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.