Cognitive Decline Following Cardiac Surgery
The common features of delirium are:
1. Disturbance of consciousness, that is, reduced clarity of consciousness
2. Cognition disturbances
3. Memory impairment
4. Fluctuating tendency
5. Slow thinking
Delirium is quite common after cardiac surgery. Jane Saczynski and colleagues conducted a study to assess the prevalence of delirium and cognitive decline after cardiac surgery.
Though delirium has been studied extensively, still few studies have been carried out on patient undergoing cardiac surgery.
The experts enrolled 225 volunteers in the age group of 60 to 90 years who had either heart valve replacement surgery or coronary artery bypass grafting (CABG) at the Beth Israel Deaconess Medical Center (BIDMC), UMass Memorial Medical Center or the Boston VA Medical Center.
They were reviewed for both cognitive impairment and delirium before and after surgery. The patients were followed up for a year after surgery.
Mini-Mental State Examination (MMSE) was used to evaluate cognitive function. MMSE score ranged from 0 to 30 with low score indicating poor performance. Confusion Assessment Method was employed to determine delirium.
Edward Marcantonio, MD, section chief for research in BIDMC's Division of General Medicine and Primary Care and professor of Medicine at Harvard Medical School, "One of the real strengths of our study is that we assessed patients' cognitive function preoperatively and an average of five times during the year after surgery."
A total of 103 participants who developed delirium postoperatively in the study had low preoperative Mini-Mental State Examination scores. The delirium lasted for 1 to 2 days in 65% of these patients and 3 or more days in 35% patients. Most of these patients were older, less educated, more likely to be women, and less likely to be white. They were also more likely to have a history of stroke or TIA and a lower level of preoperative cognitive function.
These 103 patients showed a remarkable drop in cognitive performance. They also took longer time to recuperate back to their preoperative level as compared to patients who did not developed delirium.
The patients developing delirium generally took long to recover back to their normal preoperative levels of cognitive performance. The study findings suggested that substantial benefits can be achieved by identification of high-risk patients for delirium before surgery and promoting adequate interventions for the prevention of delirium in cardiac surgery patients.
Cognitive screening at the time of discharge can also help in identifying patients requiring closer monitoring and care to facilitate the return of cognitive functions.
Jane Saczynski, PhD, assistant professor of Medicine at the University of Massachusetts Medical School said, "Our findings now suggest that postoperative delirium, once thought of as an acute, transient cognitive disorder, may have longer-term effects on cognitive function in patients undergoing cardiac surgery."
One of the authors of the paper said, "Since patients who experience delirium continue to show improvement in cognitive function six months after surgery, extending additional rehabilitation services to these patients may have added benefits. "Another author stated, "The findings from this study highlight the clinical importance of the identification of delirium and the potential of preventive interventions like the Hospital Elder Life Program [HELP]."
Cognitive Trajectories after Postoperative Delirium; Jane Saczynski et al; N Engl J Med 2012; 367:30-39