This is a substudy of a prospective study designed to evaluate risk factors for preoperative and postoperative delirium in elderly hip fracture patients . Patients aged ≥ 65, acutely admitted for a hip fracture, who spoke Norwegian, had no severe aphasia, head injury or terminal illness, and were admitted for at least 48 hours, were eligible. Patients admitted to Oslo University Hospital or Diakonhjemmet Hospital, Oslo, Norway, in the period from May through December 2006, providing a written informed consent and from whom at least one blood sample was drawn, were included in the current study.
The study was undertaken in accordance with the Declaration of Helsinki and approved by the Eastern Norway Regional Committee for Ethics in Medical Research (Project # 05075) and Ullevaal University Hospital Data Protection Officer. The patients were observed for a minimum of 48 hours and a maximum of 5 days after the operation.
Patients were screened for delirium within 48 hours of admission, thereafter on a daily basis (weekdays) until discharge or the fifth postoperative day. Delirium was diagnosed using the Confusion Assessment Method (CAM) criteria : change in mental status with acute onset and/or fluctuating course, inattention, and disorganized thinking or altered level of consciousness. Details on the procedure have been published .
Pre-fracture cognitive function was determined using the short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE), and patients with IQCODE scores 3.44 or greater were considered as probably suffering from pre-fracture cognitive decline . The patients’ overall physical health was assessed according to the American Society of Anesthesiologists (ASA) score. The Barthel Index (maximum score 20) was scored by a close caregiver to give an indication of pre-fracture functioning in activities of daily living .
Blood samples were collected preoperatively and postoperatively, centrifuged at 3500 rpm for 10 minutes and stored at-70C. MCP-1 was measured by an enzyme-linked immunosorbent assay (ELISA) method with commercially available kits (R & D Systems Europe, Abingdon, Oxon, UK). To minimize run-to-run variability, serial samples from the same individuals were analyzed in the same microtiter run. In our laboratory the inter-assay coefficient of variation for MCP-1 was 9.2%.
Mann–Whitney U test was conducted to compare levels of MCP-1 markers in patients with and without delirium. For change in MCP-1 concentration, we had to dichotomize the variable (raise versus steady state or fall) and use the chi-square test as the distribution was not homoscedastic, and the conditions for using the Mann–Whitney U test thus not fulfilled . For this analysis, every raise in the concentration (above zero) was defined as a raise.