Between 32 and 50 percent of elderly patients undergoing cardiac surgery experience symptoms of delirium post surgery (Hammeke & Hastings, 1988; Smith & Dimsdale, 1989). Further, a sizable proportion of coronary artery bypass graft (CABG) surgery patients (between 25 and 80 percent) show some cognitive decline at one year (McKhann et al., 1997a). Delirium may be a key precipitant of long-term cognitive decline in elderly cardiac surgery patients, but few outcome studies have examined this potential link. This information is needed before interventions can be developed to improve long-term cognitive outcomes in elderly cardiac surgery patients. In the proposed Intervention Development Study (IDS), we will perform a prospective cohort study in older patients undergoing CABG surgery to determine the incidence and duration of post-operative delirium, the incidence of long-term cognitive decline, and the relationship between the two. We will also determine the time course of several potential biochemical markers (serum anticholingeric activity and serum amino acid levels, specifically phenylalanine/large neutral amino acid and tryptophan/large amino acid ratios) and their relationship to delirium. Risk factors will be measured at pre-surgery baseline, intraoperatively, and at one, six, and twelve months post-operatively to identify factors that put individuals at risk for delirium, and given delirium, risk factors associated with long-term cognitive decline. This project will facilitate the development of an intervention trial to prevent or abate delirium in high-risk CABG patients and to improve post-CABG cognitive outcomes whether or not delirium is confirmed to be a risk factor for cognitive decline.
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