Introduction Cardiopulmonary bypass (CPB) is a machine used in open cardiac surgeries and has been linked to many complications, one of which is acute kidney injury (AKI). Also, the Kidney Disease Improving Global Outcomes (KDIGO) criteria are used to diagnose AKI in the pediatric population. The study aimed to investigate the association between cardiopulmonary bypass duration and renal function impairment in pediatric patients who had cardiac surgery. Methods This was an observational, cross-sectional study conducted at the King Abdulaziz Medical City, King Faisal Cardiac Center, the section of the Pediatric Cardiac Intensive Care Unit (PICU), Ministry of National Guard Health Affairs, from January 2016 to December 2019. Patients younger than 14 years old, those having a cardiac surgery where CPB was implemented, normal pre-operative kidney functions, and having a cardiac surgery longer than 60 minutes (min) were included. The exclusion criteria were patients known to have pre-operative renal impairment and patients with pre-operative hemodynamic instability or cardiac arrest. Demographics of pre-operative, intra-operative, and post-operative data were extracted, and Statistical Package for the Social Sciences (SPSS) version 25 (Armonk, NY: IBM Corp.) was used for analysis. For descriptive statistics, frequencies and percentages for qualitative data were examined, while mean and standard deviation (SD) or median and interquartile range (IQR) quantitative data were used accordingly. Student's t-test, Mann-Whitney (median test), chi-square, or Fisher's exact tests were used for univariate analysis accordingly. Logistic regression analysis was used to determine significant predictors for developing AKI. A p-value of <0.05 would be considered significant. Results Of the 111 patients, 87 patients were included in the analysis. The median age was six months, IQR two to 13 months, body mass index (BMI) mean of 13.8, and SD 3.6. There was similar sex distribution, male 47.1% vs. female 52.9%. There were no patients in Risk Adjustment for Congenital Heart Surgery (RACHS) who scored 5 or 6. The AKI prevalence was 31% (27/87) within three days after surgery. One patient had stage 2 AKI; the rest were mild. One patient (3.7%) died. The CPB time was significantly longer in patients who developed AKI 150 (104-202), vs. non-AKI 104 (82-142) min, p=0.004. In the AKI group, the mean baseline (pre-operative) serum creatinine (sCr) was significantly lower, whereas, it was significantly higher at 24 hours (h), and 48 h post-operation (p=0.001, 0.001, and 0.036, respectively). Additionally, the estimated Glomerular Filtration Rate (eGFR) was significantly higher in the AKI group at 24 h (p=0.007). In logistical regression analysis, CPB time (per min unit time) was a significant predictor for developing AKI, OR 1.015, p=0.011 as a measured outcome. However, only CPB time >180 min was highly significant with OR 16.2, p=00.6 compared to CPB time 121-180 min OR 2.3, p=0.29 and CPB time 91-120 min OR 1.2, p=0.84. Conclusion Acute kidney injury is an expected complication of pediatric congenital heart surgery receiving CPB. Although in our single-center experience, CPB duration was a significant predictor for AKI; however, it is considered a mild complication that does not contribute significantly to short-term morbidity or mortality. A larger multicenter, national prospective data registry is recommended to explore long-term effects.
Keywords: acute kidney injury; cardiac surgery; cardiopulmonary bypass; creatinine; renal function.
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