We found that postoperative infection occurred relatively frequently (9.3%) in our pediatric cardiac population. These patients had greater postoperative CRP, WBC and BUN values, and also increased occurrence of S. aureus and positive bloodstream results and more adverse outcomes. Bacterial colonization was significantly more common in this population (15.2%), and after propensity matching analysis, our results showed that the occurrence of CNS, Gram-positive bacteria, and positive cannula associated results were greater in this group.
Wound associated infections following cardiac surgery contribute considerably to morbidity and mortality [20, 21]. The estimated SSI risk associated with cardiothoracic procedures is as great as 33% . S. aureus is the most common pathogen responsible for wound infections, and its colonization of the anterior nares appears to be a major factor in the development of SSIs [23–25]. Delayed sternal closure is associated with not only increased risk of SSI but also an increased occurrence of bloodstream infections . Management strategies, such as preoperative eradication of S. aureus, are shown to be effective in preventing SSI and controlling Methicillin-resistant S. aureus (MRSA) outbreaks [27, 28]; however, the continuation of prophylactic antibiotic therapy after delayed sternal closure raises questions regarding the induction of antimicrobial resistance [29, 30]. Intranasal mupirocin and perioperative naso- and oropharyngeal application of chlorhexidine have been shown to reduce the rates of deep sternal wound, lower respiratory tract infection and SSIs .
The initiation of inflammatory processes during CPB is now widely recognized [32–35]. Although our findings of a relationship between greater CRP, leukocyte count and conversion in the first two days of the postoperative course hints at a possible role of intraoperative initiation of the immune system, these laboratory results have already failed at predicting the occurrence of infection . The association between high CRP and leukocyte levels and infection might be explained as an augmented reaction to CPB and infective agents. There have been attempts at creating simple risk prediction rules, which may be useful for prevention, but because of a lack of widespread validation, there are still major differences in local management strategies [37, 38].
After assessing the spectrum of pathogens appearing in our patients, the occurrence of strains capable of entering through and growing on intravenous catheters has evidently been greater in patients lacking any signs of clinical infection, which further indicates the importance of nosocomial transfection of these pathogens. Local catheter treatment solutions, e.g., chlorhexidine-impregnation, have been around for some time but with mixed results , while the effectiveness of barrier precaution alone is shown to have a 25% benefit in preventing nosocomial bloodstream infections in the ICU .
Death in pediatric sepsis is associated with severe hypovolemia and low cardiac output. Compared to adults, oxygen delivery in children, not oxygen extraction, is the major determinant of oxygen consumption . Complex intensive therapy is needed to stop the vicious circle induced by systemic inflammatory cytokines . Furthermore, the diagnosis of postoperative infection can be difficult because the clinical and laboratory signs of an inflammatory process can be caused not only by infection but also the systemic response activated by CPB or tissue damage .
The limitations of this study arise from the issues of heterogeneity of the infection cases. After assessing all types of postoperative infection, we still cannot define which risk factors specifically predict the conversion of colonization in a surgical site or a bloodstream infection. We did not use sepsis severity scoring systems for the prediction of possible conversion, although no system has been validated in this context for pediatric cardiac patients. Further limitations come from the fact that we did not compare the antibiotic therapies in our patients. A large, single-center study usually results in a more homogenous group of patients as far as treatment strategy is concerned, and the specific perioperative management of our hospital may differ from others, although our infection cases were similar to those reported in the literature.