Perioperative predictors of delirium and incidence factors in adult patients post cardiac surgery

Background: Delirium is a quite common complication in adult patients post-cardiac surgery. The purpose of our study was to identify perioperative characteristics and also focus on incidence factors that could predict delirium in the cardiac surgery intensive care unit (CICU) postoperatively. Methods: We conducted a prospective study of 179 consecutive patients, who underwent open-heart surgical operation and were admitted to the CICU of a general tertiary hospital in Athens, Greece. The patients were screened for delirium by using the diagnostic tools of Richmond Agitation Sedation Scale (RASS score) and the Confusion Assessment Method - ICU (CAM-ICU). The delirium assessment was carried out on the 1st and the 2nd postoperative day, and was conducted twice every nursing shift. A short questionnaire on sociodemographics and clinical patient characteristics was used for data collection purposes. Results: A total of 179 patients who underwent open-heart surgical operation with cardiopulmonary bypass (CPB) were enrolled in our study. The 2-day incidence of postoperative delirium in ICU was 11.2% (n=20/179). The main independent predictors of delirium on the 2nd postoperative day were neutrophil-to-lymphocyte ratio (p=0.001) and urea levels (p=0.016). Additionally, increased perioperative creatinine (p=0.006) and sodium (p=0.039) levels were significantly associated with delirium occurrence. Furthermore, elevated EuroSCORE (p=0.001), extended length of stay (LOS) in ICU (p<0.001), and extended LOS with endotracheal tube (p=0.001) were also statistically significant indicators. Conclusion: Patients with extended LOS with endotracheal tube and prolonged stay in ICU in accordance with peaked urea, neutrophil-to-lymphocyte ratio, creatinine, and sodium levels seem to have a significantly greater probability of developing delirium in the ICU. Further research is needed in the field of postoperative cardiac patients in order to determine the causality and etiology of certain risk factors for delirium.