Mean arterial blood pressure during the first 24 hours after cardiac surgery and acute kidney injury: an observational cohort study
Abstract
Objective(s):
Mean arterial pressure (MAP) after cardiac surgery may contribute to acute kidney injury (AKI). We sought to identify threshold MAP values during the first 24 hours (h) postoperatively below, or above, which the risk for AKI increased.
Design:
Retrospective cohort study.
Setting:
Single, academic medical center.
Participants:
1368 adult patients undergoing cardiac surgery from October 2020 to September 2022.
Interventions:
Nil
Measurements & Main Results:
Using minute-by-minute MAP values throughout 24h postoperatively seven mutually exclusive MAP range-bands (<55, 55–59, 60–64, 65–69, 70–74, 75–79, ≥80 mmHg) were created, with the primary exposure defined as total number of minutes a patient spent within each MAP range-band throughout this period. The primary outcome was AKI, identified between 24h and 7 days postoperatively. Multivariable logistic regression models quantified the association between increasing time spent in each individual MAP range-band during the first 24h postoperatively, relative to a reference range-band of 65–69 mmHg, and AKI. Mean (SD) patient age was 63.9 (12.8) years, with 1,313,568 observed MAP data points from 1,895,133 ICU person-minutes through 24h postoperatively. After prespecified exclusions, AKI occurred in 190 (15.3%) patients. There was no association between increasing time spent in any MAP range-band, relative to time spent between 65–69 mmHg, and AKI. For example, the odds ratio for AKI per 15 minutes with MAP 60–64 mmHg was 0.98 [95% CI 0.88–1.08], and 1.03 [95% CI 0.93–1.13] with MAP 55–59 mmHg.
Conclusions:
We were unable to demonstrate association between increasing time spent in any MAP range-band throughout 24h postoperatively and AKI.