Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_3723_Библиотеки_им_академика_М_И_Перельмана

SWIs are usually the consequence of wound con­tamination during the procedure, which can occur despite optimal precautions, especially in long interventions. The vast majority of SWIs are caused by bacteria, with the most frequent organ­isms being Staphylococcus aureus followed by Gram-negative bacilli and streptococci [8, 9]. Infections with fungus and mycobacterium are rare and represent only a small fraction of SWI cases. Mycobacterium chimaera infections have been associated with contamination of heater­cooler devices [10]. In addition, Candida medi­astinitis accounts for a very small fraction (<10%) of DSWIs but is fatal in nearly half of cases [11]. Aspergillus mediastinitis, which can occur in both immunosuppressed and immunocompetent patients, often results from airborne contamina­tion by spores, especially in cases of prolonged chest opening after surgery [12]. Fungal and mycobacterial DSWIs represent a clinical chal­lenge given their high mortality rates, the dif­culty to culture organisms, and their atypical presentations, which is often paucisymptomatic.

Several factors, related to the patient or to the surgical procedure itself, have been associated with an increased risk of SWIs (Table17.1) [2,

sity, and smoking, are all associated with increased risks of SWI.Of note, several of these factors are also associated with CAD and are therefore highly prevalent in the population of patients undergoing coronary artery bypass graft (CABG) surgery. Procedure-related risk factors include elements that may contribute to sub­optimal sternal union such as misalignment of the sternal edges and asymmetric sternotomy. Further, maneuvers which can promote sternal ischemia, including bilateral harvesting of the mammary arteries and excessive cauterization, are associated with increased risk of SWIs [14]. The type of procedure also affects the risk of SWIs, with heart transplant and CABG (with the use of internal mammary artery) being associated with higher incidence of both SSWIs and DSWIs compared to other procedures such as valve replacement surgery [11]. The use of minimally invasive methods such as robot-assisted surgeries are associated with lower incidences of mediasti­nitis [15]. Various classication systems for SWIs have been proposed but have seen limited use in clinical settings and in research. One of the most cited is the Jones classication, presented in Table 17.2, which classies SWI based on the anatomical extent and disease severity [16].

suspected, further testing, including CT and PET imaging may be helpful as it may provide valu­able information with regard to infection extent and severity, and aid in surgical planning [20].

Zhang et al. retrospectively analyzed 73 patients who underwent FDG-PET/CT study for suspicion of DSWI 1 month or more following surgery [29]. Of the 73 patients, one had super­cial SWI, 64 had sternal osteomyelitis, 54 had

mediastinitis, and 28 had costal chondritis. In addition, 6 out of 6 patients with vascular grafts had vascular graft infection. They observed a sensitivity and specicity of 98% and 78% for sternal osteomyelitis, 100% and 95% for medias­tinitis, and 82% and 100% for costal chondritis, respectively. They used a 4-level visual scale to rate tracer uptake in the sternum, the mediasti­num, the costal cartilage, and the vascular pros­thesis. The grading system was as follows: Grade I, uptake similar to fat; Grade II, uptake greater than fat but inferior to vertebra; Grade III, moder­ate uptake greater than vertebra and below physi­ological myocardium; and Grade IV, intense uptake greater than physiological myocardial uptake. Grade IV uptake was only observed in infected tissue. Low-grade uptake (I and II) was associated with a high negative predictive value for mediastinal, sternal, and vascular prosthesis infection. Of note, 5/28 (18%) subjects with con­rmed costal cartilage infection showed low grade uptake (I and II) [29]. Despite the good performance reported, this grading system is lim­ited by the fact that myocardial uptake is highly variable. In addition, this system does not take into account the distribution of uptake, which may prove more useful to distinguish between sterile postsurgical inammation and infection [30–32].

Yin et al. retrospectively analyzed the pro­spectively collected data of 108 patients who underwent CT and FDG-PET/CT for suspicion of DSWI [33]. They evaluated the diagnostic per­formance of FDG-PET/CT for DSWI and com­pared it to that of unenhanced CT for three separate sites consisting of the sternum, ribs/cos­tal cartilage, and mediastinum. Focal or diffuse uptake greater than “surrounding structures” was considered infected while mild uptake was con­sidered benign inammation. They reported a 100% sensitivity of FDG-PET/CT for the detec­tion of sternal and mediastinal infection com­pared to 91% and 17% for unenhanced CT, respectively. Specicity of FDG-PET/CT was inferior to CT for the detection of mediastinitis (62% vs. 94%) but higher than CT for sternal osteitis (100% vs. 50%). As for rib and cartilage infection, FDG-PET/CT was more sensitive than