The relationship between intraoperative hypotension and risk of postoperative acute kidney injury

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BACKGROUND Intraoperative hypotension (IOH) is a common, modifiable risk factor for postoperative complications, including acute kidney injury (AKI). While the association between IOH and postoperative AKI has been extensively studied, the exposure-response relationship and the relative contribution of IOH within the multifactorial pathophysiology of AKI remain incompletely characterised. OBJECTIVE To determine the relationship between the duration and depth of IOH on the risk of AKI and its incremental risk over time. DESIGN AND DATA This study was designed as a single-centre retrospective observational cohort study conducted at an academic tertiary care hospital. We analysed intraoperative blood pressure data from 10 444 surgical procedures involving 8676 adult patients between 2014 and 2024. IOH duration was measured as the time spent with mean arterial pressure (MAP) below specific thresholds. Logistic regression and natural splines were used to model the relationship between IOH and AKI, with the predictive power assessed using the area under the receiver-operating characteristic (ROC) curve (AUC). Age, ASA classification, body mass index, sex and preoperative glomerular filtration rate were included as covariate analyses. SETTING Single-centre academic hospital with primarily secondary and tertiary care. RESULTS AKI occurred in 4.33% of cases. The risk of AKI increased with the cumulative duration of IOH below certain MAP thresholds. A nonlinear relationship was observed, where the initial minutes of IOH seem to contribute the most to the significantly increased the risk of AKI. AUC values of the ROC curves for the association between IOH and AKI were close to 0.5, suggesting that IOH contributes only marginally to the multifactorial aetiology of AKI. CONCLUSIONS IOH significantly increases the likelihood of postoperative AKI, but the relationship is nonlinear. Short periods of hypotension already significantly increase AKI risk, with the impact of prolonged hypotension being relatively small. The multifactorial aetiology of AKI underscores the importance of other risk factors in understanding postoperative renal dysfunction.