Association Among Preoperative Cognitive Performance, Regional Cerebral Oxygen Saturation, and Postoperative Delirium in Older Portuguese Patients

BACKGROUND: Postoperative delirium is common among older patients and preoperative identification of high-risk patients is widely recommended. The aim of this study was to assess whether preoperative cognitive performance using brief screening tools or regional cerebral oxygen saturation (Scto(2)) was associated with the development of postoperative delirium in older Portuguese patients undergoing elective surgery. METHODS: Prospective observational cohort study where preoperative cognitive screening tools (Mini-Cog, Mini-Mental State Examination, verbal fluency) and Scto(2) (INVOS 5100C; Medtronic, Ireland) were assessed in 238 patients >= 65 years old undergoing elective surgery between July 2017 and May 2019 at a tertiary academic center in Portugal. The primary outcome was postoperative delirium detected by the 3D-Confusion Assessment Method. Data were analyzed by univariate analysis and multivariable logistic regression. RESULTS: Delirium was identified in 53 patients (22%); 162 patients (68%) had completed only 4 years of education. On multivariable analysis, probable cognitive impairment tested by the Mini-Cog (odds ratio [OR] = 1.57; 95% confidence interval [CI], 0.70-3.53; corrected P value >.999), by the Mini-Mental State Examination (OR = 2.75; 95% CI, 1.23-6.13; corrected P value = .052), and by the animal verbal fluency test (OR = 1.24; 95% CI, 0.49-3.16; corrected P value >.999) were not significantly associated with the development of postoperative delirium. In contrast, lower preoperative Scto(2) (OR = 1.08; 95% CI, 1.02-1.14; corrected P value = .024 for each point decrease in Scto(2)) was associated with postoperative delirium. CONCLUSIONS: We did not find enough evidence to suggest that poor preoperative cognitive performance was significantly associated with the development of postoperative delirium in an older Portuguese surgical population with an overall low level of formal education, but rather that preoperative Scto(2) may be helpful in identifying patients at risk for delirium.