Risk factors of post-anaesthesia care unit delirium in patients undergoing non-cardiac surgery in Singapore

Abstract

Introduction: Post-anaesthesia care unit (PACU) delirium affects 5%–45% of patients after surgery and is associated with postoperative delirium and increased mortality. Up to 40% of PACU delirium is preventable but it remains under-recognised due to a lack of awareness for its diagnosis. Nursing Delirium Screening Scale (Nu-DESC) has been validated in diagnosing PACU delirium but is not routine locally. This study aim was to use the Nu-DESC to establish the incidence and risk factors of PACU delirium in patients undergoing non-cardiac surgery in the surgical population. Methods: With IRB approval and informed consent, we conducted an audit of eligible patients undergoing major surgery in three major public hospitals in Singapore over one week. Patients were assessed for delirium 30–60 minutes following their arrival in the PACU using the Nu-DESC with a score of ≥ 2 as indicative of delirium. Results: A total of 478 patients were assessed. The overall incidence rate of PACU delirium was 18/478 (3.8%) and 9/146 (6.2%) in patients over 65 years old. PACU delirium was more common in females, patients with malignancy and those who underwent longer operations. Logistic Regression analysis showed that the use of BIS (p < 0.001) and the presence of malignancy (p<0.001) were significantly associated with a higher incidence of PACU delirium. Conclusion: In this first local study, the incidence of PACU delirium was 3.8%, with the incidence increasing to 6.2% in those older than 65 years old. Understanding these risk factors will form the basis for which protocols can be established to optimise resource management and prevent long term morbidities and mortality of PACU delirium.