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

Abstract

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. This retrospective cohort study analyzed adult non-cardiac surgeries at a single academic medical center in South Korea (2011 to 2020). Patients were stratified by median intraoperative pulse pressure: Narrow (<40 mmHg), Reference (40 to 70 mmHg), and Wide (>70 mmHg). Entropy balancing adjusted for covariates, including cumulative vasopressor load and hypotension duration. A 2×2 risk matrix evaluated the interaction between MAP (<65 vs. ≥65 mmHg) and pulse pressure. A mechanistic sub-study correlated pulse pressure with stroke volume index. Among 30,039 patients (median age 60, 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% confidence interval 1.42 to 1.94; p < 0.001). Hypotension with Reference pulse pressure did not significantly increase risk (odds ratio 1.09; 95% confidence interval 0.86 to 1.38; p = 0.475). Conversely, normotension with Narrow pulse pressure elevated AKI risk (odds ratio 1.56; 95% confidence interval 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% confidence interval 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/m²). Risk became significant after 40 minutes of exposure. 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.