Study Explores Link Between Intraoperative Hypotension, Norepinephrine Dose, and Acute Kidney Injury After Noncardiac Surgery

Intraoperative low blood pressure is linked to acute kidney injury (AKI). Therefore, medical professionals commonly utilize vasopressors like norepinephrine to stabilize blood pressure. Nevertheless, vasopressors could potentially contribute to AKI. A recent investigation aimed to establish whether both intraoperative low blood pressure and the total amount of norepinephrine given during surgery are independently linked to the development of AKI after noncardiac surgical procedures. This retrospective cohort study analyzed data from 38,338 adult patients undergoing noncardiac surgery to examine the independent associations between intraoperative hypotension, cumulative intraoperative norepinephrine dose, and postoperative acute kidney injury (AKI). The key findings were: 1. Both intraoperative hypotension and higher intraoperative norepinephrine dose were independently associated with increased risk of postoperative AKI. Patients who developed AKI had about one-third more intraoperative hypotension, as measured by the area under a mean arterial pressure (MAP) threshold of 65 mmHg. The risk of AKI increased by over 50% per 1 mmHg\*day increase in the area under a MAP of 65 mmHg. 2. The intraoperative cumulative norepinephrine dose was also independently associated with AKI. The risk of AKI increased by 1.6% per 1 μg/kg increase in the cumulative norepinephrine dose. For example, norepinephrine at 0.076 μg/kg/min for 132 minutes (median surgery duration) would increase the AKI risk by 16%. 3. Intraoperative hypotension was independently associated with AKI in high-risk patients (ASA 3-4) but not in low-risk patients (ASA 1-2). Baseline patient factors were more strongly associated with AKI than intraoperative hypotension. 4. While the study cannot establish causality, the findings suggest that clinicians should aim to avoid both intraoperative hypotension and high doses of norepinephrine to reduce the risk of postoperative AKI. Further interventional trials are needed to determine the optimal hemodynamic management strategy. In summary, this large retrospective analysis found that both intraoperative hypotension and higher intraoperative norepinephrine use were independently associated with increased risk of postoperative AKI in noncardiac surgery patients.

Key Points

1. Intraoperative hypotension and higher intraoperative norepinephrine dose were independently associated with an increased risk of postoperative acute kidney injury (AKI) in adult patients undergoing noncardiac surgery.

2. Patients who developed AKI had about one-third more intraoperative hypotension, as measured by the area under a mean arterial pressure (MAP) threshold of 65 mmHg, and the risk of AKI increased by over 50% per 1 mmHg\*day increase in the area under a MAP of 65 mmHg.

3. The intraoperative cumulative norepinephrine dose was also independently associated with AKI, with the risk of AKI increasing by 1.6% per 1 μg/kg increase in the cumulative norepinephrine dose.

4. Intraoperative hypotension was independently associated with AKI in high-risk patients (ASA 3-4) but not in low-risk patients (ASA 1-2), and baseline patient factors were more strongly associated with AKI than intraoperative hypotension.

5. While the study cannot establish causality, the findings suggest that clinicians should aim to avoid both intraoperative hypotension and high doses of norepinephrine to reduce the risk of postoperative AKI.

6. Further interventional trials are needed to determine the optimal hemodynamic management strategy to prevent postoperative AKI.

Reference –

B. Saugel et al. (2024). Association Of Intraoperative Hypotension And Cumulative Norepinephrine Dose With Postoperative Acute Kidney Injury In Patients Having Noncardiac Surgery: A Retrospective Cohort Analysis. *BJA: British Journal Of Anaesthesia*, 134, 54 - 62. https://doi.org/10.1016/j.bja.2024.11.005.