Understanding risk factors for postoperative delirium after elective surgery in a university-based tertiary hospital

Background & Objectives: The incidence and associations of postoperative delirium (POD) varies in the literature. The objectives of this study were to determine the incidence and preoperative risk factors for POD in elective surgical patients and its association with one month mortality and length of hospital stay (LOS) in a tertiary hospital in Malaysia. Methods: A prospective observation study on patients above 65 years old was conducted. Demographic and perioperative data was collected for 5 days postoperatively or until discharge with delirium assessment tools 4- Abbreviation Test (4AT) and Confusion Assessment Method (CAM). Results: 447 elective cases were recruited over 6 months. 11.2% developed POD, most frequently on the first day postoperatively. The strongest independently associated risks factors were dependence on activities of daily living, ADL (Odd Ratio, OR:3.92, 95% Confidence interval, CI:1.52-10.11, p<0.01) followed by poor cognitive function (Montreal Cognitive Assessment, MOCA scores =19, OR:3.90, 95% CI:1.82-8.34, P<0.01. Univariate logistic regression showed that pre-existing cerebrovascular event, electrolyte imbalance, nature of surgery, frailty, malnutrition, and depression contribute significant risks. POD itself was associated with longer LOS, median 4(2-5) days with POD vs 1(1-3) day without (p<0.01) and one month mortality rate (p=0.02). Cases performed under combined regional anaesthesia and general anaesthesia had OR of 3.44 (95% CI:1.57-7.53, p<0.01) for POD. Conclusions: Early identification of high risk patients should include recognizing poor cognitive function especially in ADL dependent elderly patients. Significant risks with types of anaesthesia and surgeries also indicate that future studies should focus on identifying underlying mechanisms of neurocognitive function in POD.