Incidence and risk factors of delirium in post-anaesthesia care unit

Introduction: Post-anaesthesia care unit (PACU) delirium is a potentially preventable condition that results in a significant long-term effect. In a multicentre prospective cohort study, we investigate the incidence and risk factors of postoperative delirium in elderly patients undergoing major non-cardiac surgery. Methods: Patients were consented and recruited from 4 major hospitals in Singapore. Research ethics approval was obtained. Patients older than 65 years undergoing non-cardiac surgery >2 hours were recruited. Baseline perioperative data were collected. Preoperative baseline cognition was obtained. Patients were assessed in the post-anaesthesia care unit for delirium 30-60 minutes after arrival using the Nursing Delirium Screening Scale (Nu-DESC). Results: Ninety-eight patients completed the study. Eleven patients (11.2%) had postoperative delirium. Patients who had PACU delirium were older (74.6 +/- 3.2 versus 70.6 +/- 4.4 years, P=0.005). Univariate analysis showed those who had PACU delirium are more likely to be ASA 3 (63.6% vs 31.0%, P=0.019), had estimated glomerular filtration rate (eGFR) of <60mL/min/1.73m2 (36.4% vs 10.6%, P=0.013), higher HbA1C value (7.8 +/- 1.2 vs 6.6 +/- 0.9, P=0.011), raised random blood glucose (10.0 +/- 5.0mmol/L vs 6.5 +/- 2.4mmol/L, P=0.0066), and moderate-severe depression (18.2% vs 1.1%, P=0.033). They are more likely to stay longer in hospital (median 8 days [range 4-18] vs 4 days [range 2-8], P=0.049). Raised random blood glucose is independently associated with increased PACU delirium on multivariate analysis. Conclusion: PACU delirium is common in elderly patients with risks factors presenting for major surgery.