The importance of renal function for the management of the sick newborn with congenital heart disease

Acute kidney injury (AKI) is increasingly recognized as a cause of increased morbidity and mortality in neonates and infants with congenital heart disease. The list of putative causes of AKI in this population is long, however, the true etiology is multifactorial. Some of the possible factors related to AKI in neonates with heart disease could be neonatal adaptation to extrauterine life (immature kidneys, low glomerular filtration rate, high renal vascular resistance, high plasma renin activity), or perioperative factors affecting renal blood flow (ischemia, reperfusion injury, use of cardiopulmonary bypass, peri-operative hemodynamics), or renal injury due to hormonal, biochemical and cytokine related factors. There is lack of consensus definition for AKI in neonates with congenital heart disease. Use of novel biomarkers such as neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule (KIM-1), cystatin C, and interleukin-18 (IL-18) has emerged as a possible alternative to diagnose early AKI. The challenge with all these biomarkers is the lack of good reference intervals by post-conceptual age. Neonates with congenital heart disease may have varying degrees of renal impairment with multiple alternatives for treatment. The therapy of AKI revolves around optimizing renal perfusion pressure and oxygenation through judicious management of fluid balance, electrolyte status, acid–base balance, nutrition, and initiation of renal replacement therapy when appropriate. The focus of this review is to evaluate the prevalence of renal impairment in patients with congenital heart disease before and after surgery, to explore the impact of several risk factors for AKI in this population, to evaluate potential variables for early detection and to review the available treatment options for AKI with renal failure.