Abstract
BACKGROUND: Post-operative acute kidney injury (AKI) remains a major complication in paediatric surgery. Serum creatinine is an insensitive marker, that increases only after significant impairment. Neutrophil gelatinase-associated lipocalin (NGAL) has emerged as an early biomarker capable of detecting tubular injury before functional decline. This study aimed to determine the incidence of clinical AKI and subclinical AKI in paediatric spine surgery using plasma NGAL levels and to evaluate the associations of intraoperative hypotension with kidney injury. METHODS: In this prospective single-centre study, 66 children (mean age 15.2 ± 1.7 years) who underwent elective posterior spinal instrumentation were enrolled. Plasma NGAL was measured after induction (T1, baseline), and subsequently at 6 and 24 h after induction (T2 and T3, respectively). Clinical AKI was defined by the KDIGO criteria. ROC analysis was used to determine NGAL cut-off values; patients with NGAL above the the cut-off but without KDIGO-AKI were classified as having subclinical AKI. Potential risk factors, particularly intraoperative hypotension, were analysed. RESULTS: Clinical AKI occurred in 12% of patients. The NGAL-T2 cut-off for AKI was 86 ng/mL (AUC = 0.817; sensitivity = 100%; specificity = 63.8%). Twenty-nine patients exceeded this cut off; 8 developed clinical AKI and 21 (31.8%) had subclinical AKI. In multivariable analyses, intraoperative hypotension exposure remained independently associated with kidney injury. Durations of MAP < 70 and < 65 mmHg were significantly longer in the clinical AKI and subclinical AKI groups than in the non-AKI group, whereas time spent below MAP < 60 mmHg was significantly prolonged only in the clinical AKI group compared with both the subclinical AKI and non-AKI groups. CONCLUSIONS: Although 12% of the children developed clinical AKI, approximately one-third had subclinical AKI detectable only by NGAL. Plasma NGAL at the 6th hour demonstrated excellent sensitivity for predicting AKI, with a threshold of 86 ng/mL. Intraoperative hypotension was a major predictor, with a MAP < 70 mmHg linked to tubular damage whereas deeper hypotension (MAP < 60 mmHg) was linked to clinical AKI. This study is the first to define NGAL cut-off values and intraoperative MAP thresholds for postoperative AKI in paediatric non-cardiac surgery.