Methods: This retrospective cohort study included consecutive children < 2 years of age who were undergoing their first cardiac surgical procedure with cardiopulmonary bypass at Arkansas Children’s Hospital from January2003 to June 2005. We excluded children less than 2 years of age who were undergoing procedures without cardiopulmonary bypass or those undergoing orthotopic heart transplantation, inasmuch as heart transplantation is not included the Risk Adjusted classification for Congenital Heart Surgery (RACHS-1) used. Estimated glomerular filtration rate (eGFR) was calculated using the modified Schwartz formula and compared to normal eGFR for age. eGFR less than the predicted 3rdpercentile was used as a baseline for assigning pRIFLE scores. Univariate and multivariate statistics were used to investigate association of AKI with outcomes. A p value of < 0.05 was considered statistically significant.
Results: Of the 280 patients identified, 164 (61%) had pre-operative AKI. A total of 76 subjects did not recover eGFR ≥75% of the predicted 3rdpercentile by post-operative day 7. The group of patients who failed to recover: were younger at the time of surgery, had lower weight at the time of surgery, had greater need for dialysis, saw a larger drop in post-operative eGFR, had a longer ICU stay and total hospital stay, longer time of ventilation, and increased mortality (all p<0.001). For pre-operative AKI, a logistic regression to predict death using indicators for age<30 days, lymphopenia, RACHS score (1:1-2, 3-4, 5-6) , and the percentage difference between eGFR at baseline and the normal eGFR for age indicated that pre-operative AKI was not associated with increased in-hospital mortality (p value=0.07). Only pre-operative absolute lymphocyte count less than 3000 (O.R.=6.84, 95% CI-1.34 to 34.86) was significantly associated with mortality.
Conclusions: Pre-operative AKI was present in 61% of patients but was not associated with increased risk of in-hospital mortality. However, failure to recover eGFR ≥75% of the predicted 3rd percentile by post-operative day 7 after cardiopulmonary bypass was associated with increased risk of mortality and morbidity.