Doris Hutschala

Cefazolin and linezolid penetration into sternal cancellous bone during coronary artery bypass grafting

OBJECTIVES Deep sternal wound infection is a severe complication after cardiac surgery. Insufficient antibiotic target site concentrations may account for variable success of perioperative prophylaxis. Therefore, we measured perioperative penetration of cefazolin and of linezolid into sternal cancellous bone after sternotomy in coronary artery bypass grafting (CABG) patients by in vivo microdialysis. METHODS Nine patients underwent CABG using a skeletonized left internal mammary artery. Standard antibiotic prophylaxis consisted of 4 g cefazolin prior to skin incision and additional 2 g during skin closure. In addition, 600 mg of linezolid were administered prior to skin incision and after 12 h for study purposes. Two microdialysis probes were inserted into the sternal cancellous bone (left and right side) after sternotomy. RESULTS First mean peak cefazolin and linezolid plasma concentrations were 273 ± 92 µg/ml and 22.1 ± 8.9 µg/ml, respectively. Mean peak concentrations of antibiotics in sternal cancellous bone on the left and right sternal side were 112 ± 59 µg/ml and 159 ± 118 µg/ml for cefazolin and 10.9 ± 4.0 µg/ml and 12.6 ± 6.1 µg/ml for linezolid, respectively. Cefazolin exceeded the required tissue concentrations for relevant pathogens by far, but linezolid did not gain effective tissue concentrations in all patients for some relevant pathogens. Mammary artery harvesting had no significant effect on antibiotic tissue penetration. CONCLUSIONS Direct measurement of antibiotic concentration in sternal cancellous bone with in vivo microdialysis is technically demanding but safe and feasible. We could demonstrate sufficient antibiotic coverage with our standard cefazolin-dosing regimen in the sternal cancellous bone during cardiac surgery. Mammary artery harvesting had no clinically relevant effect on tissue penetration. Linezolid concentrations were not sufficient for some relevant pathogens.

Letter to the editor regarding “In vitro flow investigations in the aortic arch during cardiopulmonary bypass with stereo-PIV”

This project was funded by the Medical Scientific Fund of the Mayor of the City of Vienna We read the report by Buesen et al. regarding in-vitro flow measurements in patients on cardiopulmonary bypass with great interest (Busen et al., 2015). We do see the clinical need for cannula optimization and believe that there are several obstacles for the correct assessment of flow patterns in patients undergoing cardiopulmonary bypass. MR-based flow-assessment is not possible in patients on cardiopulmonary bypass due to the metallic components of a heartlung machine. Animal experiments may help to assess the effect of flow patterns on the aortic wall and on circulation. However, human anatomy cannot be assessed in these models. Therefore, in-vitro experiments may present the only tool for this crucial question to reduce embolic stroke or aortic dissection. These novel methods have to be validated. We studied a novel setup to measure endothelial leakage in pigs undergoing on-pump cardiac surgery by in-vivo Evans blue administration andmay provide an additional method to validate in-vitro results regarding the stress applied to the aortic wall.

Direct sternal administration of Vancomycin and Gentamicin during closure prevents wound infection

OBJECTIVES Deep sternal wound infection is still a major complication in patients undergoing cardiac surgery. We previously identified mammary artery harvesting as a risk factor for decreased antibiotic tissue penetration. In addition, other risk factors including diabetes may inhibit sufficient tissue penetration of perioperative antibiotic prophylaxis. A novel closure protocol applying 2 topical antibiotics and further recommendations for sternal wiring was introduced at our department to decrease the incidence of sternal wound infections. METHODS A 12-month period prior to (March 2013-February 2014) and after (July 2014-June 2015) the introduction of a novel sternal closure protocol was studied. All sternal wound infections resulting from an operation during this period were analysed. The closure protocol consisted of the intra-sternal application of vancomycin and the subcutaneous application of gentamicin. Furthermore, we increased the number of sternal wires for more uniform distribution of lateral forces. RESULTS Patients in both groups were comparable regarding demographic data and risk factors. Fifty-three out of 919 patients operated prior to the protocol change developed an infection (5.8%). The introduction of the novel sternal closure protocol reduced this number to 19 out of 932 patients (2.0%; P  < 0.001). A binary regression including common risk factors revealed a strong independent risk reduction by the novel protocol (OR 0.322, P  < 0.001). The number of sternal wires was not significant in this analysis. CONCLUSIONS The topical application of 2 antibiotic agents significantly reduced sternal wound infection. However, the results of this trial should be confirmed in a randomized trial.

Organ Preservation During Open Thoracoabdominal Reconstruction

Abstract Surgical repair of thoracoabdominal aortic aneurysms continues to be a challenging and demanding task. Ischemic injury to the visceral organs and spinal cord remains the most severe complication during this extensive surgery. Several organ perfusion techniques have dramatically decreased the incidence of this serious intra- and postoperative complication.