P4‐309: BRAIN B‐AMYLOID IN COGNITIVELY NORMAL SUBJECTS IS A PREDICTOR OF EARLY POSTOPERATIVE COGNITIVE DYSFUNCTION

Postoperative cognitive dysfunction (POCD) can adversely affect short- and long-term surgical outcomes. Recent evidence implicates Alzheimer's disease neuropathology as a risk factor for POCD. AD-neuropathology is readily detectable with PET imaging using the β-amyloid (Aβ) specific tracer florbetapir-F18. This prospective study examined whether brain Aβ-burden at the preoperative baseline predicts POCD at hospital discharge. Here, we provide preliminary results. We enrolled 23 subjects with normal cognition, ≥65 years-old, scheduled for hip or knee replacement under general anesthesia. Preoperative baseline PET with Aβ-specific tracer florbetapir-F18 was acquired. Cognitive testing of 3 cognitive domains (e xecutive function, working and declarative memory) was performed at preoperative baseline and hospital discharge (or on postoperative day 7, whichever was first). ApoE-ε4 status was determined. Seventeen control subjects with orthopedic problems (no surgery) also underwent cognitive testing at similar time intervals (with no PET). We defined POCD as either: criterion 1) Z-score >1.95 in executive and memory function (working or/and declarative memory), or criterion 2) composite Z-score of >1.95. Of the 23 subjects, 8 were Aβ positive(+) and 15 Aβ negative(-). Aβ(+) subjects were older (75yrs vs. 68yrs, p=0.001) and had higher prevalence of ApoE-ε4 status than Aβ(-) patients (57% vs. 14%). No differences were found in years of education, cognitive performance at the preoperative baseline, co-morbidities, or length of stay. The overall incidence of early POCD in the 23 subjects was 30% and 48% (criterion 1 and 2, respectively; Table 1). The incidence of POCD in the Aβ(+) group was 50% and 75% compared to 20% and 33% in Aβ(-) group, for criterion1 and 2, respectively [p=0.06] (Table 1). Finally, t he mean change in all 3 cognitive domains from baseline to hospital discharge demonstrated more marked deterioration in Aβ(+) group compared to the Aβ (-) group (Figure 1). ApoE-ε4 status was not related to POCD. This study identified preexistent brain β-amyloid as a predictor of early POCD in cognitively normal subjects; brain Aβ doubled the incidence of POCD. Preexistent Aβ-burden in cognitively normal subjects potentially increases brain vulnerability to perioperative stressors, thereby increasing the risk of POCD. These results could have significant impact on perioperative care in the elderly. Mean change in test scores from baseline to hospital discharge (or on the 7th postoperative day, whichever was first). Executive functioning and working memory were assessed using the Executive Abilities: Methods and Instruments for Neurobehavioral Evaluation and Research (EXAMINER) battery. Declarative memory was assessed using the California Verbal Learning Task II.