Postoperative differences between colonization and infection after pediatric cardiac surgery-a propensity matched analysis

BACKGROUND The objective of this study was to identify the postoperative risk factors associated with the conversion of colonization to postoperative infection in pediatric patients undergoing cardiac surgery. METHODS Following approval from the Institutional Review Board, patient demographics, co-morbidities, surgery details, transfusion requirements, inotropic infusions, laboratory parameters and positive microbial results were recorded during the hospital stay, and the patients were divided into two groups: patients with clinical signs of infection and patients with only positive cultures but without infection during the postoperative period. Using propensity scores, 141 patients with infection were matched to 141 patients with positive microbial cultures but without signs of infection. Our database consisted of 1665 consecutive pediatric patients who underwent cardiac surgery between January 2004 and December 2008 at a single center. The association between the patient group with infection and the group with colonization was analyzed after propensity score matching of the perioperative variables. RESULTS 179 patients (9.3%) had infection, and 253 patients (15.2%) had colonization. The occurrence of Gram-positive species was significantly greater in the colonization group (p=0.004). The C-reactive protein levels on the first and second postoperative days were significantly greater in the infection group (p=0.02 and p=0.05, respectively). The sum of all the positive cultures obtained during the postoperative period was greater in the infection group compared to the colonization group (p=0.02). The length of the intensive care unit stay (p<0.001) was significantly longer in the infection group compared to the control group. CONCLUSIONS Based on our results, we uncovered independent relationships between the conversion of colonization to infection regarding positive S. aureus and bloodstream results, as well as significant differences between the two groups regarding postoperative C-reactive protein levels and white blood cell counts.