Pre-ICU characteristics in cardiac surgery patients with CPB developing AKI

Abstract

Aims. AKI is common after cardiac surgery involving CPB. Lack of reliable early detection methods for post-op AKI limits timely therapeutic intervention. A number of new biomarkers for AKI await validation in this setting. Analysis of a database was performed to define baseline patient and biomarker characteristics in patients developing AKI. Methods. 259 patients were enrolled. Patients with severe pre-existing renal insufficiency were excluded (eGFR<15ml/min). Urine and blood samples were obtained immediately before initiation of CPB. Patients were retrospectively divided into 2 groups, AKI (n=84) and non-AKI (n=175), based on the AKIN criteria (increase in s-Creat ≥ 0.3 mg/dl or ≥ 50% compared to baseline within 48h or reduction in Urine output <0.5 ml/kg/h for more than 6h). Statistical analysis of all characteristics before arrival on the ICU was performed. Results. AKI patients (32% of total) were older (70 yrs (SD= 9) vs 67 (11), p=0.043) with higher BMI’s (27.7 (4.8) vs. 26.7 (4.3), p=0.036). As to be expected baseline eGFR (CKD-EPI, in ml/min) was lower in the AKI-group (69.49 (20.30) vs. 76.45 (15.01), p=0.024). Both baseline urinary-NGAL (μg/l)(1211 (2172) vs. 749 (946), p=0.020) and serum-cystatin C (in mg/L)(0.98 (0.39) vs 0.86 (0.36), p=0.0175) were statistically higher in the AKI group and CPB time (in minutes) was significantly longer: 163 (63) vs 121 (51), p<0.0001. Conclusion. u-NGAL and s-Cystatin most likely reflect pre-existing kidney dysfunction (like eGFR). CPB time is a significant factor for development of AKI, which is amenable to improvement.