Impaired cognition among older adults who undergo elective surgery is significantly associated with adverse postoperative outcomes, including increased complications, length of stay, and long-term mortality, results from a single-center study showed.
In addition, delirium was found to be an effect modifier in the relationship between impaired cognition and adverse postoperative outcomes.
"The most striking finding is that delirium appears to work as part of a causal pathway between baseline impaired cognition and long-term mortality," lead investigator Dr. Thomas N. Robinson said in an interview before the annual meeting of the Western Surgical Association, where the work was presented.
In what he said is the first study of its kind, Dr. Robinson, of the department of surgery at the University of Colorado, Denver, and his associates prospectively evaluated 186 adults aged 65 and older who underwent an elective operation requiring postoperative ICU admission.
To assess preoperative baseline cognitive function, they used the validated Mini-Cog test, which combines an uncued three-item recall test with a clock drawing task. Impaired cognition was defined as a Mini-Cog score of 3 or less.
To assess delirium, the researchers used the Confusion Assessment Method for the ICU, a validated tool that evaluates delirium based on fluctuation in mental status, inattention, disorganized thinking, and altered level of consciousness.
"Delirium appears to work as part of a causal pathway between baseline impaired cognition and long-term mortality."
To determine adverse outcomes, they used definitions from the Veterans Affairs Surgical Quality Improvement Program.
Dr. Robinson, who also holds an appointment in the department of surgery at the Denver Veterans Affairs Medical Center, reported that the mean age of the 186 patients was 73 years and 96% were male. Nearly half (44%) had impaired cognition.
Compared with their counterparts who had normal cognition at baseline, those with impaired cognition had a higher rate of one or more complications (41% vs. 24%, respectively), a higher incidence of delirium (78% vs. 37%), longer hospital stays (a mean of 15 vs. 9 days), a higher rate of discharge to an institutional care facility (42% vs. 18%), a higher 30-day readmission rate (21% vs. 10%), and a higher 6-month mortality (11% vs. 5%). All differences were statistically significant.
Dr. Robinson also reported that the hazard ratio for death was 2.77 higher among patients with impaired cognition and delirium at baseline compared with patients with normal cognition and delirium. On the other hand, the hazard ratio for death was 1.86 times higher among patients who had impaired cognitive function but no delirium at baseline.
In their abstract, the researchers noted certain limitations of the study, including the fact that nearly all patients were male and that a wide variety of operations were included, which "leads to large variability in measurements such as blood loss, operating room time, and length of stay."
They went on to conclude that "recognition of the brain’s function as a relevant marker of postoperative events has implications on the clinician’s ability to counsel their older patients about the anticipated postoperative course. In the future, preoperative risk stratification will likely not be based on physiologic compromise of a single organ system alone. Instead, the sum of compromise across multiple health-related domains (e.g., cognition, function, nutrition, disease burden) will likely be used to forecast postoperative outcomes."
The study received financial support from the National Institute on Aging and the American Geriatrics Society. Dr. Robinson said that he had no relevant financial disclosures.