Effect of preoperative risk on the association between intraoperative hypotension and postoperative acute kidney injury in cardiac surgery

Acute kidney injury (AKI), a common and severe complication after cardiac surgery, has been demonstrated to be associated with intraoperative hypotension (IOH). The reproducibility of this finding and whether preoperative risk modifies the association remain unclear. We hypothesised that the relationship between IOH and AKI after cardiac surgery varies by preoperative risk. We conducted a single-centre, retrospective cohort study to analyse the association between IOH and postoperative AKI by stratifying patients using preoperative risk factors. IOH was defined as a mean arterial pressure (MAP) of less than 65 mmHg and characterised by the cumulative duration and area under the curve (AUC). Ten variables could be identified as risk factors: age, smoking status, NYHA III/Ⅳ, emergency surgery, peripheral vascular disease, cerebrovascular disease, heart failure, hypertension, previous cardiac surgery, and NT-proBNP concentration. The risk prediction model divided the patients into three equal-sized preoperative risk groups. Low-risk patients demonstrated no association between AKI and IOH of any severity, while high-risk patients demonstrated a statistically significant association between AKI and IOH with a cumulative duration greater than 104 min (adjusted odds ratio [OR]: 2.27, 95% confidence interval [CI]: 1.10−4.74; and adjusted OR: 3.63, 95% CI: 1.77−7.58) and an AUC greater than 905 mmHg min (adjusted OR: 2.08, 95% CI: 1.01−4.36; and adjusted OR: 4.00, 95% CI: 1.95−8.43). IOH is a significant independent risk factor for AKI after cardiac surgery. Patients with higher baseline risk showed a more prominent relationship between IOH and postoperative AKI than low-risk patients.