Subtle deficits of attention after surgery: quantifying indicators of sub syndrome delirium

To determine whether attentional impairments are reliable neuropsychological markers of sub syndrome delirium.

A prospective cohort study with repeated assessment beginning pre-operatively and continuing through the first post-operative week. Computerized assessments of attention and the Mini-Mental State Examination were administered with one hundred patients admitted for elective orthopedic surgery, 70 years and over and free of dementia. Acute change of cognitive status was used to identify cases of sub syndrome delirium.

There were significant differences of post-surgical performance between the 'no delirium' and 'sub-syndrome delirium' groups of reaction time, global cognition, accuracy and greater variability of reaction time (p < 0.041). There were significant within subject main effects on reaction time (p = 0.001), variability of reaction time (p = 0.022) and MMSE (p = 0.000) across the cohort; but no significant interaction effect of 'diagnosis' * 'time' on the computerized measures of attention (p > 0.195).

The distinction between people with sub syndrome delirium and no delirium is difficult to quantify but computerized measures of attention might provide a sensitive indicator. Sub syndrome delirium is an observable marker of a clinical abnormality that should be exploited to improve care management for vulnerable patients.