Surgery and Anesthesia Exposure Is Not a Risk Factor for Cognitive Impairment After Major Noncardiac Surgery and Critical Illness

Abstract

Objective: The aim of this study was to determine whether surgery and anesthesia exposure is an independent risk factor for cognitive impairment after major noncardiac surgery associated with critical illness.

Summary of background data: Postoperative cognitive impairment is a prevalent individual and public health problem. Data are inconclusive as to whether this impairment is attributable to surgery and anesthesia exposure versus patients' baseline factors and hospital course.

Methods: In a multicenter prospective cohort study, we enrolled ICU patients with major noncardiac surgery during hospital admission and with nonsurgical medical illness. At 3 and 12 months, we assessed survivors' global cognitive function with the Repeatable Battery for the Assessment of Neuropsychological Status and executive function with the Trail Making Test, Part B. We performed multivariable linear regression to study the independent association of surgery/anesthesia exposure with cognitive outcomes, adjusting initially for baseline covariates and subsequently for in-hospital covariates.

Results: We enrolled 1040 patients, 402 (39%) with surgery/anesthesia exposure. Median global cognition scores were similar in patients with surgery/anesthesia exposure compared with those without exposure at 3 months (79 vs 80) and 12 months (82 vs 82). Median executive function scores were also similar at 3 months (41 vs 40) and 12 months (43 vs 42). Surgery/anesthesia exposure was not associated with worse global cognition or executive function at 3 or 12 months in models incorporating baseline or in-hospital covariates (P > 0.2). Higher baseline education level was associated with better global cognition at 3 and 12 months (P < 0.001), and longer in-hospital delirium duration was associated with worse global cognition (P < 0.02) and executive function (P < 0.01) at 3 and 12 months.

Conclusions: Cognitive impairment after major noncardiac surgery and critical illness is not associated with the surgery and anesthesia exposure but is predicted by baseline education level and in-hospital delirium.

FIGURE 1

Global cognition and executive function scores in patients with versus without surgery/anesthesia exposure. The RBANS is a validated tool that examines global cognitive function and has a mean (standard deviation) population age-adjusted score of 100 ± 15 with lower scores indicating worse global cognitive function. The Trails B is a validated tool that examines executive function and has an age-, sex-, and education-adjusted mean score of 50 ± 10 with lower scores indicating worse executive function. RBANS scores were similar in patients with surgery/anesthesia exposure versus those without exposure, approximately 1.5 standard deviations below adjusted mean. Likewise, Trails B scores were similar in patients with surgery/anesthesia exposure versus those without exposure, approximately 1 standard deviation below the adjusted mean. The horizontal bar indicates the median, the upper and lower limits of the boxes indicate the interquartile range, the ends of the whiskers indicate 1.5 times the interquartile range, and the black dots indicate outliers. The green dashed line indicates the adjusted population mean for normal adults, and the green band indicates the standard deviation. Also shown are the expected RBANS mean scores for traumatic brain injury and Alzheimer disease from other cohort studies (patients >65 years of age in Alzheimer disease).