FACTORS ASSOCIATED WITH ACUTE POSTOPERATIVE CREATININE RISE AFTER OPEN-HEART SURGERY WITH CARDIOPULMONARY BYPASS

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a frequent complication of open-heart surgery performed with cardiopulmonary bypass (CPB). The aim was to assess the frequency of, and factors associated with, a postoperative rise in serum creatinine defined by the absolute KDIGO criterion (increase ≥26.5 µmol/L) among patients in an institutional cardiac surgery registry managed with standard perioperative care. Data from 63 of 112 consecutive registry patients who underwent open-heart surgery with CPB and had paired pre- and postoperative creatinine values were analysed. The defined creatinine rise occurred in 10 of 63 patients (15.9%). Patients with a creatinine rise had a significantly lower baseline creatinine than those without (82 [78–97] vs 98 [88–110] µmol/L; p = 0.028), with a non-significant trend towards longer operative time (260 [250–300] vs 203 [176–255] min; p = 0.126). In multivariable analysis including baseline creatinine and operative duration, lower baseline creatinine remained independently associated with the outcome (adjusted odds ratio 0.92 per 1 µmol/L; 95% CI 0.85–0.99; p = 0.027); the model discriminated the outcome with an AUC of 0.786 (n = 59, 9 events). Given the small number of events and that the criterion captured an absolute rather than relative rise from differing baselines, this association likely partly reflects a statistical artefact (regression to the mean) rather than a protective effect of low creatinine, as confirmed by comparison with a larger prior institutional analysis (n = 300) in which higher baseline creatinine was associated with AKI. The findings are exploratory and highlight the limitations of retrospective registries with a single postoper­ative creatinine measurement for full KDIGO staging.