Association between postoperative delirium in the postanaesthesia care unit and subsequent ward delirium: A retrospective cohort study

BACKGROUND – The ageing surgical population underscores the need for routine postoperative delirium (POD) screening, particularly in the immediate postoperative period. The postanaesthesia care unit (PACU) presents a critical window for early detection and intervention, yet the clinical significance of PACU-diagnosed POD (PACU-POD) remains underexplored. OBJECTIVES – To examine whether PACU-POD is associated with subsequent ward-POD and other adverse postoperative outcomes. DESIGN – Retrospective cohort study. SETTING – Tertiary academic hospital, single-centre, conducted between 2020 and 2022. PATIENTS – Three thousand seven hundred and eighty-one patients aged at least 70 years who underwent elective noncardiac, noncranial surgery under general anaesthesia. POD was assessed using the 4AT and supplemented by CHART-DEL review. MAIN OUTCOME MEASURES – Primary outcome: ward-POD. Secondary outcomes: in-hospital falls, unplanned ICU admission, nonhome discharge and 30-day mortality. Exploratory outcomes: PACU and hospital length of stay. RESULTS – PACU-POD was diagnosed in 9.1% of patients (341/3781), who were more likely to be older, 77.1 (73.7 to 82.7) vs. 75.7 (72.9 to 80.6) years; frailer (52 vs. 40%); cognitively impaired (36 vs. 18%); and undergoing high-risk (52 vs. 27%); prolonged surgeries, 196 (133 to 275) vs. 142 (95 to 204) minutes (all P < 0.001). Ward-POD occurred in 6.2% of patients (234/3781) and was significantly more common among those with PACU-POD (24.6 vs. 4.3%, P < 0.001). PACU-POD was independently associated with ward-POD [adjusted odds ratio (aOR) 4.4; 95% confidence interval (CI), 3.2 to 6.3], in-hospital falls (aOR 2.3; 95% CI, 1.2 to 4.4) and 30-day mortality (aOR 4.4; 95% CI, 1.5 to 13.0), as well as prolonged PACU, 185 [144 to 265] vs. 150 [115 to 210] minutes, P < 0.001, and hospital stays, 6 [3 to 10] vs. 3 [2 to 6] days, P = 0.01. CONCLUSION – PACU-POD is a strong early marker of increased risk for ward-POD and other postoperative complications. Routine PACU screening enables early diagnosis, risk stratification and targeted interventions. Future studies should evaluate whether early intervention starting during the PACU stay can improve the trajectory of POD and related complications.