Risk factors and outcome of aortic surgery patients with hypothermic circulatory arrest: can urine NGAL predict acute kidney injury?

Introduction: Hypothermic circulatory arrest (HCA) is useful to protect visceral organs during aortic operations. The degree of hypothermia and the influence of renal damage remain controversial. Aim: To evaluate the incidence of acute kidney injury (AKI) comparing moderate HCA (MHCA) and deep HCA (DHCA) and determine risk factors and ability of urine neutrophil gelatinase associated lipocalin (u-NGAL) to predict AKI. Material and methods: We prospectively enrolled 58 patients who underwent aortic replacement with HCA during May 2019-August 2021. Patients were divided into 2 groups: DHCA (15-20°C) and MHCA (20-25°C). The primary outcome was incidence of AKI. Secondary outcomes included risk factors of AKI. Results: Baseline characteristics were not different between the 2 groups. There were 37 patients in the DHCA group and 21 patients in the MHCA group. Each group was mostly diagnosed with acute type A aortic dissection (60.3%). The operation was hemiarch replacement (51.7%). The overall incidence of AKI was 65.6% according to KDIGO criteria; there was no statistically significant difference between DHCA and MHCA groups. Urine NGAL level at cut-off point > 20 ng/ml at hour 0 and > 70 ng/ml at hour 6 could predict AKI. Operation time more than 360 minutes was found to be a risk factor for AKI. In hospital mortality rates and neurological outcomes were not statistically significantly different between DHCA and MHCA groups. Conclusions: AKI is common in patients undergoing HCA with an overall incidence of more than 60%. Risk factors of AKI after aortic surgery include long operative time. U-NGAL in the early post-operative period can predict AKI.