Plasma neutrophil gelatinase-associated lipocalin as an early biomarker for prediction of acute kidney injury after cardio-pulmonary bypass in pediatric cardiac surgery dated in pediatric patients and renamed as the pediatric RIFLE (pRIFLE) criteria. Pediatric RIFLE stratifies AKI from mild (RIFLE: R, risk) to severe (RIFLE: F, failure) based on changes in serum crea- tinine or estimated creatinine clearance (eCCl) and urine output. The first study that defined AKI using the pRIFLE criteria found that AKI occurred in 82% of the most critically ill children admitted to a pedi- atric intensive care unit (PICU) [3]. The AKI represents a significant problem in clin- ical medicine, with devastating immediate and long-term consequences [4, 5]. The incidence of AKI varies from 5% of hospitalized patients to 30% of patients in intensive care units. Cardiopulmonary bypass (CPB) surgery is considered one of the most frequent major surgical procedures performed worldwide [6], in which AKI represents a frequent and serious complication in about 30-50% of patients [7]. The AKI requiring dialysis occurs in up to 5% of these cases, in whom the mortality rate approaches 80% [8]. Diagnosis and management of AKI constitutes one of the most important roles of the pediatric nephrologist in an intensive care unit (ICU) [9]. In current practice, AKI is typically diagnosed by measuring serum creatinine, which is a reliable marker of kidney function. Unfortunately, its con- stant and slow production makes its rise small and late in the case of acute injury. There remains a need for a much earlier marker in order to diag- nose AKI as soon as possible [10]. Neutrophil gelatinase-associated lipocalin (NGAL), a 25 kDa protein, is generally expressed in very low concentrations in several human tissues, and is greatly elevated in the case of epithelial dam- age [11, 12]. In healthy kidneys, it is barely detectable in either plasma or urine. However, in the setting of acute tubular injury, NGAL undergoes rapid and profound up-regulation with large increases in both urine and plasma [13]. There are many ongoing studies to elucidate the nature of the association between NGAL and AKI in different critical care settings. This includes dif- ferent types of cardiac surgery, contrast-induced nephropathy, worsening renal function in patients who suffer heart failure and sepsis. The aim of the present study was to evaluate the efficiency of NGAL plasma level as an early AKI biomarker after CPB in pediatric cardiac surgery. Material and methods The present study was carried out in the cardio- thoracic ICU, Children’s Hospital, Cairo University and the Clinical Pathology Department of the National Research Centre (NRC) during the period from January 1st, 2010 to June 1st, 2010. Forty children aged 2 to 78 months were enrolled in the study. They underwent CPB for variable peri- ods ranging from 10 up to 180 min depending on the type of anomaly and procedure done, which included surgical correction or palliation of con- genital heart disease. Patients with pre-existing renal insufficiency, or suffering from peripheral vas- cular diseases, or on nephrotoxic drugs before sur- gery, as well as known diabetics were excluded from the study. The development of acute kidney injury was assessed using the pediatric RIFLE classifica- tion [2] (AKI grade I equivalent to RIFLE: risk, AKI grade II equivalent to RIFLE: injury, AKI grade III equivalent to RIFLE: failure). Informed consent from the patients' caregivers was obtained and approved by the Ethical Committee of the NRC and Cairo Uni- versity Children's Hospital. Patients included in the study were subjected to full history taking and thorough clinical examina- tion focusing on blood pressure, central venous pressure, urine output, and respiratory and venti- latory support by assessment of fraction of inspired oxygen and mean airway pressure recorded before surgery and at 2, 12, and 24 h following surgery. Laboratory investigations included complete blood count (CBC) including white blood cell and differential counts using ADVIA 60 (Bayer Diagnos- tics, UK); assessment of renal functions by estima- tion of serum levels of urea, creatinine, sodium, potassium, calcium and phosphorus; serum albu- min level (Synchron CX5 automated chemistry ana- lyzer); blood gas analysis using Nova 9 (Nova Biome- dical, USA); blood cultures and sensitivity using Bactec 9050 (Becton Dickenson Diagnostic System, USA); plasma NGAL levels using Human Lipocalin-2/NGAL ELISA (BioVendor Research and Diagnostic Prod- ucts, Czech Republic). Blood cultures and sensitiv- ity tests were done for selected patients as clini- cally indicated at any time of the study depending on progression of the condition. Serum urea, crea- tinine, sodium, potassium and plasma NGAL levels were assessed preoperatively as well as at 2, 12 and 24 h following surgery. Sampling Preoperatively: 6 ml of peripheral venous blood was withdrawn from every patient under complete aseptic conditions, 3 ml of the withdrawn blood was anticoagulated with EDTA for performing quantitative measures of NGAL, and the rest was left to clot at room temperature, then centrifuged and sera were separated for assessment of urea, creatinine, sodium, potassium, calcium, phospho- rus and albumin. Postoperatively: Monitoring of the patients was accomplished by serial assessments of CBC, serum urea, creatinine, sodium, potassium and plasma NGAL; and 3 ml of arterial blood was withdrawn from every patient through an inserted arterial cannula and was added to heparinized tubes for assessment of arterial blood gases as well as acid base status. Arch Med Sci 2, April / 2012 251