Article of the Month - Aug 2021

Evaluation of neonatal acute kidney injury after critical congenital heart disease surgery

Pediatr Nephrol. 2021 Jul;36(7):1923-1929. doi: 10.1007/s00467-020-04890-z. Epub 2021 Jan 25. PMID: 33492453.

Beken S, Akbulut BB, Albayrak E, Güner B, Ünlü Y, Temur B, Aydin S, Ödemiş E, Erek E, Korkmaz A.

Reviewed by Arwa Nada


Congenital heart diseases (CHDs) are among the most common congenital anomalies and account for approximately 4% of all neonatal deaths. Recent advances in neonatal care and early diagnosis of CHD have improved outcomes and survival rates. Neonatal CHD is a risk factor for AKI; almost half of CHD cases are complicated with AKI, and AKI is more common in newborns undergoing cardiac surgery and cardiopulmonary bypass.

What was the purpose of the study?

The study was designed to define the frequency and characterize the clinical course of AKI in postoperative neonates with CHD using neonatal modified KDIGO criteria and demonstrate the risk factors and short-term outcomes of AKI in postoperative CHD infants.

What were study design and methods?

This was a retrospective single center study from January 2015 to December 2018 conducted in the NICU of the Acibadem University Atakent Hospital, a level III referral NICU in Istanbul, Turkey.

AKI was defined using the serum creatinine criteria of the neonatal modified KDIGO AKI definition. For neonates with multiple episodes of AKI, the highest stage reached for any episode was used for the analyses.

Enrollment criteria included neonates with GA> 37 weeks with CHD who required surgical intervention and survived beyond the first day of admission. Neonates with congenital kidney and urinary tract anomalies and/or multiple congenital anomalies were excluded.

CHD were categorized as left heart obstructive defects (i.e., coarctation of the aorta, hypoplastic left heart syndrome, aortic interruption/arcus aorta anomalies and aortic valve stenosis), right heart obstructive defects (i.e., pulmonary atresia, pulmonary stenosis, and tricuspid atresia), and outflow tract defects (i.e., transposition of great arteries, tetralogy of Fallot and truncus arteriosus).

STAT score was used to analyze the risk of mortality associated with congenital heart surgery procedures (i.e., the STS-EACTS Mortality Risk Category). A vasoactive-inotropic score (VIS) was used to quantify the amount of inotropic support provided in the postoperative period. The VIS was calculated as follows: dopamine dose (μg/kg/min) + dobutamine dose (μg/kg/min) + 100 epinephrine dose (μg/kg/min)] + 10 milrinone dose (μg/kg/min) + 10,000 vasopressin dose (units/kg/min) + 100 norepinephrine dose (μg/kg/min)).

What are the results?

Out of 317 neonates, 199 fulfilled the enrollment criteria. 44% neonates had left heart obstructive CHD, 13% had right heart obstructive CHD, and 43% had outflow tract defects.

35.6% of the 199 neonates enrolled with CHD had AKI, of which 93% of the episodes occurred during the first week of cardiac surgery. 33.8% had stage 1, 19.7% had stage 2, and 46.5% had stage 3 AKI. 85% of neonates with stage 3 AKI received kidney replacement therapy (53.6% had peritoneal dialysis and 46.4% had continuous venovenous hemodiafiltration).

AKI (+) patients had longer invasive ventilatory days (11 vs. 7; p = 0.001), and higher VISs (37 vs. 23; p = 0.001). The occurrence of AKI was higher in newborns who received ECMO (29.6% vs. 3.9%; p = 0.001).

In the regression analysis, birth weight, sepsis, cardiopulmonary bypass, and STAT risk category were not associated with the development of AKI in neonates with CHD. After adjustment, a higher VIS (OR,1.02; 95% CI, 1.0–1.04; p = 0.008) and receiving ECMO (OR, 7.9; 95% CI, 2.6–24.4; p = 0.001) were associated with the risk of developing AKI in neonates with CHD

The mortality rate was 52.1% in AKI (+) neonates vs. 13.4% in AKI (-) neonates (p= 0.001). Having AKI was associated with mortality (OR 7.1; 95% CI, 3.5–14.18). Mortality rates were significantly increased in infants with the highest stages of AKI (75.8% at stage 3, 35.7% at stage 2, and 29.2%at stage 1). Higher stages of postoperative AKI were associated with greater odds of mortality, with a stage 1 OR of 2.6 (95% CI, 0.97–7.43; p = 0.05), a stage 2 OR of 3.6 (95% CI, 1.08–12.12; p = 0.02), and a stage 3 OR of 20.4 (95% CI, 7.92–52.53; p = 0.001).

Of the 71 cases with AKI, 34 patients survived (47.8%), and the median survival time was 49.89 ± 5.15 days. When the survival curves were evaluated using a log-rank test according to AKI status, a statistically significant difference was found between the survival of patients with and without AKI (p = 0.001). The survival rate was lower in AKI patients

What was the conclusion?

AKI is a common early complication of neonatal critical CHD after cardiac surgery and is associated with increased morbidity and mortality. Higher VIS score and ECMO are important predictors of AKI in CHD patients. AKI is associated with prolonged respiratory support and mortality. Stage 3 AKI is associated with significantly higher mortality rates.

Why is this important?

This study adds to the growing body of data on risk factors of neonatal AKI and its association with higher morbidity and mortality.

With increasing evidence associating neonatal AKI with CKD,  we require more research to determine predictive factors of neonatal AKI, and practices and policies which may decrease the risk of neonatal AKI.