A total of 11651 subjects were included in the study. Among them, there are 85 newborns, 6183 infants, and 5383 children. Nosocomial infection rates in neonates, infants, and children with congenital heart disease were 32.9%,15.4%, and 5.2%, respectively. The overall nosocomial infection rate was 10.8%. There were 3739 patients who underwent surgery between 2012 and 2014, and the incidence of nosocomial infection was 12%. There were 7912 patients who underwent surgery between 2015 and 2018, the hospital infection rate was 10.3%. Among 1259 cases of nosocomial infection, there were 989 ventilator-associated pneumonia, 188 urinary system infections, 71 systemic infections, 10 catheter-related bacteremia, and 1 upper respiratory tract infection (Table 1). The interval from the end of surgery to infection of catheter-related bacteremia was 193.3h (137.9, 267.0), the time interval for ventilator-associated pneumonia, urinary tract infection, upper respiratory infection and systemic Infection were 24.5h (21.0, 48.8), 96.2h (87.2, 120.7), 21.9h (21.9, 21.9) and 46.6h (14.0, 98.5). The deaths were found in ventilator-associated pneumonia patients (3.03%), urinary tract infection patients (1.06%), and systemic infection (4.23). Postoperative length of stays was 8-17.5 d in all infection patients (Table 1).
Newborns
Baseline characteristics and postoperative outcomes of newborns with and without nosocomial infection
Of all 85 neonatal CHD patients, there were 28 nosocomial infections and 91 controls. There were no significant differences in length of hospital stay and mortality after operation between nosocomial infection patients and control (P=0.124, P=0.329) (Table 2). General characteristics were similar for nosocomial infection and control in CHD newborns. Significant differences were found in age (19.5d vs. 14d, P=0.039), Neutrophil count (P=0.026) between of nosocomial infection and control (Supplemental table).
Infants
Baseline characteristics and postoperative outcomes of infants with and without nosocomial infection
Among 6183 CHD infants (median age 188d, range: 122-250d), there were 952 nosocomial infections, and 5231controls. Among baseline characteristics, CPB time (69 min vs. 51 min, P<0.001) and aortic clamping time (42min vs. 31min, P<0.001)of nosocomial infections infant was significantly higher than control group, but age (138d vs. 196d, P<0.001) was significantly younger. BMI, STS risk grade, delayed sternal closure, serum creatinine level, lymphocyte count, neutrophil count, lymphocyte/white blood cell (WBC) ratio and neutrophil/WBC ratio were all significantly different between nosocomial infection and control in CHD newborns (Table 3). The length of hospital stay and mortality were significantly different between nosocomial infection and control after cardiac surgery (both P<0.001) (Table 2).
Univariate and multivariate analysis of risk factors for nosocomial infection in CHD infants
Significant risk factors in the univariate analysis associated with nosocomial infection were age, STS risk grade, delayed sternal closure, BMI < 5th percentile, CPB time, aortic clamping time, lymphocyte count ﹥cut off value, lymphocyte/WBC ratio, neutrophil count ﹥cut off value, neutrophil/WBC ratio and serum creatinine ﹥cut off value (Table 4).
After adjusted confounding factors, the study found age (OR 0.798, 95%CI: 0.769-0.829; P<0.001), STS risk grade (OR 1.267, 95%CI: 1.159-1.385; P<0.001), BMI <5th percentile (OR 1295, 95%CI: 1.023-1.639; P=0.032), BMI >95th percentile (OR 0.792, 95%CI: 0.647-0.969; P=0.023), CPB time (OR 1.008, 95%CI: 1.003-1.012; P<0.001), aortic clamping time (OR 1.009, 95%CI: 1.002-1.015; P=0.008) were significantly associated with nosocomial infection in CHD infants (Table 4).
Nomograms predicting nosocomial infection risk of CHD infant after cardiac surgery
Nosocomial infection probability can be estimated with the nomograms (Figure 1). In order to calculate the probability of nosocomial infection after heart surgery in infants with congenital heart disease, each parameter has a corresponding score on the point axis, and the sum of the scores is plotted on the “total point” axis. The probability of nosocomial infection is the value at a vertical line from corresponding total points. The area under the curve (AUC) of nomograms predicting nosocomial infection risk of CHD infant after cardiac surgery was 0.738 (95% CI: 0.721-0.755, P<0.001). After cross validation, AUC of nomograms was 0.730 (Figure 2).
Children
Baseline characteristics and postoperative outcomes of children with and without nosocomial infection
Among 5383 CHD children (median age 929 d, range: 545-1458 d), there were 279 nosocomial infections and 5104 controls. Few characteristics were similar for nosocomial infection and control patients. Nosocomial infection CHD children had longer CPB time (88min vs. 48min, P<0.001) and aortic clamping time (52min vs. 28min, P<0.001). Characteristics of nosocomial infection CHD children including proportion of patients with a history of cardiac surgery, BMI, STS risk grade, proportion of patients with delayed sternal closure, abnormal ALT, AST, WBC counts, lymphocyte counts, neutrophil count, lymphocyte/WBC ratio and neutrophil/WBC ratio were all significantly different with those of control in CHD children (Table 5). The length of hospital stay and mortality were significantly different between nosocomial infection and control after cardiac surgery (both P<0.001) (Table 2)
Univariate and multivariate analysis of risk factors for nosocomial infection in CHD children
Univariate analysis found that history of cardiac surgery, STS risk grade, delayed sternal closure, BMI < 5th percentile, CPB time, aortic clamping time, lymphocyte counts, lymphocyte/WBC ratio, neutrophil count﹥cut off value, neutrophil/WBC ratio﹥cut off value, ALT ﹥cut off value and AST﹥cut off value of nosocomial infection CHD children were all significantly different with control CHD children.
Multivariate analysis found that STS risk grade (OR 1.38, 95%CI: 1167-1.633; P<0.001), BMI < 5th percentile (OR 1.934, 95%CI: 1.377-2.715; P<0.001), CPB time (OR 1.018, 95%CI: 1.015-1.022; P<0.001), lymphocyte/WBC ratio﹤cut off value (OR 3.818, 95%CI: 1.529-9.533; P=0.004) and AST﹥cut off value (OR 1.546, 95%CI: 1.119-2.136; P=0.008) were significantly associated with nosocomial infection in CHD children (Table 6).
Nomograms predicting nosocomial infection risk of CHD children after cardiac surgery
Nosocomial infection probability of CHD children after cardiac surgery can also be estimated with the nomograms, and calculation method is similar with that of CHD infant (Figure 3). The AUC of nomograms predicting nosocomial infection risk of CHD children after cardiac surgery was 0.818 (95% CI: 0.792-0.844, P<0.001). After cross validation, AUC of nomograms was 0.808 (Figure 4).