Acute confusional state in the elderly following hip surgery: incidence, risk factors and complications

Objective: To determine incidence and risk factors for the development of postoperative acute confusional state (ACS) in the elderly.

Design: A prospective cohort study.

Setting: University hospital.

Patients: One hundred and five consecutive patients without ACS at baseline who underwent hip surgery because of hip fracture or elective hip replacement. All patients were 60 years or older.

Measurements: All patients underwent preoperative and daily postoperative evaluation by a research psychiatrist. Standardized instruments were used for cognitive screening, baseline assessment of depression, screening for alcohol abuse, comorbidity, and functional status. ACS was diagnosed by using the Confusion Assessment Method (CAM). Additional medical data were taken from patients' charts and anaesthetic records.

Results: Postoperative ACS developed in 23.8% of the study sample, in 40.5% of the hip fracture group and in 14.7% of the hip joint replacement group. The prevalence was highest between postoperative days 2 and 5. Multiple logistic regression analysis demonstrated the following risk factors of ACS: higher age (OR = 1.14, 95% CI 1.07-1.22), prior cognitive impairment as measured by Mini-Mental State Examination (OR = 1.32 for each point less, 95% CI 1.06-1.64), depression (OR = 3.67, 95% CI 1.12-12.02), low educational level (OR = 3.59, 95% CI 1.14-11.25), and preoperative abnormal sodium (OR = 4.32, 95% CI 1.01-18.38). Other risk factors showing statistically significant differences in the univariate analyses were: living in nursing home, vision or hearing impairment, higher comorbidity, regular use of psychotropic drugs before admission, fracture on admission, preoperative leucocytosis. A considerable proportion of patients with ACS showed self-destructive behaviour postoperatively, whereas self-destructive behaviour was not observed among non-delirious patients.

Conclusions: ACS is common among elderly hip surgery patients. The occurrence of ACS is influenced by several predisposing and precipitating factors. Further knowledge of these risk factors will contribute to the early identification of high risk patients and to the development of preventive measures.