Gentamicin-enriched, water-soluble polymer wax reduces the burden of infection after sternotomy in pigs

OBJECTIVES: One of the most frequent complications in cardiac surgery is postoperative bleeding from the sternum. To diminish the risk of bleeding, bone wax is frequently used for haemostasis. However, we have previously shown that bone wax impairs bone healing and induces inflammation in the sternum. A new, water-soluble polymer wax enriched with gentamicin has haemostatic properties similar to bone wax and may diminish the risk of infection. The purpose of this study was to determine whether the gentamicin-enriched, water-soluble polymer wax could reduce infection rates when compared with bone wax in a porcine model. METHODS: Thirty-two Landrace/Yorkshire pigs were sternotomized and randomized to haemostasis by gentamicin-enriched, water-soluble polymer wax (Gen group) or bone wax (Wax group). After 4 weeks the pigs were euthanized. Blood samples were analysed for the fraction and concentration of neutrophil granulocytes and C-reactive protein and the surgical site was biopsied. Stereology was performed on histological samples, and the magnitude of infection was quantified as the areas of microabscesses, granulomas and tissue with acute inflammation compared with the total tissue area. RESULTS: The temperature was 38.2 degrees C in the Gen group vs 38.6 degrees C in the Wax group, P < 0.05. No animals in the Gen group and three in the Wax group showed a temperature > 39.3 degrees C. Neutrophil granulocyte concentration was 5.00 x 10(9)/l in the Gen group and 6.92 x 10(9)/l in the Wax group, P = 0.277, with a leucocyte fraction of 20.9% vs 29.3%, P = 0.119. C-reactive protein (CRP) was 142 mg/l in the Gen group compared with 318 mg/l in the Wax group, P = 0.106. Histological samples showed acute inflammatory changes in 5.0% of the tissue in the Gen group vs 18.3% in the Wax group, P < 0.001. Microabscesses were present in 0.3% of the sample tissue in the Gen group vs 2.2% in the Wax group, P < 0.001. Concentrations of gentamicin were > 100 mg/l in mediastinal fluid and < 2 mg/l in venous blood. CONCLUSIONS: When used for haemostasis after sternotomy in a porcine model, gentamicin-enriched, water-soluble polymer wax reduces sign of infection when compared with bone wax and therefore appears to be a more suitable choice for preventing postoperative, sternal osteomyelitis.