Association Between Preoperative Albumin Corrected Anion Gap and Postoperative Delirium in Cardiac Surgery Patients

BackgroundDelirium, a common and multifactorial complication after cardiac surgery, is influenced by several factors including inflammation, metabolic disturbances, and cerebral hypoperfusion. Because these factors can be reflected in an elevated anion gap (AG), we hypothesized that a higher preoperative albumin corrected anion gap (ACAG) is associated with increased risk of delirium and 1-year mortality after cardiac surgery. MethodsWe examined a retrospective cohort of adult patients within our healthcare system who underwent cardiac surgery between 2014 and 2022 and had a recorded Confusion Assessment Method for the ICU (CAM-ICU) evaluation. Patients were excluded if they had documented preoperative delirium during the index hospital admission or a history of dementia. The final cohort included 4,482 patients. Preoperative laboratory values were collected, using the most recent results obtained within 48 hours prior to surgery. The primary outcome was delirium after cardiac surgery (DACS), defined as delirium occurring within postoperative days 1 through 5. The secondary outcome was all-cause 1-year mortality. ResultsThe incidence of DACS and 1-year mortality were 9.5% and 4.8%, respectively. A multivariable logistic regression model adjusting for baseline characteristics showed that higher ACAG was significantly associated with higher risk of DACS (adjusted odds ratio (AOR) = 1.56, 95% Confidence Interval (CI) = 1.40-1.74, p < 0.001). Other predictors of DACS included increasing age (AOR = 1.31, CI = 1.16-1.48, p < 0.001), surgery duration (AOR = 1.35, CI = 1.22-1.49, p < 0.001), and history of delirium (AOR = 1.70, CI = 1.29-2.24, p < 0.001). Moreover, increasing ACAG was also associated with 1-year mortality (AOR = 1.35, CI = 1.16-1.56, p < 0.001). Finally, receiver operating characteristic (ROC) analysis demonstrated that ACAG exhibited superior predictive performance compared with AG and anion gap to bicarbonate ratio (AGBR) for both DACS and 1-year mortality outcomes. ConclusionsHigher preoperative ACAG was associated with elevated risk for DACS and 1-year mortality. Preoperative ACAG is an accessible and cost-efficient biomarker that may improve risk stratification for cardiac surgery patients.