardiac and mediastinal tissues during cardiac surgery. However in both groups, some patients had van comycin tissue levels below MICS for potential pathogens.