Association of Intraoperative Narrow Pulse Pressure during Normotension with Postoperative Acute Kidney Injury: A Retrospective Cohort Analysis

BACKGROUND: The association between narrow pulse pressure and acute kidney injury (AKI) remains controversial. We hypothesized that normal mean arterial pressure (MAP) with narrow pulse pressure is independently associated with postoperative AKI. METHODS: This retrospective cohort study analyzed adult noncardiac surgeries at a single academic medical center in South Korea (2011 to 2020). Patients were stratified by median intraoperative pulse pressure: narrow (less than 40 mmHg), reference (40 to 70 mmHg), and wide (greater than 70 mmHg). Entropy balancing adjusted for covariates, including cumulative vasopressor load and hypotension duration. A two-by-two risk matrix evaluated the interaction between MAP (less than 65 vs . 65 mmHg or greater) and pulse pressure. A mechanistic substudy correlated pulse pressure with stroke volume index. RESULTS: Among 30,039 patients (median age 60 yr; 54.6% male), AKI incidence was 6.7%. Compared to reference pulse pressure, narrow pulse pressure was independently associated with AKI (odds ratio, 1.66; 95% CI, 1.42 to 1.94; P < 0.001). Hypotension with reference pulse pressure did not significantly increase risk (odds ratio, 1.09; 95% CI, 0.86 to 1.38; P = 0.475). Conversely, normotension with narrow pulse pressure elevated AKI risk (odds ratio, 1.56; 95% CI, 1.27 to 1.89; P < 0.001). Patients experiencing a "double hit" of concurrent hypotension and narrow pulse pressure exhibited the highest risk (odds ratio, 1.85; 95% CI, 1.21 to 2.81). Mechanistically, stroke volume index was significantly lower in the normotensive narrow pulse pressure group than the hypotensive reference group (27 vs . 47 ml/m 2 ). Risk became significant after 40 min of exposure. CONCLUSIONS: Narrow pulse pressure is independently associated with postoperative AKI, even when MAP is maintained above 65 mmHg. A MAP-centric approach may obscure low-flow states, highlighting the potential value of incorporating pulse pressure into perioperative assessments.