About 30-50% patients develop acute kidney injury (AKI) after cardiac surgery, which is still diagnosed by serum creatinine on clinic. However, the increase of serum creatinine is insensitive and delayed. The aim of this study is to test the hypothesis that neutrophil gelatinase-associated lipocalin (NGAL) and interleukin-18 (IL-18) are early biomarkers for AKI in patients after cardiac surgery.
Thirty-three cases undergoing cardiac surgery were classified into an AKI group and non-AKI group, according to the AKI definition (> 26.5 micromol/L increase of serum creatinine, more than or equal to 50% increase of serum creatinine within 48 h, or a reduction in urine output < 0.5 mL/Kg per hour for more than six hours). The concentrations of serum NGAL, urine NGAL, and urine IL-18 at different time-points were measured.
Nine cases (27.27%) developed postoperative AKI, but diagnosis with serum creatinine was 12-48 h postoperation. The concentrations of serum NGAL were not significantly increased postoperation. The concentrations of urine NGAL and IL-18 were significantly increased in the AKI group, which reached the peak at 2-4 h postoperation, and a more significant difference could be seen after correction for urine creatinine. The concentrations of urine NGAL and IL-18 2 h postoperation, either corrected for urine creatinine or not, showed good sensitivity and specificity. Increased levels of urine NGAL and IL-18 2 h postoperation were significantly correlated with increased level of serum creatinine 12 h postoperation. Logistic regression analysis showed that urine NGAL corrected for urine creatinine 2 h postoperation and urine IL-18 2 h postoperation emerged as powerful independent predictors of AKI after cardiac surgery.
The concentrations of urine NGAL and IL-18 could be useful biomarkers for AKI in patients after cardiac surgery, especially after correction for urine creatinine.
"In previous studies, plasma and urine NGAL levels were considered good predictive markers in children and adult patients immediately after surgery         . Among these studies, only a small number included cardiac surgery patients, and a plasma NGAL cut-off value predictive of AKI was not clear in these patients  . "
[Show abstract][Hide abstract] ABSTRACT: Objectives:
Development of acute kidney injury (AKI) after cardiopulmonary bypass (CPB) is relatively common and associated with increased mortality. Recently, plasma neutrophil gelatinase-associated lipocalin (NGAL) was used for the prediction of AKI. We evaluated the clinical usefulness of plasma NGAL.
Design and methods:
One hundred twelve adult patients undergoing cardiovascular surgery with CPB were included. Blood samples were obtained at baseline, at intensive care unit (ICU) admission, and 24h after ICU admission. The development of AKI, which is defined as an increase in serum creatinine by more than 50% within 3 postoperative days, was monitored. NGAL levels were analyzed by a Biosite Triage meter (Alere Medical, USA). Diagnostic performance of NGAL was analyzed using the area under the receiver operating characteristic curve.
In AKI patients (n=13), plasma NGAL levels at ICU admission were significantly higher than those at baseline [177 (122-402) vs. 121 (74-158) ng/mL, median (interquartile range), p=0.028], whereas serum creatinine showed no significant change. The predictive value of NGAL at ICU admission was 0.812 [95% confidence interval (CI), 0.68 to 0.95] with a cut-off value of 168.5ng/mL (sensitivity, 61.5%; specificity, 88.9%). After the exclusion of 35 patients with preoperative decreased renal function, the predictive value was increased to 0.911 (95% CI, 0.82 to 1.00).
This study showed that plasma NGAL may serve as a useful biomarker for the early detection of AKI in adult patients following CPB.
"In our study, none of our patients classified under pre-renal AKI had increased NGAL levels. In a study by Xin et al. (19), 33 patients undergoing CPB were classified as AKI (50% increase in serum creatinine within 48 h after CPB) and no AKI. Urine NGAL and IL-18 were increased in the AKI group at 2-4 hours postoperatively. "
"Thus the question arises whether NGAL release after CPB is a marker of renal tubular injury or of a general inflammatory response. In particular, as urinary NGAL is a more specific biomarker of tubular injury than plasma NGAL (Xin et al., 2008), measuring both plasma and urine NGAL in patients receiving either on-CPB or off-CPB CABG may help differentiate between the inflammatory and tubular effects of CPB and relate such effects to measures of glomerular filtration rate (creatinine) typically used clinically to diagnose AKI in the clinic. We hypothesised that patients receiving off-pump CABG would have a different plasma and urinary NGAL profile compared to patients receiving CABG on-pump. "
[Show abstract][Hide abstract] ABSTRACT: Abstract Context: Cardiac surgery. Objective: To compare plasma and urinary neutrophil gelatinase-associated lipocalin (P-/U-NGAL) in on-pump (n = 43) versus off-pump (n = 40) surgery. Materials and methods: We obtained perioperative P-/U-NGAL and outcome data. Results: P-/U-NGAL increased after surgery. P-NGAL was higher post-surgery in on pump patients (139 versus 67 µg L(-1); p < 0.001), but not at 24 h. There were no differences in U-NGAL. Correlation between P-/U-NGAL and plasma creatinine was weak. Discussion: P-NGAL acts like a neutrophil activation biomarker and U-NGAL like a tubular injury marker. Conclusion: On-pump patients had greater neutrophil activation. On- versus off-pump surgery had similar impact on tubular cells.
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