Feasibility and candidate risk factors for postoperative delirium in older ward patients: a prospective pilot study

Postoperative delirium (POD) is a frequent neuropsychiatric complication after surgery, characterized by acute disturbances in attention, awareness, and cognition. This pilot study assessed the feasibility of a multidimensional assessment protocol and investigated candidate risk factors for POD in older patients undergoing elective surgery.

This prospective, observational, non-interventional, single-center pilot study enrolled 150 patients aged ≥ 65 years undergoing elective surgery lasting ≥ 60 min. Patients with dementia, neurological disorders (documented diagnoses), or emergency procedures were excluded. After enrollment, 10 patients were excluded due to surgery postponement or unplanned ICU admission, leaving 140 patients for analysis. Data were collected preoperatively, on postoperative days 1-3. Intraoperative and laboratory data were obtained from databases. Handgrip strength was measured by dynamometry. POD was assessed using the CAM-ICU once daily on postoperative days 1-3 by a single trained investigator. Cognitive function and reserve were evaluated using MMSE and MWT-B, frailty with the Clinical Frailty Scale, nutritional status with screening tools, and pain via the Numeric Rating Scale. Descriptive and inferential statistics were applied.

POD incidence was 5.0% (n = 7/140; 95% CI: 2.0%-10.0%). Frailty (n = 4/7 [57%] vs. n = 26/133 [20%]) and malnutrition (n = 4/7 [57%] vs. n = 29/133 [22%]) were more common in the delirium group. In an exploratory, unpowered male subgroup analysis, patients with POD had lower preoperative handgrip strength; no statistically meaningful difference was testable in women (n = 3 with POD). During anesthesia induction, patients with POD experienced more hypotensive episodes (MAP<55 mmHg), (n = 3/7 [43%] vs. n = 11/133 [8.0%]). No comparison remained significant after Holm-Bonferroni correction.

This pilot study demonstrates the feasibility of prospective POD assessment on a general surgical ward and provides an incidence estimate (5.0%) to inform sample-size calculation for confirmatory trials. Frailty, lower preoperative handgrip strength in men, and induction hypotension were more frequent among patients with POD. Given the low event rate and multiple comparisons, these associations are hypothesis-generating and require validation in adequately powered studies.

German Clinical Trials Register DRKS00031157. Registered 20.03.2023.