Defining a postoperative mean arterial pressure threshold in association with acute kidney injury after cardiac surgery: a prospective observational study.

Abstract

Acute kidney injury (AKI) is a common but fatal complication after cardiac surgery. In the absence of effective treatments, the identification and modification of risk factors has been a major component of disease management. However, the optimal blood pressure target for preventing cardiac surgery-associated acute kidney injury (CSA-AKI) remains unclear. We sought to determine the effect of postoperative mean arterial pressure (MAP) in CSA-AKI. It is hypothesized that longer periods of hypotension after cardiac surgery are associated with an increased risk of AKI. This prospective cohort study was conducted on adult patients who underwent cardiac surgery requiring cardiopulmonary bypass at a tertiary center between October 2018 and May 2020. The primary outcome is the occurrence of CSA-AKI. MAP and its duration in the ranges of less than 65, 65 to 74, and 75 to 84mmHg within 24h after surgery were recorded. The association between postoperative MAP and CSA-AKI was examined by using logistic regression. Among the 353 patients enrolled, 217 (61.5%) had a confirmed diagnosis of CSA-AKI. Each 1h epoch of postoperative MAP less than 65mmHg was associated with an adjusted odds ratio of 1.208 (95% CI, 1.007 to 1.449; P = 0.042), and each 1h epoch of postoperative MAP between 65 and 74mmHg was associated with an adjusted odds ratio of 1.144 (95% CI, 1.026 to 1.275; P = 0.016) for CSA-AKI. A potentially modifiable risk factor, postoperative MAP less than 75mmHg for 1h or more is associated with an increased risk of CSA-AKI.