Abstract
Background: Acute kidney injury (AKI) following cardiac surgery is one of the most serious complications during the postoperative period with an incidence of up to 30%. It is associated with strikingly high mortality rates during hospitalization that usually exceed 50%.
Neutrophil gelatinase associated lipocalin (NGAL) appears to be a promising biomarker for the early diagnosis of AKI. Objective: To assess the reliability of the urinary NGAL examination as an early biomarker of renal injury following cardiac surgery in adults.
Methods: We studied 10 adult patients (mean age 62.9 +- 8.3 years, 8 males and 2 females) having undergone cardiac surgery (9 patients had an aortocoronary bypass and 1 patient had an aortic valve replacement due to severe stenosis). Urine and serum samples for NGAL and creatinine analyses were collected: 1) before the beginning of the operation, 2) 1 hour, 3) 5 hours, and, finally, 4) 10 hours after the operation.
The concentration of urine NGAL (U-NGAL) was assessed using Chemiluminiscent Microparticle Immunoassay technology (CMIA, Architect i4000 automatic immunoanalyser, Abbott, cut-off value: 131.7 μg/l). The concentration of serum and urine creatinine was assessed using the enzymatic colorimetric method (automatic biochemical analyser Advia 1800, Siemens).
Postoperative renal complications were defined as 100% or greater increase in serum creatinine from the baseline, diuresis Results: 4 of 10 patients developed postoperative renal complications. Average concentrations U-NGAL (μg/l) in the group with renal complications in above-mentioned times were following: 1) 10.7, 2) 4.4, 3) 7.7, 4) 8.0 and U-NGAL/U-creatinine ratio (μg/mmol): 1) 0.52, 2) 1.10, 3) 2.54, 4) 1.87.
In the group without renal complications were found these average concentrations U-NGAL (μg/l): It follows that average concentrations (and also medians) of both postoperative U-NGAL and U-NGAL/U-creatinine ratio were higher in the group without renal complications. There was no patient with U-NGAL above the cut-off value in both groups (with or without decrease below 0.7 ml/kg/h or the requirement of furosemide in a dose greater than 1 mg/kg/day. 1) 6.3, 2) 10.3, 3) 13.4, 4) 24.8 and U-NGAL/U-creatinine ratio (μg/mmol): 1) 0.55, 2) 2.96, 3) 3.96, 4) 7.15. renal complications).
Conclusion: Although the results of our study are limited mainly by the small number of patients, the results imply: 1) renal complications following cardiac surgery in adults do not necessarily correspond with the increase of urine NGAL concentrations, 2) NGAL/creatinine ratio in urine is more suitable initial marker of acute kidney injury than U-NGAL.